Igneous and metamorphic basement rocks of Florida

STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Randolph Hodges, Executive Director

DIVISION OF INTERIOR RESOURCES
Robert O. Vernon, Director

BUREAU OF GEOLOGY
Charles W. Hendry, Jr., Chief

BULLETIN NO. 55

IGNEOUS AND METAMORPHIC
BASEMENT ROCKS OF FLORIDA

By
Charles Milton

Prepared by the
GEORGE WASHINGTON UNIVERSITY
and the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
BUREAU OF GEOLOGY
FLORIDA DEPARTMENT OF NATURAL RESOURCES

TALLAHASSEE
1972

DEPARTMENT
OF
NATURAL RESOURCES

REUBIN O'D. ASKEW
Governor

RICHARD (DICK) STONE
Secretary of State

THOMAS D. O'MALLEY
Treasurer

FLOYD T. CHRISTIAN
Commissioner of Education

ROBERT L. SHEVIN
Attorney General

FRED O. DICKINSON, JR.
Comptroller

DOYLE CONNER
Commissioner of Agriculture

W. RANDOLPH HODGES
Executive Director

LETTER OF TRANSMITTAL

Bureau of Geology
Tallahassee
October 5, 1972

Honorable Reubin O'D. Askew, Chairman
Department of Natural Resources
Tallahassee, Florida

Dear Governor Askew:

The Department of Natural Resources, Bureau of Geology, is publishing
Bulletin No. 55 entitled "Igneous and Metamorphic Basement Rocks of
Florida" by Charles Milton, U.S. Geological Survey.

This report describes the basement rocks that have been penetrated by
wells in the State of Florida. These deep-seated igneous and metamorphic
rocks form the structural backbone of the peninsula and can be invaluable
in the determination of the structural history of the State.

Respectfully yours,

Charles W. Hendry, Jr., Chief,
Bureau of Geology

Completed manuscript received
April 25, 1972
Printed for the Florida Department of Natural Resources
Division of Interior Resources
Bureau of Geology
by News-Journal Corporation
Daytona Beach, Florida

Tallahassee
1972

iv

CONTENTS

A cknow ledgm ents ..................................................... i
Previous studies ................................... .................... x
Location of wells in Florida (Map, Figure 1A) ............................... xi
List of w ells in Florida (Table 1) ........................................... xii
Introduction........... ...................................... ........ 1
Petrography of Florida igneous-metamorphic rocks ........................... 2
Dating of Florida and Georgia igneous-metamorphic rocks ..................... 8
Chemical analyses of Florida igneous-metamorphic rocks ...................... 9
Descriptions of Florida "basement rocks" ................................... 12
Nassau County, St. Mary's River Oil Corp., Hilliard Turpentine No. 1 .......... 12
Columbia County, Humble, Cone No. 1 ................................. 13
M adison County, Hunt, Gibson No. 1 .................................... 19
Taylor County, Gulf, Brooks-Scanlon No. 1 ............................... 20
Taylor County, Humble, Hodges No. 1 ................................... 21
Jefferson County, Coastal Petroleum, Larsh No. 1 .............. ...... ..... 26
Franklin County, California and Coastal Petroleum, No. 2 Statelease .......... 31
Jackson County, Humble, Tindel No. 1 .................................. 31
W alton County, Pan American, Sealy No. 1 ............................... 37
Flagler County, Humble, Campbell No. 1 ................................. 38
Putnam County, Sun, W estbury No. 1 .................................... 44
M arion County, Sun, Camp No. 1 ....................................... 49
Levy County, Humble, Robinson No. 1 .................................. 51
Volusia County, Grace Drilling, Retail Lumber No. 1 ....................... 55
Volusia County, Sun, Powell No. 1 ....................................... 57
Lake County, Lake County Development, South Lake No. 2 .................. 64
Orange County, W arren, Terry No. 1 ..................................... 66
Indian County, Amerada, Mitchell No. 1 .................................. 66
St. Lucie County, Amerada, Cowles Magazine No. 2 ....................... . 76
Osceola County, Humble, Hayman No. 1 ................................. 76
Osceola County, Humble, Carroll No. 1 ................................... 81
Okeechobee County, Amerada, Swenson No. 1 .. ........... .......... 84
Okeechobee County, Amerada, Harris-Holmes No. 1 ........................ 84
Highlands County, Humble, Carlton Estate No. 1 ........................... 92
Highlands County, Continental, Carlton et al. No. 1 ....................... 101
Hardee County, Humble, Keen No. 1 ..................................... 109
Hillsborough County, Humble, Jameson No. 1 ............................. .113
References ............ ..................................... ........ 124
V

Figure
1

Columbia County

Madison County
Taylor County

Jefferson County

14
15
16a, b

17 Franklin County

18
19
20 Jackson County

21 a, b

22 Walton County

23
24 Flagler County

25
26 a, b

27 Putnam County

Marion County

32 Levy County

ILLUSTRATIONS
Page
Humble, Cone No. 1, 3520'-3529', top 7'.
Baked shale with andalusite (?) ............ 3
3520'-3529', bottom 1'. Altered diabase ...... 14
3543'-3555', top. Diabase. ................. 15
4181'-4206' bottom. Amygdular basalt ..... 16
4181'-4206' bottom. Basalt-calcite
(hydrothermal ?) contact .................. 17
4256'-4281' middle. Amygdular basalt. ....... 18
Hunt, Gibson No. 2, 5200'-5210'. Diabase... 19
Gulf, Brooks Scanlon No. 1, 5512'-5517'
bottom. Diabase-basalt ................... 21
Humble, Hodges No. 1, 615312'.
Calcitized basalt. ....................... 22
6155'. Calcitized basalt-diabase ........... 23
61651/'. Calcitized explosion breccia ........ 24
6216'-6219'. Unaltereddiabase ............. 25
Coastal Petroleum, Larsh No. 1, 7789'-7791'.
D iabase ................ ... ......... . 27
7791'-7795' top. Baked shale (?)............ 28
7791'-7795' bottom: Calcitized basalt. ....... 29
7909'-7911'. Sandstone, ordinary light and
crossed nicols .......................... 30
California Co. and Coastal Petroleum,
No. 2 State Lse. 224-A, 10325'-10326'.
Sandstone with calcite and dickite (?)....... 32
10520'-10530'. Calcitized basalt ........... 33
10520'-10530'. Baked shale ................ 34
Humble, Tindel No. 1, 8881'-8891' top 54'.
Siltstone................................ 35
8881'-8891' bottom 1'. Amygdular-quartz
basalt, ordinary light and crossed nicols ..... 36
Pan American Petroleum, J. R. Sealey No. 1,
11935'-11940'. Sericitized rhyolite porphyry
orash................................. 37
11935'-11940'. Sericitized rhyolite, or ash. .... 38
Humble, Campbell No. 1, 4624%4'-4626'.
Volcanic agglomerate. ................... 40
4638'-4639'. Volcanic agglomerate ash. .... 41
4643'-4644'. Volcanic agglomerate ash,
ordinary light and crossed nicols ........... 43
Sun, Westbury No. 1, 3879'-3881'.
Ash with fossil .......................... 45
3885'-3887'.Pyroclastic .................... 46
3887'-3891'.Pyroclastic ................... 47
3890'-3892'.Pyroclastic ................... 48
Sun, Camp No. 1, 4574'-4584'. Arkose
with rhyolite ........................... 50
Humble, Robinson No. 1, 4331'-4336'.
Calcitized basalt ....................... 52

Figure
33
34
35

36

37
38
39 a, b

40
41 a, b

Volusia County

Lake County

42 Indian River County

43
44
45
46
47 a, b

St. Lucie County

48 a, b

49 a, b

50 Osceola County

51 a, b

52 a, b

53 a, b

54 Okeechobee County

55

56

57
58
59
60

61 Highlands County

4344'-4356'. Calcitized basalt .............. 53
4358'-4359'. Diabase .....................54
Grace Drilling, Retail, Lumber No. 1,
5424)2'. Rhyolite.........................56
Sun, Powell Land No. 1, 5922'-5925'.
"Weathered" igneous rock ................ 58
5954'-5955'. Diorite ................... 60
5954'-5955'. Diorite with epidote. .......... 61
5955'-5956'. Homfels, ordinary light and
crossed nicols .......................... 62
5957,2-5958'. Hornfels. ................. 63
Lake County Oil Devel. South Lake
No. 2, 6107'-6128'. "Granite", ordinary
light and crossed nicols ................... 65
Amerada Petroleum Corp.,
Fondren Mitchell No. 1,
9444'-9449'. Basalt. ................... 67
9444'-9449'. Diabase ..................... 68
9469'-9474'. Amygdules in basalt ........... 69
9469'-9474'. Amygdule in basalt ............ 70
9484'-9489' T. D. Quartzitic basalt .......... 71
Amerada, Cowles Magazine No. 2, 12734'.
Amygdaloidal basalt, ordinary light and
crossed nicols .......................... 72
12744'. Granite, ordinary light and
crossed nicols .......................... 74
12748' Diorite, ordinary light and
crossed nicols .................. .........75
Humble, Hayman No. 1, 8750'-875.3'.
Rhyolite ................................ 78
8765'-8770'. Rhyolite, ordinary light and
crossed nicols ........................... 79
8786'-8787'. Rhyolite, ordinary light and
crossed nicols ........................... 80
Humble, J. Ray Carroll No. 1,
8042'-8042i''. "Granite", ordinary light
and crossed nichols .................... 82-83
Amerada Petroleum Corp., Marie Swenson
No. 1, 10760'-10770'. Amygdular basalt ..... 85
10760'-10770'. Basalt, non-amygdular
(3 fragments) ............................ 86
10760'-10770'. Altered shale, and
amygdular basalt (3 fragments) ............ .87
10760'-10770'.Basalt. ................... .88
10760'-10770'. Bakedshale .................89
10770'-10780'. Amygdular basalt ............ 90
10830'-10840' T. D. Hydrothermal
quartz, etc..............................91
Humble, Carlton Estate No. 1,
12694'-12699'. Basalt. .................... .93

Figure
62
63
64
65
66

67
68

69

Hardee County

75 a, b

76 a, b

77a, b

78 a, b Hillsborough County

79 a, b

80
81 a, b
82
83
84
85

Page
12715'-12721'.Basalt. ................... 95
12721'-12722'.Basalt ................... 96
12721'-12722'. Basalt with veinlets .......... 97
12771'-12775. Basalt ..................... 98
12826'-12867'. Amygdular basalt with
veinlets ............................... 99
12826'-12867'. Amygdule in basalt ......... 100
Continental Oil, Carlton et al. 12600'-12609'
top. Altered basaltic ash with veinlets ...... 102
12600'-12609' bottom. Basalt with
calcite bands ......................... 103
12614'-12630' lower middle. Zoned
chlorite amygdule in basalt. ............ 105
12641'-12630' lower middle. Amygdaloidal
basalt with veinlets. .................... 106
12629' bottom of hole.
Amygdaloidal basalt with chalcedony (?)... 107
12614'-12630' bottom. Amygdaloidal basalt. 108
Humble, Keen No. 1, 11853'-11857'.
Basalt with quartz veinlet ................ 110
11867'-11877'. Basalt with quartz chlorite
amygdule, ordinary light and crossed nicols. 111
11867'-11877'. Amygdular brecciated
basalt, ordinary light and crossed nicols .... 112
11932'-119:33'. Basalt, ordinary light and
crossed nicols ......................... 114
Humble, Jameson No. 1, 9995'-10003'.
Arkosic sandstone, ordinary light and
crossed nicols......................... 115
10003'-10010. Grit or arkose, ordinary
light and crossed nicols. ............... 116
10010'-10019. Rhyolite .................. 117
10010'-10019'. Rhyolite flow structure ..... 118
10025'.Rhyolite ........................ 120
10040'-10043'. Rhyolite or welded tuff. .... 121
10043'-10053'. Rhyolite ................. 122
10115'-10125'. Basaltic rock .............. 123

TABLES

Tables

Page

la Location M ap ........................................................xi
1 Florida wells drilled into Igneous or Metamorphic rocks ... .. ............ .. xii
2 Isotope dating of Florida (and Georgia) rocks ............................. 5
2a Age determinations Amerada Petroleum Corp. Cowles Magazine No. 1......5
3 Chemical analyses of Florida Igneous-Metamorphic rocks ................... 10
3a Florida igneous-metamorphic rock norms ................................ 11

ACKNOWLEDGMENTS

This work was begun in 1949, with study of the petrography of
the cores and cuttings from Florida, Georgia, and Alabama reported
on by Paul L. Applin (1951) in "Preliminary Report on Buried pre-
Mesozoic Rocks in Florida and Adjacent States" (U.S. Geol. Survey
Circular 91). This was the basic compendium of data than available.
For Florida, the present report may be considered as final or compre-
hensive summary report on these igneous rocks, with inclusion of
much data accumulated during the two decades following the 1951
circular. Mr. Applin and the Bureau of Geology have continued their
helpful interest in this study, and furnished part of these additional
data. George V. Cohee gave valuable counsel and assistance, and Miss
Jean Berdan also of the U. S. Geological Survey contributed paleonto-
logic-stratigraphic data, besides critically reviewing this report. I am
indebted to Dr. A. A. Meyerhoff, Publication Manager of the Ameri-
can Association of Petroleum Geologists for permission to use mater-
ial from a brief account of these rocks published in the Bulletin (Milton
and Grasty, 1969). A grant from the National Science Foundation pro-
vided facilities which were used in the preparation of this report.

PREVIOUS STUDIES

The basic reference work on the petrology of the igneous-metamor-
phic rocks beneath the coastal plain of Florida, Georgia, and Alabama
is by Applin (1951), who gave data on 100 wells drilled in those three
states. Sixty-five wells were drilled in Florida (of which 3 were reported
to have reached granite or diorite, 8 to have reached rhvolitic or other
volcanic rock, and 10 to have reached basalt or diabase). Applin sug-
gested a Precambrian age for the granite-diorite rocks, as well as for
the Peidmont metamorphic rocks in Georgia and Alabama not far
south of the Fall Line. This report indicates no ages greater than Pale-
ozoic, and most of them are much younger.
Data of fossiliferous Mesozoic strata underlying the Florida coastal
plain have been summarized by Applin and Applin (1965, 1967). As
only a few wells have penetrated igneous rocks since Applin's (1951)
publication, comparatively little is added to previous knowledge of Flor-
ida igneous-metamorphic petrology, and most of their discussion is of
previously published data. They describe the coastal plain floor in north-
ern and central Florida as a truncated surface of igneous and sedimen-
tary rocks of "mostly Precambrian(?) and early Paleozoic" age, and
in northern Florida as "late Triassic(?)" igneous rocks. Additional data
on Florida wells, in part unpublished, have been given to us by P. L.
Applin (written common., 1967).
Milton and Hurst (1965) described samples from 13 wells in Georgia
which were drilled into Paleozoic or older granite and crystalline
schist, and from another 26 wells which were drilled beneath the coastal
plain formations into volcanic or sedimentary rock more or less
metamorphosed by igneous contact.
Grasty and Wilson (1967) discussed the Florida igneous rocks
with reference to continental drift. Several of the age determinations
given here were made for their study.
Bass (1969) reported on the petrography of nine Florida basement
rocks and gave three age determinations, cited here in Table 1.

0

/
I /

--x

Table 1. Florida Wells Drilled into Igneous or Metamorphic Rocks

Depth to Thickness
Top of Of Igneous
Well Applin Type of Igneous or or Meta- Total
Locality (1951) County Rock Meta- Morphic Depth of Bottom Rock Remarks
Fig. I No. morphic Rock Well (ft)
Rock Penetrated
(ft) (ft)

67 Nassau Diabase

42 Columbia Diabase

62 Madison Diabase

4 82 Taylor

5 83 Taylor

Diabase

Basalt
"gabbro"
diabase

6 54 Jefferson Diabase or
basalt

7 Franklin Diabase

4,808

4,824 Diabase

Intrudes lower Paleozoic black
shale.

