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Group Title: Diversity and community structure of the Brush Creek marine interval (Conemaugh Group, Upper Pennsylvanian), in the Applachian basin of western Pennsy (FLMNH Bulletin v.19, no.2)
Title: Diversity and community structure of the Brush Creek marine interval (Conemaugh Group, Upper Pennsylvanian), in the Applachian basin of western Pennsylvania
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Title: Diversity and community structure of the Brush Creek marine interval (Conemaugh Group, Upper Pennsylvanian), in the Applachian basin of western Pennsylvania
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Language: English
Creator: Shaak, Graig D.
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Place of Publication: Gainesville, Fla.
Publication Date: 1975
Copyright Date: 1975
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General Note: Bulletin of the Florida State Museum, Biological Sciences, volume 19, number 2
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    Back Matter
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Full Text










of the

FLORIDA STATE MUSEUM
Biological Sciences

Volume 19 1975 Number 2





DIVERSITY AND COMMUNITY STRUCTURE OF THE BRUSH
CREEK MARINE INTERVAL (CONEMAUGH GROUP,
UPPER PENNSYLVANIAN), IN THE APPALACHIAN
BASIN OF WESTERN PENNSYLVANIA


GRAIG D. SHAAK



QH
1
.F6
vol.19


UNIVERSITY OF FLORIDA


GAINESVILLE,








Numbers of the BULLETIN OF THE FLORIDA STATE MUSEUM,
BIOLOGICAL SCIENCES, are published at irregular intervals. Volumes con-
tain about 300 pages and are not necessarily completed in any one cal-
endar year.








CARTER R. GILBERT, Editor
RHODA J. RYBAK, Managing Editor


Consultants for this issue:
GARRY G. ANDERSON
DAVID NICOL









Communications concerning purchase or exchange of the publications
and all manuscripts should be addressed to the Managing Editor of the
Bulletin, Florida State Museum, Museum Road, University of Florida,
Gainesville 32611.


Publication date: January 6, 1975


This public document was promulgated at an annual cost of
$2,249.10 or $2.249 per copy. It makes available to libraries,
scholars, and all interested persons the results of researches in the
natural sciences, emphasizing the Circum-Caribbean region.


Price: $2.30




b /0. /' ,-



BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 2


TABLE OF CONTENTS
INTRODUCTION ... 70
Geographic and Stratigraphic Setting ..... 71
Previous Investigations .. ......74
ACKNOWLEDGMENTS 75
METHODS OF INVESTIGATION ....... 75
Field Sampling -- 75
Laboratory Preparation .. 76
Faunal Analysis .. ...- ........ 76
Data Adjustments to Reflect Standing Crop .. --- .... 77
Diversity Indices, Species Diversity, and Equitability .. 79
THEORETICAL FRAMEWORK 81
Characteristics of Level-Bottom Marine Communities ..- .............. 81
Characteristics of the Brush Creek Depositional Basin -- .. 84
FAUNAL SUCCESSION AND DIVERSITY 84
High Diversity Molluscan Faunas .... ..... ... 87
Locality 1, Kittanning, Pennsylvania ........ 87
Locality 7 (Piccolomini Quarry), Uniontown, Pennsylvania .- 89
Locality 8, Ursina, Pennsylvania 91
Locality 9, Glade City, Pennsylvania 93
Low Diversity Molluscan Faunas 97
Locality 2, Shelocta, Pennsylvania .. ..... 97
Locality 3, Barton, Pennsylvania ........... 99
Locality 4, Sewickley, Pennsylvania ........ ......... 100
Locality 5, Glenshaw, Pennsylvania .. .. -- ............ 103
Locality 6, Murrysville, Pennsylvania ..... ------105
The Limestone Problem ................. 108
COMMUNITY STRUCTURE ... ................ 110
General Statement .. ........ 110
Astartella-lanthanopsis Community 111
Glabrocingulum-Plagioglypta Community ... 112
Aclisina Community ... ..... .............-__ .....__ _... 114
Rhombopora-Septopora Community .. ....... ... 115
DIVERSITY INDICES AS PALEOECOLOGIC TOOLS ...---- ........... 115
General Statement .. 115
Comparison of the Shannon-Wiener and Simpson
Diversity Functions ..-- ..... ...... .......... ... 116
Restrictions in the Use of Diversity Indices 117
CONCLUSIONS ............ ..... ... 118
REFERENCES CITED 119
APPENDIX A. Measured Sections Showing Sampling Interval at Sample Sites .123
APPENDIX B. Faunal Data Matrix .. ..- 132


INTRODUCTION

The purpose of the investigation was to apply and test modern paleo-
ecological and ecological concepts and information theory in attempting
to resolve the present problem. It is a segment of a long-range investi-
gation, already in progress, by several faculty members of the Depart-
ment of Earth and Planetary Sciences, University of Pittsburgh, to
reconstruct and interpret the shallow benthic marine communities for
all the marine events represented in the Conemaugh Group. Compari-



















DIVERSITY AND COMMUNITY STRUCTURE OF THE BRUSH
CREEK MARINE INTERVAL (CONEMAUGH GROUP, UPPER
PENNSYLVANIAN), IN THE APPALACHIAN BASIN OF
WESTERN PENNSYLVANIA

GRAIG D. SHAAK1

SYNOPSIS: Nine Brush Creek localities in western Pennsylvania were trench sampled
for the purpose of recovering the total fauna from each visible marine horizon. The
9 localities provided 61 samples that were disaggregated by the Amine 220 tech-
nique, washed, dried, and sieved into 305 individual samples. The recovered fossils
are judged to have lived, died, and been preserved at each collecting site and are
therefore members of fossil communities. This judgement is based on qualitative
judgements of state of articulation, abrasion level, quality of preservation, and taxo-
nomic associations.
Animals from the sieve-sample splits were viewed microscopically to determine
taxonomic composition and frequencies. Raw faunal assemblage data were adjusted
to reduce the frequencies to whole numbers of individuals and, secondly, to a single
generation. The purpose of making a generation correction is to reflect standing
crop, which in turn provides a reasonable approximation of the once-living communi-
ties.
The adjusted outcrop data were examined for faunal similarities among localities
for the purpose of zoning the localities into workable groups. Two distinct faunal
groups are recognized on the basis of relative water depths and distances from shore.
Four shallow water and five deep water localities are inferred. The deep-water
localities are characterized by low diversity molluscan faunas, whereas the shallow-
water localities are characterized by high-diversity molluscan faunas.
The adjusted data were further subjected to programmed diversity and equitability
tests to decipher faunal succession and community structure. The diversity and
equitability data were graphed for each locality and the resultant curves compared
with ecological criteria such as animal habitat preferences and feeding types. These
combined types of data aided in deciphering the sea-level history of the marine
event at each locality. Transgressive, stillstand, and regressive phases are deciphered,
along with their corresponding opportunistic, stable-mature, and relict-mature faunas.
These data also show that the faunal distribution above and below the stillstand is
asymmetrical.

