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Verification of Water Mass Nd Isotopic Signature in North Atlantic Sediments during the Late Cretaceous

Permanent Link: http://ufdc.ufl.edu/UFE0045067/00001

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Title: Verification of Water Mass Nd Isotopic Signature in North Atlantic Sediments during the Late Cretaceous
Physical Description: 1 online resource (108 p.)
Language: english
Creator: Pugh, Emily R
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

Subjects

Subjects / Keywords: circulation -- cretaceous -- isotopes -- late -- nd -- ocean
Geological Sciences -- Dissertations, Academic -- UF
Genre: Geology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The Late Cretaceous represents one of the most recent major greenhouse intervals, but little is known about ocean circulation and structure at that time. Nd isotopes of fossil fish teeth are believed to preserve a record of water mass distributions. Seawater data from ODP deep sea sites at Demerara Rise highlight unusual, persistent, nonradiogenic epsilon Nd values (-14 to -17) that span the Cenomanian to Santonian. The nonradiogenic values are interrupted by a dramatic positive excursion of 8 epsilon Nd units during OAE2. The record has been interpreted to represent local formation of a warm, saline bottom water mass Demerara Bottom Water (DBW). The positive epsilon Nd excursion ~93 Ma is attributed to a temporary shutdown of DBW production or enhanced input of a North Atlantic/Tethyan water mass. An alternative explanation for the nonradiogenic epsilon Nd record might be that the signal is largely diagenetic. This study evaluated Nd, Pb, and Sr isotopic compositions of cleaned detrital silicates from Demerara Rise to verify that Nd isotopes preserved in fish debris record a water mass signal rather than sediment-seawater interactions. The isotopic record indicates that changes in epsilon Nd recorded in the fish teeth vary independently of isotopic shifts in the weathering record preserved in the detrital fractions, thus the fish teeth epsilon Nd record must reflect a circulation signal, specifically that the North Atlantic contained multiple water masses and that circulation was more vigorous throughout OAE2 compared to before and after the event.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Emily R Pugh.
Thesis: Thesis (M.S.)--University of Florida, 2012.
Local: Adviser: Martin, Ellen E.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2014-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0045067:00001

Permanent Link: http://ufdc.ufl.edu/UFE0045067/00001

Material Information

Title: Verification of Water Mass Nd Isotopic Signature in North Atlantic Sediments during the Late Cretaceous
Physical Description: 1 online resource (108 p.)
Language: english
Creator: Pugh, Emily R
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

Subjects

Subjects / Keywords: circulation -- cretaceous -- isotopes -- late -- nd -- ocean
Geological Sciences -- Dissertations, Academic -- UF
Genre: Geology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The Late Cretaceous represents one of the most recent major greenhouse intervals, but little is known about ocean circulation and structure at that time. Nd isotopes of fossil fish teeth are believed to preserve a record of water mass distributions. Seawater data from ODP deep sea sites at Demerara Rise highlight unusual, persistent, nonradiogenic epsilon Nd values (-14 to -17) that span the Cenomanian to Santonian. The nonradiogenic values are interrupted by a dramatic positive excursion of 8 epsilon Nd units during OAE2. The record has been interpreted to represent local formation of a warm, saline bottom water mass Demerara Bottom Water (DBW). The positive epsilon Nd excursion ~93 Ma is attributed to a temporary shutdown of DBW production or enhanced input of a North Atlantic/Tethyan water mass. An alternative explanation for the nonradiogenic epsilon Nd record might be that the signal is largely diagenetic. This study evaluated Nd, Pb, and Sr isotopic compositions of cleaned detrital silicates from Demerara Rise to verify that Nd isotopes preserved in fish debris record a water mass signal rather than sediment-seawater interactions. The isotopic record indicates that changes in epsilon Nd recorded in the fish teeth vary independently of isotopic shifts in the weathering record preserved in the detrital fractions, thus the fish teeth epsilon Nd record must reflect a circulation signal, specifically that the North Atlantic contained multiple water masses and that circulation was more vigorous throughout OAE2 compared to before and after the event.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Emily R Pugh.
Thesis: Thesis (M.S.)--University of Florida, 2012.
Local: Adviser: Martin, Ellen E.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2014-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0045067:00001


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1 V ERIFICATION OF WATER MASS ND ISOTOPIC SIGNATURE IN NORTH ATLANTIC SEDIMENTS DURING THE LATE CRETACEOUS By EMILY R.A. PUGH A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF T HE REQUIREMENTS FOR THE DE GREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2012

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2 2012 Emily R.A. Pugh

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3 To Derrick

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4 ACKNOWLEDGMENTS I sincerely thank my advisor Ellen Martin for continued support and guidance. She is a wonderful mentor. I also thank others who have provided help throughout this project, including Derrick Newkirk, George K amenov, and Chandranath Basak. I also thank the National Science Foundation and the University of Florida Graduate Student Council and Department of Geolo gical Sciences for financial support.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 8 A BSTRACT ................................ ................................ ................................ ................... 10 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .... 12 2 BACKGROUND ................................ ................................ ................................ ...... 21 Long lived Isotopic Tracers ................................ ................................ ..................... 21 Neodymium Isotopes in Seawater ................................ ................................ .... 22 Lead Isotopes in Seawater ................................ ................................ ............... 23 Strontium Isotopes in Seawater ................................ ................................ ........ 23 Archives of Seawater Nd, Pb, and Sr Isotopes ................................ ................. 24 Archives of Continental Nd, Pb, and Sr Isotopes ................................ .............. 26 Late Cretaceous ................................ ................................ ................................ ..... 27 Climatic and Tectonic Setting ................................ ................................ ........... 27 Ocean Anoxic Event 2 ................................ ................................ ...................... 28 Ocean Circulation ................................ ................................ ............................. 29 3 MATERIALS AND METHODS ................................ ................................ ................ 35 Description of Sample Sites on Demerara Rise ................................ ...................... 35 Sequential Chemical Extraction Procedures ................................ ........................... 36 Initial Sample Preparation and Decarbonation ................................ ................. 38 Fe Mn Dissolution ................................ ................................ ............................ 38 Oxidation of Organic Matter ................................ ................................ .............. 39 Detrital Silicate Dissolution ................................ ................................ ............... 40 Nd, Pb, and Sr Column Chemistry ................................ ................................ .......... 40 Nd, Pb, and Sr Analyses ................................ ................................ ......................... 41 Rare Earth Elemental Analyses ................................ ................................ .............. 42 4 RESULTS ................................ ................................ ................................ ............... 48 Nd Results ................................ ...................... 48 Rare Earth Elements ................................ ................................ ............................... 49 Strontium Iso topic Ratios ................................ ................................ ........................ 50 Lead Isotopic Ratios ................................ ................................ ............................... 51

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6 5 DISCUSSION ................................ ................................ ................................ ......... 79 Sequential Extraction Results and Difficulties ................................ ......................... 79 Implications for Seawater Interpretation ................................ ................................ .. 84 Changes in Detrital Inputs at Demerara Rise ................................ .......................... 86 6 CONCLUSIONS ................................ ................................ ................................ ..... 92 LIST OF REFERENCES ................................ ................................ ............................... 95 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 108

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7 LIST OF TABLES Table page 2 1 Parameters used for Sm Nd, Rb Sr, and U Th Pb decay systems. .................... 33 3 1 Information about ODP sites at Demerara Rise, Tropical Atlantic Ocean from this study. ................................ ................................ ................................ ........... 43 3 2 Sequential leaching procedures followed in th is study. ................................ ..... 44 4 1 Nd isotopic values from silicate detrital fractions from ODP Sites 1258, 1260, and 1261. ................................ ................................ ................................ ........... 53 4 2 REE values in ppm for detrital silicate fractions nor malized to the measured weights of the detrital fraction. ................................ ................................ ............ 56 4 3 Sr isotopes measured in silicate detrital fractions and HH extractions from ODP Sites 1258, 1260, and 1261. ................................ ................................ ...... 60 4 4 Pb isotopic composition from silicate detrital fractions from ODP Sites 1258, 1260, and 1261. ................................ ................................ ................................ .. 63

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8 LIST OF FIGURES Figure page 1 1 Plate reconstruction for the Cenomanian and location of sites discussed in this study. ................................ ................................ ................................ .......... 17 1 2 Nd isotopic composition preserved in fossil fish teeth through o ut the Late Cretaceous ................................ ................................ ................................ ......... 18 1 3 Plate reconstruction for the Cenomanian (~95 Mya) showing the location of Demerara Bottom Water and movement directi on ................................ ............. 19 1 4 Schematic indicating components of bulk marine sedime nt. ............................. 20 2 1 Plate reconstructions including oceans f or the Late Cretaceous. ....................... 34 3 1 Lithostratigraphic units and sedimentation breaks identified for drill sites as part o f ODP Leg 207 ................................ ................................ ........................... 45 3 2 Photograph from Site 1258 displaying a sharp con tact between lithostratigrapic Units III (calcareous nannofossil) and IV (black shale). ............. 46 3 3 Generalized schematic of the sequential leaching procedures employed on marine sediments examined in this study. ................................ .......................... 47 4 1 Nd(t) plotted versus age for detrital fractions from Demerara Rise Site 1258. ..... 67 4 2 Nd(t) plotted versus age for detrital fractions from Demerara Rise Site 1260. ..... 68 4 3 Nd(t) plotted versus age for detrital fractions f rom Demerara Rise Site 1261. ..... 69 4 4 Nd value s for Si tes 1258, 1260, and 1261. ................................ ................................ ................................ 70 4 5 Detrital fraction REE patterns from ODP Sit es 1258, 1260, and 1261 ............... 71 4 6 A compariso n of PAAS normalized HREE/LR EE vs. MREE/MREE* for detrital fractions from this study obtained and published data. .......................... 72 4 7 Detrital fraction REE patterns from ODP Site 1260. ................................ .......... 73 4 8 Sr isotopes versus age for detrital and HH fractions from OD P Sites 1258, 1260, and 1261. ................................ ................................ ................................ 74 4 9 Pb isotopes versus age for detrital fract ions from ODP Sites 1258. ................... 75 4 10 Pb isotopes versus age for detrital fractions from ODP Site 1260. .................... 76

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9 4 11 Pb isotopes versus age for detrital fractions from ODP Site 1261. .................... 77 4 12 Pb isotopes versus age for detrital fractions from O DP Sites 1258, 1260, and 1261. ................................ ................................ ................................ .................. 78 5 1 Nd, Pb, and Sr isotopic compositions versus age (50 to 100 Ma) for detrital fractions from Demerara Ri se Sites 1258, 1260, and 1261. ............................... 89 5 2 Nd, Pb, and Sr isotopic compositio ns versus age (52 to 75 Ma) for detrital fractions from Demerara Ris e Sites 1258, 1260, and 1261. ............................... 90 5 3 Pb vs. Pb diagrams for detrital fractions using method B from Sites 1258, 1260, and 126 1 compared to published data. ................................ .................... 91

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10 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements fo r the Degree of Master of Science V ERIFICATION OF WATE R MASS ND ISOTOPIC SIGNATURE IN NORTH A TLANTIC SEDIMENTS DURING THE LATE CRETACEOUS By Emily R.A. Pugh December 2012 Chair: Mike Perfit Major: Geology The Late Cretaceous represents one of the most recent major greenhouse intervals, but little is know n about ocean circulation and structure at that time. Nd isotopes of fossil fish teeth are believed to preserve a record of water mass distributions. Seawater data from ODP d eep sea sites at Demerara Rise highlight Nd values ( 14 to 17) that span the Cenomanian to Santonian. The nonradiogenic values are interrupted by a dramatic positive excursion of Nd units during OAE2. The record has been interpreted to represent local formation of a warm, saline bottom water mass [Demerara Bottom Water (DBW)]. The positive Nd excursion ~93 Ma is attributed to a temporary shutdown of DBW production or enhanced input of a North Atlantic/Tethyan water mass. An alternative explanation for Nd record might be that the signal is largely diagenetic. This study evaluated Nd, Pb, and Sr isotopic compositions of cleaned detrital silicates from Demerara Rise to verify that Nd isotopes prese rved in fish debris record a water mass signal rather than sediment seawater interactions. The isotopic record indicates that changes in Nd recorded in the fish teeth vary independently of isotopic shifts in the weathering record preserved in the detrita Nd

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11 record must reflect a circulation signal, specifically that the North Atlantic contained multiple water masses and that circulation was more vigorous throughout OAE2 compared to before and after the event.

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12 CHAPTER 1 INTRODUCTION e interval that was accompanied by very warm temperatures, elevated l evels of pCO 2 high sea level, and rapid crustal production (Jones et al., 2001; Huber et al., 2002; Bice et al., 2003; Skelton et al., 2003; Miller et al., 2005; Snow et al., 2005; Royer, 2006; Forster et al., 2007; Seton et al., 2009; Friedrich et al., 2012). The deep ocean waters experienced widespread oxygen depletion that is associated with intervals of hi gh 13 C excursions that represent major perturbations in the global C cycle (Arthur et al., 1987; Erbacher et al., 2005 ; Schlanger and Jenkyns, 1976). These phenomena are called ocean anoxic events (OAEs). One of the most Turonian boundary of the Late Cretaceous. Because the oceans store and transport heat and nutrients, reconstructing ocean circulation patterns throughout the Cretaceous is essential to understanding the role the oceans played in generating or enhancing the climate and ocean anoxia during a greenhouse state. However, little is known about ocean circulation and structure throughout the late Mesozoic, thus the relationship between circulation, climate, and o cean anoxia is not yet clear. Neodymium isotopes preserved in fossil fish teeth are one of the few ways to learn about past deep circulation patterns throughout the late Mesozoic and Cenozoic and this technique has recently been applied to Late Cretaceous samples (e.g. Thomas et al., 2003; Scher and Martin, 2006; MacLeod et al., 2008; Newkirk and Martin, 2009; Robinson et al., 2010; Martin et al., 2012; Murphy and Thomas, 2012; Robinson and Vance, 2012). In the broad North Atlantic region distinct water m asses have been

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13 identified in the Tethys (Pucat et al., 2005; Soudry et al., 2006) North Atlantic (MacLeod et al., 2008, 2011), and Demerara Rise (MacLeod et al., 2008; Jimnez Berrocoso et al., 2010; MacLeod et al., 2011; Martin et al., 2012) (Fig ures 1 1 and 1 2) An unusually non radiogenic water mass on Demerara Rise has been identified as a warm, saline bottom water and referred to as Demerara Bottom water (DBW) ( MacLeod et al., 2008 ; Jimnez Berrocoso et al., 2010; Martin et al., 2012) (Figure 1 3) DBW may have formed on the proximal Precambrian Guyana Shield, whic h is known to have produced non radiogenic sediments (Goldstein et al., 1997). DBW could have obtained its Nd isotopic composition from this continental material as the water mass formed on the shield and flowed into the Atlantic. The formation of DBW supports a controversial idea that bottom waters can form in tropical regions (MacLeod et al., 2008; Martin et al., ss that flowed along the seafloor at bathyal depths on Demerara Rise and does not imply that the water mass behaved like modern Antarctic Bottom Water, which occupies the deepest parts of the ocean wherever it is found (MacLeod et al., 2008; 2011). DBW p ersists throughout most of the Late Cretaceous with the exception of peak greenhouse gas conditions at the Cenomanian Turonian boundary (Figure 1 2) when water sourced from the North Atlantic/Tethys appears to have flowed into the Demerara Rise region and mixed with DBW (MacLeod et al., 2008; Jimenez Berrocosso, 2010; Martin et al., 2012) (Figure 1 3) This implies that circulation was more vigorous throughout OAE2 compared to before and after the event, countering arguments that ocean stagnation contri buted to the anoxia. During the Maastrichtian, Nd indicate that Northern Component Water (NCW) sourced from the North Atlantic flowed

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14 into the Demerara Rise region and production of DBW ceased (MacLeod et al., 2011) (Figure 1 2) This scenario places the influx of NCW much earlier than prev ious estimates that suggest onset of NCW in the Oligocene (Davies et al., 2001; Howe et al., 2001; Via and Thomas, 2006; Scher and Martin, 2008). The Nd isotopic record preserved in fossil fish teeth at Demerara Rise has multiple significant implications f or ocean circulation and structure during the Late Cretaceous, and therefore the relationship between seawater and fish teeth Nd for these samples needs to be rigorously evaluated and verified. The assumption based on previous studies of Nd isotopes in fish teeth is that they record bottom seawater values (Palmer and Elderfield, 1985; Martin and Haley, 2000; Martin and Scher, 2 004). Other possibilities include incorporation of a signal that was influenced by boundary exchange or diagenetic alteration due to i nteractions with pore waters. Boundary exchange is a process in which sediment deposited on continental margins exchange s Nd isotopes with the overlying seawater (Lacan and Jeandel, 2005). In this case, nonradiogenic sediments derived from the Guyana Shield and depositing at Demerara Rise might have exchanged Nd isotopes with the overlying water column, thereby altering th e isotopic ratio of the bottom water that was then incorporated into the teeth. In this scenario, fish Nd record could reflect changes in sediment composition rather than dee p water circulation. Diagenetic alteration in the pore water is also likely to introduce a sediment signature to the fish teeth. The goal of this study is evaluate the nonradiogenic Nd background signal at Demerara Rise from 100 to 65 Ma (Figure 1 2) to determine whether it represents 1) a