4,444 Black shale Samples labeled 4,181-4,206 ft
and 4,231-4,281 ft are amygdaloi-
dal basalt. Black shale overlying
diabase at 3,529 ft contains
abundant sercitized andalusite
(?) (Fig. 2a)
5,385 Paleozoic black Sampleslabeled 5,200-5,201 ft are
shale hydrothermally altered diabase.

:3,529*
3,564*
4,1910
4,193*
4,218-
4,267*
1,589-

5,438

6, 153

7,690

7,763*
7,850.
10.4600

5,517 Diabase or
basalt
6,254 Diabase

7,913 Sandstone

10,566
(Driller)
10,507
(elec. log)

Diabase

Altered diabase or basalt.

Upper 12 ft is basalt; lower 89 ft
is diabase gabbro (Applin, 1951).
Upper 10 ft of basalt highly cal-
citic and strongly brecciated. An-
alysis 5: diabase, 6,162 ft. Analy-
sis 6: diabase, 6,216-6,219 ft.

California Co. and Coastal Petro-
leum Co. No. 2 State Lease
224A. Data from P. L. Applin
(written common., 1967) Loca-
tion: Lat. 2947'03"N long. 810
22'51"W, about 13 mi offshore
from Carrabelle, Florida.

Table l. (Continued)

Depth to Thickness
Top of Of Igneous
Well Applin Type of Igneous or or Meta- Total
Locality (1951) County Rock Meta- Morphic Depth of Bottom Rock Remarks
Fig. 1 No. morphic Rock Well (ft)
Rock Penetrated
(ft) (ft)

8 53 Jackson Porphyritic
hornblende
Basalt
(Applin, 1951)
9 Walton Strongly
altered
porphyritic
rhyolite

10 19 Flagler Basaltic and
rhyolitic tuff

11 25 Putnam Volcanic ash

12 23 Marion Rhyolite or
rhyolitic ash

13 60 Levy

Diabase

14 26 Volusia "Rhyolitic(?)
volcanic rock"
(Applin, 1951

15 7 Volusia Metabasalt

16 5 Lake

"Alaskite" or
"granite"

8,890-
8,970-

11,910

4,588

3,873

4,615

4,317

5,403

5,910
5,951-
5,952

6,103

9,245 Middle Devonian
siltstone

11,948 Rhyolite ash
or prorphyry

4,632 Volcanic agglom-
erate of rhyolitic
and basaltic debris
3,982 Ash or rhyolite

4,637 Ash or rhyolite

4,609 Lower Paleozoic
quartzite and
shale
5,424 Rhyolite

5,958 Metabasalt, etc.

6,129 "Alaskite"
(II, L. Tomlinson,
unpub. data)
"Granite"
(Applin, 1951)

Basalt is amygdaloidal.

Pan American No. 1 J. E. Sealey.
Data from Applin (written com-
mun., 1967), cited in letter from
R. T. Violette to P. L. Applin,
June 3, 1960.
Analysis 8: volcanic agglomerate,
4,624 3/4 4,626 ft.

Fossils (?). Analysis 9: ash or
rhyolite, 3,879-3,881 ft.

Top of igneous rock is clayey,
bottom fresh diabase.

"No cores taken in volcanic
rock." (Applin, 1951) cuttings
(5,424 1/2 T.D.) are fresh rhyo-
lite,
Also altered calcareous shale (?).
Volcanic rock altered to clay.
Analysis 7: metabasalt, 5,919-
5,922 ft. Age more than 480 m.y.
Meta-arkose (?) "not studied
petrographically" (Applin, 1951)
(Fig. 2b).

Table 1. (Continued)

Depth to Thickness
Top of Of Igneous
Well Applin Type of Igneous or or Meta- Total
Locality (1951) County Rock Meta- Morphic Depth of Bottom Rock Remarks
Fig. 1 No. morphic Rock Well (ft)
Rock Penetrated
(ft) (ft)

17 Orange

Indian
River

"Granite"

"Andesite"

19 St. Lucie Basalt
Granite
Diorite

20 24 Osceola Rhyolite
21 6 Osceola "Granite"
Arkose(?)

22 Okeechobee "Volcanic"
rocks

6,550

9,410

12,725
12,744
12,748

8,740
8,035
8,035

10,750

6,589 "Granite"

9,488 Diabase

12,748 "Diorite"

8,798 Rhyolite
8,049 "Granite"
8,042 (Applin, 1951)
Arkose (?)
10,838 Basalt

Warner Petroleumn Co. No. 1
George Terry. Data from Applin
(written commun., 1967). Well
61 of Applin nmd Applin (1965).
C SW'. SEA. Sec. 21, T23S,
R31E. No samples available.
Amerada Petroleum Corp. No. I
Frondren Mitchell. Data from
Applin (written common., 1967).
Sec. 28, T31S, R35E.
Amerada Petroleum Corp. No. 2
Cowles Magazine. Well 68A of
Applin and Applin (1965). Anal-
ysis 2: basalt, 12,734 ft, age 89.3
- 2.2 m.y. (Fig. 2d). Analysis 3:
"granite," 12,744 ft, age226 6m.
y. (Fig. 3a). Analysis 4 "dior-
ite," 12,748 ft, age 308 -5 m.v.
(530 + m.y., Bass, 1969) (Fig. 3h).
Age 173 4 m.y.
Analysis 1: granite or arkose,
8,031-8,042 ft, age 530 m.y.
(Bass, 1969) (Fig. 2c).
Amerada Petroleum Corp. No. 1
Marie Swenson. Data from Ap-
plin writtene n common., 1967).
Well 60 of Applin and Applin
(1965). Sec. 5, T36S, R34E.

Table 1. (Continued)

Depth to Thickness
Top of Of Igneous
Well Applin Type of Igneous or or Meta- Total
Locality (1951) County Rock Meta- Morphic Depth of Bottom Rock Remarks
Fig. 1 No. morphic Rock Well (ft)
Rock Penetrated
(ft) (ft)

Okeechobee Rhyolite
porphyry

24 21 Highlands Amygdaloidal
basalt, rhyolite,
porphyry, etc.
(Applin, 1951)
25 Highlands "Volcanic
rock"

26 20 Hardee Basalt "lava
and pyroclastic
rocks" (Applin,
1951)
27 22 Hillsborough Rhyolite tuffs
and flows (Fig.
3c), and meta-
basalt (?)

9,682

12,618

12,601

11,828

10,010

9,840

12,985 Basalt

12,630 Diabase

11,934 Basalt

10,129 Metabasalt (?)

"Depth reported by Applin (1951).

Sun Oil Co.-Amerada Petrole-
um Corp. No. 1 Harris Iolmes.
Data from Applin (written com-
mun., 1967). No samples avail-
able. Sec. 8, T33S, R34E.
Basalt, 12,664 ft, age 183 10
m.y.

Continental Oil Co. No. 1 G. C.
Carlton et al. Data from Applin
(written common., 1967). Well
45 of Applin and Applin (1965).
Basalt, in part hydrothermally
altered and brecciated, also ash
(?). Altered basalt, 11,853 ft., age
143 + 3m.y.
Rhyolite and welded tuff overlies
metabasaltic (?) agglomerate
(Fig. 3d). Analysis 10: metaba
saltic agglomerate, 10,115-10,125
ft. Analysis 11: rhyolite, 10,019-
10,022 ft.

INTRODUCTION

This report describes in detail all the cores and cuttings available from
a large collection of wells which were drilled in the Florida Coastal Plain,
which penetrated rocks older than the Late Cretaceous, Tuscaloosa For-
mation. It summarizes the literature concerned with these rocks. A simi-
lar account of the corresponding rocks in Georgia was given by Milton and
Hurst (1965). The Florida rocks have recently been listed and briefly de-
scribed by Milton and Grasty (1969).
The specimens described number several hundred, from 27 drill holes
in 21 counties over most of Florida north of Lake Okeechobee, and in-
clude nearly all of the deep tests that have penetrated igneous rocks of
the basement during a half century of drilling. To the south of Lake Okee-
chobee, wells have been drilled to greater depths, but only two have
reached rock of pre-Mesozoic age, or of igneous-metamorphic character.*
Although many wells have been drilled into the Florida pre-Cretaceous
basement, and Paleozoic strata have been recognized widely in the northern
part of the state, the nature of the truly metamorphic basement underlying
Paleozoic sedimentary rocks still may be considered virtually unknown.
Twenty-seven wells have penetrated igneous or metamorphic rocks which
appear mostly to be either Mesozoic of Paleozoic intrusive and related vol-
canic sedimentary rocks, or contact-metamorphic rocks affected by such
volcanic activity. Because drilling generally was terminated when such
rocks were penetrated, little or nothing is known of what may underlie
them, or the extent and thickness of the basement rocks themselves.

*Editor's Note: Those are Humble O & R Co. No. 1 Lehigh, the discovery well of Le-
high Acres Field in Lee County, which bottomed in diabase, and Mobil Oil Co. No. 1
224-B F.S.L., a dry hole drilled about 6 miles SW of Englewood in the Gulf of Mexico.
This well bottomed in rhyolite. Age determinations by potassium-origin percentages in-
dicate late Triassic or early Jurassic intrusives for both diabase and rhyolite recovered
in cores from the wells.

BUREAU OF GEOLOGY

The petrography of basement*rock from 27 Florida wells is described
(Table 1); also some 14 isotopic dating from 6 wells in Florida and "
in Georgia (Table 2); and chemical analyses of rocks from 7 Florida
wells are given.
Figure A is a map of Florida showing the locations of the 27 wells
and the counties in which they were drilled. Eight wells in Table 1 not
listed by Applin (1951) are named and located under "Remarks,"
where the source of information also is indicated.
The collection of specimens described in this report, together with
125 thin .sections, have been deposited with the Florida State Bureau
of Geology in Tallahassee.

PETROGRAPHY OF FLORIDA
IGNEOUS-METAMORPHIC ROCKS

The igneous rocks of Florida and southern Georgia include a (prob-
ably) time-related group of diabases, basalts, and rhyolites that are
present from the state line south as far as Lake Okeechobee. Their
K-Ar dating-from 89.3 2.2 to 183 10 m.y.-indicate a Mesozoic
age, and the volcanism is presumably correlative with the widespread
Mesozoic volcanism of the North American Atlantic seaboard and the
Gulf Coast.
These Florida igneous rocks appear to be a southward continuation
of the rocks penetrated in southern Georgia (Milton and Hurst, 1965).
In Glynn County, Georgia, just north of well No. 1 (Table 1; Fig. 1),
which was drilled into diabase, the Humble Oil and Refining Co. No. 1
W. C. McDonald penetrated granophyre from 4,732 to 4,737 ft.
Granophyre commonly is found as a border phase, normally at the top,
of large bodies of diabase. In Clinch County, Georgia, Timber Pro-
ducts Co. No. 1 Wiley P. Ballard, Jr., penetrated amygdaloidal basalt
from 4,210 to 4,232 ft; Brady Belcher et al. No. 1 Lem Griffis pene-
trated rhyolite and welded tuff from 4,348 to 4,588 ft. In contiguous
Echols County, Georgia, in Hunt Oil Co. No. 1 Superior Pines, dia-
base intrudes Paleozoic black shale from 4,115 to 4,150 ft (approx.).
Table 1 and Figure 1 show the presence of very similar rocks in the
northern Florida counties.

"The term "basement" is used variously by different writers; for the purposes of this
report, we define it as crystalline, igneous, metamorphic and unmetamorphosed sedi-
mentary rocks of early Paleozoic or older age, underlying unmetamorphosed (post-
Paleozoic) sedimentary rocks that may contain oil or gas. Some Paleozoic and post-
Paleozoic pre-Cretaceous sedimentary rocks in Florida are intruded locally by ig-
neous rocks, some of which have been dated by radiometric methods and are described
in this report. Unquestioned regionally metamorphosed rocks (e.g., mica, garnet, staur-
olite, kyanite, sillimanite schists, or marbles) have not been found in Florida.

BULLETIN NO. 55

12

Baked shale
Figure 1. Columbia County, Florida, J. P. Cone No. 1, Humble Oil and Refining
Company, 3520'-3529' Top 7 feet.
Carbonaceous shale, with disseminated andalusite (?) Ordinary light,
X22.5.

The association of diabase or basalt, tuff, rhyolite, and granophyre
is so characteristic of many regions of the world that it does not re-
quire emphasis here.
These rocks are found as far south as Lake Okeechobee (e.g., basalt
in St. Lucie County on the east coast, basalt and rhyolite in Highlands
County in southern central Florida, and rhyolite in Hillsborough County
on the west coast). Evidently Mesozoic volcanism extended across
most of the state.
Bass (1969) refers to "The two wells known to penetrate basalt, the

BUREAU OF GEOLOGY

(Hardee County Humble) Keen and (Highlands County Humble) Carl-
ton" as the southernmost . "and speculates as to a distinct province
of mafic extrusive rocks in southern or southwestern Florida .. ." which
"may be considerably younger than the rhyolitic rocks . ." However,
it may be noted that basaltic rocks exist in northern Florida (Milton and
Grasty, 1969) not to mention Georgia (Milton and Hurst, 1965).
The terms "diabase" and "basalt" are used in this report with the
understanding that they may in some cases refer to essentially the same
rock, crystallized under varying conditions from the same body of
magma. The chilled upper margin may have a basaltic aspect, whereas
the more slowly cooling deeper magma may have the diabasic (ophitic)
texture.
Similar considerations apply as to Gough's (1967) geophysically-based.
interpretation of a northeast-southwest "Appalachian" belt of volcanics,
some two hundred kilometers wide, across Florida, through the Gulf of
Mexico to the Campeche region; the northern boundary of this belt is
held, following Applin (1951) to divide Silurian and Ordovician sedi-
mentary rocks from rhyolitic lava, pyroclastic rocks, and granite-diorite.
Bass cites the two basalts mentioned above as part of such a belt.
All this suggests the futility of basing broad conclusions on meager
data.
In central Florida, another group, giving much earlier dates, includes
metabasalts in Volusia County, "granites" or "alaskites" in Lake and
Orange Counties, "granite" and dioritee" in St. Lucie County, and
"metabasalt" in Hillsborough County. Age determinations on this group
range from 226 6 (or 224 3) m.y. through 308 5 m.y. to 480
100(?) m.y. or from Early Triassic or Late Permian through Middle Penn-
sylvanian to Early Cambrian. In two wells volcanic rock overlies meta-
morphic rock types-in St. Lucie County basalt overlies "granite" and
dioritee," and in Hillsborough County rhyolite and welded tuff overlie
metabasaltic agglomerate.
The relation of the basalt overlain by unaltered Upper Jurassic or
Lower Cretaceous sediments (Applin and Applin, 1965) in St. Lucie
County to the "granite" and dioritee" just below is an unsolved
problem. Is the basalt a flow over a granite-diorite floor? The age of the
basalt, which is similar in general appearance to other presumably Meso-
zoic southeastern basalts, has been determined (89.3 2.2 m.y. = Late
Cretaceous), but the underlying "granite" has been dated as Early Tri-
assic and the dioritee" as Early-Middle Pennsylvanian (Table 2). These
two disparate ages, however, may reflect decreasing thermal metamor-
phism downward from a basalt flow, with correspondingly diminished
argon loss as demonstrated by Westcott (1966). Differential argon loss
due to the degree of alteration of the dated specimens also could cause
the variation in ages.

Table 2.-Isotope dating of Florida (and Georgia) rocks.