1 The author is Assistant Curator in Invertebrate Paleontology, Florida State Museum,
and Assistant Professor in the Department of Geology, University of Florida, Gaines-
ville 32611. Manuscript accepted 25 February 1974.

SHAAK, GRAIG D. Diversity and Community Structure of the Brush Creek Marine
Interval (Conemaugh Group, Upper Pennsylvanian), in the Appalachian Basin of
Western Pennsylvania. Bull. Florida State Museum, Biol. Sci., Vol. 19, No. 2. pp.69-
133.








SHAAK: BRUSH CREEK


sons will later be made between the Conemaugh communities and con-
temporaneous faunas of similar lithologies in the more western basins of
Pennsylvanian age.
The problem is one of reconstructing and interpreting the shallow
benthic marine communities of the Brush Creek marine interval, Cone-
maugh Group (Upper Pennsylvanian) in the appalachian basin of west-
ern Pennsylvania. The Brush Creek marine event represents one of a
series of four temporally limited marine events in a succession of prin-
cipally non-marine events represented in a cyclothemic sequence, the
Conemaugh Group.


GEOGRAPHIC AND STRATIGRAPHIC SETTING

The study area is that part of the Appalachian basin lying within the
Pittsburgh Plateaus section of the Allegheny Plateaus physiographic
province. The study area lies between 79000' and 80030' west longitude
and 39030' and 41000" north latitude. It encompasses 3,960 square miles.
Nine localities in six western Pennsylvania counties (Armstrong, Indiana,


+


I----- ---I~
01
I
oi I

0 BEAVER i-

I /

Al


' SCAL
0 3 6 12 13
A II I I I I
+ -+- +
BUTLER r---------,
ARMSTRONG
I 03
/ 2 /


LI


/' INDIANA
L "HN /

+ +i + c
LEGHENY 6 -6


WESTMORELAND --'

WASHINGTON '- i /
s-- -. -.-J\ I


K -- + +
0 7 SOMERSET
GREENE /
FAYETTE 0'8 9

LA.-.._.._.. ... .. ...-.
w. VA. 7I mD.


.-Brush Creek locality map, western Pennsylvania.
FIGuRE 1.-Brush Creek locality map, western Pennsylvania.


I
24 30 36

+

* Measured
Sections


-- --7
I
/


AMBRIA 'T


40C


I


I







BULLETIN FLORIDA STATE MUSEUM


Allegheny, Westmoreland, Fayette, and Somerset) were measured and
trench sampled in this investigation (Fig. 1).
The Pennsylvanian System was named by Williams (1891) for the
state of Pennsylvania in the central Appalachians, replacing the out-
moded name "Coal Measures." The Pennsylvanian System is divided
into the Pottsville, Allegheny, Conemaugh, and Monongahela Groups
in ascending order.
The Conemaugh Series was named by Platt (1879) for the Cone-
maugh River valley of western Pennsylvania (Fig. 2). The Conemaugh


W. VA. MD.
V. MD. Conemaugh Group

FIGURE 2.-Distribution and isopachous map of the Conemaugh group, western
Pennsylvania (adapted from Branson 1962).

includes the strata from the top of the Upper Freeport coal (Upper
Allegheny) to the base of the Pittsburgh Coal (Lower Monongahela).
These boundaries correspond with those of the Lower Barren Coal Mea-
sures, as previously named by Rogers (1858). Flint (1965) proposed
subdividing the Conemaugh Group into lower (Glenshaw) and upper
(Casselman) formations for their type sections in the Glenshaw vicinity,
Shaler Township, Allegheny County, and along the Casselman River in
Somerset County, Pennsylvania, and Garrett County, Maryland, respec-
tively (Fig. 3). This nomenclature is adopted for this study.


Vol. 19, No. 2








SHAAK: BRUSH CREEK


Pittsburgh coal bed


Marine beds lacking;
freshwater limestones
relatively abundant


Ames limestone (marine)






Woods Run limestone (marine)





Pine Creek limestone (marine)


Buffalo sandstone
--- Brush Creek shale

Brush Creek limestone

- Brush Creek shale
Brush Creek coal


marine
interval


Upper Freeport coal bed

FIGURE 3.-Subdivision of the Conemaugh group and generalized Brush Creek in-
terval (adapted from Flint 1965).


--I-I


E1r







BULLETIN FLORIDA STATE MUSEUM


The Brush Creek Member is the lowest of four marine units in the
Glenshaw Formation and was named by I. C. White (1878) for exposures
along Brush Creek, Cranberry Township, Butler County, Pennsylvania.
The Brush Creek is correlated with the Kansas City Group, Missourian
age, of the northern midcontinent area, based on the common occurrences
of the fusulinid Triticites ohioensis (Moore 1944: 684).


PREVIOUS INVESTIGATIONS

Other than general faunal lists, there is a paucity of published paleon-
tological studies of the Conemaugh Group. Mark (1912) prepared the
first comprehensive taxonomic treatment of Conemaugh fossils from
Ohio. Many of her identifications were documented from Raymond's
(1910) preliminary faunal list of Allegheny and Conemaugh fossils in
western Pennsylvania. Burke (1930) described the Ames Limestone
fauna from Painter Hollow, West Virginia. The Ames fauna of the
Pittsburgh Quadrangle was described by Theiss (1940). Seaman (1940,
1941, 1942) published short papers on the Ames, Pine Creek, and Brush
Creek limestones and their associated faunas of western Pennsylvania.
Miller and Unklesbay (1942) prepared a comprehensive faunal study
of cephalopods from Conemaugh rocks of western Pennsylvania. Leigh-
ton (1947) prepared a guidebook for Pittsburgh geology in which he
figured 21 Conemaugh taxa and prepared an extensive faunal list of
Conemaugh invertebrates. Doney (1954) figured and described 11
Brush Creek bivalve species from the Pittsburgh area and the immediate
vicinity. Lintz (1958) published on the fauna of the Ames and Brush
Creek shales of western Maryland. Murphy (1967) published one short
paper on the Brush Creek bivalves from Ohio and another (1970) on
the Brush Creek coiled nautiloid cephalopods from eastern Ohio and
western Pennsylvania.
One of the most valuable taxonomic aids used during this study was
Pennsylvanian Brachiopods of Ohio (Sturgeon and Hoare 1968). Hos-
kins' (1969) Fossil collecting in Pennsylvania and Wagner et al.'s (1970)
Geology of the Pittsburgh area were two very general but valuable
taxonomic aids.
Paleoecology, although a youthful branch of geology, is becoming an
extremely valuable tool in deciphering earth history. Several recent ex-
cellent paleoenvironmental studies have been conducted that are of
great aid in paleoecological reconstructions. For example, Morris (1967)
prepared a very detailed and comprehensive environments-of-deposition
and paleogeographic study of the Appalachian basin coal fields. Griese-