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15 locally derived and ventilated water mass, or 2) local i nteractions between seawater and pore waters or material weathered off of the neighboring Guyana Shield, which then overprint a more basin wide circulation signal. In order to evaluate the relationship between Nd preserved in fossil fish teeth/debris at Demerara Rise and the local terrigenous inputs, Nd, Pb, and Sr isotopes and rare earth element (REE) patterns of the detrital silicate fraction of deep sea sediments from Demerara Rise are examined. A compariso n of absolute isotopic compositions and the patterns of change between detrital inputs and fish teeth should determine whether variations in the fish teeth are simply a response to variations in local weathering inputs or a response to changes in ocean cir cu la tion. If the fish teeth accurately record DBW, 1) their Nd values may be more radiogenic than Nd of the detrital fractions, reflecting the mixing of South American epicontinental seaway water and North Atlantic/Tethyan waters and possibly incongruent weathering of Nd, and 2) their patterns of change should be distinct from the changes observed in the detrital fractions. Evaluation of these simple hypotheses may be complicated by the fact that locally derived DBW is likely to have Nd values similar to sediments from the Guyana Shield, but distinct variations in Nd patterns between the seawater and detrital Nd records would indicate the seawater Nd is varying independently of continental weathering inputs and reflects changes in circulation and deep water ventilation (MacLeod et al., 2008; Martin et al., 201 2). An important component of this study is to isolate the detrital fraction of marine sediment from carbonates, organic matter and archives of seawater isotopic composition, which includes at least fish teeth, foraminifera, and iron manganese (Fe Mn) ox ides (Figure 1 4) A chemical leaching protocol developed by modifying Rutberg

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16 et al. (2000) as presented in Martin et al. (2010) was applied to our bulk sediment samples. Initial analyses of the detrital silicate fraction yielded Nd isotopic composition s very similar to corresponding fish teeth values, implying possible contamination from a component with a seawater signal. Subsequently, we tested several modifications of the leaching protocol proposed by Bayon et al. (2002) in an effort to obtain a det rital silicate fraction free of archives carrying a seawater signal REE concentrations and Sr isotopes of the detrital fraction are analyzed to test for seawater contamination within the detrital fraction.

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17 Figure 1 1 Plate reconstruction for the C enomanian and location of sites discussed in this study (Scotese, 2008). Modified by Martin et al. (2012).

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18 Figure 1 2. Nd isotopic composition preserved in fossil fish teeth throughout the Late Cretaceous (Martin et al., 2012). OAE2 occurs at the Ceno manian/Turonian boundary.

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19 Figure 1 3. Plate reconstruction for the Cenomanian (~95 Mya) showing the location of Demerara Bottom Water and movement direction (Scotese, 2008). Modified by Jimnez Berrocoso et al. (2010).

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20 Figure 1 4. Schema tic indicating components of bulk marine sediment. For this study, we aimed to isolate the silicate detrital fraction in order to obtain a continental weathering signal not overprinted with a seawater signal recorded by Fe Mn oxides or biogenic components Carbonates and o rganic matter were removed to further isolate the detrital fraction. Seawater Nd Continental Nd

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21 CHAPTER 2 BACKGROUND Long lived I sotopic T racers The long lived radiogenic isotopic systems important to this study are Sm Nd, Th U Pb, and Rb Sr (Table 2 1). These sy stems are used in geologic studies to trace past ocean circulation and weathering patterns. Some elements preferentially enter magma during the formation of continental crust causing isotopic heterogeneity between continental crust and mantle rock. For ex ample, strontium (Sr) samarium (Sm), and lead (Pb) preferentially remain in the mantle, while rubidium (Rb), neodymium (Nd), uranium (U) and thorium (Th) tend to enter magma. Consequently, mid ocean ridge basalts (MORB) and ocean island basalts (OIB) hav e low 87 Sr/ 86 Sr, 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb, and high 143 Nd/ 144 Nd relative to continental crust. These oceans in dissolved or particulate forms. The dissolve d forms directly imprint the water mass it enters, while particulate material may partially dissolve or exchange in the ocean to release its isotopic signature to the water column or simply settle to the seafloor. Nd and Pb are particle reactive, meaning t hey have a n affinity for solid phases and thus have short residence times in seawater. The conservative nature of these decay systems combined with isotopic heterogeneity throughout Earth and their short residence times in seawater allow Nd and Pb isotop es preserved in various archives to be used as paleoceanographic and paleoclimatic tracers. In contrast, Sr has a long residence time in seawater that limits its value as a paleoceanographic tracer, but does not impact its ability to trace sediment proven ance.

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22 Neodymium Isotopes in S eawater Neodymium is a light Rare Earth Element (REE) with seven isotopes. Radiogenic 143 Nd is produced by alpha decay of 147 Sm. 143 Nd is referenced to the stable isotope 144 Nd. This ratio ( 143 Nd/ 144 Nd) is reported as Nd whic h is calculated using the equation: Nd = [( 143 Nd/ 144 Nd) sample /( 143 Nd/ 144 Nd) CHUR 1] x 10 4 143 Nd/ 144 Nd of ~0.512638 (Jacobsen and Wasserburg, 1980). Nd has a short residence t ime in seawater (200 1000 years; Tachikawa et al., 1999, 2003; Arsouze et al. 2009) compared to the mixing time of the ocean (~1500 years; Broecker and Peng, 1982). Consequently, ocean water masses have distinct Nd values and since the ocean is stratifi ed, Nd values also vary vertically through the water column (Piepgras and Wasserburg, 1987; Bertram and Elderfield, 1993; Jeandel, 1993). Nd mainly enters the ocean via continental weathering, therefore the Nd signature for any water mass is determined by the regional geology of the location where the water low Nd values reflect the weathering of old granitic crustal rocks, which tend to have Nd = 0 to 50 (Piepgras and Wasserburg, 1980). In the modern ocean, North Atlantic Deep Water (NADW) has an Nd = ~ 13.5, which reflects the weathering of the Arch ean North American craton into the North Atlantic basin (Piepgras and Wasserburg, 1987). In comparison, Pacific Deep Wat er (PDW) has more radiogenic Nd values ( Nd = 0 to 5), signifying the influence of young volcanic source rocks which have Nd values ranging from 0 to +12 (Piepgras and Wasserburg, 1980; Piepgras and Jacobsen, 1988).

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23 Lead Isotopes in S eawater Lead is a trace metal associated with the U Pb and Th Pb decay series. The parent isotopes, 232 Th, 235 U, and 238 U, decay at different rates to 208 Pb, 207 Pb, and 206 Pb, respectively, and these Pb isotopes are referenced to stable 204 Pb. Average lead isotopic comp ositions of the Upper Continental Crust (UCC) have values of 18.93, 15.71, and 39.03 for 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb, respectively (Millot et al., 2004). In comparison, respective Pb isotopic compositions of oceanic basalts from the southeas tern Pacific are 16.90, 15.44, and 36.53 for 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb (Hoernle et al., 2010). Isotopic ratios among mantle rocks are heterogeneous, depending on the source, and continental crust isotopic compositions vary geographically a nd according to age. Lead is sourced to the ocean primarily by eolian processes that transport continental weathering products and volcanic ash (e.g. Jones et al., 2000; Pettke et al., 2002; Ling et al., 2005; Klemm et al., 2007). Pb has a short residenc e time in the oceans of ~50 200 years (Craig et al., 1973, Schaule and Patterson, 1981; Henderson and Maier Reimer, 2002). Strontium Isotopes in S eawater Strontium has four stable isotopes 84 Sr, 86 Sr, 87 Sr, and 88 Sr. Of these, 87 Sr is produced from bet a decay of 87 Rb. Due to the preferential fractionation of Rb into magma, the average 87 Sr/ 86 Sr ratio of the dissolved load of rivers ( 87 Sr/ 86 Sr = 0.7119) are more radiogenic compared to estimates for hydrothermal sources on the seafloor ( 87 Sr/ 86 Sr Sr = 0. 7035; Palmer and Edmond, 1989). Due to its long residence time (~2.5 Ma; Hodell et al., 1994), the Sr isotopic composition of seawater is spatially homogeneous, but the value varies through time with inputs of hydrothermal and continental weathering fluxe s as documented by analyses of calcitic fossil s such as

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24 foraminifera, belemnites, and oysters (Palmer and Elderfield, 1985; Jones et al., 1994; McArthur et al., 2001). Archives of Seawater Nd, Pb, and Sr Isotopes Various biogenic and authigenic phases have been shown to accurate ly r e cord seawater Nd, Pb, and Sr isotopes Due to the residence time of Nd in the oceans, these isotopes are used as proxies to reconstruct water mass circulation and have been applied to samples as old the Cretaceous. The ve ry short residence time of Pb means that these isotopes carry both an advection and local weathering signal (Abouchami and Goldstein, 1995) and therefore are used to study changes in weathering sources, regimes, and rates (Reynolds et al., 1999; Foster and Vance, 2006). Seawater Sr is typically analyzed on calcitic fossils, such as foraminifera, but can be extracted from other authigenic archives to test the robustness of that archive compared to the well defined Sr seawate r curve (e g., Burke et al., 1982 ; McArthur et al., 2001). Fossil fis h teeth and debris are one of the most robust archives for bottom water Nd (Martin and Scher, 2004) and have been applied to numerous paleoceanograph ic studies (e.g., Thomas et al. 2003; Pucat et al., 2005 ; Thomas and Via, 2007; Scher and Martin, 2008; Newkirk and Martin, 2009; Robinson et al., 2010; Martin et al., 2012; Robinson and Vance, 2012). Fish teeth are widely distributed throughout marine sediments and can be dated with the surrounding sediment using magnetostratigraphic, biostratigraphic, an d chemostratigraphic techniques. Fish teeth incorporate the Nd isotopic composition of local seawater into their crystal lattice during early dia genesis Nd signature through burial and diagene sis (Elderfield and Pagett, 1986 ; Martin and Haley, 2000; Martin and Scher, 2004). Fish teeth have been shown to be poor archives of seawater Sr (Martin and Scher, 2004). Stronti um is

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25 incorporated into biogenic apatite when Sr 2+ replaces Ca 2+ during tooth growth, but this signal is altered after burial as the tooth incorporates isotopes from the pore waters. Pb is also archived in fish teeth but a recent pilot study concluded tha t Pb isotopes stored in the teeth are a combination of initial Pb (shallow water signal) and early diagenetic enrichment (deep water signal) and that the contribution of each signal cannot be constrained since the teeth behave as open systems to Pb, U, and Th isotopes in the surrounding seawater (Basak et al., 2011). Authigenic ferromanganese (Fe Mn) oxyhydroxides dispersed on bulk sediment also archive seawater Nd, Pb, and Sr isotopes (e.g. Palmer and Elderfield, 1985; Rutberg et al., 2000; Bayon et al ., 2002; Piotrowski et al., 2004, 2005; Gutjahr et al., 2007; Haley et al., 2008; Piotrowski et al, 2008; Gutjahr et al., 2009; Martin et al., 2010; Basak et al., 2011). These oxides incorporate the isotopic chemistry of ambient seawater when they precipi tate on sedimentary particles. Fe Mn oxides are extracted from marine sediment through chemical leaching processes. These samples can be dated with the surrounding sediment using biostratigraphic, chemostratigraphic, and magnetostratigraphic techniques. Pb isotopes extracted from this oxide phase are limited to Cenozoic timescales (Gutjahr et al. 2007, 2009; Basak et al., 2011) because corrections for ingrowth of radiogenic isotopes are required for older samples, but Pb and U fractionate during the leac hing procedure. Foraminifera are routinely analyzed for Sr isotopes, and this archive was heavily relied upon for development of the seawater Sr isotopic curve since the Mesozoic (e.g., Hodell and Woodruff, 1994; McArthur et al., 2001). Records of seawa ter Nd isotopes recovered from foraminifera (Vance and Burton, 1999; Vance et al., 2004; Klevenz et

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26 al., 2008) have been quite controversial because Nd concentrations are very low in foraminiferal calcite and there is debate about how much of the signal ac tually represents Fe Mn oxide coatings, which contain much higher Nd concentra t ions (Palmer and Elderfield, 1985; Pomies et al., 2002; Roberts et al., 2010). Hydrogenous Fe Mn crusts and nodules are made of the same Fe Mn oxides as dispersed coatings and a lso record accurate Sr, Nd and Pb isotopic compositions of 1998; Reynolds et al., 1999; Bayon et al., 2002; Frank et al., 2002; van de Flierdt et al., 2004; Foster an d Vance, 2006). However, Sr isotopes have been shown to be mobile in Fe Mn crusts after deposition (VonderHaar et al., 1995). Fe Mn crusts have some disadvantages, including very slow accumulation rates (1 to 15 mm/Ma; Segl et al., 1984; Puteanus and Hal back, 1988) that limit resolution to long term trends, difficulties dating, and spatially sparse availability. Archives of Continental Nd, Pb, and Sr Isotopes Silicate detrital fractions of marine sediments record the isotopic record of the silicate cont inental material weathered into the ocean. Nd, Pb, and Sr isotopes preserved in these terrigenous silicates can be used to determine provenance (Jones et a l., 1994). For this study, isotopes of detrital fractions of marine sediments from Demerara Rise ar e mainly compared to analyses of whole rocks and suspended river s ediment (Allgre et al., 1996; Tohver et al., 2004; Carpentier et al., 2008). In order to isolate the silicate detrital fraction of ma rine sediment all of the carbonate, organic matt er, aut higenic and biogenic material must be removed using sequential leaching techniques (e.g. Rutberg et al., 2000; Bayon et al., 2002; Gutjahr et al., 2007; Basak et al., 2011; Martin et al., 2012).

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27 Late Cretaceous The Late Cretaceous (Cenomanian to Maastric htian) was a well defined greenhouse interval characterized by warm and equitable temperatures, elevated pCO 2 and high sea levels. Land masses were arranged much differently than today and there was extensive flooding on the continents. Additionally, th e deep oceans experienced episodes of widespread oxygen depletion that reflect changes in the global carbon cycle (Schlanger and Jenkyns, 1976; Arthur et al., 1990; Arthur and Sageman, 1994; Erba, 2004). Climatic and Tectonic Setting The early part of the Late Cretaceous experienced a rapid transition from a warm greenhouse state to a hot greenhouse state with peak warmth ~94 Mya at the Cenomanian Turonian boundary interval (CTBI) marking the Cretaceous Thermal Maximum (CTM) (Huber et al., 2002; Forster et al., 2007; Friedrich et al., 2012). The CTM was followed by a rapid decrease of ~4C in the late Cenomanian, but warm temperatures quickly returned and persisted to the Turonian (Forster el., 2007). A global cooling trend began in the Campanian and last ed through the Maastrichtian, indicated by low latitude bottom water temperatures in the North Atlantic decreasing from an average 12C to a minimum 9C (Clarke and Jenkyns, 1999; Huber et al., 2002; Jenkyns, 2010; Friedrich et al., 2012). Sea surface tem peratures in the equatorial Atlantic warmed from 31C to 37C (Bice et al., 2006; Forster et al., 2007; Bornemann et al., 2008) and middle bathyal waters in the same region increased from 12C in the late Albian to 20C in the late Cenomanian (Huber et al. 2002). Estimates for intermediate bottom waters in the Pacific and southern high latitudes are up 20C (Friedrich et al., 2012). The CTBI is also marked by rapid sea floor spreading and