Vol. of
Radiogenic
K20 Argon-40
%, (nmm:;l/ of
sample)

7 Age
Atmos. and
Contam. Error
(m.y.)

24 Highlands County, Florida
Humble Oil and Refining Co.
No. 1 G. C. Carlton Estate

26 Hardee County, Florida
Humble Oil and Refining Co.
No. 1 B. T. Keen

19 St. Lucie County, Florida
Amerada Petroleum Co.
No. 2 Cowles Magazine

12,664 0.308 0.007 1.96 X 10-3

19.0 183 10 RG-I. Rock is very fined-grained. holocrystalline
hasalt, with rare phenocrysts of plagioclase. Con-
tains 60 percent fresh feldspar, 25 percent cloudy
clinopyroxene, and 15 percent olive-green-brown
serpentine after olivine(?). Slightly altered.
Whole rock. Grasty.

11,853 3.49 0.05 1.71 X 10-2 8.2 143 7 RG-2. Very fine-grained basalt which has suf-
1.77 X 102 11.2 147 3 fered low-grade metamorphism with no fresh
feldspar and all mafic minerals chloritized.
Highly altered. Whole rock. Grasty.

12,734 2.085 0.048 3.59 X 10-2

12,744

12,744-8
12,748

39.4 89.3 2.2 Basalt, dark-gray granular rock with calcite
blebs up to several millimeters across. Dia-
basic texture; mostly plagioclase laths with
large olivines completely replaced by bluish-
green chlorite and ore grains. Some calcite re-
placing pyroxene(?). Whole rock. Grasty.
399 Chloritized biotite K-Ar Bass
148 Plagioclase
530 Chloritized biotite Rb/Sr
470 Hornblende K-Ar

12,744 2.29 0.01 1.79 X 10-2 13.5 226 + 6 RG-8. Rock has acid composition and granite
1.80 X 10-2 10.3 224 t 3 texture with 10 percent quartz, 30 percent bio-
tite, and 30 percent plagioclase of which 30-50
percent has been altered to sericite. Biotite shows
slight alteration to chlorite. Quite altered. Whole
rock. Grasty.
12,748 1.24 0.01 1.38 X 10-2 10.4 308 i 5 RG-9. Diorite with 20 percent quartz, 30
percent brown-green hornblende, 10 percent
pale brown biotite associated with horn-
blende, and 30 percent fresh plagioclase. Rock
is fresh. Whole rock. Grasty.

No.
(Table 1)

Location
Operator
Well

Depth of
Sample
(ft)

Remarks

Table 2. (Cotntinued)

Vol. of
Radinogcniu
K2() Argon-1
m', (m3/g pl
sample)

Age
Atoills. arld
Contain. Error
(cl.cU.)

20(1 (O)cc a Ci.(..ntl lFloridal
Hliumli Oil and cHfinicig Co.
No. 1 Hfaynima

21 Ostola Count),. Floridat
Hunimbl Oil .and 1Rfinini C(o.
Carrccll No. 1
15 Volisia Countv, Florida
Sun ()il Co.
No. 1 P'o'll L.and Co.

Mitchliel County. Georgia
Stanolind Oil and Gas Co.
No. 1. J. H. Pullen

8,781 5.32 -0.01 3.19X 10-

.,9.53-.5,95 1

5,955.5-5. ,95S
5,951-5,955

.5,95.5.5-5,9.5

7,375 0.558 o.010 .56i X 1lo-:

18.6 17:3 l(G;- 11. lihyolitic ttl' with very fine-graimed
Matrix probably of quartz and feldspar. (on-
lains rounded crystals. \.nocrasts or frag-
lmnt, of (%\r. conlllll)on quartz, (commnonl al-
tcred alkalic feldspar, and (rari ) plagioclase
alnd rock fragments of( slightly alerted bas.all.
Whole rock. (;rasl.
53;0 Felhispar Rh/Sr Bass

K2(). 0.93 )percent. K41 ppm ).93. Ar-41 p)pm
0.03:2. r.icltmo nic Ar4" 92 percent. Ar40/K40
0.032.5. Age 180I m.%. (Age ma hei los Icn 20
prcentcct or mort because (of variable argon re-
tenltivity of K-lwaering mineral. o'f sample., 11.
Thoma's. H. Marn in. P. Elimore. and H. Smitlh,
analysts, US(;S.
6:31 1lornfels biolile Hb/Sr Bass
159 Hlornblend( indiorite K-A.r Bass
c 12 P'laioclas,
524 Hiotite indioritc hornfils K-Ar Bass
:39:3 lornblendcnd ndiorite hornfels K-Ar Bass

17.5 182 5 H(G-3. Dialas sho\ ing typical dark aiglitic
pyrox\enil, and light iplialgoclase fci'(spar. Holo-
crystalline, frc e of alteration. Very fresh rock.
\'holc rock. G(ratly.

No.
(Table 1)

Location
0()f)rator
\V'.ll

Depth qof
Sampll
(ft)

HRioark.

Table 2. (Continued)

Vol. of
Radiogenic
K20 Argon-40
(% (unml3lg of
sample)

'7 Age
Atmos. and
Contain. Error
(m.y.)

Echols County, Georgia
Hunt Oil Co.
No. 2 Superior Pines

Chattahoochee County,
Georgia
Cusseta (water well)

4,130 0.813 0.037 5.42X 10 :

1,200-1,205 0.43 0.007 4.69 X 10-3

61.7 191 15

HG-5. Rock chips from same rock type but
with one fine-grained phase and one medium-
grained phase. May he from chilled margin and
coarser grained interior of either dike or flow
or, more likely, a basalt and a diabase. Fine-
grained phase has 20 percent plagioclase phe-
nocrysts in matrix of very-fine grained
opaques and pyroxene (?) with needles of pla-
gioclase and some iddingsite after olivine (?).
This phase is slightly altered. The medium-
grained phase has a diabasic texture with 30
percent fresh plagioclase, 40 percent augite,
and 10 percent interstitial iddingsite after
olivine (?). Opaques occur as accessories. This
rock is slightly altered, with 10-20 percent
material which is probably devitrified glass.
Whole rock. Grasty.

67.5 303 15 RG-6. Hornblendite consisting essentially of
Slue-green hornblende, clear quartz, cloudy al-
kalic feldspar, brown biotite, and pale-green
chlorite. Rock was run as hornblende separate
of 70-120 mesh. Whole rock. Grasty.

Table 2a. Age determinations Amerada Petroleum Corp. Cowles Magazine No. 1

Sample
Depth Material

127:34 Basalt Grast)
1274 Granite

Chloritized biotite from schist Bass
and quartz diorite gneiss

Plagioclase from quartz diorite
gneiss
12748' Diorite
Hornblende in diorite (amplhio-
lite)

Grasty
Bass

Analyst Method Age

K-Ar 89.3:2 m.y.
226 6 inm..
224 i-3 m.y.

Sr /Sr 86 53i ni.y.

K-Ar 399 m.y.
148 m.y.

308 5 m.y.
470 m.y.
503 m.y.

No.
(Table 1)

Location
Operator
Well

Depth of
Sample
(ft)

Hemarks

BUREAU OF GEOLOGY

Another question is whether the "granites" of Florida are really gran-
ites, or arkose altered by contact metamorphism. Altered sedimentary
rocks are well known in regions of Triassic volcanism in many localities
in the eastern United States; they are associated with major tectonic
disturbances that exposed large volumes of granitic rocks both to rapid
erosion, and, in places, to hydrothermal alteration. The "granite" in
the Pierce County, Georgia, Adams McCaskill wells (Milton and Hurst,
1965) may have such a history. Further, granophyres of superficially
granitic aspect and composition are well known as differentiates of large
diabase bodies, and many of the so-called "basement granites" in Georgia
strongly suggest a granophyric origin (e.g., Glynn County, Georgia,
Humble Oil and Refining Co. No. 1 W. C. McDonald).
No unambiguously metamorphic rocks-such as mica schist, garnet
schist, chlorite-kyanite-sillimanite schist, or marble-have been found
in Florida. The rocks termed "granite" or dioritee" may be contact-
metamorphosed sedimentary rocks, or thermally altered phases of
igneous intrusives. Whether or not drilling in Florida has penetrated a
truly metamorphic basement of Precambrian or even early Paleozoic
age is, in our opinion, still an open question.

DATING OF FLORIDA AND GEORGIA
IGNEOUS-METAMORPHIC ROCKS

The K-Ar dates in Table 2 were determined at the University of Tor-
onto by Robert Grasty and M. N. Bass (1969), with the exception of
that for the Volusia County, Florida, hornblende diorite or metabasalt,
which was determined at the U. S. Geological Survey. For the rocks
dated by Grasty, duplicate potassium determinations were made on each
sample, with lithium as an internal standard and sodium as a buffer.
Argon, extracted in a bakable glass fusion system, was mixed with
"spike" argon-38 and analyzed by an MS 10 mass spectrometer, as
described by Farrar et al. (1964). Six measurements of the argon-isotope
ratios were made on each gas sample. The limits of error are standard
deviations deduced from the errors in both the potassium and argon
measurements. In the University of Toronto laboratory, the standard
deviation of repeated measurements on the same sample is generally less
than 2 percent and analyses of interlaboratory standard samples show
that systematic errors are also less than 2 percent (Baksi et al., 1967, p.
6306). Repeat measurement on RG-2 and RG-8 confirmed this accu-
racy. Constants used in the calculations are XB = 4.72 X 10-10yr-1, xe =
0.584 x 10-10yr-1, K40 = 1.19 X 10-2 atom percent.
The K-Ar ages range from Late Cretaceous to Early Ordovician or
Early(?) Cambrian. Except for the youngest and the three oldest, the ages

BULLETIN NO. 55

are within a range from Late Jurassic to Early Triassic. The two dates
(middle Carboniferous) for homblendite from Chattahoochee County,
Georgia, and diorite from St. Lucie County, Florida, are similar to dates
from late Paleozoic volcanic rocks recognized elsewhere in the Appala-
chians.
The youngest age whether or not valid, 89.3 + 2.2 m.y., is by no means
the youngest to be reported in the Applachian region; Fullagar and Bottino
(1968) give a Tertiary age (30 15 m.y.) for felsite from HighlandCounty,
Virginia.
The oldest age, 480 +- 100(?) m.y. (or 524 m.y.) from Volusia County,
Florida, "metabasalt," is within the range of the Cambrian to Ordovician
age of the North Carolina "Slate Belt" rhyolites determined by Hills and
Butler (1968). Some workers have referred the Georgia-Florida volcanic
rocks in part to the "Slate Belt" series. Three ages obtained by Bass (1969)
on samples from Humble Oil and Refining Co., No. 1 Carroll, Osceola
County, Sun Oil Co., No. 1 Powell Land Co., Volusia County, and Amerada
Petroleum Corp. No. 2 Cowles Magazine Inc., St. Lucie County, are re-
spectively, 530, 524, 530+ m.y. These determinations indicate a Middle
Cambrian age.
The K-Ar and Rb/Sr dates of Bass (1969) cited in Table 2 are discussed
in detail in his paper.

CHEMICAL ANALYSES OF FLORIDA
IGNEOUS-METAMORPHIC ROCKS

Table 3 gives the chemical composition of 11 Florida igneous-metamor-
phic rocks. Because these results are from small and generally isolated spec-
imens, their present value is limited; however, as more information on the
Florida subsurface becomes available, comparative studies may be found
useful.
The analyses have been computed in terms of normative minerals, in
Table 3a. This often gives a somewhat clearer picture of what meaning the
analyses may have, although it must be emphasized that the data presently
available is altogether insufficient for any meaningful generalizations.
To illustrate this we may compare the analyses or rather the norms, 9 and
11, or volcanic ash and rhyolite, respecitvely, from Putnam County and
Hillsborough County, 150 miles apart. The two norms are indeed similar
- high normative quartz, substantial normative corundum orthoclase, and
albite plagioclase; normative hematite and magnesite. It would appear that
these two rocks are part of one body. Yet a second specimen of the Hills-
borough County rock, analysis 10, unquestionably from the same body,
shows neither normative quartz nor corundum, strongly calcic plagioclase,
much, not little, mafic minerals, and neither hematite nor magnesite.
Again, the two very similar analyses of diabase, 5 and 6 from Taylor

Table 3. Chemical Analyses of Florida Igneous-Metamorphic Rocks' '

1 2 3 4 5 6 7 8 9 10 11

SiO2 63.7 46.8 68.7 57.0 50.9 52.8 51.7 57.1 73.3 48.3 59.1
A1203 15.1 17.1 15.4 16.8 16.6 15.3 17.3 13.9 13.8 11.0 13.0
Fe20)3 3.3 3.5 .74 3.0 4.3 2.2 10.2 4.1 2.5 :3.1 3.8
FeO 2.6 6.1 2.6 4.9 4.6 9.9 .72 3.4 .51 5.7 1.2
MgO 3.3 10.5 :3.0 5.6 6.2 1.4 3.1 7.2 .93 9.2 3.0
CaO 1.1 3.2 3.7 6.8 6.3 8.9 .54 1.3 .02 8.3 4.1
Na2O 3.0 1.2 1.9 1.6 3.3 2.5 1.1 2.7 2.4 1.5 4.3
K20 2.6 3.3 .95 .90 .57 .68 5.5 2.2 3.2 3.1 3.6
H20 .32 .55 .14 .06 2.5 .46 3.5 .37 .13 1.1 .35
H2O+ 2.9 5.4 2.1 1.9 1.9 1.1 3.6 2.1 1.7 2.9 .15
T102 .62 .8.3 .45 .75 1.2 1.1 1.2 .73 .32 .94 .32
P20s .20 .12 .28 .28 .17 .17 .36 .22 .08 .16 .04
MnO .11 .11 .07 .17 .08 .22 .07 .14 .03 .19 .23
CO2 .75 .52 <.05 < .05 .46 <.05 .15 .45 <.05 .95 6.1
Sum2 100. 99. 100. 100. 100. 100. 99. 9 9. 9. 99. 99.
Powder density by
sink float 2.72 2.72 2.72 2.80 2.60 2.95 2.52 2.80 2.72 2.80 2.70

SAnalyses by Paul Elmore, L. Artig, S. Botts, G. Chloe, H. Smith. J. Kelsey, and J. Glenn, U. S. Geological Survey, using methods described by
Shapiro and Brannock (1962), supplemented by atomic absorption techniques.
2 Rounded to nearest whole number
3 For location, lab. no., and remarks see below.

Well
Analysis Locality Lab. No. Remarks
No. (Fig. 1)

21 W168611

19 W168612

19 W168613
19 W168614
5 W168615
5 W168616

Osceola County, Florida; Humble Oil and Refining Co. No. 1 Ray Carroll; 8,034-8,042 ft. "Al-
tered and veined biotite granite" (F. F. Grout in Applin, 1951). Possibly hydrothermally
altered arkose (C. M.) (Fig. 2c).
St. Lucie County, Florida, Amerada Petroleum Co. No. 2 Cowles Magazine, amygdaloidal ba-
salt, 12,734 ft. dated 89.3 2.2 m.y. (Fig. 2d).

"Granite," 12,744 ft. dated 226 6 m.y. 224 -3 m.y. (Fig. 3a).
"Diorite," 12,748 ft. dated 308 5 m.y. (Fig. 3b).
Taylor County, Florida. Humble Oil and Refining Co. No. 1 G. H. Hodges, 6,162 ft. diabase.
Diabase, 6.216-6.219 ft.

Table 3. (Continued)

Anallyis Iocality Lah. No. Remarks
No. (Fig I)

7 15 WI68fil7 Volusia County. Florida. Sun Oil Co. No. I Powell Land Co.. 5,919-5.922 ft. "weathered"
volcanic rock now clay.

8 10 W\li6Nfil Flagler County. Florida. Ilumble Oil and Refining Co. No. I j. W. Campbell. 1.62 0'.- .626 ft.
Hydrothermally altered basalt and rhyolte tuffT.

9 II W f861(9 'utnam County. Florida. Sun Oil Co. No. I II. E. W\estiury et al. 3,879-3,n8! ft. Volcanic
ash.

10 27 W 1\\ 620 IHillshorough County Florida. Humble Oil and Refining Co. No. I T. S. Jameson. IO019-10.022
ft. Hhyolite or welded tuff.