Vol. 19, No. 2







SHAAK: BRUSH CREEK


mer (1970) recognized seven faunal assemblages in the Ervine Creek
Limestone (Late Pennsylvanian) of the midcontinent region. He com-
bined both lithologic and paleontologic criteria for this reconstruction.
One of the more successful areas of paleoecological research has in-
volved the Pennsylvanian shallow marine benthic faunas. Johnson's
(1962) pioneering statistical approach to interspecific associations (often
termed fossil communities) with Pennsylvanian assemblages is an ex-
cellent work, and it is one of the most frequently cited papers among
the more recent literature. Fagerstrom (1964) described four fossil
assemblages from the Pennsylvanian of Nebraska, two of which were
named communities (fossil community and residual fossil community).
Stevens (1965, 1966, 1969, 1971) recognized communities from fossil
assemblages of the Pennsylvanian Minturn Formation in Colorado and
the Permian rocks of Nevada and Utah. Other important Pennsylvanian
studies are by Shabica (1970), West (1970), Williams (1960), and
Zangerl and Richardson (1963).
Many recent paleoecological endeavors have become quite sophisti-
cated in their approach. Cybernetics, stability, diversity, community
dynamics, and other concepts in modern ecological theory are being
tested in the fossil record. Species diversity and equitability gradients as
paleoecologic tools have been applied to carboniferous studies by Beer-
bower and Jordan (1969), Donahue and Rollins (in press), Donahue,
Rollins, and Shaak (1972), Rollins and Donahue (1971, 1972), and
West (1970).

ACKNOWLEDGMENTS
I wish to express my graditude to H. B. Rollins, N. K. Flint, J. Donahue, and
R. Lund, University of Pittsburgh, and H. Buchanan, University of West Virginia,
for their guidance and encouragement during the course of this investigation. I
wish to acknowledge V. Schmidt of the University of Pittsburgh for programming
the diversity indices.
This investigation was in part supported by the Society of the Sigma Xi grants-
in-aid of research, National Science Foundation Research Grant GA-31898 to H. B.
Rollins and J. Donahue, and the Department of Earth and Planetary Sciences,
University of Pittsburgh.

METHODS OF INVESTIGATION

FIELD SAMPLING

The stratigraphic section at each of nine selected field localities was
measured and described. Stratigraphic descriptions were recorded for
the purpose of defining major lithologic units. The lithologic units
complement the faunal analyses in deciphering paleoenvironments in that







BULLETIN FLORIDA STATE MUSEUM


the environments of deposition can sometimes be interpreted from the
resultant lithologies.
The sampling method selected for this study is the stratified sampling
technique described by Griffiths (1967: 18). The visible marine zone
(the vertical extent of macrofossils) at each locality was trench sampled
from top to bottom. Individual subsamples were taken within single
lithologies. In relatively thick homogeneous lithologies one foot intervals
were sampled, with approximately five pounds of rock taken in each bulk
sample. The entire trenched vertical marine horizon containing macro-
fossils was brought back to the laboratory. The reason for this form of
detailed sampling is to eliminate the effect of errors or biased samples.
In addition to these stratified samples, several spot samples were taken
at each locality to aid in the identification of the fauna. Observations
on the state of fossil preservation were recorded.

LABORATORY PREPARATION
The bulk random samples were brought to the laboratory, and the
total samples treated by the Amine 220 technique (Lund 1970: 578).
The Amine 220 technique is superior to the use of either kerosene or
Quaternary "O" (Geigy Chemical) for disaggregation of shales and
friable limestones. It is not successful, however, in treating dense lime-
stones. Bulk samples were left in the solution for an average of two
days and were frequently agitated to keep the fines in suspension. Many
samples, especially argillaceous shales and mudstones, were completely
disaggregated into fossils and mud.
The disaggregate was wet sieved through U.S. Standard Sieve series
numbers 2, 10, 40, 100, and 120. Numbers 2 and 10 retain the available
macrobenthos, number 40 retains the meiobenthos, and numbers 100 and
120 retain much of the microbenthos (Wigley and McIntyre 1964).
The disaggregate was thoroughly washed until all traces of the Amine
220 were removed. The washing process must be complete or upon
drying the individual grains become cemented into a gelatinous mass.
A total of 9 localities was trench sampled, providing 61 stratified
samples and 305 individual sieve fractions.

FAUNAL ANALYSIS

All sieve fractions were split with a standard sample splitter until
a workable quantity was reached. A workable quantity was determined
from a preliminary microscopic count of the fossils from the individual
sieve fractions.


Vol. 19, No. 2







SHAAK: BRUSH CREEK


Samples from each locality were analyzed, one sieve size at a time.
The +40 splits were analyzed first because this size fraction contained
an admixture of the larger microfossils and smaller macrofossils. The
+40 splits were followed in order by the +100, +120, +10, and +2
splits. An artificial subdivision of micro-macrofossils, based on size, was
established for the convenience of data accumulation and processing.
All fossils retained on the number 40, and coarser, sieves were deemed
macrofossils, and all those passing through the number 40 sieve, micro-
fossils.
A stereoscopic microscope was used for identification and counts of
the faunal elements, the microfossils at 40X and 100X magnification and
the macrofossils at 25.6X. Whenever possible, fossils were identified to
the generic level. Owing to their disarticulated state, echinoderms were
identified to class. Sponge spicules, conodonts, and vertebrates, all of
which were fragmentary, were identified to phylum. Bryozoans, except
for two readily recognizable genera, were identified only to growth form.
All fragmentary fossils greater than 50 percent complete were
counted, and the identification and frequencies were recorded on data
sheets for subsequent analyses. The counting of the individual sieve
size splits was stopped when a qualitative guess as to adequacy of sample
size was reached. This guess was adapted from the rarefaction method
arithmetic plots of Sanders (1968). If the number of species is plotted
against their frequency, the curve initially parallels the ordinate be-
cause of the high frequency of new species. As fewer and fewer new
species are added, the frequencies of already identified species are still
increasing and the curve now asymptotically approaches the abscissa.
The inflection point of the curve was used to guess the adequacy of
sample size. In most cases an adequately sized sample was reached
within the range of the initial sample splits but in several samples the
remaining fraction had to be resplit and counted to achieve adequacy
of sample size. The equitability of each split was subsequently quanti-
tatively determined in conjunction with the diversity indices.