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28 highly active volcanism on the seafloor, including the eruption of the Caribbean Large Igneous Provinces (CLIP) (Haq et al., 1988; Larson, 1991; Coffin and Eldholm, 1994; Alvarado et al., 1997; Sinton and Duncan, 1997; Sinton et al., 1998; Jones et al., 2001; Brumsack, 2005; Snow et al., 2005). Thermal expansion along w ith high rates of ocean crust production generated a sea level high of 100 170 m (Miller et al., 2005; Mller et al., 2008) and the formation of epicontinental seaways (Haq et al., 1988; Hay et al., 1993). Atmospheric CO 2 was very concentrated at levels u p to 8x pre industrial values (Freeman and Hayes, 1992; Yapp and Poths, 1996; Ekart et al., 1999; Pearson and Palmer, 2000; Retallack, 2001; Bice et al., 2003, 2006; Royer, 2006). Land masses were clustered together on one side of the globe and separated latitudinally by the northern tropical circumglobal Tethys Ocean and longitudinally by the newly forming North and South Atlantic Oceans (Figure 2 1) The extensive Panthalassa Ocean occupied the op posite side of Earth This tectonic setting restricted m eridional ocean circulation and oceanic exchange between basins until the Southern Ocean developed and the North and South Atlantic were connected. Ocean Anoxic Event 2 The Late Cretaceous deep ocean experienced episodes of widespread oxygen depletion kn own as ocean anoxic events [OAEs] (Schlanger and Jenkyns, 1976; Arthur et al., 1990; Arthur and Sageman, 1994; Erba, 2004). OAEs a re intervals of high 13 C excursions that represent major perturbations to the global carbon cycle (Schlanger and Jenkyns, 1976; Arthur et al., 1987; Erbacher et al., 2005 ). Major changes in ocean chemistry or environment must have occurred in order to create these events. OAEs occurred periodically in the geologic past. OAE2, or the Bonarelli Event, occurred at the Cenomanian Turonian boundary ~93 Mya and is

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29 the most globally pronounced OAE and is identified in the stra tigraphic record as finely laminated carbon rich shales (e.g. Schlanger and Jenkyns, 1976; Jenkyns, 1980; Arthur et al., 1987; Schlanger et al., 1987; Leckie et al., 2002; Erba, 2004; Sageman et al., 2006; Forster et al., 2007). The burial of organic carb on sequesters carbon from the atmosphere, thus this process may have created a negative feedback to remove CO 2 from the atmosphere (Arthur et al., 1988; Jenkyns et al., 1994; Kuypers et al., 1999). OAE2 is identified chemostratigraphically in the sedimen tary record by an abrupt 13 2003). The cause of OAE2 has not been firmly established. One scenario includes reduced or sluggish ocean circulation that inhibited ventilation creating oxygen poor deep water (Barron, 1983; Bralower and Thierstein, 1984). Other possibilities are enhanced primary productivity in the surface ocean from increas ed nutrient input/upwelling and subsequent organic matter decay (e.g. Schlanger and Jenkyns, 1976; Arthur et al., 1987; Arthur and Sageman, 1994; Erbacher et al., 2001; Jenkyns, 2010;) or intense volcanic activity on the seafloor that released productivity enhancing nutrients and gases (e.g., Sinton and Duncan, 1997; Snow et al., 2005; Turgeon and Creaser, 2008; Adams et al., 2010). Ocean Circulation Constraining circulation routes, the extent of water mass mixing, and mechanisms and locations for deep wat er formation is difficult; however, a few studies have aimed to understand ocean circulation throughout the Late Cretaceous using Nd isotopes (e.g., Frank et al., 2005; Pucat et al., 2005; Soudry et al., 2006; MacLeod et al., 2008; Robinson et al., 2010; Murphy and Thomas, 2012; Martin et al., 2012; Robinson and

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30 Vance, 2012). Thus far, five water masses have been recognized including the Tethys (Pucat et al., 2005; Soudry et al., 2006), North Atlantic (MacLeod et al., 2008, 2011), Pacific (Frank et al., 2005), Indian and Southern (Robinson et al., 2010; Murphy and Thomas, 2012; Robinson and Vance, 2012), and Demerara Bottom Water (MacLeod et al., 2008; Jimnez Berrocoso et al., 2010; MacLeod et al., 2011; Martin et al., 2012) (Figures 1 1 and 1 2 ). In t he Tethys basin, Pucat et al. (2005) and Soudry et al. (2006) tracked the evolution of an upper ocean water mass called the Tethys Circumglobal Current (TCC) using Nd isotopes. Data indicate westward flow during the Late Barremian (~127 Mya) to the Masst Nd excursion indicates the Tethys seaway experienced an incursion of radiogenic Pacific waters that has been attributed to global sea level rise and the widening of the Caribbean gateway (P ucat et al., 2005; Soudry et al., 2006). Frank et al. (2005) constrained circulation in the tropical Pacific throughout the 18 O, indicate an influx of warm intermediate North Pacific water during the early Maastrichtian followed by replacement by cooler water from the Southern Ocean. The cooler water mass dominated for the an influx of warm saline intermediate wate rs from the Western Tethys is believed to create a brief, abrupt increase in SST (+ 2 to 3C) and intermediate water temperatures (+ 4C). In the South Atlantic and proto Indian Oceans, a radiogenic water signal has been identified throughout the mid t o Late Cretaceous (Robinson et al., 2010; Murphy and

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31 Thomas, 2012; Robinson and Vance, 2012). Robinson et al. (2010) conclude the signal is largely dominated by dissolution of weathered volcanic terrains and seawater particle exchange, rather than incursi on of Pacific waters. At the time, the South Atlantic and proto Indian basins were restricted, inhibiting influx from other basins and permitting sluggish circulation. As the climate cooled in the Southern Hemisphere and oceanic gateways opened, this reg ion evolved to produce deep water, namely Southern Component Water (SCW) (Robinson et al., 2010; Robinson and Vance, 2012). Robinson and Vance (2012) suggest SCW bathed the deepest parts of the Atlantic basins and Murphy and Thomas (2012) propose the wate r flowed into the Eastern Tethys. SCW may have been the dominant source of deep water until the Oligoc ene (Robinson and Vance, 2012). In the Demerara Rise region, a warm saline intermediate water mass has been Nd record extensively documented in three bathyal sites along a depth transect throughout the Cenomanian to Maastrichtian although a ~10 m.y interval of the Coniacian to late Campanian is represented by a hiatus (Figure 1 2) (MacLeod et al., 2008; Martin et al., 2012). Termed Demerara Bottom Water (DBW) (Jimnez Berrocoso et al., 2010), this water mass likely formed on the proximal Precambrian Guyana Shield, which is known to produce sediments with nonradiogenic Nd values of 20 to 31 (Goldstein et al., 1997). DBW would have drained i nto the tropical North Atlantic and flowed along the bo ttom of the seafloor (MacLeod et al., 2008) (Figure 1 3) A positive Nd excursion interrupts the record during OAE2 (Figure 1 2) The abrupt change is interpreted to represent an influx of Tethyan or North

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32 Atlantic bottom waters, possibly caused by freshening of DBW during the intensified hydrologic conditions of the greenhouse environment (Martin et al., 2012). In the Maas trichtian, Nd values at all three sites on Demerara Rise begin to transition to radiogenic values similar to the North Atlantic (Figure 1 2) The transition begins ~69 Mya at the deepest site and is evident in the shallowest site 3 million years later (MacLeod et a l., 2010). An abrupt shift to radiogenic values occurs ~65 Myr suggesting intensified southward flow of water from the North Atlantic and possibly indicating the production of deep and intermediate water in the North Atlantic (MacLeod et al., 2010). Othe r studies suggest North Component Water (NCW) production did not begin until the Oligocene (Davies et al., 2001; Howe et al., 2001; Via and Thomas, 2006). Production of NCW in the Atlantic basin during the Late Cretaceous could explain regional warmth dur ing a time of global cooling (MacLeod et al., 2005). As intermediate/deep waters moved south, warm surface waters in the South Atlantic flowed north transferring heat from the South to North Atlantic (MacLeod et al., 2005; Isaza Londoo et al., 2006).

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33 Table 2 1. Parameters used for Sm Nd, Rb Sr, and U Th Pb decay systems. Decay System Isotopic ratio Present day value 147 143 Nd 143 Nd/ 144 Nd 0.512638 1 87 87 Sr 87 Sr/ 86 Sr 0.705 2 Initial Solar System 238 206 Pb 206 Pb/ 204 Pb 9.307 3 235 207 Pb 207 Pb/ 204 Pb 10.294 3 232 208 Pb 208 Pb/ 204 Pb 29.476 3 1 Jacobsen and Wasserburg (1980) 2 (1977), DePaolo and Wasserburg (1976) 3 Tatsumoto et al. (1973)

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34 Figure 2 1. Plate reconstructions including o ceans for the Late Cretaceous. A) 100 Ma (Cenomanian) B) 80 Ma (Campanian) C ) 65 Ma (late Maastrichtian) (Lawver et al., 2002). B ) 80 Ma Tethys A ) 100 Ma Panthalassa Tethys North Atlantic Panthalassa South Atlantic C ) 65 Ma Southern proto Indian Pacific South Atlantic North Atlantic

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35 CHAPTER 3 MATERIALS AND METHOD S Description of Sample Sites on Demerara Rise Sites 1258, 1260, and 1261 were drilled on Demerara Rise during the Ocean Drilling P rogram (ODP) Leg 207 (Figure 1 1 ). Demerara Rise is a shallow, northwest sloping submarine plateau located ~5N of Suriname and French Guyana, South America. The sites form a SE NW depth transect with paleowater depths of ~1500 to 600 m (Arthur and Natland, 1979; Friedrich et al., 2006). Site 1258 is the deepest site (modern water d epth = 3192 meters below sea level [mbsl]), followed by Site 1260 (2549 mbsl), and then Site 1261 (1899 mbsl) (Table 3 1). The total age range for sediments and sedimentary rock cored at these sites is Albian to Pleistocene. This study focused on Cenoman ian to Paleocene material. Lithostratigraphy is similar amongst the sites. Five units have been identified and three units are sampled for this study (Units III, IV, and V) (Figure 3 1). Unit III (Campanian to Eocene) is composed of heavily bioturbated gr eenish gray calcareous nannofossil clay, indicating the transition to open marine conditions with oxic bottom waters (Figure 3 2) Unit IV (late Albian Santonian; Hardas and Mutterlose, 2006) contains laminated black shales and limestones (clayey nannofos sil chalk with organic matter) (Figure 3 2) Unit V is the oldest (Albian) and consists of gray to black phosphoritic calcareous clay with organic matter deposited in a shallow marine setting and may represent synrift deposition (Figure 3 1) At all three sites, OAE2 is present in Unit IV and is defined by an increase o 13 C and an increase in total organic carbon (TOC) (Erbacher et al., 2005).

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36 Sequential Chemical Extraction Procedures When utilizing marine sediments f or paleoceanographic and paleoclimatic studies, it is important to separate the seawater Sr, Nd and Pb isotopic records from the terrigenous influences in order to make accurate interpretations of ocean circulation and weathering (Figure 1 4) Sequential extraction protocols are used to isolate and retrieve Fe Mn oxides and detrital fractions from bulk sediment. Procedu res used to extract Fe Mn oxide coatings from bulk marine sediment to study seawater isotopes are generally milder than procedures used to isolate the detrital fraction since only partial isolation of Fe Mn oxides is needed for anal yses. In this scenario, it is important to minimize leaching int o the detrital fraction to avoid contaminating the seawater signal with a continental signal. Multiple procedures have been designed to accomplish this goal (Chester and Hughes, 1967; Rutbe rg et al., 2000; Tovar Sanches et al., 2003; Piotrowski et al., 2004, 2005, 2008; Gutjahr et al., 2007, 2009; Gourlan et al., 2008; Martin et al., 2010; Houedec et al., 2012 ) Different protocols have been designed to retrieve Fe Mn oxides and isolate the detrital fraction from all seawater components (Bayon et al., 2002; Gutjahr et al. 2007; 2009; Martin et al., 2010). Any material carrying a seawater signal that is not removed during the sequential extraction can potentially mask the detrital signature Regardless of the desired archive, the protocols share the objectives of dissolving carbonates, reducing Fe Mn oxides, and oxidizing organic matter. Rutberg et al. (2000) modified the extraction procedure from Chester and Hughes (1967) to extract the F e Mn fraction of marine sediments to reconstruct NADW production on Pleistocene timescales. Their chemical extraction procedure includes a decarbonation step using a buffered acetic acid and extraction of Fe Mn phases using

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37 0.02M hydroxylamine hydrochlori de (HH) in 25% glacial acetic acid. Bayon et al. (2002) tested the robustness of this extraction procedure and a variety of other different procedures on marine sediment samples from northern Cape Basin in southeast Atlantic Ocean. The goal of the study was to extract the seawater signal from bulk sediment and isolate the detrital fraction. Both fractions were analyzed for Nd and Sr isotopic composition. Bayon et al. (2002) concluded that using a stronger HH solution (1 .0 M) and heating the samples in a ~95C hot bath during the 3 hour extraction more effectively removed the Fe Mn phases than using a weaker HH solution (0.04M). However, Gutjahr et al. (2007) concluded that a very similar extraction, 1 .0 M HH 25% acetic acid in a shaker at 95C for 4 hours was too aggressive for evaluation of the seawater fraction for sediments from the northwest Atlantic. After testing various leaching reagents on these sediments, Gutjahr et al. (2007) concluded that the best possible method for extracting seawater isoto pic signatures is adding 0.05M HH 15% acetic acid 0.03M Na EDTA to the sample and allowing the reaction to occur on a shaker for 2 3 hours at 20C. This extraction procedure is a modification of methods used by Chester and Hughes (1976), Rutberg et al. (2 000), Tovar Sanchez et al. (2003), and Piotrowski et al. (2004). Thus, a variety of extraction processes have been shown to effectively separate the Fe Mn oxide fraction from the detrital fraction. However, these studies evaluated very young sediments w ith typical deep sea lithologies (Pleistocene to the Holocene) and few of them analyzed the remaining detrital fractions. In contrast, Martin et al. (2010) and Basak et al. (2011) used a modified technique to extract Nd and Pb seawater isotopes from sampl es from the Miocene to Cretaceous, respectively. The current study tested numerous

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38 methodologies to isolate the detrital fraction of Cretaceous carbonate and black shale in an effort to identify the best protocol. Initial Sample Preparation and Decarbon ation For this study bulk sediment was pulverized and homogenized using an agate mortar and pestle. Approximately 1.5 g of the powdered sediment was transferred to a 50 ml centrifuge tube and dried in an oven set to 65C. Next, the sample was mixed with 20 ml of 1 .0 M Na acetate in 2.7% optima glacial acetic acid (buffered to a pH of 5). The buffered acetic acid solution was treated with 10 12 g of Chelex 100 cation exchange resin to minimize the Pb blank in the solution (Basak et al., 2011). The sample remained uncapped in the hood for 12 24 hours with occasional agitation until the reaction was complete. The sample was centrifuged, the supernatant decanted, and another 20 ml of the buffered acetic acid was added to the sample to ensure all of the carbo nate was dissolved. The centrifuge tubes were then capped and mounted on a rotator for 12 24 hours and occasionally degassed. This step was repeated until decarbonation was complete. The sample was triple rinsed with four times distilled water (4x H 2 O). Fe Mn Dissolution Initially this study followed the chemical extraction procedure described in Martin et al. (2010), which used 0.02M HH in 25% acetic. We added an organic matter oxidation step using 30% H 2 O 2 (hydrogen peroxide) due to the high organic content of the sediment, particularly the Santonian to Cenomanian black shales. This method is described in Table 3 Nd isotopic analyses of the detrital silicate fraction s were very similar to the corresponding fish teet h Nd values, indicating contamination by a component carrying a seawater signal. We then tested multiple

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39 acidic procedures in effort to remove the seawater signal (Table 3 2, Methods A2 A4). Isotopic analyses of these detrital fractions indicated insignif Nd between duplicate samples treated with A1, A3, or A4. Issues with sample analyses limited the success of detrital fractions treated by A2, thus the results of this method are inconclusive, but the one detrital fraction recovered i ndicated the acid (1N HNO 3 ) may have been too strong. Subsequently, we tested multiple reductive procedures an d determined that 1 .0 M HH in 25% acetic acid was most effective at separating seawater components from detrital fractions (Table 3 2, Methods B1 B6). For some samples, the first aliquot of 1.0M HH was collected for isotopic analyses and these samples are Oxidation of Organic Matter All procedures, except Method B3, included the oxidation of organic matter in the s ample. Up to ~15 ml of 30% H 2 O 2 was very slowly added to the sample over a period of 1 3 days, depending on the intensity of oxidation, which was unique to each sample. The sample remained uncapped in the hood for the duration of this step. Once the reac tion dissipated, the sample was centrifuged and the 30% H 2 O 2 was decanted. Approximately 10 ml of 30% H 2 O 2 was added to the sample and the centrifuge tube was capped and placed on the rotator for 12 24 hours, with occasional degassing. This step was repe ated until the reaction was deemed complete indicated by lack of or minimal reaction The sample was triple rinsed with 4xH 2 0 and then placed in an oven set to 65C to dry. Table 3 2 details all sequential leaching methods employed on marine sediments e xamined in this study while Figure 3 3 displays a generalized flow chart of the sequential leaching methods used in this study.