11 27 \VWfi621 Rhyolite, 10.115i-10.125 It.

Table 3a. Florida igneous-metamnorphic rock norms

1 22
3)9.9 9 3.18H9
7.351 7.228
I5..6(i 19.501l
25. 183 101.1. I
11.8011

1h,(16 26i.150
1.229 7.I 11

Ap.aite .171 .28I
Cal ite 1. 19 I. I I
M%.il site .179 -

Snlic 79.019 5.1,875
FImiic 17.312 11. 112

9(6i.92* 9.3.2N7
lhis and other totals a;re c onlputer figures.
T1hi norm has beiin ctliolputed with .ON', I'2o() a;td

1 .1
40.923 19.709
5.305 1.617
5.f61 5.318
16.077 1 .539
16.21(0 11.589

7.172 1 1.917
3.530 5.597

.5
7,121
.573
1. 6N8
27.921
27.2 16

15. 11
1.0(62

6 7
6.901 183.022
9.0 1 I
1.018 12.501
21.151 1 I.N16
28.517
5.933
10.958 7.1I96
14.955

1.07:3 1.350 6.235 3. 190

.855 1.121 2.279 2.089

.66( 3 .6 .3 .103 .103
.11 .11 1 1.0 16 .114

81.129 71.771 66.221 (60.591
1:3.726 236,095 28, 165 37.611

97..55 97.66( 9 1.690 98.231

10.200
1.i70
1211
.N5 I
.INN
.188

71. 113
20.M 16

92.2594

13.01100
22.817
17.450

17.9312
1.911

5.915

1. 186

.521
1.021

67.735
28,718

96. 153

9"0 10

18.91(0 Is. 19
20. 10S 12.6193
22. i12

2.202 1 .512
5.711
2. 38
.769
.911 1. 195
I.872 -
.(60 1.785

179T
2.1il1
.096 -

91.382 53.32:3
5.688 12.127

97.070 95.151

11
19.S32
2.030
21.273
36.385

.802

3.691
1.255.
.fiON

.095
7.221
5.612

79.520
19.275

98.795

.02'; CaO. ati h reduced to .IMI',. lo conforn with thi t oiiputer program.

Qu,)aIirtz
Corunldum
Orthotlase
Albite
Anorthite
\Wollastonite
Enist.tite
Ferrosilite
Forsterite
IFyiilite
Mlagnetitr
Henmatite
Ilinenit,
Hulltl.

1.785

1.17S

5.075

1.576

BUREAU OF GEOLOGY

County, referred to above (pages nmm...) do show definite difference
from the St. Lucie County amygdaloidal basalt, some 250 miles distant;
first being presumably Triassic-Jurassic, the second dated as much
younger, namely upper Cretaceous (89.3 m.y., Table 2). However, com-
paring all three analyses of the St. Lucie County rocks, while the three an-
alyses (2, 3, 4) are remarkably similar, their isotopic ages are widely dis-
parate.
Thus we may conclude by observing that the value of these analyses is
for the present limited to what they may contribute to the understanding of
the individual rock specimen, and that attempts to use them for broad cor-
relative purposes are futile.

DESCRIPTIONS OF
FLORIDA "BASEMENT" ROCKS

NASSAU COUNTY
ST. MARY'S RIVER OIL CORP.
HILLIARD TURPENTINE CO. NO. 1 4824' T.D.
Completed 1940 Well locality 1 Applin (1951) No. 67
Triassic diabase in Paleozoic shale
Cole (1944) reports that this well was begun in 1936, and completed
eight years later at a depth of 4817 feet. He briefly reviewed earlier ac-
counts by Campbell, Schuchert, and Munyon, and discussed extensively
the micropaleontology of the well. He also considered in detail the non-
fossiliferous rocks, below the marine sediments (Upper Cretaceous Tus-
caloosa).
Below the Tuscaloosa, which in this well consists of 380 feet of gray,
hard, calcareous and glauconitic sandy shale, with shark's teeth, is 155 feet
of dark gray, hard shale, devoid of fossils, followed by diabase to the bot-
tom of the well. Applin (1951) states that the diabase underlies Paleozoic
black shale, later confirmed by paleontologic studies by J. Bridge and J.
Berdan.
Cole, after considering all the evidence, observed, "It is the opinion of
the writer that the section from 4640 to I7'>, (the 155 feet of unfossili-
ferous shale) represents a non-marine phase and that the age of the rocks
is Triassic. The writer believes that they are equivalent to the Newark ser-
ies." As for the diabase which intrudes the shale, a study by T. Osborn
Fuller, cited at length by Cole, convinced him that it is of Newark (Tri-
assic) age.
Nevertheless, Applin (1948) referred to the published data as "conflict-
ing and inconclusive" but correctly included the well as among those which
entered "Paleozoic black shale."
Berdan (written communication, May, 1970) states that "a sample of

BULLETIN NO. 55

rather large chips of dark gray shale from a depth of 4700-4800 feet con-
tains a small fragment of eurypterid integument which shows the charac-
teristic scales of the genus Pterygotus. This genus ranges from the Ordovi-
cian into the Devonian. However, a core of dark gray shale from Sun Oil
Company J. H. Tillis No. 1 well in Suwannee County also contains Ptery-
gotus, which was considered to be Silurian in age by Kjelleswig-Waering
(Jour. Paleont., v. 24, no. 2, p. 229-231, 1950), who described it as P.flor-
idanus. It seems probable that the shale in the Hilliard well is correlative
with that in the Tillis well, and is also Silurian."
Two thin sections of the diabase, one from 4818'-4819', the other 4823'
are both fresh unaltered diabase; the lower one is somewhat more fine
grained.

COLUMBIA COUNTY
HUMBLE OIL AND REFINING CO.
J. P. CONE NO. 1 4444' T.D.
Completed 1949 Well locality 2 Applin (1951) No. 42
Diabase in Paleozoic shale
Applin (1951) lists six occurrences of diabase and amygdular basalt
sills in black shale of Paleozoic age at
3529'-3562' 4193'-4195'
3564'-3565' 124'"-4251'
4191'-4192' 4267'-4270'
Cores are available from 3520' to 4281'.
Core 115 3520'-3529' recovery 8'
Top 7' is gray carbonaceous (burns white) shale, with pyrite and a
little sphalerite along bedding planes. Microscopically the shale is seen to
contain innumerable clear colorless sericitic grains, with rectangular or
hexagonal cross section (Figure 1). Most show concentration of the dusty
shaly matrix material in the interior of the grain, with clear borders; this
suggests that the grains may be sericitized andalusite, in which such seg-
regation is normal.
Bottom 1' is at the contact of black shale and underlying diabase. It is
a light colored fine grained rock with calcite layers and numerous small
rounded pyrite nodules. In thin section (Figure 2) the rock is seen to
consist almost wholly ofplagioclase laths and calcite (replacing augite?) and
pyrite (replacing iron-titanium oxide?).
Core 119 3541'-3543' top part of core is hard fresh diabase.
Core 120 3543'-3555' top part of core.
This is a perfectly normal diabase, with typical mineralogy calcic
plagioclase laths and subhedral augite; with minor black ilmenite grains
and greenish chlorite (Figure 3).

BUREAU OF GEOLOGY

Altered diabase
Figure 2. Columbia County, Florida, Humble Oil and Refining Company J. P. Cone
No. 1, 3520'-3529'. Bottom foot of core.
Shows (white) plagioclase feldspar. The dark areas represent mostly cal-
cite (replacement of pyroxene?) and (most of large black aggregate left of
center) pyrite, which may have replaced ilmenite-magnetite. Ordinary light,
X28.5.

Core 121 3555'-3562' top and bottom of core, hard fresh fine
grained diabase. No different from preceding.
Core 122 3562'-3589' Sample from second 10 ft. of core. Greenish
gray shale with calcite-pyrite layers; also red heulandite(?). Orthoconic
cephalopods occur in this shale (Roland Brown, J. M. Berdan, U.S.G.S.).
Core 149 4181'-4206' Sample from bottom of core, amygdaloidal
basalt. This is a fine grained gray-green vesicular rock, with blebs of coarse
white calcite up to an inch across; some of the smaller ones are reddish in
part. There are also small pyritic segregations.

BULLETIN NO. 55

tilb
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Diabase
Figure 3. Columbia County, Florida, Humble Oil and Refining Company J. P. Cone
No. 1, 3543'-3555'. Top part of core.
Normal diabase, with typical laths of calcic plagioclase and euhedral
augite between the feldspars. Ordinary light, X28.5.

In thin section, the rock shows a poorly crystallized dark turbid ground-
mass, in which are strewn in abundance small colorless or faintly reddish
augites. A few of these are larger than the others, and consist of interpene-
trating twins of several individuals. Iddingsitized (?) euhedral olivines
are small but numerous. The more definitely colored augites are reddish-
violet, show axial dispersion and are probably titaniferous. The calcite
segregations often show an irregular peripheral zone of brown substance,
perhaps serpentine, and some have spherulitic development (Figures 4
and 5).
Core 151 4231'-4256' middle third, gray amygdular basaltic rock,
with irregular calcitic amygdules.

** ;?'

P' da8:"'
--. ...

BUREAU OF GEOLOGY

Amygdular basalt
Figure 4. Columbia County, Florida, Humble Oil and Refining Company J. P. Cone
No. 1, 4181'-4206' Sample from bottom of core.
Amygdular basalt; at the lower right is a large amygdule of radially fi-
brous calcite, at the upper right, a similar amygdule with olive brown ser-
pentine and calcite. The crystals in the basalt are mostly serpentinized oliv-
ine and unaltered augite. Ordinary light, X14.

Core 152 4256'-4281' Sample from middle of core. Recovery 24'
"1 ft. of core is like material submitted, remainder is black shale" Louise
Jordan (Sun Co. geologist, now deceased).
The sample of the 1' zone consists of two somewhat different rocks, one
in contact with black slaty shale. The contact phase, about one inch wide,
is light gray-green, markedly pyritic and vesicular; it grades into a darker
more uniformly-textured rock, like the second specimen, which, however,

BULLETIN NO. 55

4 x2t~ *I.,
4.44

Basalt-calcite (hydrothermal) contact
Figure 5. Columbia County, Florida, Humble Oil and Refining Company J. P. Cone
No. 1, 4181'-4206'. Sample from bottom part of core.
Shows contact of basalt and coarse (hydrothermal) calcite. Near the center
is a mass of calcite partly enclosed by olive-brown serpentine. (The clear
area is where the section broke apart during grinding.) Crossed nicols, X14.

also shows scattered pyritic-calcite amygdules. In thin section, the contact
shows a poorly crystallized turbid '.r -I I., with small poorly-developed
plagioclase crystals, and no well-developed augite. There are large ill-
defined light colored areas, with skeletal magnetite and thin laths of brown
hornblende. Often the middle of these areas is calcitic. (Figure 6). The
darker rock, however, away from the contact, is well crystallized, and
consists largely of reddish-violet tinted augite in stubby prisms, some
larger than the others. There are also chloritized olivines, and inconspic-
Uous poorly-developed feldspar in the groundmass. The few large calcite

BUREAU OF GEOLOGY

Amygdular basalt
Figure 6. Columbia County, Florida, Humble Oil and Refining Company J. P.
Cone No. 1, 4256'-4281'. Sample from middle of core. Ordinary light, X14.

vesicles contain euhedral pyrite and are associated with a colorless iso-
tropic mineral, possibly analcite.
In this well basalt-diabase sills are found from 3529' to 4281', or through
about 750 feet. The sills are intruded into 962 feet of fossiliferous black
shale considered to be Late Silurian or Early Devonian in age (Berdan
and Bridge, 1951, p. 69). The association of typical diabase with typi-
cal basalt suggests that the two rock types reflect differences of physical
conditions under which these bodies crystallized, from a common mag-
matic source.

BULLETIN NO. 55

MADISON COUNTY
HUNT OIL COMPANY
J. W. GIBSON NO. 2 5385' T.D.
Completed 1945 Well locality 3 Applin (1951) No. 62
Diabase in Paleozoic shale
Igneous rock was not noted by Applin (1951) but cuttings from ,"i'-
5210' are greenish granular diabasic rock. It appears to be weathered,
but microscopic examination indicates hydrothermal alteration rather
than weathering. Calcite and bright green chlorite are abundant; very
little feldspar remains, it being replaced by fine grained serpentinic or
chloritic material. Black magnetite grains are numerous. Figure 7 shows
the microscopic aspect of this rock.

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Diabase (hydrothermally altered)
Figure 7. Hunt Oil Company J. W. Gibson No. 2, Madison County, Florida, 5200'-
5210' (cuttings).
This is volcanic rock, still showing original texture though the constituent
minerals have been altered considerably. Ordinary light, X28.

BUREAU OF GEOLOGY

The rock is a hydrothermally altered diabase. A core above it, at the
depth of 5154-5162 feet, is dark gray shale containing the trilobite Colpo-
coryphe exsul Whittington, 1953, which is considered late Early or early
Middle Ordovician in age (Berdan, 1970, written communication).

TAYLOR COUNTY
GULF OIL COMPANY
BROOKS SCANLON BLK. 42, NO. 1 5517' T.D.
Completed 1949 Well locality 4 Applin (1951) No. 82
Diabase-basalt
"5438'-5517' T.D. is diabase, probably a lava flow. Underlies elastic
rocks of Triassic (?) or Jurassic (?) ages." Applin (1951)
Specimens from Core 39 5448'-5453' (recovery 2 ft.) to Core 43 5512'-
5517' T.D. (4 ft. recovered, top) were studied. All are of very similar rock,
namely brown basalt with conspicuous green serpentinic material. Zeoli-
tization (red heulandite?) is locally conspicuous.
In thin section Core 43, 5512'-5517' T.D. (sample from bottom of
core), it is seen to have the characteristic texture of a basalt or diabase;
the calcic plagioclase feldspars and augite remain little altered, but the
larger crystals of olivine have been completely replaced by iron oxide and
iddingsitic material (Figure 8).

BULLETIN NO. 55

Figure 8. Gulf Oil Company Brooks-Scanlon Blk. 42, No. 1, Taylor County, Florida,
5512'-5517' (bottom of core).
Olivine (?) diabase. The black areas are limonitic replacements of olivine
(?) which is also represented by olive-brown serpentinic areas. Calcic
plagioclase and augite are fairly unaltered. Ordinary light, X22.

TAYLOR COUNTY
HUMBLE OIL AND REFINING CO.
HODGES NO. 1 6254'T.D.
Completed 1948 Well locality 5 Applin (1951) No. 83
Diabase-basalt
Applin (1951) states that this "well terminated in diabase gabbro. Un-
derlies early Mesozoic plastic rocks" and "6153'-6165' basaltic rocks; un-
derlies elastic rocks of Triassic (?) or Jurassic (?) age. 6165'-6254' T.D.
diabase gabbro."
Core samples are available representing some 96 feet of igneous rock,
from 6153'/ to 6249', all igneous rock.

BUREAU OF GEOLOGY

The upper ten or twelve feet of the volcanic rock differs from the
eighty-five feet of volcanic rock drilled below. The upper zone is highly
calcitic, with abundant calcite veins, micro-breccia, and other evidence
of possible contamination by ingested limestone. The lower zone is nor-
mal diabase. In detail:
Core 111 6151'-61' recovery 71', sample at 6153!2'
This is a light gray granular volcanic rock, cut by a vertical vein of cal-
cite, a quarter of an inch wide. (Fig. 9)
Gray or green volcanic rock, sample at 6155', and another core frag-
ment, somewhat coarser, with abundant oligoclase-andesine, are almost
completely chloritized and calcitized mafics. (Fig 10)
6156' calcitic agglomerate
6159'-60' gray green volcanic, with calcite veins

Figure 9. Humble Oil and Refining Co., Hodges No. 1, 6153;2', Taylor County,
Florida.
Basalt with calcite contact (?); somewhat calcitized basalt-diabase on
left, fine grained calcite on right. Ordinary light, X22.