DATA ADJUSTMENT TO REFLECT STANDING CROP

Ager (1963: 184) provides a comment on the tenuity of reconstruct-
ing fossil communities from fossil assemblages:

"The Paleoecologist must never forget that he is studying not
the living inhabitants of the village but only the bodies in the
churchyard, and then only after many visits by grave robbers."

The fossil assemblage, as quarried from the outcrop, may reflect little


1975







BULLETIN FLORIDA STATE MUSEUM


about its predecessor, the living community. However, by adjusting the
raw faunal assemblage data to reflect standing crop, a realistic approxi-
mation of the once living community is possible. One important condi-
tion that must be met before making these adjustments is that the as-
semblage cannot be biased by transport and mixing. Indicators of trans-
portation, such as the right-left value-sorting phenomenon, size sorting,
and abrasion were judged at the outcrops and in the washed samples
to be at a minimum. The concept of post-mortem transportation has long
been a deterrent to paleoecological reconstructions. Johnson (1972:152)
stresses this overemphasis and states that transportation is rare. He also
provides a most refreshing statement: "It is about time that paleontol-
ogists stop apologizing about this possible source of bias as there are
enough probable sources to worry about."
Recorded taxonomic frequencies must be adjusted to a common stan-
dard to enable comparison not only between the different samples within
an outcrop but among outcrops. These adjustments are necessary because
of the combined fossil and sediment weight differences of the individual
sieve sample splits. Initial frequencies were adjusted to a weight stan-
dard of 500 grams. For example, if the weight of the counted sample
(both fossils and sediment) was 1.25 grams, the individual frequencies
were increased by a factor of 400, which approximated the total that
would be found if 500 grams were initially counted.
Taxonomic frequencies in raw faunal assemblage data are strongly
biased by the various taxa that fragment or disarticulate during taphon-
omy. These biases should be compensated for before the data can
validly be subjected to statistical tests. The frequencies of fragmented
or disarticulated taxa must be reduced to a whole number of individuals.
For example, in only the rarest reservations are the radix, column, and
calyx of a crinoid preserved in an articulated state. The calyx usually
disarticulates into single crystal calcite plates that literally "cleave"
themselves out of existence. The column disarticulates into individual
columnals. Inasmuch as these columnals often are the only crinoid
remnants in an outcrop, the whole number of individuals must be de-
rived from the frequency of individual columnals. Frequencies of cri-
noid columnals, sponge spicules, echinoid spines, holothurian sclerites,
conodonts, and vertebrate fragments were reduced by a factor of 20
(Lund, pers. comm.).
Bryozoan frequencies were reduced by a factor of 6.3, based on the
ratio between the average zoarial lengths of nearly complete specimens
on slabs and those retained on the intermediate sized sieve ( + 40).
Ostracods average nine ecdysis stages; thus their frequencies were
reduced by a factor of nine (Kesling 1961: Q19).


Vol. 19, No. 2








SHAAK: BRUSH CREEK


Final adjustments to the taxonomic frequencies are intended to re-
duce the values to a "reflection" of standing crop (Shaak and Rollins
1972). Molluscs, which probably enjoy the longest average longevity
(five years), were selected to be the "standard bearer." This five-year
average molluscan longevity value is here defined as unity. The fre-
quencies of all remaining taxa with either longer or shorter estimated
longevity were reduced in proportion of their longevities to the average
molluscan value (Table 1). For example, most foraminifers and ostra-

TABLE 1.-SUMMARY OF LONGEVITY VALUES OF BRUSH CREEK TAXA.
Taxon Loneevity Source


Gastropoda
small
large
Bivalvia
epifaunal
infaunal
Foraminifera

Ostracoda

Echinodermata
Crinoidea

Echinoidea
Holothuroidea
Asteroides

Ophiuroidea
Bryozoa


Brachiopods


3 years
5 years

5 years
3 years
3 generations
per year
3 generations
per year

5 years

5 years
5 years
5 years

15 years
5 years'


4 years


Trilobita 5 years2
Porifera 12 years
Coelenterata
Anthozoa 5 years3
I Based on sexual maturity at five years.
2 Average longevity of Malacostraca.
3 Based on annual growth increments of 20 mm per year.


Comfort 1964: 82-83
Comfort 1964: 82-83

Comfort 1964: 84-85
Comfort 1964: 84-85
Thorson 1971: 152

Thorson 1971: 152


Fell and Pawson 1966: 50
Meyer (pers. comm.)
Moore 1966: 75
Pawson 1966: 63
Feder and Christensen
1966: 109
Fell 1966: 130
Ryland 1971: 82-85
Boardman and Cheetam
1969: 225
Hymen 1959: 590
Rudwick 1971: 156
Comfort 1964: 80
Comfort 1964: 81

Wells (pers. comm.)


cods average three generations per year; thus their frequencies were
reduced by a factor of 15. These longevity data were compiled from
estimated values of fossils as well as recent analogs.

DIVERSITY INDICES, SPECIES DIVERSTrY, AND EQUITABILITY

Diversity can vary in two ways; thus there are two different groups
of diversity indices (Donahue and Carothers 1972). One type is the







BULLETIN FLORIDA STATE MUSEUM


numerical percentage composition (Sanders 1968) of the various taxa
in the sample. This is based on numerical dominance. If all taxa are
numerically dissimilar, dominance is high and diversity low. The second
variety is known as species diversity (Whittaker 1965) and is determined
by the number of taxa present in the sample. The more species present
in the sample, the higher the diversity. With the two types of diversity
and their two types of numerical variance, it was decided to use a repre-
sentative diversity index of each type.
The Simpson index (1949) is calculated from the following equation
(N = number of taxa per sample and n = number of individuals per taxon):


Ds= N(N-1)
Yn (n-1)

The observed Simpson values range from 1.00 to 6.441.
The second index used is the Shannon-Wiener information function
(Lloyd and Ghelardi 1964) (s= total number of species and pr= observed
proportion of individuals that belong to the r'" species [r=l, 2, . ., S]):

s
H(s)=-pr log0,p
r=l
The calculated Shannon-Wiener values range from 0.0 to 3.030.
Donahue (pers. comm.) developed an equitability test used in this
study that not only measures numerical equality or evenness of the

distribution but also the adequacy of sample size: Simpson Index where
number of taxa
the calculated Simpson Index (Ds) for a particular sample is divided by
the number of taxa in that sample. The calculated equitability values
range from 1.0 to 0.064. An equitability value of 1.0 denotes a perfect
equitable distribution, and decreasingly lower values reflect increased
dominance. The equitability values also provide a numerical test for
adequacy of sample size. The ratio between equitability and the num-
ber of taxa in each sample should approximate a value of one, omitting
the decimal in the equitability value, if the sample size is adequate.
Unfortunately there are no data to define the range of acceptable values
in either rejecting or accepting the sample as being of statistically sound
size. Because the Simpson index is affected by sample size, a ratio near
a value of one suggests that the particular Simpson value used here is
not overly biased by sample size.
The taxonomic frequency values were plotted for each sample from


Vol. 19, No. 2







SHAAK: BRUSH CREEK


each outcrop for total fauna, molluscs only, and without molluscs to aid
in the interpretations of diversity and equitability fluctuations.