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40 Detrital Silicate Dissolution The remaining residue was homogenized using an agate mortar and pestle and 0.10 g of the solid sam ple was weighed and tr ansferred to a Teflon beaker. Optima grade a qua regia (1 ml) was added to the sample as a final attempt to oxidize any remaining organic matter. The beaker was placed on a hotplate to dry down the acid. The sample was then dissolve d in 6 8 ml of concentrated (27N) optima grade hydrofluoric acid (HF) and 1 2 ml of concentrated (16N) optima grade HNO 3 using a hotplate at >100C for ~72 hours with occasional agitation and degassing. Once the sample was dissolved, it was dried down on the hotplate. To ensure break down of fluorides, the sample was re dissolved in 1 ml optima grade 16N HNO 3 and dried down. This step was repeated 1 2 more times, until the fluorides were disso l ved. Next, 5 ml of 8N optima grade HNO 3 was added to the sam ple. One milliliter of the acid sample solution was removed for REE analysis while the remaining 4 ml was again dried and used for column chemistry. Nd, Pb, and Sr Column Chemistry The aliquot separated for isotopic was work re dissolved in 1N seastar HB r. The sample acid solution was passed through Dowex 1X 8 (100 200 mesh) resin (Manhes et al., 1978). The Pb fraction was collected in 20% O ptima HNO 3 then the REEs and Sr were eluted in 1N HBr. The blank for this procedure was 20 pg Pb. The combined REE and Sr aliquot was dried down and re dissolved in 1N optima HNO 3 and then passed through Eichrom TRUspecTM Resin. Sr and Rb were collected in 1N optima grade HNO 3 and bulk REEs were eluted in 1N optima grade HCl. The Sr and Rb aliquot was then dried down, re dissolved in 3.5M HNO 3 and passed through cation exchange columns containing Sr spec resin to isolate the Sr cut in 4xH 2 O. The

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41 procedural blank for Sr is 100 pg. The bulk REE cut was dried down, re dissolved in 0.25N HCl, and passed through Eic hrom Ln resinTM to isolate Nd in 0.25N HCl. Blanks for this procedure were 14 pg Nd. Nd, Pb, and Sr Analyses Nd and Pb isotopic ratios were measured on the Nu Plasma Multi Collector Inductively Coupled Plasma Mass Spectrometer (MC ICPMS) using a DSN1000 desolvating nebulizer at the University of Florida. The Nd aliquot was dried and re dissolved in 2% O ptima HNO3 prior to analysis. Sample dilutions were adjusted individually to achieve a beam voltage of 4 6 V for 142 Nd, although so me samples ran as low as 2V. 143 Nd/ 144 Nd ratios were corrected for mass fractionation using 146 Nd/ 144 Nd = 0.7219. The JNdi 1 standard was analyzed every 4 to 6 samples and the average value for JNdi 1 for the day was compared to the published value 0.512115 0.000007 (Tanak a et al., 2000) to calculate the correction factor for samples analyzed that day. The long Nd units. For Pb analysis, a Tl normalization technique was used (Kamenov et al., 2004). The Pb concentrate was dri ed down an d re dissolved in Tl spiked 2% O ptima HNO 3 Sample dilutions were adjusted to achieve 4 5 V beam of 208 Pb but some samples ran as low as 2 V. The NBS 981 standard was measured at the beginning and end of each age NBS 981 values measured at the University of F lorida are 206 Pb/ 204 Pb=16 = 0.004), 207 Pb/ 204 = 0.003), and 208 Pb/ 204 = 0.008). Sr isotopes were analyzed on the Nu Plasma MC ICPMS in the early part of the study, but difficulties with Kr impurities in the Ar gas yielded high errors. Sample ana lyses later in the study were performed on a TIMS (Micromass Sector 54 Thermal

PAGE 42

42 Ionization Mass Spectrometer). Samples were dissolved in 1.0N HCl and loaded on Tungsten filaments using Ta 2 O 5 as an activator. Samples were analyzed for 200 ratios at an inte nsity of 1.5V 88 Sr. Fractionation was corrected to 86 Sr/ 88 Sr = 0.1194. The long term NBS 987 values measured for 87 Sr/ 86 Sr values is 0.71025 samples were analyzed using both techniques and differences between the techniques were less than 0.0003. Rare Earth Elemental Analyses REE analyses were performed on an Element II ICP MS at the U niversity of F lorida Aliquots wer e dried down and re dissolved in 5% HNO 3 spiked with Re Rh to serve as an internal standard to correct for instrument drift. A portion of the acid sample solution was extracted and diluted with 5% HNO 3 to ~2000 times dilution for analysis. All REE were a nalyzed at medium resolution. REE concentration measurements for each sample were normalized to PAAS (Post Archean Austr alian Shale) (Taylor and McLenna n, 1985).

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43 Table 3 1. Information about ODP sites at Demerara Rise, Tropical Atlantic Ocean from th is study. Site 1258 1 Site 1260 2 Site 1261 3 Latitude, longitude 926'N/5444'W 916'N/5433'W Modern wtr depth (mbsl) 3192 2549 1899 Max core depth (mbsf) 484.87 507.37 665.98 Environment Lower bathyal Mid bathyal Upper bathyal Carb wt% 4.1 95.6 0.1 91.7 0.92 97.44 Sed rate (m/m.y.) 3 15 4.3 20.5 3.3 8.5 1 Erbacher et al. (2004 b ) 2 Erbacher et al. (2004 c ) 3 Erbacher et al. (2004 d )

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44 Table 3 2 Sequential leaching procedures followed in this study. The sample and reagent mixture was centrifuged and the supernatant decanted after each reaction was complete. The sample was triple rinsed with 4xH 2 0 before introducing a new solution to the sample. Method Step 1 Step 2 Step 3 Step 4 Step 5 A1 15 ml of 0.02M HH 25% acetic acid 1 repeat S tep 1 10 15 ml of 30% H 2 O 2 3 A2 15 ml of 0.02M HH 25% acetic acid 1 repeat Step 1 10 ml of 1N HNO 3 1 ; 10 15 ml of 30% H 2 O 2 3 A3 15 ml of 0.02M HH 25% acetic acid 1 repeat Step 1 10 ml of 0.1N HCl 1 10 15 ml of 30% H 2 O 2 3 A4 15 ml of 0.02M HH 25% aceti c acid 1 repeat Step 1 10 ml of 1N HCl 1 10 15 ml of 30% H 2 O 2 3 B1 15 ml of 1M HH 25% acetic acid 10 15 ml of 30% H 2 O 2 3 B2 15 ml of 1M HH 25% acetic acid 2 10 ml of 0.1N HCl 1 Repeat Step 1 10 15 ml of 30% H 2 O 2 3 B3 15 ml of 1M HH 25% acetic acid 2 10 ml of 0.1N HCl 1 Repeat Step 1 B4 15 ml of 1M HH 25% acetic acid 2 10 15 ml of 30% H 2 O 2 3 10 ml of 0.1N HCl 1 Repeat Step 5 B5 15 ml of 1M HH 25% acetic acid 2 10 15 ml of 30% H 2 O 2 3 Repeat Step 1 B6 15 ml of 1M HH 25% acetic acid 2 10 15 ml of 3 0% H 2 O 2 3 10 ml of 0.1N HCl 1 Repeat Step 5 Repeat Step 1 1 Mixed 24 hours on a rotator. 2 Mixed and placed in ~95C hot bath for 3 hours, with agitation and degassing every ~30 minutes. 3 Reacted very slowly over 1 3 days.

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45 Figure 3 1 Lithostratigr aphic units and sedimentation breaks identified for drill sites as part of ODP Leg 207. Units III, IV, and V are investigated in this study. Unit III is mainly pelagic nannofossil clay, Unit IV is dominated by organic matter, and Unit V contains calcareo us clay with organic matter. (http://www odp.tamu.edu)

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46 Figure 3 2. Photograph of a core from Site 1258 displaying a sharp contact between lithostratigrapic Units III (calcareous nannofossil) and IV (black shale).

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47 Figure 3 3. Generalized schematic of the sequential leaching procedures employed on marine sediments examined in this study. Procedures modified from Rutberg et al. (2000) and Bayon et al. (2004).

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48 CHAPTER 4 RESULTS For accurate evaluation of detrital Sr, Nd and Pb isotopes it is necess ary to verify that any seawater contaminant has been removed. A series of sequential leaching protocols was tested to determine the most effective method for isolating the detrital silicate sediment (Table 3 2) Nd Resu lts Multiple acidic and reductive procedures were tested on the sediment samples in an effort to remove Fe Mn oxide coatings and other potential contaminants that record seawater isotopes (Table 3 Nd results are listed in Table 4 1 and Nd for each s ite (1258, 1260, and 1261) is plotted vs. age in Figures 4 1, 4 2, and 4 3. Nd preserved in fossil teeth are plotted in the figures for comparison. At all three sites, d etrital fraction samples of b lack shale lithology produce more scatter in Nd values than detrital fractions of carbonate lithology regardless of the leaching protocol used. The behavioral difference between the two lithologic units is likely related to the reducing conditions the black shales experienced during deposition. Detrital fr actions from the black shale interval obtained u sing 0.02M HH (A1 A4) are non radiogenic ( Nd = ~ 14 to 17) throughout the Cenomanian Turonian except during OAE2 when Nd spikes up as high as ~ 8 (Figures 4 1 to 4 3) Similarly, samples obtained from 1.0M HH (B1 B6) have backg r ound Nd = ~ 14 to 17 and shift to ~ 9 to 11 during OAE2 (Figure s 4 1 to 4 3). Although the two methods produce a similar overall range of Nd values, detrital fractions obtained using 1.0M HH tend to have less radiogenic values at all three sites It should be noted that fewer samples were processe d using methods B1 B6. Figure 4

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49 4 shows offsets between detrital fraction and fish teeth Nd and emphasizes scatter in the detrital fractions of black shale lithology Silicate d etrital fraction sampl es from the carbonate interval at all three sites c onsistently have les s radiogenic Nd values than corresponding fish teeth, regardless of the sequential ext raction employed. For samples obtained using 0.02M HH (A1 A4) Nd is non radiogenic throughout the Campanian ( Nd = 19), then gradually transitions to ~ 15 by 62 Ma, a nd shifts to Nd = ~ 11 to 12 by 59 Ma (Figures 4 1 to 4 3) Samples from 1.0M HH ( B 1 B6) follow similar trends but Nd values are less radiogenic. Nd is ~ 19 during the Campanian, shifts to ~ 17 to 18 from ~69 to 62 Ma, and then shifts to ~ 12 to 13 by 59 Ma (Figures 4 1 to 4 3) Repetition of HH steps and/or addition of acid and H 2 O 2 leaching steps did not significantly impact the results. The factor that most significantly effects the isotopic composition of the detrital fraction is the strength of the reducing agent. Therefore, throughout the remainder of this study, the sequential extraction procedures are grouped according to the strength of the reducing agent, with g to samples treated with 1.0M HH 25% acetic acid (Table 3 2) Rare Earth Elements Typical REE patterns for detrital fraction samples prepared using methods A (0.02M HH) and B (1.0M HH) are plotted in Figure 4 5 and data are listed in Tab le 4 2 Samples from method B of b oth black shale and carbonate lithologies have a less pronounced Ce anomaly and a flatter REE pattern than most of the samples from method A. These features are present for data from all three sites. The flat REE patterns for method B s amples resemble those of average continental crust ( Taylor and McLennan, 1985). REE distinctions between the two methods and lithologic units are

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50 more pronounced in HREE/LREE vs. MREE/MREE* plots. Figure 4 6 includes REE ratios of detrital fractions from this study along with fish teeth, Fe Mn oxides, HH fractions, acetic fractions and modern day seawater values. Most of the detrital fractions from the carbonate interval treated by method A plot within the detrital fraction field range documented by Mart in et al. (2010) while samples treated by method B plot around the detrital field but have lower MREE/MREE* ratios. Method A black shale detrital fractions generally plot within the detrital fraction field but method B samples are generally offset toward higher HREE/LREE ratios. Interestingly, multiple detrital fraction samples from method A that were treated with HCl have extremely high HREE/LREE ratios that plot outside of the scale in Fig ure 4 6, including values from 5.41 13.33. Figure 4 7 emphasize s LREE depletion that may have occurred during the HCl treatment. Strontium Isotopic Ratios Strontium isotopes were analyzed on 1.0M HH fractions collected using the B extraction p rocedures (Table 3 2) and data are listed in Table 4 3. These samples are expected to record seawater and in fact do plot close to published seawater values (Fig ure 4 8; MacArthur et al., 2001). Isotopic values from the 1.0M HH fractions range from 0.70737 to 0.70816 in the Cenomanian Turonian and from 0.70766 to 0.70870 in the Campanian Paleocene, while published seawater values for this time interval range from 0.7073 to 0.7074 for the Cenomanian to Turonian and 0.7075 to 0.7078 for the Campanian through Paleocene (Figure 4 8) Strontium isotopes for detrital fractions are h ighly variable at all three sites throughout the entire record and within each method (Table 4 3). The average isotopic composit ion obtained from all of the A methods and all of the B m ethods is plotted for

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51 each detrital fraction sample in Figure 4 8. Sa mples from Site 1260 have the greatest variability in 87 Sr/ 86 Sr values throughout the Cenomanian Turonian interval ranging from 0.70598 to 0.75464 for method A and 0.70685 to 0.75141 for method B. For this black shale interval, both methods produce detrit al fraction values with a similar total range, but a greater proportion of the method A samples plot closer to the seawater curve, again indicating this method did not effectively remove all of the seawater signal. The scatter in the detrital fraction da ta in the black shale section again suggests the reducing conditions during deposition led to greater alteration of the isotopic composition of the silicate detrital fraction Throughout the carbonate marl portion of the record, detrital fraction data fro m method A typically plot closer to seawater values than data from method B (Figure 4 8) In addition the isotopic ratios obtained by the B method are similar to values expected from continental sources. Therefore, the Sr isotopes in the carbonate interv al also indicate the detrital fractions processed by this technique represent a purer detrital end member; however, it is impossible to determine whether all of the seawater components have been removed. B method detrital fractions also document a dramati c shift from more radiogenic to less radiogenic values at ~60 Mya. Lead Isotopic Ratios Lead isotopes of detrital fractions are highly variable and radiogenic throughout the black shale interval. 207 Pb/ 204 Pb and 206 Pb/ 204 Pb values among all three sites ar e more variable among method A samples (15.812 to 16.102 and 20.321 to 25.512, respectively) compared to method B samples (15.816 to 15.944 and 20.215 to 22.035 respectively; Table 4 4 and Figures 4 9 to 4 12). 208 Pb/ 204 Pb values are highly variable throu ghout the study interval for all three sites, with values ranging from 39.172 to

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52 39.925 for method A and 39.155 to 39.725 for method B. Much of the variability in 207 Pb/ 204 Pb and 206 Pb/ 204 Pb values for detrital fractions of black shale lithology can be at tributed to preferential uptake of U under reducing conditions. For detrital fractions of the carbonate interval all three Pb isotopic systems seem to record at least one, and possibly two, shifts. From ~72 66 Ma, method B detrital fractions have less ra diogenic and less variable ranges of 207 Pb/ 204 Pb and 206 Pb/ 204 Pb values (15.739 to 15.820 and 18.372 to 19.361, respectively) than respective values from detrital fractions using method A (15.812 to 15.853 and 19.268 to 19.786). Detrital fractions from both methods have wide ranges of 208 Pb/ 204 Pb values (39.235 to 39.666 for method A; 38.236 to 39.282 for method B). The first isotopic shift occurred ~6 6 Ma in all three Pb systems (Figures 4 9 to 4 12) 207 206 Pb/ 204 Pb values for detrital fractions fr om method A became less radiogenic (ranges =15.779 to 15.85 and 19.596 to 20.002, respectively) while 207 206 Pb/ 204 Pb values from method B shift to more radiogenic values (ranges = 15.806 to 15.894 and 19.683 to 20.2640). Isotopic compositions of detrital fractions from both methods continue to maintain a narrow range of 207 206 Pb/ 204 Pb values. 208 Pb/ 204 Pb values from data set B abruptly shift to more radiogenic values (range = 39.371 to 39.837). The second shift occurs sometime bet ween 59 to 62 Ma and is more sub tle than the s hift at 66 Ma. Method B detrital fractions shift to less radiogenic values with ranges of 19.683 to 19.964, 15.816 to 15.824, and 39.371 to 39.634 for 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb, respectively.