BULLETIN NO. 55

Core 112 6161'-6.2' recovery 1' sample at top gray green volcanic
Core 113 6162'-80' recovery 18', sample at 6162' top gray green
volcanic agglomerate, with pyrite and calcite veins.
at 6162' bottom gray volcanic rock, chloritized mafics but feldspars
(oligoclase-andesine) perfectly fresh. Some fresh brown biotite. Calcite
veins. Texture rather coarse, grading into diabase.
This rock has been analyzed (Tables 3 and 3a, No. 5)
at 6165,2' gray volcanic rock, highly calcareous, probably a volcanic
breccia. (Fig. 11)
at 6167' coarse diabase
at 6175' coarse diabase

Figure 10. Humble Oil and Refining Co., Hodges No. 1, 6155', Taylor County, Florida.
Basalt-diabase. The pyroxenes, etc. are completely calcitized, but the
plagioclase feldspar is unaltered. Ordinary light, X22.5.

BUREAU OF GEOLOGY

S-J

Figure 11. Humble Oil and Refining Co., Hodges No. 1, 616533', Taylor County, Flor-
ida.
Calcitic explosion breccia? The rock consists of a calcite matrix with
rounded fine grained ash (?) and chloritic debris, as well as coarse fresh
angular particles of pyroxene, calcic plagioclase, highly altered biotite
and micro-pegmatite. Most of the lighter area in the figure is calcite; sev-
eral rounded ash (?) grains are shown. Ordinary light, X17.

BULLETIN NO. 55

Figure 12. Humble Oil and Refining Co., Hodges No. 1, 6216'-6219', Taylor County,
Florida.
Coarse fresh normal diabase, completely unaltered. Ordinary light, X17.

Core 115 6204'-6219'
at 6216'-19' diabase, no chlorite or calcite in thin section; a per-
fectly fresh normal diabase. (Fig. 12) This rock has been analyzed (Tables
3 and 3a, No. 6)
Core 116 6229'-6254'
at 6246'-49' diabase, with pyrite along cracks.
The two rock analyses are in general quite similar, as might be expected,
both being of diabase; however, the first shows both more oxidation of
iron and considerably more water especially H20-.

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BUREAU OF GEOLOGY

JEFFERSON COUNTY
COASTAL PETROLEUM CO.
E. P. LARSH NO. 1 7913' T.D.
Completed 1949 Well Locality 6 Applin (1951) No. 54
"Diabase and related kinds of volcanic rocks (7763'-7792' and 7850'-
7890'). Sills or dikes in elastic rocks of Triassic (?) age."
Applin (1951)
Samples (cores and cuttings) were examined from 7650' to 7913', in-
cluding the two igneous intrusives.
They are as follows:
7650'-7660' cuttings mostly red sandstone; no igneous rock.
7680'-7690' cuttings red and gray sandstone; no igneous rock.
7690'-7700' cuttings much diabase with red and gray sandstone.
This indicates a third sill or dike, besides the two indicated above.
7720'-7730' cuttings These are fresh unweathered diabase.
7760'-7770' cuttings diabase
7789'-7791' core (1 ft. recovered). This is fresh unweathered diabase,
similar to that from 7720'-7730', but somewhat finer grained. Figure
13 shows the typical diabasic micro-structure of this rock.
Another sample from this depth is cuttings, containing much diabase.

BULLETIN NO. 55

Diabase
Figure 13. Coastal Petroleum Company, E. P. Larsh No. 1, Jefferson County, Florida,
7789'-7791'.
This shows the characteristic texture ("ophitic") and mineralogy (essen-
tially augite, calcic plagioclase and ilmenite). The rock is practically un-
altered, the only replacement being of olivine (?) by chloritic or ser-
pentinic material. Crossed nicols, X28.

BUREAU OF GEOLOGY

7791'-7795' core (3 ft. recovered). Top foot this is a very fine
grained gray micro-porphyritic basaltic rock, showing some alteration -
calcitization and chloritization. It is illustrated in Figure 14. This abrupt
change in texture and composition within a few feet indicates that a given
magma may crystallize either as basalt or diabase in response to very lo-
cal conditions; and that correlations based on one or the other type of rock
are likely to lead to error. Below this, only sedimentary rock was found.
middlefoot. This is a shaly sandstone.
bottom foot. This is similar to the preceding, with less quartz. It may
be baked shale (Fig. 15).

Calcitized basalt
Figure 14. Coastal Petroleum Company, E. P. Larsh No. 1, Jefferson County, Florida,
7791'-7795'.
Although the plagioclase feldspars are unaltered, the mafic minerals
of the basalt are replaced by calcitic material. Ordinary light, X 28.

BULLETIN NO. 55

Baked shale (?)
Figure 15. Coastal Petroleum Company, E. P. Larsh No. 1, Jefferson County, Florida,
7791'-7795'.
Shows angular quartz particles in very fine grained dark crystalline
matrix. Ordinary light, X 28.

7909'-7911' (1,' recovery) This is a whitish sandstone, almost wholly
quartz, with strong evidence of recrystallization almost all the quartz
grains show peripheral secondary growth, and clay is recrystallized to seri-
cite. There is also green tourmaline, in minute grains, also probably auth-
igenic (Fig. 16 a, b).
7911'-7913' (1' ft. recovery) Sample from bottom 1 ft. 10 in. of core.
Two different specimens: One is hard rather coarse sandstone, light col-
ored; the matrix of the quartz grains however is well recrystallized into
pale green chlorite. The other specimen is rounded pebbles (1 cm. across)
of red very fine grained shale, possibly volcanic ash.

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Figures 16 a, b.

Sandstone

Coastal Petroleum Company, E. P. Larsh No. 1, Jefferson County, Florida, 7909'-7911'.
This shows features which may perhaps be related to thermal metamorphism. Many of the quartz grains show second-
ary enlargement, the original detrital grains being outlined by the dark rims seen in the illustrations, with new quartz

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BULLETIN NO. 55

In summary, a series of sandstones and shales was intruded by diabase
or related rock at (or not far above) 7690', 7720'-7730', and again at
7789'-91', 7791'-95'. Below this to 7913' T.D. there are indications of
volcanic activity, but no specimens of actual volcanic rock.

FRANKLIN COUNTY
CALIFORNIA CO. AND COASTAL PETROLEUM CO., NO. 2
Well locality 7
State Lease 224a. Latitude 29047'03" N Longitude 84'22'51" W
South Shoal area about 13 miles offshore from Carrabelle, Florida T.D.
10566' (driller), 10507' (electric log). Completed 1961.
This well drilled into 10 feet of diabase at 10460 ft. (Data from P. L.
Applin, written communication 1967).
Specimens are available as follows:
10318-19 10324-25
10320-21 *10325-26
10321-22 10326-27
10322-23 10327-28
10323-24 *10328-3212
These are all pinkish quartzitic sandstone (cored), well-indurated some
with white clayey specks. Figure 17 illustrates 10325'-10326'. The Sand-
stone from 10328'-1033212' contains much calcite.
S10460-70 10510-20
10470-80 *10520-30 (Figure 18, basalt-diabase). Figure19 baked shale.
10480-90 10530-40
10490-10500 10540-50
10500-10 10550-60
These all contain diabase fragments, admixed with sandstone.
"Thin sections

JACKSON COUNTY
HUMBLE OIL AND REFINING COMPANY
C. W. TINDEL NO. 1 T.D. '-2 1-,
Completed 1949 Well locality 8 Applin (1951) No. 53
Applin (1951) refers to this as follows:
"8890'-8932' Porphyritic hornblende basalt. A small intrusive or flow in
Paleozoic rocks," with a thickness of 42 feet. However, the overlying sand-
stone 8881'-8891' (top 5'2 feet) is a fine grained reddish sandstone show-
ing structures interpreted as being due to contact metamorphism, indi-
cating an intrusion rather than a surface flow. A specimen from the bottom
632 feet of this core is hard fresh fine grained basalt, showing marked
calcitization.

BUREAU OF GEOLOGY

Six specimens of the core from this well are:
Core 100 8521'-8526' (sic) fine grained red siltstone
Core 120 8737'-8742' fine grained gray siltstone
Both of these are similar to the siltstone specimens below the igneous rock.
Core 130 8881'-8891' (top 5, feet) fine grained light reddish brown
siltstone. It shows disturbance and internal dislocation (fig. 20), and is
interpreted as a mildly contact-metamorphosed siltstone overlying the
intrusive rock, represented by the following specimen.
Core 130 8881'-8891' (bottom 1 ft. of 62 ft. recovery) This is hard
fresh fine grained basalt, strongly calcitized. Abundant calcic plagioclase
is fairly fresh, as is also minor brown hornblende; but large areas in the

7'-.
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Figure 17. California Co. and Coastal Petroleum Co. No. 2, Franklin County, Florid2
10325'-10326'.
Sandstone with rounded quartz grains showing secondary growth. Wel
crystallized calcite and dickite (?) aggregates occur interstitially. Ordi
nary light, X36.

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BULLETIN NO. 55

thin section, formerly pyroxene or olivine, are now vague brownish ag-
gregates of calcite, chlorite, and clayey material. Small brownish euhedral
opaque ore grains, with somewhat large masses of pyrite, are fairly
abundant; and quartz filled amygdules are present. Figures 21a, b illus-
trate this rock.
Core 136 8987'-8997' is fine grained red standstone.
Core 141 9232'-9237' is fine grained gray calcareous siltstone, uni-
form in thin section, unlike the siltstone overlying the basalt.
Core 142 9237'-9242' is similar.

0.5 mm" ,

Figure 18. California Co. and Coastal Petroleum Co. No. 2, Franklin County, Florida
10520'-10530'.
Calcitized Basalt. The basalt consists almost wholly of fresh plagioclase
inan obscure matrix largely calcite; with some ilmenite. Ordinary light
X29.

BUREAU OF GEOLOGY

In summary, these four samples indicate that a 42 foot basaltic sill in-
truded a siltstone series in which the well bottomed 313 feet below the
igneous rock, at ''24- T.D. The siltstone contains plant fragments iden-
tified by S. IH. Mamay as Psilophyton s.l., indicative of an Early or Mid-
dle Devonian age (Berdan, written communication, May, 1970).

Figure 19. California Co. and Coastal Petroleum Co. No. 2, Franklin County, Florida
10520'-10530'.
Baked shale. The dark areas are calcareous, and appear to represent
foraminifera. The gray matrix is a mud-stone with minute angular quartz
particles. Ordinary light X17.

BULLETIN NO. 55

Figure 20. Humble Oil and Refining Company C. W. Tindel No. 1, Jackson County,
Florida, 8881'-8891' (top 5%).
Fine grained siltstone overlying basalt and showing flowage and other
metamorphic effects. Ordinary light, X13.

4. -. *

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Amygdaloidal (quartz) Basalt
Figures 21 a, b. Humble Oil and Refining Company C. W. Tindel No. 1, Jackson County, Florida, 8881'-8891'.
Quartz amygdule (bottom) surrounded by highly calcitized zone in basalt. Another large calcitized area, with very
minor quartz, is seen upper left. The slightly darker smaller areas are calcitized pyroxenes. Ordinary light and
crossed nicols, X28.

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BULLETIN NO. 55

WALTON COUNTY
PAN AMERICAN PETROLEUM CO.
J. R. SEALY NO. 1 T. D. 11948 FT.
Sec. 9 T1S R18W Center SEk SE }.
Completed 1950. Well locality No. 9.
Top ofvolcanic rocks 11910 ft. Fragments (cuttings) 11935'-11940' heav-
ily altered porphyritic rhyolite.
Data from P. L. Applin (written communication 1967). Specimens were
examined as follows:
11920'-11930' Sandstone, arkose and felsite
11930'-11935' Sandstone, arkose and felsite
11935'-11940' Rhyolite porphyry ash with obscure shard structures in
trix of plagioclase, phenocrysts. Also much sandstone,
etc. Figures 22, 23.

Figure 22. Pan American Petroleum Sealey No. 1, 11935'-40'; Walton County, Flor-
ida.
Sericitized rhyolite porphyry or ash, with feldspar phenocrysts. Ordinary
light X35.

BUREAU OF GEOLOGY

Figure 23. Pan American Petroleum Sealey No. 1, 11935'-40', Walton County, Florida.
Sericitized rhyolite or ash. Ordinary light X35.

11940'-11945' Rhyolite porphyry ash with obscure shard structures in
matrix of plagioclase, phenocrysts. Also much sandstone,
etc.
11945'-11950' Rhyolite porphyry ash with obscure shard structures in
matrix of plagioclase, phenocrysts. Also much sandstone,
etc.

HUMBLE OIL AND REFINING COMPANY,
J. W. CAMPBELL NO. 1 FLAGLER CO., FLORIDA
Completed 1947 T. D. 4632' Well locality 10. Applin (1951) No. 19.
"Mixed tuff derived from an igneous complex. Origin, sedimentary or ex-
plosive igneous action." F. F. Grout. P. L. Applin (1951) Applin notes that
the igneous rock was encountered at 4588' and drilling continued in such to
4632' T. D.

BULLETIN NO. 55

The samples available have two recorded depths, one of them "corrected"
12' less than the other. The depths cited above are "corrected."
Cores for the interval 4560' to 4575' were studied as follows:
Core 67 4560'-70' recovery 83' feet top, middle and bottom, all
friable white sandstone.
Core 68 4570'-75' top friable white sandstone; middle buff to red
friable sandstone; bottom hard indurated red sandstone.
The top of the igneous rock in this well is at 4588'. Possibly the change
noted in the last core 68 may be caused by the igneous rock found 13 feet
lower down; but this interval is not represented by any sample.
Cores beginning at 4601' in the igneous section were studied as follows:
Core 69 (top) 4613'-18' recovery 3 ft. corrected measurement 4601'-06'
(bottom) 4613'-18' recovery 3 ft. corrected measurement
4601'-06'
Both samples are rather fine grained volcanic rock, the first reddish, the
second darker. Whitish clayey material coats the surfaces and veins the core
pieces.
Core 70 (top) 4618'-4624' recovery 3' corrected measurement
4606'-12'
(middle)
(about 6" above bottom)
These three samples are similar to preceding.
(bottom 6" approximately) This is dark gray fine grained rock, showing
(in 1 inch fragments) no agglomerate structure or clay veining or coatings.
Core 71 4624'-4624%' recovery 6" corrected measurement 4612'-
4612%' This is a fine grained dark gray rock.
Core 72 4624V'-4626' corrected measurement 4612%'-4614' This
specimen is a fine grained gray rock, with white clayey patches. In thin sec-
tion shows a heterogeneous agglomerate of heavily altered basaltic debris
and quartzite particles, seamed with veinlets of calcite and, possibly, pum-
pellyite. Figure 24 illustrates this rock. Without the thin section, the rock
could be termed fine grained basalt, but this rock, and presumably the
others above it, are almost certainly altered volcanic ash.
Core 73 No recovery
Core 74 4627'-29' recovery 6" corrected measurement 4615'-
4617'
No thin section is available, but careful inspection under a binocular micro-
scope suggests that it is like the preceding.
Core 75 4627'-29' recovery 1' corrected measurement 4615'-17'
Similar dense dark gray fine grained.
Core 76 4630'-31' recovery 1' corrected measurement 4618'-19'
Similar
Core 77 4631'-32' recovery 1' corrected measurement 4619'-20'
Similar

40 BUREAU OF GEOLOGY

41... :V

/ t, .,

Figure 24. Humble Oil and Refining Company, J. W. Campbell No. 1, Flagler
County, Florida. 4624 -4626.