THEORETICAL FRAMEWORK

CHARACTERISTICS OF LEVEL-BOTTOM MARINE COMMUNITIES
With respect to hard parts and probability of rapid burial, the marine
benthic communities are the most preservable communities of the bio-
sphere (Johnson 1964: 120). If one accepts this premise, the level-bot-
tom marine community concept should be relatively easy to define, but
a review of the literature indicates just the opposite.
The term biocoenose community is applied where the importance is
placed on species interdependence. This approach, however, is not
applicable to modern marine communities because of the relative in-
dependence of marine level-bottom species (Speden 1966: 411). The
habitat community approach of Newell et al. (1959: 200) is based on
"environmental" species, or the relationship between environmental pa-
rameters and certain index taxa. A third kind of definition is based on the
classical work of Petersen (1911, 1913, 1914, 1915, 1918), in which the
most "characteristic" species of animals were used to designate the com-
munity. The Petersen communities are synonymous with the organism
communities of Newell et al. (1959). The Petersen community is based
on numerically dominant, recurring species which are designated as the
standard-bearers (Thorson 1957: 467). This concept was expanded by
Thorson (1955), who designated "parallel level-bottom communities."
These parallel communities inhabited the same type of substrate in areas
scattered geographically (Odum 1971: 340). The Petersen concept for
naming communities has been adopted in this investigation.
The species compositions of communities are not fixed and bordering
communities commonly integrate (Johnson 1964: 108). This inhomo-
geneity of communities is an argument against communities being real
units. The disagreement among marine biologists as to the validity of
communities being real ecological units is probably the least critical in
level-bottom marine communities. Probably the most uniform place in
the biosphere is the level-bottom area of the sea (Thorson 1957: 469).
Johnson (1964: 108) convincingly sums up the defense: ". . All species
living today do not occur in all possible combinations in natural assem-
blages. Rather, we observe around us a finite number of recurring asso-
ciations of species." The high recurrence rates of suites of species in
modern environments, especially level-bottom marine environments, are
probably not chance associations. Thus it seems reasonable to accept
level-bottom communities as real or natural entities.







BULLETIN FLORIDA STATE MUSEUM


In a paleoecological study, the recognition of communities is not an
end but only the means to an end. It is well documented that the species
composition of communities is not constant, and communities also change
with time. There is a natural succession during the stages of community
development. Species diversity increases during the pioneering stages
of succession and will peak and then decline in the climax (Margalef
1963). The concept of climax is valid; however, documentation of a
climax community that would develop in an ecosystem at equilibrium
is very tenuous indeed. All systems strive to reach a condition of equi-
librium or environmental stability, and the principal limiting factor is
time. Dunbar (1960), Margalef (1968), and Wilson (1969) provide
excellent accounts of stability evolution in marine environments.
The application of the concepts of community succession and sta-
bility is difficult in recent benthic marine studies, and these difficulties
are compounded when applied to the fossil record. Fortunately, the
level-bottom marine communities and their related environments are
relatively simple in comparison with complex systems such as rocky in-
tertidal, reef, and terrestrial regimes. Upon recognition of the level-
bottom benthic communities, it is necessary to interpret their temporal
and spatial variations. These variations are reflected by variations in
species diversity. Several workers have attempted to explain variations
in species diversity between marine communities (e.g., Buzas and Gib-
son 1969, Johnson 1970, Stevens 1971). The most attractive concept
at this time is the "stability-time" hypothesis of Sanders (1969). Sanders
defines two end members in explaining differences between communities.
At one end is the physically controlled, or "physically accommodated,"
community in which diversity is low, stress is high, and adaptations are
controlled by the physical environment. This type of community is not
resource-limited (Valentine 1971: 51). At the opposite end of the spec-
trum is the biologically controlled, or "biologically accommodated," com-
munity in which diversity is high, stress is low, and adaptations are con-
trolled biologically. This type of community is resource-limited. These
end-member communities parallel the immature and mature community
of Margalef (1968), and perhaps the non-interactive, interactive equi-
libria model of Wilson (1969). Any natural or real community prob-
ably falls somewhere between these end points and is an admixture of
the two. If local environmental conditions remain nearly constant, the
community undergoes succession toward the state of biological accom-
modation. If the stresses remain low, a biologically accommodated com-
munity evolves; if the stresses remain high, a physically accommodated
community develops (Johnson 1970:286).
A marine transgressive-stillstand-regressive faunal sequence can be


Vol. 19, No. 2







SHAAK: BRUSH CREEK


recognized by the presence or absence of various taxa, taxonomic asso-
ciations, inferred feeding types of modes of life, sedimentologic criteria,
and geochemical techniques (Stevens 1971). The transgressive phase,
is marked faunally by opportunistic communities composed of relatively
few eurytopic species living in rigorous near-shore marginal environ-
ments. The stillstand represents the time of maximum marine inunda-
tion and supports the most diverse fauna, that of the stable-mature com-
munities. Both eurytopic and stenotopic species are found in this higher
stability regime. The regressive phase results in a biological winnowing
out of the stenotopic species, resulting in relict-mature communities
composed of the more eurytopic components of the stable mature phase
(Rollins and Donahue 1971).
Certain suites of fossils are recurrent both vertically and laterally,
and adequately reflect regional shallow-benthic communities. Detailed
paleoecological analyses, including species diversity, equitability, taxo-
nomic frequencies, and feeding and habitat preferences, serve to docu-
ment the similarities between the faunal successions at the different
localities and warrant the naming of recurrent regional communities.
One of the greatest attributes of the "stability-time" hypothesis is
that it predicts recognizable changes within marine communities. Spe-
cies diversity varies directly with environmental stability (Donahue and
Rollins 1972: 4) and is predictable in a transgressive-stillstand-regressive
sequence.
The Brush Creek marine transgressive front provided numerous new
habitats for colonization by marine organisms (Rollins and Donahue
1972: 3). The frontal environments would have been of high stress
and fluctuation and would have supported only a few eurytopic species.
The communities would have been opportunistic, and in the stability-
time framework nearer the physically accommodated end. The species
diversity values would be low with the exception of localized "chance"
patches of high diversity.
As environmental stress decreased or fluctuated less and transgression
continued, colonization would increase at a given locality. Stenotopic
species would invade the area and physical accommodation would de-
crease, whereas biological accommodation would increase. Increased
stability would be paralleled by diversity increases. Eventually maxi-
mum transgression would be reached and if maintained, stillstand com-
munities would develop. The highest stability at a given locality would
be reached during the stillstand, and communities would approach bio-
logical accommodation, increase in diversity, enjoy low stress environ-
ments, and, if time allowed, would continue through succession to ap-
proach equilibrium. These stillstand communities would be stable-