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53 Table 4 1. Nd isotop ic values from silicate detrital fractions from ODP Sites 1258, 1260, and 1261. Sample Age (Mya) 1 Method A 2 143 / 144 Nd 3 Error (Nd) 4 Method B 2 143 / 144 Nd 3 Error (Nd) 4 Seawate (Nd) 5 Site 1258 A 21 3 98 99.5 56.88 1 0.511990 0.0000086 11.23 10.35 A 25 3 58.5 60 59.22 1 0.511938 0.0000070 12.18 1 0.511923 0.0000220 12.47 10.63 5 0.511933 0.0000074 12.28 A 27 3 107 110 65.09 1 0.511793 0.0000096 14.87 1 0.511685 0.0000186 16.97 13.24 4 0.511720 0.0000098 16.3 0 A 27 5 78 80 65.32 1 0.511675 0.0000070 17.16 15.44 A 28 1 118 119.5 65.63 1 0.511731 0.0000086 16.05 1 0.511664 0.0000280 17.36 13.38 5 0.511667 0.0000062 17.31 A 30 4 47.5 49 67.52 1 0.511693 0.0000102 16.75 15.28 A 32 5 48 49.5 69.30 1 0.511657 0.0000086 17.41 1 0.511612 0.0000320 18.29 15.51 6 0.511647 0.0000070 17.61 A 42 1 8 11 92.52 1 0.511752 0.0000112 14.98 14.90 B 45 1 96 98 92.88 1 0.511769 0.0000106 14.65 14.54 C 17 1 10 12 93.86 1 0.511803 0.0000106 13.96 1 0.511791 0.0000176 14.19 12.49 C 17 1 48.5 51 93.94 1 0.512133 0.0000100 7.52 1 0.512027 0.0000076 9.59 7.12 1 0.512115 0.0000112 7.87 C 17 2 68 69.5 94.18 1 0.511680 0.0000102 16.35 1 0.511 666 0.0000104 16.62 16.15 A 44 2 5 6.5 94.69 1 0.511704 0.0000220 15.86 15.85 A 48 2 44 45.5 96.32 1 0.511761 0.0000160 14.70 14.47 Site 1260 A 33 3 28.5 30 57.44 1 0.511937 0.0000108 12.25 1 0.511956 0.0000300 11.87 10.83 2 0.511935 0.0000104 12.27 3 0.511943 0.0000134 12.13 4 0.511927 0.0000118 12.44 A 35 3 49 52 58.18 1 0.511947 0.0000184 12.02 2 0.511909 0.0000114 12.78 10.72 3 0.511943 0.0000196 12.11 3 0.511906 0.0000080 12.78 4 0.511918 0.0000240 12.59 A 36 2 48 51 62.14 1 0.511798 0.0000088 14.85 1 0.511684 0.0000108 17.06 13.44

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54 Table 4 1. Cont. 1 0.511775 0.0000098 15.29 1 0.511694 0.0000126 16.87 A 36 6 94.5 96 66.09 3 0.511673 0.0000108 17.18 2 0.511679 0.0000102 17.07 14.13 4 0.511677 0.0000076 17.11 A 38 3 43 46 68.91 1 0.511703 0.0000156 16.50 2 0.511610 0.0000146 18.33 16.30 1 0.511652 0.0000196 17.51 B 26 7 8 9.5 72.49 3 0.511543 0.0000190 19.55 1 0.511547 0.0000092 19.47 15.39 4 0.511543 0.0000126 19.55 2 0.511549 0.0000128 19.43 3 0.511577 0.0000146 18.89 6 0.511462 0.0000096 21.13 B 32 2 32 35 90.10 1 0.511756 0.0000188 14.96 1 0.511712 0.0000094 15.81 17.53 B 34 2 7.5 10.5 91.37 1 0.511668 0.0000084 16.64 15.70 B 35 4 30 32 93.25 1 0.511767 0.0000186 14.67 1 0.511800 0.0000148 14.03 14.35 1 0.511733 0.0000140 15.33 3 0.511743 0.0000148 15.13 4 0.511715 0.0000198 15.68 B 35 4 93 94 93.50 1 0.511873 0.0000134 12.60 1 0.511717 0.0000138 15.63 11.23 B 35 5 50 51 94.09 1 0.511857 0.0000182 12.88 1 0.511767 0.0000186 14.65 13.75 B 35 5 55 57 94.13 1 0.512010 0.0000132 9.90 1 0.511967 0.0000048 10.74 9.65 2 0.511898 0.0000136 12.09 4 0.511924 0.0000116 11.58 B 35 5 118.5 120 94.19 1 0.511741 0.0000126 15.15 1 0.511708 0.0000100 15.79 15.64 A 49 2 36.5 38 95.52 1 0.511806 0.0000122 13.85 1 0.511721 0.0000340 15.5 2 11.35 A 50 1 105 108 96.06 1 0.511800 0.0000064 13.96 13.31 1 0.511812 0.0000108 13.73 A 50 2 78 79 96.14 1 0.511822 0.0000136 13.52 12.81 A 52 1 75.5 78 97.26 1 0.511793 0.0000146 14.06 13.70 Site 1261 A 33 2 14 15.5 55.33 1 0.511920 0.0000118 12.63 1 0.511901 0.0000280 13.01 12.03 3 0.511930 0.0000300 12.43 4 0.511902 0.0000174 12.99

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55 Table 4 1. Cont. A 35 2 8 9.5 58.12 1 0.511962 0.00 00118 11.73 1 0.511920 0.0000220 12.56 11.07 5 0.511905 0.0000070 12.86 A 37 2 11 13 60.91 1 0.511938 0.0000096 12.14 11.28 B 2 1 72 73.5 62.06 1 0.511792 0.0000152 14.95 1 0.511679 0.0000320 17.16 14.08 5 0.511681 0 .0000102 17.13 B 3 1 86 89 66.89 1 0.511686 0.0000124 16.90 1 0.511701 0.0000186 16.61 15.89 B 4 1 76 79 70.43 1 0.511583 0.0000074 18.82 16.05 A 44 8 116 119 89.74 1 0.511697 0.0000106 16.12 16.16 A 47 4 92 95 93.04 1 0. 511730 0.0000100 15.40 15.05 1 0.511738 0.0000128 15.25 A 48 1 123 125 93.50 1 0.511838 0.0000174 13.28 13.07 A 48 4 139 141 93.65 1 0.511947 0.0000148 11.15 1 0.511944 0.0000068 11.21 12.01 1 0.511984 0.0000124 10.42 A 48 3 81 82 93.73 1 0.511818 0.0000220 13.66 12.79 B 13 2 13 14.5 94.08 1 0.511818 0.0000122 13.65 13.65 B 118 119 94.15 1 0.511926 0.0000200 11.55 10.85 1 0.511915 0.0000110 11.76 B 13 3 33 34.5 94.19 1 0 .511703 0.0000106 15.89 15.49 A 50 2 127 129 95.16 1 0.511781 0.0000062 14.35 13.80 3 0.511531 0.0000158 19.22 4 0.511720 0.0000142 15.54 1 Ages from Erbacher et al., 2004 and 2005. 2 Refer to Table 3 2 for descri ption of sequential leaching procedure. 3 143 Nd / 144 Nd values are normalized to the JNdi 1 average on the day the samples were analyzed and then normalized to JNdi 1 = 0.512103 (TIMS average). 4 Nd(t) = [( 143 Nd/ 144 Nd) sample(t) /( 143 Nd/ 144 Nd) CHUR(t) 1] x 10 4 using 147 Sm/ 144 Nd = 0.125. 5 Values from Martin et al. (2012).

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56 Table 4 2. REE values in ppm for detrital silicate fractions normalized to the measured weights of the detrital fraction. Sample Age (mya) Method La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Lu Site 1258 A 21 3 98 99.5 56.88 A1 15.61 27.45 3.70 13.44 2.31 0.50 2.13 0.30 1.73 0.33 0.97 0.13 0.12 A 25 3 58.5 60 59.22 A1 1.69 10.55 0.49 1.79 0.32 0.06 0.27 0.04 0.25 0. 05 0.14 0.02 0.01 A 25 3 58.5 60 59.22 B1 19.03 30.21 4.08 13.90 2.15 0.42 1.71 0.24 1.46 0.30 0.95 0.14 0.14 A 27 3 107 110 65.09 A1 3.86 10.94 0.85 3.06 0.48 0.11 0.43 0.07 0.40 0.07 0.21 0.03 0.03 A 27 3 107 110 65.09 B1 20.31 26.88 4.40 14.42 2. 11 0.39 1.54 0.21 1.20 0.24 0.72 0.10 0.10 A 27 5 78 80 65.32 A1 2.93 16.84 0.62 2.17 0.36 0.06 0.31 0.05 0.32 0.06 0.21 0.03 0.03 A 28 1 118 19.5 65.63 A1 13.51 31.73 3.52 12.76 2.16 0.44 1.78 0.24 1.32 0.26 0.72 0.10 0.08 A 28 1 118 119.5 65.63 B1 1 6.93 17.70 3.51 11.61 1.67 0.31 1.24 0.17 0.97 0.19 0.59 0.09 0.08 A 30 4 47.5 49 67.52 A1 6.58 8.01 1.59 5.69 0.85 0.18 0.67 0.09 0.55 0.10 0.29 0.04 0.03 A 32 5 48 49.5 69.30 A1 18.43 36.96 4.48 16.14 2.53 0.63 2.05 0.28 1.59 0.33 1.01 0.14 0.14 A 32 5 48 49.5 69.30 B1 16.79 25.82 3.35 11.11 1.60 0.32 1.19 0.16 0.93 0.19 0.61 0.09 0.09 A 42 1 8 11 92.52 A1 2.93 13.54 0.74 2.96 0.66 0.18 0.81 0.15 1.03 0.24 0.70 0.10 0.09 B 45 1 96 98 92.88 A1 3.62 11.83 1.03 4.14 0.85 0.22 0.86 0.14 0.91 0.20 0.60 0.09 0.09 C 17 1 10 12 93.86 A1 8.64 13.94 1.75 6.24 1.09 0.30 1.08 0.15 0.86 0.18 0.57 0.09 0.10 C 17 1 10 12 93.86 B1 0.98 1.85 0.16 0.53 0.08 0.03 0.07 0.01 0.07 0.02 0.04 0.01 0.01 17 1 48.5 51 93.94 A1 12.52 13.65 2.87 11.30 2.31 0.64 2.55 0.42 2.79 0.53 1.45 0.17 0.11 17 1 48.5 51 93.94 A1 5.29 10.03 1.26 5.21 1.10 0.32 1.29 0.24 1.69 0.32 0.89 0.11 0.07 C 17 1 48.5 51 93.94 B1 2.89 8.71 0.65 2.73 0.68 0.25 0.87 0.15 0.97 0.21 0.60 0.09 0.08 C 17 2 68 69.5 94.18 A1 4.01 4.72 1.04 3.93 0.60 0.13 0.46 0.06 0.36 0.06 0.17 0.02 0.02 C 17 2 68 69.5 94.18 B1 4.50 10.80 1.00 3.57 0.65 0.16 0.62 0.08 0.50 0.10 0.33 0.05 0.06 A 44 2 5 6.5 94.69 A1 0.42 2.05 0.10 0.37 0.07 0.02 0.07 0.01 0.09 0.02 0.06 0.01 0.01 A 48 2 44 45.5 96.32 A1 0.38 1.40 0.09 0.32 0.05 0.01 0.05 0.01 0.06 0.01 0.04 0.01 0.01 Site 1260 A 33 3 28.5 30 57.44 A1 3.79 18.88 0.92 3.41 0.67 0.15 0.69 0.11 0.72 0.14 0.43 0.06 0.06 A 33 3 28.5 30 57.44 B1 11.91 17.16 2.60 8.82 1.36 0.26 1.00 0.14 0.83 0.1 7 0.52 0.08 0.07 A 33 3 28.5 30 57.44 B2 18.07 28.14 3.57 11.96 1.88 0.38 1.62 0.22 1.32 0.28 0.90 0.14 0.15 A 33 3 28.5 30 57.44 B3 20.36 33.10 4.02 13.39 2.09 0.43 1.81 0.24 1.43 0.31 0.99 0.16 0.18 A 35 5 49 52 58.18 A3 1.78 3.48 0.60 2.49 0.62 0.16 0.64 0.14 1.15 0.29 1.02 0.18 0.22 A 35 3 49 52 58.18 A4 3.24 7.61 1.15 4.90 1.20 0.27 1.31 0.25 1.82 0.42 1.40 0.22 0.25

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57 Table 4 2 Cont. A 35 3 49 52 58.18 B2 22.15 36.41 4.50 15.04 2.38 0.47 2.10 0.28 1.68 0.36 1.14 0.18 0.20 A 35 2 49 52 58.18 B3 13.97 21.82 2.92 9.88 1.52 0.29 1.27 0.16 1.01 0.21 0.66 0.10 0.11 A 36 2 48 51 62.14 A1 27.99 45.19 6.23 22.56 3.71 0.77 3.29 0.46 2.72 0.55 1.62 0.23 0.21 A 36 2 48 51 62.14 B1 23.40 34.09 4.64 15.48 2.38 0.49 2.00 0.29 1.79 0.38 1.22 0.19 0.21 A 36 2 48 51 62.14 B1 29.25 51.55 5.55 18.37 2.95 0.65 2.64 0.39 2.47 0.52 1.73 0.28 0.32 A 36 2 48 51 62.14 B2 21.25 32.05 4.18 13.77 2.15 0.41 1.98 0.26 1.59 0.33 1.06 0.17 0.19 A 36 6 94.5 96 66.09 A3 13.19 26.00 3.39 12.16 2.10 0.46 1.69 0.25 1.60 0.35 1.10 0.17 0.19 A 36 6 94.5 96 66.09 A4 11.16 22.44 3.13 11.72 2.10 0.45 1.71 0.25 1.59 0.34 1.04 0.16 0.17 A 36 6 94.5 96 66.09 B2 24.96 38.53 5.00 16.40 2.48 0.49 2.07 0.27 1.57 0.33 1.04 0.16 0.18 A 38 3 43 46 68.91 A1 19.01 36.28 4.8 6 18.06 3.05 0.83 2.61 0.34 1.89 0.37 1.04 0.14 0.12 A 38 3 43 46 68.91 B2 17.26 28.03 3.46 11.59 1.83 0.48 1.73 0.22 1.37 0.29 0.92 0.15 0.17 B 26 7 8 9.5 72.49 A3 7.13 17.72 2.25 8.72 1.75 0.37 1.56 0.26 1.76 0.40 1.36 0.23 0.28 B 26 7 8 9.5 72.49 A 4 3.24 7.23 1.04 4.22 0.91 0.20 0.81 0.14 0.98 0.24 0.77 0.13 0.16 B 26 7 8 9.5 72.49 B1 9.27 18.76 1.86 6.28 0.97 0.19 0.79 0.10 0.62 0.13 0.43 0.07 0.08 B 26 7 8 9.5 72.49 B2 24.56 40.66 5.03 16.99 2.61 0.52 2.26 0.29 1.77 0.38 1.23 0.21 0.24 B 26 7 8 9.5 72.49 B3 16.66 27.32 3.51 11.79 1.78 0.38 1.65 0.21 1.25 0.27 0.85 0.14 0.15 B 32 2 32 35 90.30 B1 10.95 16.06 1.95 6.58 1.09 0.25 1.06 0.14 0.83 0.18 0.56 0.08 0.09 B 34 2 7.5 10.5 91.37 A3 0.47 0.86 0.15 0.56 0.14 0.06 0.15 0.02 0.25 0.08 0.21 0. 04 0.05 B 34 2 7.5 10.5 91.37 A4 0.33 0.58 0.12 0.47 0.11 0.04 0.13 0.02 0.17 0.06 0.15 0.03 0.03 B 34 2 7.5 10.5 91.37 A1 5.63 8.95 1.25 4.62 0.86 0.25 0.84 0.11 0.67 0.14 0.41 0.06 0.07 B 35 4 30 32 93.25 A1 0.62 2.05 0.14 0.48 0.08 0.02 0.06 0.01 0.0 7 0.02 0.05 0.01 0.01 A 35 4 30 32 93.25 A3 1.38 3.43 0.40 1.62 0.36 0.12 0.38 0.07 0.56 0.15 0.48 0.08 0.10 B 35 4 30 32 93.25 A4 3.68 6.93 1.05 4.38 1.00 0.27 0.97 0.16 1.13 0.28 0.88 0.14 0.17 B 35 4 30 32 93.25 A1 7.78 13.35 2.01 8.07 1.71 0.44 1 .88 0.31 2.08 0.48 1.54 0.24 0.27 B 35 4 30 32 93.25 B1 31.20 41.78 5.76 20.93 3.91 0.99 4.13 0.59 3.70 0.82 2.59 0.40 0.44 B 35 4 93 94 93.50 A1 10.17 13.76 2.15 8.12 1.36 0.42 1.38 0.19 1.11 0.22 0.62 0.08 0.06 B 35 4 93 94 93.50 A1 9.81 12.84 2.05 7.76 1.37 0.39 1.28 0.18 1.12 0.22 0.61 0.08 0.06 B 35 4 93 94 93.50 B1 4.87 10.04 0.89 3.06 0.52 0.17 0.52 0.07 0.41 0.09 0.28 0.04 0.05 B 35 5 50 51 94.09 B1 2.37 8.48 0.46 1.60 0.29 0.07 0.29 0.04 0.31 0.07 0.25 0.04 0.06 B 35 5 55 57 94.14 B1 17.08 21.92 3.01 11.03 1.93 0.44 2.17 0.31 1.93 0.45 1.33 0.20 0.20 B 35 5 118.5 120 94.19 A1 15.23 24.45 2.85 10.16 1.73 0.42 1.82 0.25 1.53 0.34 1.07 0.16 0.18