This is a volcanic agglomerate, perhaps hydrothermally altered ash.
Calcite hornblende veinlets cut the rock. The two light colored areas at the
left edge are aggregates of acicular pale green hornblende; the clear
areas at the right are granular quartz. The dark areas are mostly aggre-
gates of extremely fine black opaque material; a few are magnetite-
ilmenite. Under high i, ,,,,.,. r..... yellow epidote (?) and brown sphene
in irregular grains are seen. Ordinary light, X22.

Core 78 4632'-33' recovery 1' corrected measurement 4620'-21'
Similar
Core 79 4633'-34' recovery 6" corrected measurement 4621'-22'
Similar
Core 80 4634'-35' recovery 10" corrected measurement 4622'-23'
Similar
Core 81 4635'-36' recovery 1' corrected measurement 4623'-24'
Similar
Figure 24.. Hubl OladRfngCopanJ .CmbllN.1 ge

This~~~~~~~~~~;~ isavlcncaglmrte ehashdrtemll lerdah
Calit horblnd venesctterok h wih clrdaesa h
let dg ae g regte o aciula pale gre horblne th la
areas- attergtaegaua urz h akaesaemsl gr
gats f xtemlyfie bac oaqe atril; fw remaneit
ilmenite Une ihi...,,,..yllweioe()adbonshn

Similarlai agoeatpras yrteral ltrdah

BULLETIN NO. 55

Core 82 4636'-37' recovery 1' corrected measurement 4624'-25'
Similar. Some of the preceding have white, greenish, or in this core,
reddish veinlets. Some veinlets are mostly calcite; this one is a zeolite.
Core 83 ,I.:; -38' recovery 8" corrected measurement 4625'-26'
Similar
Core 84 4638'-39' recove:7 1' corrected measurement 4626'-27'
Similar; fine grained dark gray, with greenish veinlets one or two
millimeters wide. In thin section, an aggregate of rhyolitic and other igne-
ous fragments, including altered feldspars and pale green hornblende. Some
of the rhyolite fragments have micro-pegmatitic structure. (Fig. 25)
Core 85 4639'-40' recovery 1' corrected measurement 4627'-28'
Similar

S .-A

S,~ ,-.. -o ... .

Figure 25. Humble Oil and Refining Company, J. W. Campbell No. 1, Flagler
County, Florida. 4638'-4639'.
Volcanic agglomerate-ash. The clear areas are quartz; the finely dotted
area, lower left, devitrified glass. Coarse feldspar grains, and greenish
pyroxene (?), both heavily altered, can be seen. Ordinary light, X22.

42 BUREAU OF GEOLOGY

Core 86 4640'-41' recovery 1' corrected measurement 4628'-29'
Similar
Core 87 4641'-42' recovery 1' corrected measurement 4629'-30'
Similar
Core 88 4642'-43' recovery 9" corrected measurement 4630'-31'
Similar, with fine salmon colored zeolite in veinlets.
Core 89 4643'-44' recovery corrected measurement 4631'-32' T.D.
Similar. In thin section an agglomerate of shattered quartz grains,
basaltic fragments, altered feldspars and mafic minerals, and black opaque
dust and iron oxide. (Figs. 26a, b)
Bass (1969) gives petrographic date for a sample designated as
"4641-4642 ft. A sample of Core 87, from this depth, 1 ft. recovery is
fine grained dark gray tuff."

Figures 26a. b.

Humble Oil and Refining Company, J. W. Campbell No. 1, Flagler County, Florida. 4643'-4644'.
Volcanic agglomerate ash. The clear areas are mostly quartz, others are feldspathic. Large Carlsbad twinned
feldspars are seen in thin section, as large or even larger than the quartz aggregates, suggesting that the latter too
are of volcanic origin (phenocrysts) and not fragments of engulfed sedimentary quartzite or sandstone. Ordinary
light and crossed nicols, X22.

BUREAU OF GEOLOGY

PUTNAM COUNTY
SUN OIL COMPANY
H. E. WESTBURY ET AL. 3892' T.D.
Completed 1949. Well locality 11 Applin (1951) No. 25
"Volcanic ash and tuff." Applin (1951).
Bass (1969) has described core specimens from this well, as noted
below.
This well drilled into 19 feet of volcanic ash. Samples are available
from 3872' to 3892' T. D.
Core 190 3872'-74' recovery 7" mid 3 inches (specimen).
Hard reddish clayey rock with rounded quartz grains. The clay swells
and disintegrates in water, suggesting bentonitic volcanic ash.
bottom 3 inches: rather friable white clayey rock, no quartz grains.
Bass (1969) describes the material from 3871.5 to 3874 ft. as perhaps
a silty mudstone or a thoroughly weathered tuff; from 3876 to 3878 ft.
as microcrystalline welded tuff or pumice.
Core 193 3878'-3879' recovery 12" hard very fine grained reddish
rock.
Bass (1969) describes this rock as laminated tuff.
Core 194 3879'-3881' recovery 20" like the preceding with ellip-
soidal bleached areas a centimeter or two across. In thin section, it is
seen to be volcanic ash (Figure 27). It contains a marine (?) fossil.
This sample has been analysed (Table 3).
Core 195 3881'-3883' recovery 24"
top 1 inch: similar to preceding.

BULLETIN NO. 55

27. Sun Oil Company, H.S E. Westbury et al. 1. Putnam County, Florida.
'I .,

3879'-3881'.
Ash with fossil, upper right. The other structures seem to be intensely
altered fine-grained volcanic fragments. The dark areas are iron-stained.
Ordinary light X2232.

Figure

46 BUREAU OF GEOLOGY

Bass (1969) describes this core as lithic-crystal tuff with relict shard
structure.
bottom 1 inch: similar to preceding, grading from reddish to white.
Core 196 3883'-3885' recovery 12" Similar to preceding. In thin
section the reddish areas in the specimen are seen to be colored by red-
dish hematitic (?) dust, whereas the white areas are pale green, and
chloritic. A few highly altered fragments of coarser volcanic rock are
imbedded in an extremely fine grained clayey/matrix.
Core 197 3885'-3887' recovery 17" This is more grayish in color,
but otherwise like the preceding. In thin section it shows shard structures.
Bass (1951) gives further details. (Fig. 28)

Figure 28. Sun Oil Company, H. E. Westbury et a.No. Putnam County Florida.

Fine-grained rock, with scattered sodic plagioclase feldspar crystals
(white). The white streaks are minute fissures filled with quartz. Ordinary
,light X ,.

I -

S-, '. : .

.3885' 3887'.

Fine grained rock, with scattered sodic plagioclase feldspar crystals
(white). The white streaks are minte fissures filled with qartz. diary

light X17'2.
light X17:2.

BULLETIN NO. 55

Core 198 3887'-3889' recovery 12" This is bluish gray ash, with
numerous reddish grains a millimeter or two across. They are usually feld-
spar, either single large crystals, or granular aggregates, or highly feld-
spathic rhyolite. Some fragments consist of aggregates of almost color-
less spherulitic chlorite.
Bass (1969) describes this core: Clastic vaguely laminated welded tuff.
Core 199 3889'-3890' recovery 10" Similar to preceding with fairly
large (several millimeters or more) fragments of well crystallized rhyolite
and single unaltered plagioclase feldspars; also quartz grains.
Bass (1969) describes this core as plastic volcanic conglomerate or ag-
glomerate. (Fig. 29)

Figure 29. Sun Oil Company, H. E. Westbury et al. No. 1, Putnam County, Florida.
3887'-3891'.
Shows heterogeneous character. The large fragment (lower left) sug-
gests either a shattered quartz crystal or a fine-grained sandstone. Ordinary
light X17;2.

48 BUREAU OF GEOLOGY

Core 200 3890'-3892' T.D. recovery 24" Similar to preceding. (Fig.
30)
Bass (1969) describes this as similar to his preceding sample, with
laminated welded tuff.

4AT;V4

Figure .30. Sun Oil Company, H. E. Westbury et al. No. 1, Putnam County, Florida.
3890'-3892' T.D.
Shows variegated structure (fine and coarse). The coarse is largely quartz.
Ordinary light X17I.
Fiue:0 unOlCmayH .Wsbrye l o 1 unr outFoia
3890'-392'T.D
Shw areae srcue fn adcase.Tecoreislrey urz
Ordnay lgh X132

BULLETIN NO. 55

MARION COUNTY, FLORIDA
SUN OIL COMPANY
HENRY N. CAMP NO. 1 T.D. 4637'
Completed 1947 Well locality 12 Applin (1951) No. 23
"Vocanic agglomerate or tuff of rhyolitic composition. 'Mixed tuff de-
rived from an igneous complex.' F. O. Grout." Applin (1951)
Applin gives 22 feet of volcanic rock beginning at 4615 ft.
Bass (1969) describes specimens from this well, as noted below. He
describes cuttings from 4500 to 4610 ft. and core from 4574 to 4584 ft.
as coarse grained conglomeratic sandstone loosely cemented by chlorite;
about 1 percent or less of the sandstone is rhyolitic ash.
Only two samples are available:
Core 22 4574'-4584' (two different rock types)
a) fine grained ash?
b) coarse grained agglomerate or arkose fragments a milimeter or two
in size. (Figure 31)
There is such a difference between these two specimens that it is pos-
sible that the coarse grained rock (b) is mislabeled. It shows definite indi-
cations of metamorphism by igneous contact, and contains fragments of
rhyolitic rock (fig. 28) with coarse quartz and feldspar. The matrix has
been recrystallized to micaceous aggregates.
Core 23 (bottom) 4623' Again there are two somewhat contrasting
specimens, one a coarse volcanic agglomerate, the other rhyolitic welded
tuff or rhyolite, with large quartzes and sodic feldspars. Both however,
could well represent variant phases of a single ash fall, shifting winds and
variations in explosive activity in the crater causing marked changes in
material deposited at any one point.
Ross (1958) cited by Bass (1969) found 4618 to 4653 ft. to be welded
tuff. Bass also found cuttings from 4610 to 4630 ft. to be rhyolitic welded
tuff.
Dorothy Carroll (1963, p. All, Fig. 6) found her heavy mineral assem-
blage A in quartzite at the Camp well at a depth of 4376-4383 feet below
sea level (core 121). This assemblage also occurs in quartzite in Humble
Oil and Refining Co. C. E. Robinson No. 1 (Levy County) which is con-
sidered to be Early Ordovician in age on the basis of fossils. The quart-
zite in core 121 from the camp well is also probably Early Ordovician (Ber-
dan, 1970, written communication).
Three other wells have been drilled in Marion County in none of which
igneous rock was reported. They are:
J.S. Cosden, W. L. Lawson No. 1 4334' T.D.
Ocala Oil Corp., Clark-Ray-Johnson No. 1 (York) 6180' T.D.
Sun Oil Co., H. T. Parker No. 1 3845' T.D.
All are reported to have bottomed in quartzitic sandstone (P. L. Applin,

I S
aV

l o'

'-7' k-hII

*1

4.
N.

Figure 31. Sun Oil Company, Henry N. Camp No. 1, 4574'-4584', Marion County, Florida.
Coarse agglomerate or arkose. Shows large quartz grains with micro-brecciated structure. The dark grain lower right
is rhyolite, with typical rounded quartz phenocryst. Ordinary light X14.

BULLETIN NO. 55

1951), of probable Early Ordovician age (Berdan, 1970, written com-
munication).
The Sun Henry N. Camp N. 1 with volcanics at 4623' is only about
20 miles east of Ocala Oil Corp. Clark-Ray-Johnson No. 1 (York), which
reportedly found no igneous rock down to 6180' T.D.

LEVY COUNTY, FLORIDA
HUMBLE OIL AND REFINING CO.
C. E. ROBINSON NO. 1 T.D. 4609'
Completed 1949 Well locality 13 Applin (1951) No. 60
"4317'-4344' decomposed igneous rock; underlies lower Cretaceous
sandstone. 4344'-4377' basalt; overlies altered black shale of Paleozoic age."
(Applin 1951)
Three very small samples are available. There is some question as to
exactly which cores they represent. The depths, however, are believed to
be correct.
Core 59 (?) 4331'-4336' This is a rather coarse granular aggregate,
mostly greenish, but also brownish grains. In thin section, the rock is seen
to consist of a chlorite-clay(?) matrix with abundant carbonate (dolomite?)
areas, both with rather obscure radial crystallization. Coarse opaque
grains, some ilmenite, other leucoxene and limonite, are numerous. Quartz
is almost absent. (Figure 32).

i:r

IA""e

y i,,
-i *2 ,''
fl^ ,ps

-* t

t4~t

Calcitized basalt
Figure 32. Humble Oil and Refining Company, C. E. Robinson No. 1, Levy County, Florida, 4331'-4336'.
Radially crystallized masses of dolomite (?) in a chloritized matrix. Feldspars are replaced by obscurely radial clay (?)
material, mafic minerals by pale green chlorite. Ordinary light, X2232.

_ _

6.'49

BULLETIN NO. 55

Core 59 (or 60?) 4344'-4356' near top "overlain by 8 ft. of red clay"
- Applin. This is a fairly hard light gray rock. In thin section, it is seen
to be a diabasic rock, with fresh plagioclase and calcitized augite. It shows
to a relatively minor degree the same type ofhydrothermal alteration seen
in the preceding specimens (Fig. 33). Pyrite unaltered to limonite, and
ilmenite unaltered to leucoxene, are present. The "red clay" of Applin
may represent an intensely altered part of the igneous body.
Core 59(?) 4358'-4359' This is augite diabase, showing none of
the alteration of the preceding samples (Fig. 34).

I~ I

;Ii

'to

"

K, 'C:

'I I.

7 '. ; / '. 5
."I

a'"
-" -i^

I~ '. ^: .r

*~~~~ : f^^''

7-f'I .- ,A' tt I'^
% '. '; ''w ,, 14 .^ ^ '
A -- i -

I .-*" '

-" .' ,.* ^ t 1 ^ -
,r g i ri. :7 A! P -'

'I --

-L"'

A

I"
-? r
-; 72'
/1.
'.4: )
1'r:~ '4'~~~ .*
4., '4'f dr
.Lr7 ct

Calcitized basalt or diabase
Figure 33. Humble Oil and Refining Company, C. E. Robinson No. 1, Levy County,
Florida, 4344'-4356' (near top).
Although the plagioclase is unaltered, nearly all the augite is replaced
by calcite. The black areas are mostly fresh magnetite-ilmenite with a
little pyrite. Minor quartz is present and green chlorite. Ordinary light,
X22.5.

t

Almost unaltered diabase
Figure 34. 'Humble Oil and Refining Company, C. E. Robinson No. 1, Levy County, Florida, 4358'-4359'. Ordinary light, X22.5

I

~

BULLETIN NO. 55

Although the 28 feet of igneous section appears to show a progressive
degree of alteration from top to bottom, this may not be the result of
weathering, but ofhydrothermal alteration.
"The diabase in the Robinson well overlies 232 feet of quartizitic sand-
stone with minor amounts of shale, which is dated as Early Orodivician
on the basis of linguloid brachiopods" (Berdan and Bridge, 1951, p. 70).

VOLUSIA COUNTY
GRACE DRILLING CO.,
RETAIL LUMBER CO. NO. 1 T.D. 5424'
Completed 1949 Well locality 14 Applin (1951) No. 26
"Rhyolitic (?) volcanic rock" Applin (1951).
Applin (1951) reports that this well drilled 21 feet in volcanic rock. A
specimen of cuttings from 5-124'. T.D. show arhyolitic rock almost
wholly plagioclase feldspar (near oligoclase-andesine) with a little quartz
and little or no mafic minerals. It is illustrated in Figure 35.
This well is less than 20 miles NNW of the Sun Co. Powell Land Co.
No. 1, which at a depth (! ','-i-22 drilled rock reported as over 400 m.y. age.

BUREAU OF GEOLOGY

'.

44.