BULLETIN FLORIDA STATE MUSEUM


mature communities with both stenotopic and eurytopic species, and
their successional level or maturity would be a function of time. A high
diversity stillstand average for several localities would suggest a rela-
tively lengthy period of stability and ecosystem maturity.
The regressive phase should show almost the reverse of the trans-
gressive phase. Increasing environmental stress and fluctuations would
cause a deterioration of the communities. Physical accommodation would
become increasingly important as the stenotopic species are biologically
winnowed out. The residual communities would be the relict-mature
communities composed of the more eurytopic species left over from the
degraded stable-mature communities. Theoretically, the relict-mature
communities would be numerically represented by diversities intermedi-
ate between those of the transgressive and stillstand phases.

CHARACTERISTICS OF THE BRUSH CREEK DEPOSITIONAL BASIN
The Brush Creek marine depositional basin covered parts of Pennsyl-
vania, Maryland, Ohio, Kentucky, and West Virginia. In early Brush
Creek time the sea was essentially landlocked (thus brackish), with only
a narrow seaway or strait that was the connection with the major mid-
continent Pennsylvanian sea extending through portions of Muskingum,
Guernsey, and Noble counties in Ohio. The majority of the terrigenous
sediments were being shed from the southeastern bordering Appalachian
highlands by a river system that built an extensive deltaic plastic edge,
prograding toward the center of the basin (Morris 1967: 111).
The Brush Creek marine deposition commenced with transgression
of the Brush Creek sea from the midcontinent region, through the Ohio
straits, and into the Brush Creek depositional basin. Concurrently,
along with the transgression, the basin (originally brackish) took on a
marine aspect (Morris 1967: 2). The study area (western Pennsylvania)
was that part of the basin bounded by a low delta plain to the east and
the pro-delta portion of the basin to the west (Ferm, pers. comm.).
Therefore the Brush Creek basin within the study area was directly
influenced by both the prograding deltaic wedge and the transgressing
sea.

FAUNAL SUCCESSION AND DIVERSITY
In order to avoid a cumbersome outcrop-by-outcrop treatment of
faunal succession and species diversity, the taxonomic data were grouped
and examined to ascertain faunal trends. Total outcrop faunal composi-
tion, stillstand composition (the samples from each locality judged to
represent the stillstand), stillstand, sub-stillstand, and supra-stillstand


Vol. 19, No. 2







SHAAK: BRUSH CREEK


composition, as well as associated lithologic types are the bases for sub-
dividing the total fauna into two gross faunal groups, namely high and
low diversity molluscan faunas.
Of the nine localities studied (Fig. 1), the geographically peripheral
localities (1, 7, 8, and 9) contain high diversity molluscan faunas, where-
as the more central localities (2, 3, 4, 5, and 6) contain low diversity
molluscan faunas. Although very general in scale, this grouping is very
real and critical in the interpretation of diversity and community struc-
tures.
Taxonomic frequencies in the samples considered representative of
the stillstand average 15 molluscan taxa for the high diversity molluscan
faunas, whereas the low diversity molluscan faunas in stillstand samples
average 10 molluscan taxa (Table 2). The high diversity faunas average
62% molluscan taxa of the total number of taxa, as opposed to 46%
molluscs for the low diversity faunas. Though ubiquitous, Astartella
(a small rhomboidal to ovate eurytopic bivalve of the family Astartidae)
is 10 times more abundant in the high density molluscan faunas than in
the more central ones.
Total outcrop faunal compositions, although less useful than stillstand
data, show similar relationships. Molluscs average 15 taxa in the high
diversity faunas, whereas the low diversity faunas average 11 molluscan
taxa. The molluscan taxa from the high diversity faunas average 61%
of the total number of taxa, and the low diversity average is 47% mollus-
can taxa. Astartella is four times more abundant in the high diversity
molluscan outcrops (Table 3).
These data lead to a suggestion of relative water depth and distance
from shore for the depositional environments of these two outcrop
groups. Pennsylvanian molluscan faunas in shallow benthic communities
in Colorado increase in diversity nearshore according to Stevens (1971:
406), whereas other faunal components increase in diversity offshore.
Thus the high diversity molluscan faunas of the western Pennsylvania
Brush Creek marine unit represent marginal or shoal water localities
(Rollins and Donahue 1972).
There is also lithologic support for these conclusions. Locality 7,
near Uniontown, Pennsylvania, has its diversity peak at the position of
a sideritic ironstone layer containing a molluscan dominant fauna and
associated phylloid algae, representing an interdistributary bay facies
(Donahue, Rollins, and Shaak 1972: 8). Similarly, the remaining high
diversity molluscan localities (1, 8, and 9) have bedded ironstone no-
dules below the position of their diversity peaks. In the low diversity
molluscan outcrops the first occurrence of ironstone nodules, either
bedded or scattered upward from the base of the fossiliferous zone, is








TABLE 2.-SUMMARY OF STILLSTAND SAMPLE FREQUENCIES.
Sample Locality
1 2 3 4 5 6 7 8 9


Shansiella
Plagioglypta
Aclisina
Crinoids
Ornamented Ostracods
Smooth Ostracods
Cyclogyra
Glabrocingulum
Astartella
Inathanopsis
Molluscan taxa
Number of taxa
Molluscan % of taxa


13445 18011 3 748 48810 0 0 0 0
9942 0 106528 0 6894 6190 10398 392 12066
7753 919 3272 444 3705 28378 5218 9100 284
1370 0 81 2271 3148 3228 0 60 981
970 0 1879 1174 110 0 298 100 653
2891 5450 2767 5373 525 3480 5783 1656 6577 n
657745 243071 246744 630958 16652 179599 0 665 967639 3
180720 2521 275042 19700 1399 221960 108066 7999 92502
189335 26173 699 296 7844 312337 312337 10397 93512
54936 5304 5602 0 34012 556 8726 5193 13181
19 10 11 10 10 12 13 13 16 4
31 23 25 22 21 23 25 18 26
61 43 44 45 48 52 52 72 61


TABLE 3.-SUMMARY OF TOTAL OUTCROP TAXONOMIC FREQUENCY AVERAGES.