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58 Table 4 2 Cont. B 35 5 118.5 120 94.19 B1 15.25 9.42 2.77 9.94 1.71 0.38 1.63 0.24 1.47 0.33 1.04 0.16 0.17 B 35 5 118.5 120 94.19 B1 8.29 13.35 1.57 5.42 0.93 0.24 0.93 0.12 0.77 0.17 0.55 0.09 0.10 A 49 2 36.5 38 95.52 A1 2.69 3.73 0.56 2.11 0.35 0.09 0.32 0.05 0.33 0.07 0.20 0.03 0.03 A 49 2 36.5 38 95.52 A3 0.26 0.49 0.10 0. 39 0.11 0.02 0.12 0.03 0.28 0.09 0.27 0.05 0.06 A 49 2 36.5 38 95.52 A4 1.26 2.53 0.41 1.70 0.41 0.09 0.43 0.08 0.60 0.15 0.49 0.08 0.09 A 49 2 36.5 38 95.52 B1 5.29 12.22 1.01 3.48 0.60 0.15 0.56 0.08 0.52 0.11 0.38 0.06 0.07 A 50 1 105 108 96.06 A1 2.81 5.60 0.57 1.99 0.36 0.08 0.36 0.05 0.36 0.07 0.24 0.03 0.03 A 50 1 105 108 96.06 A1 0.24 1.65 0.06 0.25 0.05 0.01 0.05 0.01 0.07 0.02 0.06 0.01 0.01 A 50 1 105 108 96.06 A3 0.56 1.09 0.19 0.79 0.22 0.04 0.25 0.05 0.45 0.13 0.39 0.07 0.09 A 50 1 105 108 96.06 A4 1.20 2.30 0.40 1.69 0.45 0.10 0.52 0.10 0.80 0.19 0.64 0.10 0.12 A 50 1 105 108 96.06 B1 7.91 23.20 1.59 5.55 0.96 0.20 0.93 0.13 0.82 0.18 0.60 0.10 0.11 A 50 2 78 79 96.14 A1 1.29 3.74 0.24 0.86 0.15 0.03 0.13 0.02 0.15 0.03 0.10 0. 02 0.01 A 50 2 78 79 96.14 A1 9.07 12.40 2.16 7.78 1.29 0.24 1.02 0.14 0.85 0.17 0.49 0.07 0.06 A 52 1 75.5 78 97.26 A1 12.49 14.27 2.67 9.10 1.45 0.29 1.20 0.17 1.03 0.19 0.59 0.08 0.07 Site 1261 A 33 2 14 15.5 55.33 A1 4.07 9.98 1.6 6 7.37 1.89 0.58 2.11 0.37 2.49 0.53 1.59 0.23 0.23 A 33 2 14 15.5 55.33 A3 2.19 4.56 0.69 2.72 0.61 0.23 0.62 0.11 0.84 0.21 0.72 0.12 0.15 A 33 2 14 15.5 55.33 A4 2.27 5.05 0.80 3.38 0.83 0.32 0.88 0.16 1.20 0.28 0.94 0.15 0.17 A 33 2 14 15.5 55.33 B1 10.01 16.28 2.06 7.03 1.12 0.24 0.90 0.12 0.77 0.16 0.53 0.08 0.09 A 35 2 8 9.5 58.12 A1 18.96 37.72 4.59 17.14 3.12 0.71 2.88 0.42 2.43 0.49 1.43 0.20 0.18 A 35 2 8 9.5 58.12 B1 13.24 19.96 2.69 9.10 1.45 0.30 1.16 0.16 0.97 0.21 0.67 0.10 0.11 A 37 2 11 13 60.91 A1 25.70 42.59 5.62 20.78 3.50 0.90 3.36 0.48 2.77 0.57 1.65 0.23 0.20 B 2 1 72 73.5 62.06 A1 17.21 32.76 4.35 16.11 2.82 0.73 2.43 0.33 1.78 0.33 0.90 0.12 0.09 B 2 1 72 73.5 62.06 B1 10.22 11.58 2.03 6.61 1.01 0.31 0.81 0.11 0.65 0 .13 0.44 0.07 0.07 B 3 1 86 89 66.89 A1 15.54 37.28 3.15 11.31 1.75 1.95 1.83 0.21 1.27 0.27 0.82 0.12 0.11 B 3 1 86 89 66.89 B1 15.94 23.97 3.32 11.33 1.72 0.73 1.38 0.18 1.04 0.21 0.66 0.10 0.10 B 4 1 76 79 70.43 A1 11.81 28.36 2.91 10.49 1.74 0.52 1.56 0.21 1.20 0.25 0.80 0.13 0.14 A 44 8 116.5 119.5 89.74 A1 37.29 43.75 6.77 24.80 4.30 1.01 4.41 0.64 4.18 0.90 2.70 0.40 0.34 A 47 4 92 95 93.04 A1 14.95 28.92 2.82 10.15 1.69 0.44 1.71 0.24 1.49 0.33 0.95 0.14 0.12 A 47 4 92 95 93.04 A1 8.69 10.22 1.43 5.06 0.78 0.22 0.75 0.10 0.60 0.12 0.37 0.05 0.04

PAGE 59

59 Table 4 2 Cont. A 48 1 123 125 93.51 A1 11.47 11.06 2.39 8.76 1.43 0.41 1.24 0.17 1.04 0.21 0.62 0.08 0.07 A 48 4 139 141 93.65 A3 0.39 0.63 0.13 0.52 0.13 0.22 0.18 0.03 0 .26 0.08 0.22 0.04 0.05 A 48 4 139 141 93.65 A4 0.39 0.79 0.15 0.66 0.21 0.07 0.30 0.06 0.51 0.14 0.42 0.07 0.07 A 48 4 139 141 93.65 A1 2.67 4.31 0.51 1.86 0.38 0.24 0.40 0.06 0.37 0.08 0.23 0.03 0.03 48 4 139 141 93.65 A1 2.48 5.68 0.48 1.73 0.36 0. 20 0.39 0.06 0.34 0.07 0.21 0.03 0.03 A 48 4 139 141 93.65 B1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 A 48 3 81 82 93.73 A1 8.40 7.86 1.61 5.79 0.91 0.39 0.82 0.11 0.64 0.13 0.36 0.05 0.04 B 13 2 13 14.5 94.08 A1 13.57 12.30 2. 65 9.69 1.62 0.39 1.51 0.20 1.23 0.26 0.73 0.09 0.07 B 13 2 118 119 94.15 A1 22.36 23.72 4.07 15.72 2.80 0.67 3.29 0.48 3.07 0.70 2.07 0.29 0.24 B 13 2 118 119 94.15 A1 21.34 21.03 3.77 14.60 2.57 0.59 2.90 0.43 2.78 0.62 1.86 0.26 0.22 B 13 3 33 34.5 94.19 A1 5.50 7.75 1.27 4.72 0.81 0.18 0.70 0.10 0.59 0.11 0.31 0.04 0.03 A 50 2 127 129 95.16 A3 2.70 5.99 0.83 3.39 0.75 0.17 0.73 0.12 0.89 0.21 0.66 0.11 0.12 A 50 2 127 129 95.16 A4 3.24 6.92 1.02 0.83 0.83 0.17 0.81 0.12 0.88 0.20 0.60 0.09 0. 09 A 50 2 127 129 95.16 A1 1.07 5.46 0.24 0.93 0.18 0.05 0.20 0.03 0.23 0.05 0.17 0.02 0.02

PAGE 60

60 Table 4 3 Sr isotopes measured in silicate detrital fractions and HH extractions from ODP Sites 1258, 1260, and 1261. Sample Age (Mya) 1 Method A 2 Detrital Fraction 86 Sr/ 87 Sr Error Method B 2 Detrital Fraction 86 Sr/ 87 Sr Error HH Fraction 86 Sr/ 87 Sr Error Site 1258 A 21 3 98 99.5 56.88 1 0.71883 0.000001 A 25 3 58.5 60 59.22 1 0.71469 0.000014 1 0.71901 0.000054 A 27 3 107 110 65.09 1 0.71648 0.000017 1 0.74559 0.000026 A 27 5 78 80 65.32 1 0.73294 0.000014 A 28 1 118 119.5 65.63 1 0.71490 0.000012 1 0.75431 0.000022 A 30 4 47.5 49 67.52 1 0.71750 0.000015 A 32 5 48 49.5 69.30 1 0.71814 0.000016 1 0.73956* 1 0.73980 0.000044 A 42 1 8 11 92.52 1 0.71897 0.000027 B 45 1 96 98 92.88 1 0.71318 0.000058 1 0.71565* C 17 1 10 12 93.86 0.715645* 0.70771* 0.000013 C 17 1 48.5 51 93.94 1 0.71103 0.000017 1 0.71246* 0.000016 0.70765* 0.0000 17 1 0.71049 C 17 2 68 69.5 94.18 1 0.71504 0.000013 1 0.73508* 0.70816* 0.000011 Site 1260 A 33 3 28.5 30 57.44 1 0.71071 0.000015 1 0.71715 0.000049 A 35 3 49 52 58.18 1 0.71005 0.000071 1 0.75634* 3 0.71009 0.00 0019 4 0.71000 0.000059 A 36 2 48 51 62.14 1 0.70992 0.000027 1 0.75341 0.000031 0.70791* 0.0023 1 0.71450 0.000025 1 0.74945 0.000095 2 0.75278* A 36 6 94.5 96 66.09 3 0.71217 0.000026 0.70765* 0.000017 A 38 3 43 46 68.9 1 1 0.71245 0.000029 0.70870* 0.000013

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61 Table 4 3 Cont. 1 0.71954 0.000022 B 26 7 8 9.5 72.49 3 0.71950 0.000040 1 0.73727* 0.70786* 0.000017 4 0.71916 0.000049 1 0.73857* 1 0.73839 0.000026 B 32 2 32 35 90.10 1 0.71 163 0.000025 0.70772* 0.000016 B 35 4 30 32 93.25 1 0.71060 0.000030 1 0.71070* 0.000016 3 0.71078 0.000036 4 0.70982 0.000047 B 38 4 93 94 93.50 1 0.71000 1 0.71714* 0.70765* 0.000013 B 35 5 6 9 93.81 1 0.70598 0.000054 1 0.70 685* 0.000017 0.70737* 0.000014 C 17 1 10 12 93.86 1 0.71308 0.000016 B 35 5 50 51 94.09 1 0.71122 0.000039 1 0.72468* 0.70774* 0.000013 B 35 5 55 57 94.13 3 0.71042 0.000057 1 0.71648* 0.000016 0.70769* 0.000011 B 35 5 118 120 94.19 1 0.71210 0.000030 1 0.72207* 0.000018 0.70775* 0.000013 A 49 2 36.5 38 95.52 1 0.75389 0.000018 1 0.756338 0.000016 1 0.73170 0.000180 A 50 1 105 108 96.06 1 0.74881 0.000026 1 0.75141* 0.000016 0.70815* 0.00014 A 50 2 78 79.5 96.14 1 0.75399 A 52 1 75.5 78.5 97.26 1 0.75464 0.000033 Site 1261 A 33 7 14 15.5 55.33 3 0.71143 0.000072 1 0.72150* 4 0.71048 0.000025 1 0.72150 0.000045 A 35 2 8 9.5 58.12 1 0.71017 A 37 2 11.5 13 60.91 1 0.70976 B 2 1 72 7 3.5 62.06 1 0.70997 0.000095 1 0.74082 B 3 1 86 89 66.89 1 0.71305 0.000055 1 0.73155 1 0.73155 A 44 8 116 119 89.74 1 0.71151 A 47 4 92 95 93.04 1 0.71119 0.000017

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62 Table 4 3 Cont. 1 0.71085 0.0000 22 A 48 4 139 141 93.65 1 0.70951* 0.000017 0.70758* 0.000013 A 48 3 81 82 93.73 1 0.71063 B 13 2 13 14.5 94.08 1 0.71109 0.000020 B 13 2 118 119.5 94.15 1 0.71225 1 0.71271 0.000023 A 50 2 127 129 95.16 3 0.72621 0 .000037 4 0.72457 0.000039 1 Ages from Erbacher et al. 2004 and 2005. 2 Refer to Table 3 2 for description of sequential leaching procedure. Measured 87 Sr/ 86 Sr of the NBS 987 standard = 0.7120250 and normalized to 86 Sr/ 87 Sr = 0.1194. *Analysis performed on a TIMS.

PAGE 63

63 Table 4 4. Pb isotopic composition from silicate detrital fractions from ODP Sites 1258, 1260, and 1261. Sample Age (Ma) 1 Method A 2 208 Pb/ 204 Pb 207 Pb/ 204 Pb 206 Pb/ 204 Pb Method B 2 208 Pb/ 204 Pb 207 Pb/ 204 Pb 206 Pb/ 204 Pb Site 12 58 A 21 3 98 99.5 56.88 1 39.402 15.790 19.629 A 25 3 58.5 60 59.22 1 39.454 15.779 19.609 1 39.576 15.816 19.881 5 39.619 15.820 19.941 A 27 3 107 110 65.09 1 39.621 15.822 19.736 1 39.702 15.854 20.036 4 39.695 15.852 20.002 A 27 5 78 80 65.32 1 39.878 15.858 19.960 A 28 1 118 19.5 65.63 1 39.648 15.846 19.851 1 39.591 15.861 19.937 1 39.587 15.859 19.934 5 39.470 15.846 19.788 A 30 4 47.5 49 67.52 1 39.666 15.853 19.786 A 32 5 48 49.5 69.30 1 38.897 15.789 18.957 6 38.987 15.792 19.000 C 17 1 10 12 93.86 1 39.644 15.994 21.894 1 39.513 15.932 20.742 C 17 1 48.5 51 93.94 1 39.831 16.024 22.557 1 39.637 15.933 20.995 1 39.825 16.021 22.571 C 17 2 68 69.5 94.18 1 39.64 6 15.961 21.742 1 39.549 15.913 20.575 A 44 2 5 6.5 94.69 1 39.261 15.812 20.321 A 48 2 44 45.5 96.32 1 39.360 15.883 20.824 Site 1260 A 33 3 28.5 30 57.44 1 39.576 15.807 19.825 1 39.617 15.824 19.962 4 39.652 15.827 19.973 2 3 9.575 15.817 19.897 3 39.582 15.819 19.909 A 35 3 49 52 58.18 1 39.492 15.787 19.677 2 39.634 15.816 19.945 3 39.627 15.819 19.964 3 39.532 15.793 19.753 4 39.521 15.795 19.747

PAGE 64

64 Table 4 4 Cont. A 36 2 4 8 51 62.14 1 39.466 15.786 19.598 1 39.827 15.882 20.259 1 39.838 15.882 20.264 2 39.541 15.810 19.759 A 36 6 94.5 96 66.09 3 39.611 15.836 19.769 2 39.553 15.856 19.849 4 39.465 15.830 19.699 A 38 3 43 46 68.91 1 39.607 15.847 19.5 77 2 39.081 15.805 19.139 1 39.512 15.845 19.626 B 26 7 8 9.5 72.49 3 39.235 15.812 19.268 1 38.716 15.779 18.767 4 39.258 15.820 19.333 2 39.240 15.815 19.251 3 39.282 15.820 19.361 6 38.236 15.739 18.372 B 32 2 32 35 90.30 1 39 .421 15.868 21.224 1 39.415 15.873 20.915 B 34 2 7.5 10.5 91.37 1 39.881 16.005 22.676 3 39.836 15.995 22.365 4 39.832 15.996 22.469 B 35 4 30 32 93.25 1 39.383 15.861 20.893 1 39.342 15.871 20.952 1 39.373 15.850 20.736 3 39 .363 15.860 20.783 4 39.194 15.819 20.416 B 35 4 93 94 93.50 1 39.609 15.938 21.713 1 39.459 15.897 20.404 B 35 5 50 51 94.09 1 39.764 15.994 22.127 1 39.629 15.944 20.844 B 35 5 55 57 94.14 1 39.272 15.913 21.952 1 39.225 15.866 21.077 4 39.256 15.862 21.508 2 39.233 15.887 21.823 B 35 5 118.5 120 94.19 1 39.278 15.862 21.251 1 39.155 15.816 20.215 A 49 2 36.5 38 95.53 1 39.358 15.888 22.978 1 39.211 15.877 21.518 1 39.337 15.876 22.952 3 39.248 15.901 22.495 4 39.172 15.895 22.025