=-4

-- "

.% *. 4

.' .4

.rr - ^
* "" ; I 2. .

r~F Mla
6~

I,

,1

r . ,A

~2<

'it
.4 ~ -. 1
5. ) P' -

N.-

4., 4i

* .1
.1

*11
- 4 h '

.4, Is -'
'<-~ * V- ,5'li

S ..

k *' *:, ."
ri ,

*~~~~~1 4 _,tA .-. .

^4' ..- ; A
.7"`~

Rhyolite

Figure 35. Grace Drilling Co., Retail Lumber Co. No. 1, Volusia County, Florida.
542432 T.D.
The volcanic rock consists almost entirely of moderately sodic plagioclase
in interlocking aggregates of lath shaped crystals, some porphyritic and
euhedral, and very minor interstitial quartz. The feldspar is slightly
sericitized, with reddish dust giving it a brownish tint in section. Some
black ore grains, and a little calcite, are present. The large rectangular
crystal is plagioclase feldspar. Ordinary light, X27.

4t'
V.

S-* I It

44

4)

4f

,' .1

a

1W

0"
*

/* -
-. If

BULLETIN NO. 55

VOLUSIA COUNTY
SUN OIL CO.
POWELL LAND CO. NO. 1 5958 ft. T.D.
Completed 1946 Well locality 15 Applin (1951) No. 7
Hornblende diorite (Applin 1951)
This is one of the three wells in east central Florida that Applin (1951)
considered to have reached the "metamorphic basement," the others being
Lake County, J. Ray Arnold No. 1 and Osceola County, N. Ray Carroll
No. 1. Later the St. Lucie County, Amerada Cowles Magazine No. 2
and Hillsborough County, Humble T. S. Jamison No. 1 drilled into similar
"metamorphic" rock.
Bass (1969) has studied specimens from this well in great detail as
noted below.
Nineteen specimens from this well, representing depths from 5903' to
5958' T.D. have been studied. "According to D. J. Munroe (Sun Co.
Geologist*) this well encountered a weathered zone? beginning at 5910'
S. .memo to Watson Monroe from Applin, April 3, 1947. The follow-
ing are notes on the samples studied:
Side Wall Core 5903' White Sandstone
Side Wall Core 5906' White sandstone
Cuttings 5910'-20' White sandstone, etc.
Cuttings 5920'-30' White sandstone, etc.
Core 178 5922'-25' 3' recovery, top ofcore. Soft coarse volcanic
rock, now clay, but with original texture.
(Figure 36)
Core 178 5922'-25' has been interpreted as possibly a weathered zone,
and indeed there is a striking contrast between the white sandstone and
the underlying volcanics, with no indication that the sandstone has been
metamorphosed by the volcanics. In other words, the sandstone deposi-
tion is subsequent to the consolidation of the igneous rock. In thin section,
the rock is seen in Figure 36. Rather than weathering, intense hydrother-
mal alteration is possible. The rock is illustrated in Figure 36. Minute ang-
ular fragments of fairly fresh alkalic feldspar are seen sparingly, surrounded
by clay. Vivid green, strongly pleochroic (yellowish to bright green) platy-
fibrous chlorite-like mineral may be ferrostilpnomelane. Small apatite crys-
tals are present.
Bass (1969) classes the rock from >'-22-25 ft. as "either transported
material or weathered basement rock that was mixed with overlying ma-
terial during mass movement."
Cuttings 5930'-40' White sandstone, volcanic debris
Cuttings 5940'-50' Volcanic debris, white sandstone, etc.
Cuttings 5950' Volcanic debris, white sandstone, etc.

"Deceased.

"Weathered" igneous rock
Figure 36. Sun Oil Co., Powell Land Co. No. 1, 5922'-5925', Volusia County, Florida.
The light colored areas are cryptocrystalline clayey material; the dark, chloritic aggregates; and the black, limonitic
material. Shattered quartz grains (white) suggest explosive hydrothermal activity. The limonitic material may have re-
placed ferromagnesian silicates; a few black ore grains are unaltered. Ordinary light, X15.5.

BULLETIN NO. 55

MARION COUNTY, FLORIDA
SUN OIL COMPANY
HENRY N. CAMP NO. 1 T.D. 4637'
Completed 1947 Well locality 12 Applin (1951) No. 23
"Vocanic agglomerate or tuff of rhyolitic composition. 'Mixed tuff de-
rived from an igneous complex.' F. O. Grout." Applin (1951)
Applin gives 22 feet of volcanic rock beginning at 4615 ft.
Bass (1969) describes specimens from this well, as noted below. He
describes cuttings from 4500 to 4610 ft. and core from 4574 to 1i~4 ft.
as coarse grained conglomeratic sandstone loosely cemented by chlorite;
about 1 percent or less of the sandstone is rhyolitic ash.
Only two samples are available:
Core 22 4574'-4584' (two different rock types)
a) fine grained ash?
b) coarse grained agglomerate or arkose fragments a milimeter or two
in size. (Figure 31)
There is such a difference between these two specimens that it is pos-
sible that the coarse grained rock (b) is mislabeled. It shows definite indi-
cations of metamorphism by igneous contact, and contains fragments of
rhyolitic rock (fig. 28) with coarse quartz and feldspar. The matrix has
been recrystallized to micaceous aggregates.
Core 23 (bottom) 4623' Again there are two somewhat contrasting
specimens, one a coarse volcanic agglomerate, the other rhyolitic welded
tuff or rhyolite, with large quartzes and sodic feldspars. Both however,
could well represent variant phases of a single ash fall, shifting winds and
variations in explosive activity in the crater causing marked changes in
material deposited at any one point.
Ross (1958) cited by Bass (1969) found 4618 to 4653 ft. to be welded
tuff. Bass also found cuttings from 4610 to 4630 ft. to be rhyolitic welded
tuff.
Dorothy Carroll (1963, p. All, Fig. 6) found her heavy mineral assem-
blage A in quartzite at the Camp well at a depth of 4376-4383 feet below
sea level (core 121). This assemblage also occurs in quartzite in Humble
Oil and Refining Co. C. E. Robinson No. 1 (Levy County) which is con-
sidered to be Early Ordovician in age on the basis of fossils. The quart-
zite in core 121 from the camp well is also probably Early Ordovician (Ber-
dan, 1970, written communication).
Three other wells have been drilled in Marion County in none of which
igneous rock was reported. They are:
J.S. Cosden, W. L. Lawson No. 1 4334' T.D.
Ocala Oil Corp., Clark-Ray-Johnson No. 1 (York) 6180' T.D.
Sun Oil Co., H. T. Parker No. 1 3845' T.D.
All are reported to have bottomed in quartzitic sandstone (P. L. Applin,

BUREAU OF GEOLOGY

-~ ~ A.:'\ '"1'

C

*; a k' **

,t F *

? r -j, ..~ ;
.'* t **'. ". ', *< 5
A4 '

~i
tr A .'

.f/| tA^ A( : tA

..~~ *A'," ^'^
t.I
-. : '., ,.. c '^ > -
"i - c .'. .- I (

*^- .r' -'"^,": ^^* "R. *

. < .;a 3 -^ 1t ". *'

q

1
"s;

I"
t,~:

r.-n*-,--

Figure 37. Sun Oil Co., Powell Land Co. No. 1, 5954'-5955', Volusia County, Florida.
The small smooth rectangular area bottom center is green chlorite;
another area is at the center. The clear areas are quartz, the darker
hornblende; the gray mostly feldspar. Ordinary light, X27.

WA
A'
~ 34
-4

'A

(>111

'' ?jr sl

B~tl

; a

BULLETIN NO. 55

Diorite with epidote
Figure 38. Sun Oil Co., Powell Land Co., No. 1, 5954'-5955', Volusia County, Florida.
Shows epidote veinlet (lower left). Ordinary light, X20.5.

6r'- F*

0.5 m h

0.5 g" .

Hornfels
Figures 39a, b. Sun Oil Co., Powell Land Co. No. 1, 5955'-5956', Volusia County, Florida.
Shows brown biotite and pale green hornblende with quartz-sodic plagioclase. Concentrations of either or both
together, the ferromagnesian minerals are seen; here the quartz-feldspar is finer grained (lower left). All grains
are anhedral, and the texture is granitic. Ordinary light and crossed nicols, X27.

e'T

i _e^ ?yi *. ItC, *1

.. .., ,.-- ,, ; - :
t .%'r-r *' "
-. ' -

r- : "V R r't
a -r

-. a..- ..... .

W b1 - t" -'" .*
1.-

Figure 40. Sun Oil Co., Powell Land Co . 1, 5957,'-5958', Volusia County, Florida.
Rock similar to preceding figures, showing ma concentration. Orindary light, X16.
Fig e; o.U 1, 5 8 lu N id.

BUREAU OF GEOLOGY

Rock from core 180 5953-5954 ft. has been dated by H. Thomas, R.
Marvin, P. Elmore, and H. Smith of the U. S. Geological Survey (Meuhl-
burger, W. R., et al., 1966) as |sii- m.y. (by K-Ar).
Bass (1969) found for the rock from 5951 to 5958 ft.
5951'-5955' Hornblende in diorite 459 m.y. (K-Ar)
5951'-5955' Plagioclase in diorite 342 m.y. (K-Ar)
5955.5'-5958' Biotite in hornfels 524 m.y. (K-Ar)
5955.5'-5958' Hprnblende in hornfels 393 m.y. (K-Ar)
5955.5'-5958' Biotite in hornfels 634 m.y. (Rb-Sr)
Bass offers various explanations of these discrepancies.
To summarize these data, it appears that these dates aggree in indicating
an age for the rock in excess of 342 m.y., that is, an age older than Miss-
issippian.

LAKE COUNTY, FLORIDA
LAKE COUNTY OIL DEVELOPMENT COMPANY OF FLORIDA
SOUTH LAKE NO. 2, (J. R. Arnold No. 1) T.D. 6129'
Completed 1937 Well locality 16 Applin (1951) No. 5
"Granite at 6103" Applin (1951)
In a letter to Watson Monroe, Applin (Nov. 4, 1937) wrote ".... in
1937 a sample was submitted to W. H. Tomlinson at Swarthmore, Pa.,
who reported it to be alaskite, 'a granitoid rock having 50 percent ortho-
clase, 40 percent quartz, 10 percent oligoclase, and 2 percent biotite.'
Tomlinson's opinion expressed at that time was to the effect that the alas-
kite was probably a dike ... ." Later, a few tiny fragments of this rock
were inspected by Charles Milton who agreed with Tomlinson's findings
as to lithology.
A thin section obtained from Mr. A. P. Bennison, of the Sinclair Oil and
Refining Company labeled "Oil Dev. Co. of Fla. South Lake Well Core
6107'-'1 Granite 17-24S-25E" made by Tomlinson, is definitely the same
rock. It shows no trace of weathering (Figures 41a, b).
It may be noted that this type of rock is quite similar to "granitic" rock
encountered by drilling in Perce County, Georgia.
This is one of the most controversial of the Florida wells. Schuchert
(1943) mentions a miliolid limestone, referred to middle Cretaceous at
5383'; anhydrite between 5383' and 6050'; followed by red clays, gravels,
sands and then granite. The owner of the well denied the presence of
granite. Campbell (1939) observes that "granite or not, the miliolid lime-
stones at 5383', some beds of anhydrite, and the red sands and gravels

"The original report to Charles Milton, dated Nov. 1, 1962, noted that "this age may
be low by 20 percent or more due to the variable argon retentivity of the potassium-bear-
ing minerals of this sample."

*T
Sf_

0.5 mr
w_

Figures 41a, b.

Oil Development Company of Florida South Lake No. 1,6107'-28'
The clear areas are quartz, the grey mostly microcline and oligoclase. A very little brown biotite and black mag-
netite is present. Very similar rock is known to be arkose more or less metamorphosed by nearby doleritic intrusives.

BUREAU OF GEOLOGY

are regarded in this paper as representing middle Cretaceous rocks, and
the well is assumed to be in Jurassic at the bottom of the hole. In this con-
nection it might be mentioned that Schuchert regards granites in Central
Cuba as having been intruded at the end of the Jurassic. Dickerson also
notes the association of granite with his Oxfordian."

ORANGE COUNTY
WARREN PETROLEUM CORP. GEORGE TERRY NO. 1
Sec. 21 T23S R31E Center SWi SEi T.D. 6589'
Completed 1955 Well locality 17.
Top of granite at 6550'. Only cuttings. No samples available.
Data from Applin (personal communication, 1967).

INDIAN RIVER COUNTY
AMERADA PETROLEUM CORP.
FONDREN MITCHELL NO. 1 T.D. 9488'

Section 28, T31S R35E 1980' S and 1980' E of NWM Sec. 28
Completed 1956 Well locality 18.
Top of weathered (?) igneous rocks at 9410'. Rock reported as "ande-
site". Applin (personal communication, 1967).
Samples (cuttings) available as follows:
9424-29 9454-64
9429-34 9464-69
2434-39 '9469-74 Figures 44, 45
9439-44 9474-79
*9444-49 Figures 42, 43 9479-84
9449-54 *9484-89 T.D. Figure 46 All in volcanic rock.
* Thin sections as follows.
9444-49 Brown basalt, consists of fresh calcic plagioclase laths with
colorless to greenish or reddish monoclinic pyrogene, and black ilmenite.
Green to brown chlorite with ilmenite forms small segregations in the
rock.
9469-74 Amygdaloidal calcitic basalt; basalt with much calcite veins
and chlorite amygdules.
Figures 44 and 45 (?)
9484-89 Amygdular basalt. Much calcite, chlorite and quartz in
amygdules.
Figure 46
The rock could be termed a moderately altered amygdaloidal basalt.
It appears to be very similar to the amygdaloidal basalt from Appling
County, Georgia, described and illustrated by Milton and Hurst (1965);

BULLETIN NO. 55

Basalt
Figure 42. Amerada Fondren Mitchell No. 1, Indian River County, 9444'-9449',
Ordinary light x 35.

BUREAU OF GEOLOGY

3a .~a 1, tr N

I _st*$v1&4

t "-~" L ~ A

'' ""zagi
i ~
f
r.
,. ,1 ;~5

.cF
"F"jb t ~~-;

Diabase with interstitial chlorite-ilmenite.
Figure 43. Amerada Fondren Mitchell No. 1, Indian River County, 9444'-9449'.
Shows plagioclase laths and augite with ilmenite, and green chlorite
with black ilmenite aggregates. The chlorite varies in color from green to
brown. Ordinary light x 150.

BULLETIN NO. 55

Figure 44. Amerada Fondren Mitchell No. 1, Indian River County, Florida 9469'-
9474'.
Calcite-chlorite-quartz segregations in basalt. The large mass (left of
center) is calcite, bordered with (clear) quartz. Ordinary light x35.

BUREAU OF GEOLOGY

0 1ni

Figure 45. Amerada Fondren Mitchell No. 1, Indian River County, Florida, 9469'-
9474'.
Detail of Figure.
Amygdaloidal basalt. Shows amygdaloid in center of picture with green
chlorite (gray areas), plagioclase laths, quartz, and ilmenite; the large
grey areas at top, left and right are calcite, and the clear areas bordering
the calcite are quartz. Ordinary light x 150.

BULLETIN NO. 55

'1t2r AI "~~i.

Figure 46. Amerada Fondren Mitchell No. 1, Indian River County, Florida, 9484'-
9489' T.D.
Basalt, with considerable quartz (most of the light-colored areas in the
picture). Green chlorite, calcite, and ilmenite are also abundant. The
plagioclase feldspar is fairly fresh, but the augite is mostly altered to ob-
scurely crystallized chloritic aggregates. Ordinary light, x12.

and indeed, to the amygdaloidal basalts of northern Florida dk. IIIl .- i
elsewhere in this report.
Figures 47a and 47b show the appearance of the rock in thin section. A
chemical analysis is given in Table 3.
Dating by Grasty (Table 2) gave a K-Ar age of 89.3 + 2 m.y. (middle
Cretaceous).
12744' In hand specimen resembles the preceding. In thin section how-
ever it is markedly different. The texture is fine grained granitic, and the
rock consists essentially of quartz and moderately sodic plagioclase, near

'C1

0.5 mm
I 1

Figures 47a, b.