Shansiella
Plagioglypta
Aclisina
Crinoids
Ornamented Ostracods
Smooth Ostracods
Cyclogyra
Glabrocingulum
Astartella
lanthanopsis
Stillstand number of taxa
Molluscan taxa
Number of taxa
Molluscan % of taxa


Locality
1 2 3 4 5 6 7 8 9
2421 23127 3 1732 63242 789 0 29 10 Q
985 1 33403 62 2862 4095 12294 87 13604
1298 4074 3269 788 2834 36727 870 14485 3618
764 2 361 1107 1560 655 2111 127 341
209 159 353 8926 95 199 139 17 92
3517 3113 1136 8654 917 1523 5161 3296 3106
255826 359156 91268 608586 8175 113118 0 612 434907
33373 1452 68000 6812 646 239608 63026 26499 11835
36868 46811 984 10692 21971 103480 442384 13845 82243
8623 1246 1152 161 6020 959 11103 46264 33276
31 23 25 22 21 23 25 18 26
26 15 11 15 13 17 20 21 20 z
46 38 28 31 25 32 39 29 31
57 39 39 49 52 53 51 72 65


sample






SHAAK: BRUSH CREEK


above the position of the diversity peak; that is, in the regressive sequence
(Appendix A). The significance of the bedded nodules and their rela-
tionship to the sideritic ironstone layers at Loc. 6 and the overall rela-
tionship to water depth and distance from shore is that many of the
aforementioned bedded nodules contain fractures resembling desicca-
tion cracks, further suggestive of shoal conditions (Wilson 1967: 85,
Emery 1950: 220).
One other taxonomic group provides excellent supportive evidence
for a shallow water origin of the high diversity molluscan samples. The
ornamented ostracods may require near normal marine salinities for the
precipitation of their elaborate shells (Benson 1961: Q58). Looking at
total outcrop taxonomic frequency averages (Table 3), the ornamented
ostracods are 17 times more abundant in the low diversity molluscan
outcrops, whereas smooth ostracods are more abundant in the high
diversity molluscan localities.
Such treatment of data, which was originally intended only for a
general grouping of faunas from the nine localities, proves to be a sur-
prisingly valuable paleoecological tool in this investigation. It is within
the framework of low versus high diversity molluscan faunas that the
individual localities are discussed with respect to species diversity and
faunal succession.

HIGH DIVERSITY MOLLUSCAN FAUNAS
LOCALITY 1, KITrANNING, PENNSYLVANIA.-Eleven trench samples,
excluding the limestone (1.5 ft.), were trenched in an 11 foot interval
from 17-28 ft. above the Brush Creek coal. Data derived from the 11
samples show a distinct molluscan dominancy, as evidenced by the
number-of-taxa curves (Fig. 4). The equitability curve shows an in-
verse relationship to the molluscan curve. At molluscan lows there are
corresponding equitability highs, and molluscan highs are paralleled by
equitability lows. This inverse relationship is explained by dominance
within the molluscan fauna of the omnipresent bivalve Astartella.
The diversity index curves essentially parallel the equitability curve
and roughly parallel the species diversity curves. These relationships, as
well as the numerical values calculated for these curves, delineate the
transgressive-stillstand-regressive phases of the marine event. The ma-
rine faunal stillstand is judged to occur at the position of Sample 8, 1.0-
2.0 ft. above the limestone. This sample contains 31 taxa, of which 19
(61%) are molluscs. This species diversity high is paralleled by Shan-
non-Wiener and Simpson index highs of 2.7 and 4.3 respectively (Table
4). The equitability values for this sample (0.14) is an intermediate


1975













27 -


I I I I I I
0 1 2 3 4 5
DIVERSITY INDICES
Shannon Wiener
Simpson - -


11


10


9


8

7
6
5

limestone




4



3


*


I,










i
'\I
\ \









/





//




V/






0 5 10 15 20 25 30
NUMBER OF TAXA
total fauna -
molluscs only -
without molluscs -


FIGURE 4.-Summary of sample locations, diversity indices, number of taxa, and equitability for
Locality 1, Kittaning, Pennsylvania.


feet sample
28 r- r


0 .1 .2 .3 .4
EQUITABILITY


25 -


24 -


23 -


22


20 -


19 -


187


17L







SHAAK: BRUSH CREEK


value for this locality and again reflects an internal dominance within
the molluscs.
There are several anomalous peaks on the curves that require an ex-
planation. First, diversity index highs (2.6 and 4.6) occur within sample
2 (2.5-3.5 ft. below the limestone). These highs correspond to an
equitability high of 0.29. The explanation is that only 16 taxa are re-
corded from the sample and the frequencies are evenly spread among
these taxa. Thus the diversity index highs are controlled, in this case
by an equitability high. This same factor controls the diversity index
peaks in Sample 6. Secondly, at sample 4 there is a marked species
diversity high which closely approximates the stillstand values at Sample
8. However the diversity indices are intermediate in value (2.3, 3.0) at
Sample 4, and the corresponding equitability value is low (0.1). This
anomalous sample probably reflects patchiness in the areal distribution
of the fauna and reflects a local diversity and density high (garden or
oasis) within the transgressive phase that was a "chance" find in the
sampling. Such patchiness is evidently more common in both the fossil
record and in modern faunas than is generally recognized (Speden 1966:
413). The assumption that this sample represents a local diversity high
is further evidenced by the fact that both species diversity and diversity
index values are intermediate in the subjacent and suprajacent samples.
This transgressive high represents an opportunistic fauna dominated by
eurytopic organisms such as Cyclogyra and Glabrocingulum.
The transgressive-regressive phases are distributed asymmetrically
above and below the stillstand. The stillstand contains the stable mature
fauna.
LOCALITY 7, UNIONTOWN, PENNSYLVANIA (PICCOLOMINI LOCALITY).-
A report on a paleoecological investigation of this locality has been pub-
lished (Donahue, Rollins, and Shaak 1972); only the salient features are
mentioned here. Faunal analysis of six trenched samples taken within
a three foot continuous interval suggests the following conclusions. First,
species diversity, diversity indices, and equitability data (Fig. 5) suggest
that the stillstand occurred within a limestone-ironstone unit and asso-
ciated subjacent and suprajacent shales. Secondly, the diversity indices
at the stillstand are qualitatively estimated to be 3.0 and 4.0 (Table 5),
with an equitability values of 1.3. The estimates were made from hand
picked specimens of the highly fossiliferous limestone-ironstone that
could not be treated with the conventional laboratory techniques (a
discussion of the limestone problem is found at the end of this section).
Thirdly, a second diversity peak occurs within Sample 5, which is domi-
nated by a productid-chonetid brachiopod fauna with smaller numbers
of bivalves. This regressive high represents a somewhat stable relict-












sample


5



:4



limestone -
ironstone


I I I I
0 1 2 3 4
DIVERSITY INDICES
Shannon -Wiener
Simpson - -


13 -


FIGURE 5.-Summary of sample locations, diversity indices, number of taxa, and equitability for Locality 7 (Piccolomini
locality), Uniontown, Pennsylvania.