PAGE 65

65 Table 4 4 Cont A 50 1 105 108 96.06 1 39.360 16.026 24.478 1 39.255 15.935 22.035 1 39.360 16.026 24.479 3 39.195 15.955 22.515 4 39.183 15.958 22.242 A 50 2 78 79.5 96.14 1 39.308 16.0 70 24.835 1 39.332 16.065 24.627 A 52 1 75.5 78 97.26 1 39.293 15.977 22.335 Site 1261 A 33 2 14 15.5 55.33 1 39.414 15.786 19.596 1 39.371 15.806 19.683 3 39.429 15.788 19.605 4 39.425 15.786 19.596 A 35 2 8 9. 5 58.12 1 39.612 15.824 19.885 5 39.621 15.819 19.900 B 2 1 72 73.5 62.06 1 39.508 15.801 19.643 1 39.778 15.894 20.225 5 39.736 15.883 20.173 B 3 1 86 89 66.89 1 38.987 15.802 19.100 B 4 1 76 79 70.43 1 39.596 15.832 19.446 A 44 8 116.5 119.5 89.74 1 39.423 15.933 22.290 A 47 4 92 95 93.04 1 39.472 15.887 21.132 A 48 1 123 125 93.51 1 39.582 15.921 21.364 A 48 4 139 141 93.65 1 39.820 15.966 22.515 1 39.727 15.941 21.447 1 39.829 15.966 22.469 3 39.768 15.966 21.916 4 39.730 15.952 21.662 A 48 3 81 82 93.73 1 39.632 15.967 21.708 B 13 2 13 14.5 94.08 1 39.925 16.102 23.322 B 13 3 33 34.5 94.19 1 39.906 16.079 23.373

PAGE 66

66 Table 4 4 Cont. A 50 2 127 129 95.16 1 39.250 15.938 25.512 3 39.277 15.940 25.153 4 39.218 15.937 25.177 1 Ages from Erbacher et al. 2004 and 2005 2 Refer to Table 3 2 for description of sequential leaching procedure. Long term NBS 981 values analyze d on the MC ICPMS at the University of Florida are 206 Pb/ 204 207 Pb/ 204 208 Pb/ 204

PAGE 67

67 Figure 4 1. Nd(t) plotted versus age for detrital fractions from Demerara Rise Site 1258. R efer to Table 3 2 for details on sequential extraction procedures. Fish teeth data from Martin et al. (2012) Gray shading represents samples of black shale lithology. The blue rectangle outlines OAE2. Blue = weak reducing agent Red = strong reducing agent

PAGE 68

68 Figure 4 2. Nd(t) plotted versus age for detrital fractions from Demerara Rise Site 1260. R efer to Table 3 2 for details on sequential extraction procedures. Fish teeth data from Martin et al. (2012) Gray shading represents samples of black shale lithology. The b lue rectangle outlines OAE2. Blue = weak reducing agent Red = strong reducing agent

PAGE 69

69 Figure 4 3. Nd(t) plotted versus age for detrital fractions from Demerara Rise Site 1261. R efer to Table 3 2 for details on sequential extraction procedures. Fish teeth data from M artin et al. (2012) Gray shading represents samples of black shale lithology. The blue rectangle outlines OAE2 Blue = weak reducing agent Red = strong reducing agent

PAGE 70

70 Figure 4 4 Offset between the detrital fraction and fish teeth Nd values for Sites 1258, 1260, B6. The blue rectangle outlines OAE2. Gray shading represents samples of black shale lithology. Blue = weak reducing agent Red = strong reducing agent

PAGE 71

71 Figure 4 5. Detrital fraction REE patterns from ODP Sites 12 58, 1260, and 1261. Samples are normalized to Post Archean Australia n Shale (PAAS, Taylor and McLenn an, 1985) and initial bulk sample weights.

PAGE 72

72 Fig ure 4 6. A comparison o f PAAS normalized HREE/LREE (Tm + Yb + Lu)/(La + Pr + Nd) vs. MREE/MREE* (Gd + Tb + Dy/average of HREE and LREE) for detrital fractions from this study obtained using methods A and B and detrital [green], seawater (HH fraction, fish teeth, nodules, and po re water) [black], acetic [red], and modern seawater [purple] fields defined by Martin et al. (2010).

PAGE 73

73 Figure 4 7. Detrital fraction REE patterns from ODP Site 1260. Samples are normalized to Post Archean Australia n Shale (PAAS, Taylor and McLenn an, 19 85) and initial bulk sample weights.

PAGE 74

74 Figure 4 8. Sr isotopes versus age for detrital and HH fractions from ODP Sites 1258, 1260, and 1261. The average isotopic composition for detrital fractions obtained from al l of the A Methods and all of the B Methods is plotted for each sample. Open symbol with cross = sample(s) analyzed on a Nu ICPMS, open symbols = sample(s) were analyzed on a TIMS, and open symbol with a dot = samples(s) analyzed on TIMS and Nu ICPMS 87 Sr / 86 Sr for seawater (black line) is plotted for comparison. The thickness of the line represents the range of seawater composition (0.7073 to 0.7078) throughout the timeline (McArthur et al., 2001). The blue rectangle outlines OAE2. Blue = weak reducing agent Red = strong reducing agent

PAGE 75

75 Figure 4 9. Pb isotopes versus age for detrital fractions from ODP Sites 1258. The average isotopic composition obtained from all of the A Methods and all of the B Methods is plotted for each sample. Error is smaller than symbol size. R efer to Table 3 2 for details on sequential extraction procedures. Gray shading represents samples of black shale lithology and the blue rectangle outlines OAE2. Blue = weak reducing agent Red = strong reducing agent

PAGE 76

76 Figure 4 10. Pb isotopes versus age for detrita l fractions from ODP Site 1260. The average isotopic composition obtained from all of the A Methods and all of the B Methods is plotted for each sample. Error is smaller than symbol size. R efer to Table 3 2 for details on sequential extraction procedure s. Gray shading represents samples of black shale lithology and the blue rectangle outlines OAE2. Blue = weak reducing agent Red = strong reducing agent

PAGE 77

77 Figure 4 11. Pb isotopes versus age for detrital fractions from ODP Site 1261. The average isotopic composition ob tained from all of the A Methods and all of the B Methods is plotted for each sample. Error is smaller than symbol size. R efer to Table 3 2 for details on sequential extraction procedures. Gray shading represents samples of black shale lithology and the blue rectangle outlines OAE2. Blue = weak reducing agent Red = strong reducing agent

PAGE 78

78 Figure 4 12. P b isotopes versus age for detrital fractions from ODP Sites 1258, 1260, and 1261. The average isotopic composition obtained from all of the A Methods and all of the B Methods is plotted for each sample. Error is smaller than symbol size. Refer to Table 3 2 for d etails on sequential extraction procedures. Gray shading represents samples of black shale lithology and the blue rectangle outlines OAE2. Blue = weak reducing agent Red = strong reducing agent

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79 CHAPTER 5 DISCUSSION Sequential Extraction Results an d Difficulties Nd values recorded in samples from Demerara Rise have been interpreted to represent bottom water values (MacLeod et al., 2008; 2010; Martin et al., 2012) since fish teeth have been shown to be robust archives of seawater Nd (Ma rtin and Scher, 2004). The objective of this study was to verify that the signal preserved in the fish teeth i s not controlled by detrital input Initial analyses of detrital fractions treated using method A (0.02M HH) tended to produce Nd and 87 Sr/ 86 Sr values very similar to fish teeth values, suggesting that the seawater signal was not quantitatively removed from the detrital fraction. This possibility prompted us to test more rigorous sequential leaching protocols. A range of techniques were tested, but the common denominator in the techniques that tended to produce isotopic ratios that were more distinct from seawater (fish teeth) values was the addition of 1 .0 M HH and a hot water bath, similar to the protocol developed by Bayon et al. (2002). Addi tion of multiple reducing steps or dilute acid leaches had little impact on the final outcomes, thus all of the techniques that employed 1 .0 M HH are grouped as method B. Compared to Nd values and more r adiogenic 87 Sr/ 86 Sr values, suggesting more effective removal of components carrying a seawater signal (Figure 5 1). There are also clear behavioral distinctions between the carbonate/marl and black shale lithologic units, regardless of the leaching protoc ol employed. Detrital fractions from t he carbonate interval te Nd of detrital fractions are consistently mor e negative than fish teeth Nd (Figure 4 4). Pb

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80 isotopic ratios, particularly 206 Pb/ 204 Pb and 207 Pb/ 204 Pb, tend to be highly radiogenic in the detrital fra ctions from black shales (Figures 4 9 to 4 12) which can be explained by U enrichment in the sediments formed under reducing conditions. During this process insoluble, reduced U + IV precipitates out and accumulates in the sediment (Klinkhammer and Palmer, 1991). Carpentier et al. (2008) document similar trends in Pb isotopic data from bulk sediment samples from Demerara Rise spanning the Albian to the Early Oligocene. They also document very radiogenic 207 206 Pb/ 204 Pb values in Albian to Cenomanian black shales and less radiogenic values in Campanian Maastrichtian marls and Late Paleocene to Early Oligocene carbonate rich sediment, which they attributed to U enrichment during the reducing conditions, as exemplified by U/Pb ratios ranging from 1.6 and 8.5 in the black shales with peak values during OAE2 when t otal organic contents also peak This interpretation is consistent with Pb isotopic trends reported for Paleozoic black shales as well (Fisher et al., 2003; Lev and Filer, 2004). Nd and Sr isotopic patterns in detrital fractions from the black shales also appear to be influenced by the extreme reducing conditions which may have enhanced alteration of the isotopic composition of the sediment Redox reactions might have mixed silicate, oxide, carbonat e, and sulfate isotopic compositions and the Fe Mn oxides in the black shales might have incorporated an altered isotopic signal during deposition This is evident when comparing isotopic trends between detrital fractions of carbonate and black shale lith ology. Neodymium isotopic compositions of detrital fractions from carbonate intervals are consistently negatively offset from corresponding fish teeth values while Nd of detrital fractions from the b lack shale interval are offset in both negative and pos itive directions from corresponding fish teeth values, regardless of

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81 the reducing agent strength (Figure 4 4). For the 87 Sr/ 86 S r isotopic composition of detrital fractions from the black shale interval both reducing agents (0.02M HH and 1.0M HH) did not quantitatively remove the seawater signal suggesting more difficult removal of seawater components from these detrital fractions compared to detrital fractions from carbonate intervals (Figure 4 8). Alteration o f the fish teeth might not be as evident sin ce some of the isotopes released would have compositions similar to seawater values. Thus, isotopes preserved in the detrital fractions of the black shale interval may not accurately reflect weathering sources to Demerara Rise. For this reason, we focus on the interpretation of detrital fractions from the carbonate interval only. In addition to method B producing Nd and Sr isotopic values with a more continental signature than the fish teeth and seawater curve respectively, REE patterns can also be used to suggest method B produces purer detrital signals than method A. Specifically, REE patterns of detrital fractions produced from method B are flat and similar to average continental crust ( Taylor and McLennan, 1985) while many of the detrital fractions treated with method A show a MREE bulge typical of Fe Mn oxides and a pronounced Ce anomaly (a few typical pa tterns are represented in Figure 4 5). This contrast can be seen most clearly in cross plots of HREE/LREE vs. MREE/MREE*. These plots create dist inct fields for different components in marine sediment samples (Figure 4 6). Although most of the detrital fractions obtained using method A plot within the field defined for detrital fractions by Martin et al. (2010), most of the B method detrital fract ion samples (particularly those from the carbonate interval) have lower MREE/MREE* ratios (Figure 4 6) The A method samples are offset in the direction of

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82 HH fractions (0.02M HH) suggesting that these detrital fractions and the detrital fractions from M artin et al. (2010) may have had residual oxide coatings that carry a seawater signature that were not removed during the reduction procedure. In general the method A samples are more scattered and several even plot between the detrital field and the acet ic leach field, which presumably reflects an influence from carbonate that also carry a seawater signature (Gourlan et al., 2008). The Pb data do not provide any constraints on the extent of contamination of a seawater signature because seawater Pb isotope s are heterogeneously distributed throughout the ocean, and no values have been reported for samples within the age range and location of this study fraction data. However, based on the ana lys es of Nd and Sr isotopes and REE patterns (Figures 4 1, 4 2, 4 3, 4 5, and 4 8 ) we assume the detrital fractions from method B represent a purer detrital signal and therefore the method A samples are offset in the direction of seawater values. Additio nal interpretations of the data will focus on samples from the carbonate interval that were processed using method B. It is perplexing that the leaching procedures used in this study did not remove all seawater components from the detrital fraction since t he procedures we used are slightly modified versions of validated protocols (Rutberg et al., 2000; Bayon et al., 2002, 2004; Piotrowski et al., 2004; 2005; Gutjahr et al., 2007, 2008; Piotrowski et al., 2008; Martin et al., 2010). One consideration is th at many of these studies aimed to extract Nd isotopes from the Fe Mn oxides, rather than isolating the detrital fraction from seawater components (Rutberg et al., 2000; Piotrowski et al., 2004; 2005; 2008). Thus, they only needed to extract enough Fe Mn o xide to obtain a seawater Nd signal. Their

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83 primary goal was to avoid leaching into the clay fraction and contaminating the seawater signal extracted by the reducing agent with a continental weathering signal. Other considerations include the age and lith ology of the samples and the depositional environment. Previous studies have focused on geologically young samples (Pleistocene to the Holocene; Rutberg et al., 2000; Bayon et al., 2002, 2004; Piotrowski et al., 2004; 2005; Gutjahr et al., 2007, 2008; Pi otrowski et al., 2008), although Basak and Martin (in review) worked with Eocene to Oligocene marine sediments and produced coherent and distinct patterns for seawater and detrital fractions. Samples used in this study are ~55 85 Ma and have had significa ntly more time and greater burial depths (500 600 m) to enhance alteration and lithification. Lithologically, our records also include extensive black shales deposited under eutrophic conditions that could lead to more diagenesis. The sequential leachin g procedure by Bayon et al. (2002) was designed to remove Fe Mn oxides and isolate the detrital fraction of marine sediment. Method B replicates their technique, but again their samples are much younger, ranging in age from 4 to 13 kyr. Using REE plots, they verified that the extracted Fe Mn oxides had pronounced negative Ce anomalies and a MREE bulge and produced Nd isotopes that recorded seawater values, while the corresponding detrital fractions produced flat REE patterns and Nd isotopic values that we re not contaminated by seawater components. Martin et al. (2010) followed the procedure developed by Bayon et al. (2002) to isolate the detrital fractions of the >63 m fraction of nannofossil oozes of Miocene to Eocene age. They also found that the proc edure did not effectively remove the seawater component from all of their samples. Nd isotopes for two of the seven detrital fractions analyzed were

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84 within error of the corresponding acetic leach, Fe Mn coatings, and fish teeth, suggesting a strong seawat er component, but the other five samples had much less radiogenic isotopes. One of the four detrital fractions analyzed for Sr isotopes also appeared to be dominated by a seawater signal. Thus, both Martin et a l. (2010) and the current study used the 1 .0 M HH method from Bayon et al. (2002) and documented difficulties in obtaining clean detrital separates. Results of this study suggest that the extraction of Nd, Pb, and Sr isotopes from detrital fractions may be less complicated for samples of geologicall y younger ages or more typical open ocean conditions. They also indicate that studies of provenance based on bulk dissolution of marine sediments (White and Dupre, 1985; Carpentier et al., 2008) may produce isotopic results that do not accurately reflect the detrital composition. Implications for Seawater Interpretation A comparison of Nd isotopes derived from fish teeth and detrital fraction samples illustrates that in a general sense there are similarities between the data sets, but in detail there are a number of differences that can be used to evaluate the relationship between the fish teeth and detrital isotopic values (Figures 5 1 and 5 2). Similarities in long term Nd patterns between the detrital fraction and fish teeth records are evident. Here we focus on the carbonate Campanian to Paleocene interval since isotopic ratios of the detrital fraction in the older black shale interval appear to be affected by chemica l reactions related to the reducing environ ment. Both archives record non radiogenic values throughout the Campanian and Maastrichtian and transition to more radiogenic values by the end of the Paleocene (Figure 5 2) These similar trends could suggest th e kind of coupling between the fish teeth and detrital fraction values that might be expected from boundary exchange, meaning that exchange between the seawater and