.5 mm
_ _j

Amygdaloidal basalt
Amerada Petroleum Co., Cowle Magazine No. 2, St. Lucie County, Florida, 12734'.
47a (ordinary light). Shows proportion of black ore grains and feldspar, and shape and size of amygdules which
contain pale green chlorite apparently identical to the interstitial chlorite replacing augite, etc. which is completely
gone.
47b (crossed nicols). The twinned plagioclase feldspars are the most abundant mineral; the black areas are
mostly pale green chlorite and ilmenite. Ordinary light and crossed nicols, X16.

BULLETIN NO. 55

andesine in composition. It shows little alteration, usually no more than
a few minute chloritic flecks. There is very little of the green chlorite
abundant in 12734'; what there is, is mostly associated with opaque ore
grains, surrounding and filling cracks in these. One or two areas suggest
olivine now replaced by ore and chlorite. No hornblende, abundant in
the following 12748' rock, is present; but there is much brown biotite
mostly heavily altered to brown chlorite? serpentine? Often the biotite
and its alteration product contain a network of rutile needles, hexagon-
ally oriented. Apatite is a minor accessory. Many of the rather coarse
black ore grains are shattered and chlorite-serpentine fills the cracks.
Figures 48a and 48b show the microscopic aspect of this rock; and a
chemical analysis is given in Table 3.
Dating by Grasty (Table 2) of this rock by K-Ar gave 226 6 m.y. and
224 3 m.y. (late Permian or early Triassic). Bass, however (Table 2, ob-
tained two widely different K-Ar ages for samples from this core from
148 m.y. (middle Jurassic) to 399 m.y. (late Silurian or early Devonian),
and for a third, by strontium isotopes, 530 m.y. (middle Cambrian).
12748' This rock also resembles the two preceding superficially, but in
thin section differs markedly from both.
It has a rather coarsely granular texture, and consists essentially of un-
altered green hornblende, quite fresh calcic plagioclase, and quartz. The
coarse black ore grains (ilmenite?) are unfractured. A little brown bio-
tite is present, some fresh, but most heavily altered to vague brown chlor-
itic material. Very few and small areas of pale green chlorite similar to
that in 12734' and 12744' with irregular outlines are present. Typical
areas in thin section are shown in Figures 49a and 49b.
This rock has been K-Ar dated by Grasty (Table 2) 308 5 m.y. (upper
Mississippian or lower Pennsylvanian) and the hornblende from it by
Bass, also K-Ar (Table 2) 470-503 m.y. (upper Cambrian or lower Ordovi-
cian).
Obviously, these dates do not agree too well, and their precise signifi-
cance is uncertain.

, ,_ .W 1. :: .l^ _*'*' *" '. .
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t. ***^ *^^** r r
t4. *^ .p ^ '-%i";'-

S, .. . , ,r;i

S .. : -; .-
4 1-.:

.: ,''. '" ^ I *. ^ .'. *' .. ...
i.-f "- 1v / ;'* ^. **' '*? *- ^
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,,. r' .' --3 ,
",A :K *,. -, '

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^. "" 'As '
f. .. .. s '
St* i

. U ," ,, .,, ,- , r <

-'" I ^ -- r. ,:,
L .- ,n.i. ....; 11
-, ,if tr -' i '' "
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.^f' ~~ *- I i^ .

Y -f s ^ *.; .. .. *r.Ci C
t- ~~E .. I L ;*
1:15 m A r rf. ?.- i~ *.
I_______ F x*,B *-.. .* *

Figures 48a, b.

Granite
Amerada Petroleum Co., Cowles Magazine No. 2, 12744', St. Lucie Co., Fla. Thin section, ordinary light and crossed
nicols, X6.
The light colored areas (ordinary light) are quartz and andesinic plagioclase; the gray areas are brown alteration
produces of hornblende, now mainly altered biotite, serpentine or chlorite. The small black areas (lower right) are
mostly black iron (titanium) oxide, probably ilmeni, with a little pyrite. They have been shattered and the cracks
filled with serpentinic-chloritic material.

Diorite
II

Figures 49a, b. Amerada Petroleum Co., Cowles Magazine No. 2, 12748', St. Lucie Co., Fla. Thin section, ordinary light and crossed
nicols, X6.
Shows abundant unaltered green hornblende and calcic plagioclase, with minor quartz and black opaque ilmenite (?). c.a

BUREAU OF GEOLOGY

ST. LUCIE COUNTY
AMERADA PETROLEUM CO., COWLES MAGAZINE NO. 2
Completed 1957 Well locality 19 12749'T.D.
Three specimens of large size core were received from Paul L. Applin,
through E. J. Henderson, Geologist, Amerada Petroleum Co., August 20,
1957, from 12734', 12744', and 12748'. The three rocks, although they
cover a range of only 14 feet, show remarkable diversity. Whereas the up-
permost rock, 12734', can be readily identified as basaltic, the middle
specimen 12744' has a granitic aspect, and the bottom rock 12748' would
pass as common diorite. The two lower core samples have been studied in
considerable detail by Bass (1969) with age determinations; similar studies
of all three cores are given here.
12734' is a hard gray rock, mottled with white flecks of calcite a centi-
meter across, and showing black slickensided surfaces.
In thin section it shows a uniform aggregate of andesinic plagioclase
laths, with abundant small euhedral black iron oxide (ilmenite?) grains.
Almost as abundant as the plagioclase is green chlorite, interstitial to the
feldspar and evidently a replacement of pre-existing mafic minerals,
probably pyroxene. Similar chlorite showing low bluish interference
colors under crossed nicols, also forms spherical vesicles or blebs, a couple
of millimeters across. Around and contiguous to these, the black ore grains
are replaced by brown sphene. Irregular small patches of calcite are strewn
through the rock. The feldspars in this rock are fairly fresh, mostly appar-
ently unaltered. They are somewhat fissured, the fissures being filled with
greenish chlorite.

OSCEOLA COUNTY, FLORIDA
HUMBLE OIL AND REFINING CO.
W. P. HAYMAN NO. 1 T.D. 8798'
Completed 1946 Well locality 20 Applin (1951) No. 24
This is one of two wells in Osceola County (the other being the
Humble Oil and Refining Co., Ray Carroll No. 1). Samples are available
from 8619' to 8793%', with interruptions.
Rhyolite from 8781' has been K-Ar dated 173 4 m.y. (Lower Jurassic)
by Grasty (Table 2).
58 feet of rhyolite, to 8798' (T.D.) were drilled.
Core No. Depth
253 8619'-8629' Friable gray sandstone
254 8655'-8658' Gray slickensided shale with coarse quartz
grains. In thin section, seen to be largely
volcanic debris, probably ash. The quartz
grains show no rounding, and many show
secondary enlargement.

BULLETIN NO. 55

255 8734'-8744'
recovery 5 ft.

256 8744'-8750'
257 8750'-8756'

8753'-8756'
8756'-8759'
8759'-8765'
8765'-8770'

8770'-8772'
8772'-8775'
8775'-8778'
8778'-8780'
8781'-87811%'

273 87812'-8783'
275 8786'-8787'

276 8789'-8790'

"Top 4 ft. of core is gray and black con-
glomerate sand. Bottom 1 ft. of core is por-
phyry with sand intrusions." (Drillers' log).
Sample consists of small hard gray igneous
rock fragments with sandy debris.

Top 1 ft. gritty clayey rhyolitic arkose.
Consists largely of sub-angular fragments
of quartz, micro-pegmatite, and sodic feld-
spar, with interstitial clayey matrix. An-
other sample of the same piece of core in-
cluded both sandstone and volcanic rock
fragments. Next to the top 1P ft. rather
firm carbonaceous (coal?) material. Bottom
six inches rhyolite fragments.

Slate-gray stony tuff (?) with small aphani-
tic inclusions and white kaolinized feld-
spars.
Microscopic: quartz and oligoclase-ande-
sine phenocrysts in feldspathic ground-
mass. Quartz euhedral (rhombohedra and
prisms), also spheroidally rounded. Plag-
ioclase in part calcitized; no albite twin-
ning, only Carlsbad. No mafics, very
scanty chlorite and apatite. (Fig. 50, Rhyo-
lite)

Very much like core 257 8750'-8753' -
very small hornblende and biotite, calcite
patches. (Figs. 51a and 51b)

"Rhyolite 173 4 m.y." Lower Jurassic
(Table 2)

Dark gray stony rock with red feldspar
phenocrysts. Quartz and albitic-oligoclase
phenocrysts in microcrystalline matrix. No
mafics. (Figs. 52a and 52b)
Same

BUREAU OF GEOLOGY

277 8790'-87903i'
279 8792%'-8793%'
280 8795%'-8796'1

Same

Rhyolite
Figure 50. Humble Oil and Refining Company, W. P. Hayman No. 1, Osceola
County, Florida, Core 257, 8750'-8753'
Rounded and sub-rounded quartz phenocrysts in fine grained felsic
groundmass. Near the center is a small sodic plagioclase phenocryst.
Ordinary light X17%.

0 5 mm 0.5 mm

Porphyritic rhyolite
Figures 51a, b. Humble Oil and Refining Co., W. P. Hayman No. 1, Osceola County, Florida, Core 262, 8765'-8770 ft.
Shows rounded quartz phenocrysts and large sodic plagioclase in fine-grained felsic groundmass. Ordinary
light and crossed nicols X17,.

00

i,

Rhyolite
Figures 52a, b. Humble Oil and Refining Co., W. P. Hayman No. 1, Osceola County, Florida, Core 275, 8786-8787 ft.
Rounded quartz and sodic plagioclase phenocrysts in a fine-grained felsic groundmass, which is coarser in
irregular streaks. Ordinary light and crossed nicols X17l.

BULLETIN NO. 55

OSCEOLA COUNTY
HUMBLE OIL AND REFINING CO. J. RAY CARROLL NO. 1
80441' T.D. Well locality 21 Applin (1951) No. 6
Applin ( 1951) lists the 14 feet of bottom rock in this well as "altered
and veined biotite granite" as determined by F. F. Grout. He also gives
T.D. as 8049 ft.
This is one of the three "metamorphic basement" wells in central eastern
Florida (the other two Volusia County Powell Land Co. No. 1 and Lake
County Oil Development Co. South Lake No. 2 J. R. Arnold No. 1)
which led Applin (1951, Fig. 1) to indicate a triangular area of several
thousand square miles, including all or part of Volusia, Seminole, Lake,
Orange, Osceola, Polk, and Brevard Counties as underlain by "pre-Cam-
brian granite, diorite, and metamorphic rocks."
Bass (1969) describes rock from this well as quartz monzonite.
Material studied from this well is:
Core 174 7904'-7914'
Core 175 7965'-7975'
Core 176 7975'-7984'
All of these are sand and friable sandstone.
Core 177 8034'-8042' The top of the igneous rock is in this core
(P. L. Applin).
Core 178 8042'-80421' T.D.
Both of the last two cores are of similar rock, granitic in appearance,
with much coarse pink feldspar and green chloritic areas. Microscopically
it resembles a hydrothermally altered aplite, containing abundant quartz
and kaolinized-sericitized albite-oligoclase with veins and replacements
of calcite; potash feldspar, with small optic angle (sanidine?) is sparingly
present. Green chlorite, strongly pleochroic, apparently originally biotite
is the only mafic mineral. Minor accessories are magnetite ilmenite,
leucoxene, apatite, and an occasional zircon.
Three thin sections show little variation.
This rock has been dated by Bass (1969) by Sr87/Sr86 as 530 m.y. The rock
is shown in Figures 53a and 53b.

06
Asn

5? P

-U

a 0
,i: 0
0

*'-
3 ,

1 mn r

~. *,

Figure 53a. Humble Oil and Refining Company, Ray Carroll No. 1, Osceola County, Florida, 8042'-8042%'
The light colored areas are anhedral quartz, whose sutured aggregates are shown well under crossed nicols. The
gray areas are euhedral sodic plagioclase; the black area, right center, is magnetite-ilmenite, with many fractures
filled with green chlorite; the dark mass just to the right of this is chlorite with many small inclusions of leucoxene,
originally magnetite-ilmenite. Ordinary light X15.

.Ar

* ^
i"" '-

J ,i.
''- ~~
~

L:.~J~L~d-,T~il... . V

r;'

PMAS*
'7'. A
WhLl IN

'. V

Figure 53b. Humble Oil and Refining Co., Ray Carroll No. 1, Osceola County, Florida. 8042'-80421'.
The light colored areas are anhedral quartz, whose sutured aggregates are shown well under crossed nicols. The
gray areas are euhedral sodic plagioclase; the black area, right center, is magnetite-ilmenite, with many fractures
filled with green chlorite; the dark mass just to the right of this is chlorite with many small inclusions of leucoxene,
originally magnetite-ilmenite. Ordinary light X15.

r: :5~1~4~:; 1iA

-.i

~~ ~~~~- i

.:,"~?i~'
2~ i-i-

: 'ii~~~*i:-EC~
i .Z -~
-;

~1 ~

~; "i;

BUREAU OF GEOLOGY

OKEECHOBEE COUNTY
AMERADA PETROLEUM CORP.
MARIE SWENSON NO. 1 T.D. 10838'
Completed 1955 Well locality 22 Sec. 5, T. 36 S., R. 34 E.
Center NW.'. N \\
"Top of volcanic rocks 10,750 ft." P. L. Applin (written commun.,
1967).
Reference: Applin and Applin (1965)
9 samples (cuttings) available:
10750'-60' All mostly grains of quartz, anhydrite and more or
*10760-70' less igneous rock, with contact rock ("baked shale")
*10770'-80' fragments.
10780'-90'
10790'-10800'
10800'-10'
10810'-20'
10820'-30'
*10830'-40' "Thin sections
10760'-10770' Thin sections were made of 6 grains; these were basalt,
consisting of fairly fresh calcic plagioclase laths with green chlorite, cal-
cite, and ilmenite; the fourth was perhaps a chilled phase of this basalt
with obscurely crystallized feldspar in a heterogeneous fine grained ma-
trix with much ilmenite; the other two were hydrothermally altered
shale (Figures 56 and 58).
Fig. 54 shows a chlorite-quartz amygdule in the basalt. Fig. 55 shows
another calcitic basalt fragment, not amygdular.
10770'-10780' Thin sections were made of 8 grains, all basalt, some
amygdular. Figure 59 shows an amygdule consisting of quartz and chlor-
ite. The basalt consists of plagioclase feldspar (reddish in thin section),
chloritized amphibole, chlorite, with much rather coarse black ilmenite.
10830'-10840' Includes 6 thin sectioned grains, all but one basalt sim-
ilar to the preceding. The other consists of chalcedonic quartz with pale
greenish chlorite or clay mineral with calcite and black ilmenite; per-
haps hydrothermally deposited. Figure 60.

OKEECHOBEE COUNTY
SUN OIL CO.
AMERADA PETROLEUM CORP.
HARRIS-HOLMES NO. 1 T.D. 9840 ft.
Completed 1966 Well locality 23 Sec. 8, T. 33 S., R. 34 E.
"Top of rhyolite porphyry 9682 ft." P. L. Applin (written commun.,
1967).
No specimens available.

BULLETIN NO. 55

Amygdular basalt
Figure 54. Okeechobee County, Florida, Amerada Swenson No. 1, 10760'-10770'.
Amygdule, consisting of quartz and chlorite. The basaltic matrix is
obscurely crystallized with much ilmenite. Ordinary light X150.

	Title Page
	Front Matter
	Table of Contents
	Acknowledgement
	Front Matter
	Main

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