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85 detrital inputs altered bottom water values which were then incorporated into the fish teet h. In this case the shift in Nd recorded by the teeth might reflect changes in continental weathering rather than ocean circulation. Nd offsets between the fish teeth and detrital fractions and the magnitude of the off set is variable (Figure 5 2) There are also clear differences in the timing of shifts in Nd values. Fish teeth Nd values from ~75 to 69 Mya are consistently non radiogenic ( Nd = 16) and then begin to shift to more positive values beginning at 69 Ma. This shift is time and depth transgressive with the earliest increase observed at the deepest site (1258), followed by site 1260 and finally by the shallowest site (1261) at 66 Ma (MacLeod et al., 2010). At ~65 Ma Nd abruptly shifts to more radiogenic v alues ( Nd = ~ 11) and stay at approximately that value for ~6 myr to the end of sampling in the Paleocene. Detrital fraction Nd values do not have the same resolution as the fish teeth data, however, the pattern of change is distinct from the fish teeth. For the det Nd values are ~ 19 at ~72 Ma and gradually transition to Nd = ~ 17 over the next ~6 myr. By ~59 Ma, values have increased to ~ 13. Thus, the increase in detrital values lags the increase in fish teeth values by at least 4 myr implying the fish teeth values are varying independently of changes in the continental Nd record documented by the detrital fractions. Detrital Sr and Pb isotopes also show changes that correlate with the increase in Nd and possibly indica te a change in continental source rocks or weathering conditions ~59 Ma (Figure 5 2) This is most apparent in the Sr data which decrease dramatically between samples at 62 Ma and 59 Ma. The direction of change is consistent with the Nd data because less radiogenic Nd and more radiogenic Sr

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86 isotopes both signify a shift to material with less of an old, continental signature. Therefore, it is unlikely that the fish teeth reflect an altered seawater sig nal. The most apparent shift in detrital fraction Pb i sotopes is a dramatic increase at ~66 Ma, which may coincide with a small increase in detrital fraction Sr isotopes, but does not seem to correspond to any change in Nd isotopes of detrital fractions (Figure 5 2) There is a small decrease in Pb isotopes at 59 Ma, whic h is less distinct than the earlier shift, but would also indicate a contribution from a source with a less continental signature. Combined these isotopic data suggest there may have been a change in the detrital source material that led to a shift in Nd, Sr, and Pb isotopes in the detrital fractions around 59 Ma, but changes in the seawater value, as recorded by fish teeth precede this shift, supporting the idea that the change in fish teeth Nd isotopes records a change in water mass circul ation that was independent of local continental inputs. Changes in Detrital Inputs at Demerara Rise Pb isotopic compositions of detrit al fractions are plotted in Figure 5 3 along with Pb data from the SW Amazon craton (whole rock) (Tohver et al., 2004), Demerara Rise (whole rock) (Carpentier et al., 2008), Amazon Fa n mud (McDaniels et al., 1997), Ceara Rise detrital fractions from 11 to 8 Ma (Newkirk, 2012), and suspended sediment from the Congo and Amazon rivers (Allgre et al., 1996). It is often possi ble to use cross plots of Pb isotopes to determine the age of source inputs if they fall along an isochron, or identify end member source compositions if there are mixed sources. Our detr ital fraction data are divided into three age groups that correspond to i sotopic shifts displayed in Figure 5 2 and discussed above. These are <62 Ma, 62 66 Ma, and > 66 Ma. The 208 Pb/ 204 Pb vs. 206 Pb/ 204 Pb data for detrital fractions from this study plot along the same trend and have similar values to the bulk sediment fr om Demerara Rise

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87 published by Carpentier et al. (2008) and the Amazon and Congo River data from Allgre et al. (1996) (Figure 5 3) The data from Newkirk (2012) is believed to represent the composition of Amazon River outflow prior to the connection betwee n the Andes and the Amazon Basin, and this data plots at a slightly higher 208 Pb/ 204 Pb relative to 206 Pb/ 204 Pb. Also plotted are detrital frac tion data from the black shale interval of this study These samples extend to the right of carbonate detrital f ractions and some da ta plot beyond the scale in Figure 5.3 emphasizing the result of 238 U enrichment during reducing conditions on the 206 Pb/ 204 Pb composition of the black shales. 207 Pb/ 204 Pb vs. 206 Pb/ 204 Pb detrital fraction data from this study plot in three clusters along a similar slope, but with higher 207 Pb/ 204 Pb values for a given 206 Pb/ 204 Pb value, compared to the SW Amazon craton data reported by Tohver et al. (2004) (Figure 5 3) The youngest samples (<62 Ma) most closely follow the trend defi ned by the Amazon craton (Tohver et al., 2004) which has an age of 1.2 Ga. Samples with ages 62 66 Ma and >66 Ma have higher 207 Pb/ 204 Pb and 2 06 Pb/ 204 Pb values than our youngest samples and data from the Amazon Shield (Tohver et al., 2004). The offset f ro m the Tohver et al. (2004) data is in a direction that would be consistent with an older shield component (Figure 5 3). The Gu yana Shield sits adjacent to the Amazon Shield and is 3.5Ga (Montgomery, 1979). The fact that the young est detrital fractions ( <62 Ma) seem to plot along a different trend line suggests there may be a change in source linked to the isotopic changes ~60 Ma. Another possibility is that the weathering source remained the same but the weathering regimes changed Identifying and unde rstanding the weathering source and/or regime changes at Demerara Rise is beyond the scope of this project but might be accomplished with a higher resolution dataset.

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88 Surprisingly, our data do not plot along the same trend as the Demerara bulk sediment dat a from Carpentier et al. (2008) (Figure 5 3) In light of concerns expressed about contamination by components with a seawater signature, it is important to note that Carpentier et al. (2008) used bulk marine sediment samples that presumably included thi s seawater component, and in fact their data trend toward fields defined by Fe Mn crust data; however these data are from younger time intervals and different 1998 ) and the ROM fracture zone in the tropical Atlantic (Frank et al., 2003) but suggest the Carpentier et al. (2008) data may differ from ours in terms of 207 Pb/ 204 Pb vs. 206 Pb/ 204 Pb due to seawater contamination.

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89 Fig u re 5 1. Nd, Pb, and Sr isotopic compositions versus age (50 to 100 Ma) for detrital fractions from Demerara Rise Sites 1258, 1260, and 1261. The average isotopic compositions obtained from all of the A Method preparations and all of the B Method preparat ions are plo tted for each sample. A Nd(t) B ) 206 Pb/ 204 Pb. C) 87 Sr/ 86 Sr O pen symbol s with cross = sample(s) analyzed on a Nu ICPMS, open symbols = sample(s) were analyzed on a TIMS, and open symbol with a dot = samples(s) analyzed on TIMS and Nu ICPMS. Fish teeth data from Martin et al. (2012). Refer to Table 3 2 for details or sequential extraction procedures. OAE2 is outlined by the blue rectangle. Blue = weak reducing agent Red = strong reducing ag ent A) B ) C )

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90 Figure 5 2. Nd, Pb, and Sr isotopic compositions versus age (52 to 75 Ma) for detrital fr actions from Demerara Rise Sites 1258, 1260, and 1261. The average isotopic compositions obtained from all of the A Method preparations and all of the B Method preparations are plo tted for each sample. A Nd(t) B ) 206 Pb/ 204 Pb. C) 87 Sr/ 86 Sr O pen symbol s with cross = sample(s) analyzed on a Nu ICPMS, open symbols = sample(s) were analyzed on a TIMS, and open symbol with a dot = samples(s) analyzed on TIMS and Nu ICPMS. Fish teeth data from Martin et al. (2012). Refer to Table 3 2 for details or sequential extraction procedures. OAE2 is outlined by the blue rectangle Blue = weak reducing agent Red = strong reducing agent A) B ) C )

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91 Figure 5 3. Pb vs. Pb diagrams for detrital fractions using method B from Sites 1258, 1260, and 1261 compared to published data. A ) 208 Pb/ 204 Pb vs. 206 Pb/ 204 Pb. B ) 207 Pb/ 204 Pb vs. 206 Pb/ 204 Pb A) B )

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92 CHAPTER 6 CONCLUSION S We employed different sequential leaching procedures on marine sediments in effort to obtain a detrital silicate fraction free of a seawater signal. Nd, Pb, and Sr isotopic analyses indicate treating the sample with a strong reducing agent, in this case a 1.0M HH acetic acid solution, minimizes contamination from components carrying a seawater signal. Additional steps, including treating the sample with HCl, repeating reductive procedures, and oxidizing organic matter do not impact the isotopic composition of the detrital fraction. Using a weak 0.02M HH solution generally yields Nd isotopic compositions that are more radiogenic than values retrieved from samples treated by 1.0M HH, Sr isotopic values that are closer to global seawater values and REE patterns with more of a MREE bulge. Additionally, we learned that the effectiveness of the leaching procedure can depend on the sa had more difficulty isolating detrital fraction isotopic values from Late Cretaceous black shales compared to carbonate marls. In general, Nd and Sr isotopes in detrital fractions fro m the carbonate interval were consistently less similar to seawater Nd and Sr values detrital fractions from the black shale interval which displayed high scatter. The black shales likely experienced a more intense diagenetic environment related to redox conditions. The methods we employed were modifications of verified sequential leaching procedures used to isolate the detrital fraction (Bayon et al., 2002; Martin et al., 2010). These studies successfully isolated the detrital fraction but they worked with geologically young samples that were deposited under more typical deep sea conditions. Our samples are much older and were buried deeper.

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93 Nd values preserved in fossil fish teeth from Demerara Rise record a water m ass signal, rather than a signal dominated by boundary Nd trends between the fish teeth and detrital fractions suggested possible influences from boundary exchange or diagenesis within the sediment, but a detailed evalu ation of the timing of Nd isotopic shifts in the fish teeth Nd record of the fish teeth predate shifts in the detrital fraction and therefore is varying independentl y of the continental weathering signal. Thus, the Nd isotopic record preserv ed in the fish teeth is verified as a seawater signal. The seawater Nd record has significant implications for Late Cretaceous pa leoceanography. It supports the concept of exte nded formation of a bottom water mass in warm equatorial regions in the Late Cretaceous (DBW; MacLeod et al., 2008; Martin et al., 2012). It also argues that the Nd values during OAE2 represents active circul ation and introduction of North Atlantic/Tethyan waters to the Demerara region (MacLeod et al., 2008; Martin et al., 2012) during an interval when North Atlantic circulation was believed to be quite stagnant (Barron, 1983; Bralower and Thierstein, 1984). Finally, the replacement of DBW by Northern Component Water (NCW) at the end of the Maastrichtian challenges previous estimates for initial NCW formation in the Oligocene (Davies et al., 2001; Howe et al., 2001; Via and Thomas, 2006; Scher and Martin, 2008 ). Results from our study emphasize that isolating the detrital fraction of marine sediment from seawater carrying components is extremely challenging and that sequential extraction procedures are not successful on all types of sediment To

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94 improve our un derstanding of the sequential leaching process, future work should involve quantitative and mineralogical analyses of bulk marine sediment sample before the leaching process and after each step in the procedure using x ray diffraction This study did not make quantitati ve measurements of the material removed after each step in the leaching process or identify mineralogical changes the sediment may have experienced after each step. Mineralogical data would be helpful for understanding what material is remo ved after each step in the leaching procedure and verify the purity of the final material produced from the chemical extraction. Additionally, mass balance calculations could be used to determine the aggressiveness of reducing agents used to remove Fe Mn oxides from marine sediment by measuring the extent of isotopic alteration by detrital contamination in the reduced leachate. Although a few HH fractions were collected and analyzed for Sr isotopic composition in this study, REE concentrations were not me asured and the Sr concentration of the HH fraction is needed to complete mass balance calculations. Mass balance calculations would allow us to calculate the percentage of detrital Sr lea ched into the HH fraction. Using the assumption that the same perce ntage of Nd was leached from the detrital fraction as Sr, we could quantify the amount of Nd leached from the detrital fraction into HH fraction and calculate the true seawater isotopic composition. The resolution of the isotopic record of detrital fracti ons from Demerara Rise needs to be significantly improved in order to make the most accurate interpretations of the isotopic record. Several marine sediment samples need to be processed and analyzed to achieve a resolution record similar to the seawater Nd record of the fish teeth.

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96 Basak, C ., et al. ( 2011 ), Seawater Pb isotopes extracted from Cen ozoic marine Sediments, Chem. Geol. 286 3 4 Bayon, G., et al. ( 200 2 ) An improved method for extracting marine sediment fractions and its application to Sr and Nd isotopic analysis, Geochim. Cosmochim. Act a 187 170 199. Bayon, G., et al. (2004), Sedimentary Fe Mn oxyhydroxides as paleoceanographic archives and the r ole of aeloian flux in regulating oceanic dissolved REE, Earth Planet. Sci. Lett ., 224 477 494. Bertram, C. J., and Elderfield, H. ( 1993 ) The geochemical balance of the rare earth elements and ne odymium isotopes in the oceans, Geo chim. Cosmochim. Acta 57 1957 1986. Bice, K .L., et al. ( 2003 ), Extreme polar warmth during the Cretaceous greenhouse? paradox of the late Turonian O 18 at deep sea drilling proj ect site 511. Paleoceanography 18 1 7 Bice, K.L., et al. ( 2006 ) A multiple proxy and model st udy of Cretaceous upper ocean temperatures and atmospheric CO 2 conce ntrations, Paleoceanography 21 1 17 Bornemann, A., et al. (2008), Isotopic evidence for glaciation during the Cretaceous Supergreenhouse, Science 11 189 192. Bralower, T.J., and Th ierstein, H.R. ( 1984 ), Low productivity and slow deep water circulation in mid Cretaceous oceans, Geology 12 614 618 Broecker, W.S., and Peng, T. H., 1982, Tracers in the Sea: Palisades, NY, Lamont Doherty Geological Observatory, 690 p. Brumsack H.J (2005) The trace metal content of recent organic carbon rich sediments: Implications for C retaceous black shale formation, Paleogeog. Paleoclim. Paleoeco. 232 344 361. Burke, W.H., et al. (1981), Variation of seawater 87 Sr/ 86 Sr throughout Phanerozoic time, Geology 10 516 519. Burton, K. W., et al. ( 1997 ) Closure of the Central American Isthmus and its effect on deep water formatio n in the north Atlantic, Nature 386 382 385. Carpentier, A., et al. ( 2008 ) Pb Nd isotopic constraints on sediment ary input into the Lesser Antilles arc system, Geochim. Cosmochim. Acta 72 199 211. Chester, R., and Hughes, M.J. ( 1967 ), A chemical technique for the separation of

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97 ferromanganese minerals, carbonate minerals and adsorbed trace elements from pela gic s ediments, Chem. Geol ., 2 249 262. Clarke, L.J., and Jenkyns, H.C. ( 1999 ), New oxygen isotope evidence for long term Cretaceous climatic change in t he Southern Hemisphere, Geology 27 699 702. Coffin, M.F. and Eldholm, O. (1994), Large igneous provinc es crustal structure, dimensions, and e xternal consequences, Rev. Geophys ., 32 1 36 Craig H., et al. ( 1973 ), 210 Pb 226 Ra, Radioactive disequilib rium in the deep sea, Earth Planet. Sci. Lett. 17 295 305. Davies R. et al. ( 2001 ), Early Oligocene ini tiation of North Atlantic Deep Water Formation, Nature 410, 917 920. Depaolo, D.J. and Wasserburg, G.J. (1 976 ), Nd isotopic variations and petrogenetic models Transactions American Geophysical Union 57, 249 252 Ekart, D.D. et al. ( 1999 ), A 400 mill ion year carbon isotope record of pedogenic carbonate: Implications for paleoatmospheri c carbon dioxide, Am. Journ. Sci ., 299 805 827 Elderfield, H. and Pagett, R. ( 1986 ), Rare earth elements in ichthyoliths variations with redox conditions and deposi tional environment Science of the Total Environment 49 175 197. Erba, E. (2004), Calcareous nannofossils and Mesozoic oceanic anoxic events Marine Micropaleontology 52 85 106. Erbacher, J. et al. (2001) Increased thermohaline stratification as a possible cause for an ocean anoxic event in the Cretaceous Period Nature 409 325 327. Erbacher, J., et al. (2004a), Demerara Rise: Equatorial Cretaceous and Paleogene paleoceanographic transect: Proceedings of the Oceanic Drilling Program Initial R eports Leg 207 Erbacher, J., et al. (2004b), Site 1258: Proceedings of the Ocean Drilling Progr am Part A: Initial Reports Leg 207 117 pp. Erbacher, J., et al. (2004c), Site 1260: Proceedings of the Ocean Drilling Program Part A: Initial Reports, Leg 207 113 pp. Erbacher, J., et al. (2004b), Site 1261: Proceedings of the Ocean Drilling Program Part A: Initial Reports, Leg 207 103 pp.

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108 BIOGRAPHICAL SKETCH Emily Pugh is from Cory IN. She received her B.S. of g eology from Indiana State Universi ty in May 2010. In Fall 20 10, Emily began her graduate studies at the University of Florida. Her research focused on Late Cretaceous paleoceanography. Emily is undecided on her career plans.