\\







//




i,-










0 5 10 15 20 25 30
NUMBER OF TAXA
total fauna
molluscs only - -
without molluscs - -


12 -


10k-


I I I I
0 .05 .10 .15
EQUITABILITY







SHAAK: BRUSH CREEK


TABLE 4.-SUMMARY OF DIVERSITY AND EQUITABILITY VALUES FOR LOCALITY 1,
KITTANING, PENNSYLVANIA.


Sample Number Molluscs Without S-W1 S2 Equita-
Number Interval of Taxa Only Molluscs Diversity Diversity ability
11 4.0-5.0' above limestone 14 8 6 2.04 3.16 .23
10 3.0-4.0' above limestone 15 7 8 2.05 2.93 .20
9 2.0-3.0' above limestone 14 8 6 1.53 2.39 .17
8 1.0-2.0' above limestone 31 19 12 2.74 4.26 .14
7 8"-1.0' above limestone 15 7 8 1.65 2.27 .15
6 4-8" above limestone 13 6 7 2.48 3.94 .30
5 0-4" above limestone 20 10 10 1.28 1.63 .08
4 0-1.0' below limestone 30 18 12 2.29 3.04 .10
3 1.0-2.5' below limestone 20 13 7 2.06 2.96 .15
2 2.5-3.5' below limestone 16 6 10 2.65 4.57 .29
1 3.5-4.5' below limestone 10 5 5 2.00 3.09 .30
1 S-W=Shannon-Wiener
2S=Simpson

mature fauna dominated by the more eurytopic components left over
from the stable-mature (stillstand) phase. Lastly, the faunal distribu-
tion above and below the stillstand is asymmetrical.
LOCALITY 8, URSINA, PENNSYLVANIA.-This locality is a collector's
paradise for an exquisitely rich molluscan fauna. The bellerophontid
gastropod Pharkidonatus is very abundant and, because of its large size,
is the most conspicuous component of the macrofauna.
Seven trench samples were taken within a 6.5 ft. stratigraphic in-
terval. The resultant data curves (Fig. 6) are diagnostic and again
show the molluscan dominance characteristic of these shoaler localities.
The stillstand phase peaks in Sample 5 at diversity index highs of 2.6
and 5.1 (Table 6). The equitability value of 0.28 for Sample 5 explains

TABLE 5.-SUMMARY OF DIVERSITY AND EQUITABILITY VALUES FOR LOCALITY 7,
UNIONTOWN, PENNSYLVANIA.

Sample Number Molluscs Without S-W1 S2 Equita-
Number Interval of Taxa Only Molluscs Diversity Diversity ability
6 10.0-18.0" above limestone 15 7 8 1.50 1.68 .11
5 0.5-10.0" above limestone 23 12 11 2.10 2.54 .11
4 0-0.5" above limestone 19 9 10 1.67 2.20 .12
limestone-ironstone
3 0-0.5" below limestone 25 13 12 1.39 1.60 .06
2,10.5-2.0" below limestone 20 10 10 1.05 1.40 .07
1 S-W=Shannon-Wiener
2 S=Simpson

the diversity index peaks on the basis that the faunal distribution is
evenly spread among the various taxa. This sample contains a stable-


1975










sample


5

limestone

4


3


(


0 1 2 3 4
DIVERSITY INDICES
Shannon -Weiner
Simpson - -


FIGURE 6.-Summary of sample locations, diversity
Pennsylvania.


5 0 5 10 15 20
NUMBER OF TAXA
total fauna
molluscs only - -
without molluscs -


0 .1 .2
EQUITABILITY


.3 .4 .5



0)


indices, number of taxa, and equitability for Locality 8, Ursina,


tr\







SHAAK: BRUSH CREEK


TABLE 6.-SUMMARY OF DIVERSITY AND EQUITABILITY VALUES FOR LOCALITY 8,
URSINA, PENNSYLVANIA.
Sample Number Molluscs Without S-W1 S2 Equita-
Number Interval of Taxa Only Molluscs Diversity Diversity ability
7 1.5-2.5' above limestone 4 3 1 0.63 1.26 .32
6 0.5-1.5' above limestone 7 4 3 1.14 1.72 .25
5 0-0.5' above limestone 18 13 5 2.57 5.07 .28
4 0-0.5' below limestone 18 13 5 1.86 2.88 .16
3 0.5-1.5' below limestone 11 8 3 1.63 2.17 .20
2 1.5-2.5' below limestone 12 8 4 2.23 3.39 .28
1 2.5-3.5' below limestone 8 5 3 2.17 3.58 .45
1 S-W=Shannon-Wiener
2 S=Simpson


mature fauna. The very high data curve values suggest a relatively
high state of biological accommodation. There is perfect agreement be-
tween species diversity at the stillstand and Sample 4, and upon initial
inspection suggests a relatively lengthy stillstand characterized by two
lateral stable-mature faunas separated by a low diversity limestone facies.
However the lower species diversity peaks (Sample 4) have low di-
versity index and equitability counterparts. This phenomenon is ex-
plained by numerical dominance of several eurytopic taxa within the
faunas, and also by the fact that 8 of the 18 taxa have frequencies of
20 or less. Thus, the species diversity high of Sample 4 is interpreted
as a relatively stable opportunistic faunal patch that developed in the
late stages of the transgressions. This fauna perhaps gave rise directly
to the stable-mature fauna of the stillstand by a decrease in the fre-
quencies of the eurytopic components of the opportunistic fauna.
The limestone unit subjacent to the stillstand position is a trans-
gressive limestone. A qualitative analysis indicates that its fauna is
quite low in diversity and probably represents a restricted environment
in which a limy mud was deposited under brackish conditions.
The faunal succession is markedly asymmetrical above and below
the stillstand. The high diversity index values at the stillstand suggest
a relatively high level of biological accommodation.
LOCALITY 9, GLADE CITY, PENNSYLVANIA.-This locality is unique in
two aspects. First, two limestones are exposed in the sequence. The
upper limestone is clearly of channel origin, and it occures as a lens-
shaped body that grades laterally in two directions into bedded ironstone
nodules. The channel is 5 feet wide and 0.5 feet in maximum thickness.
Lithologically, the limestone is very dense, very black, and nearly devoid
of fossils. This limestone perhaps was deposited as a black mud in a
restricted abandoned channel on the lower part of a delta plain. Second,







BULLETIN FLORIDA STATE MUSEUM


the number of taxa curves graphically indicate the faunal succession
(Fig. 7).
Eight trench samples were taken within a 7.5 foot stratigraphic
interval. The resultant species diversity curves unquestionably pinpoint
the marine stillstand. Molluscs again control the faunal succession, as
shown by the parallelism of the total fauna and mollusc curves and the
opposite relationship between the mollusc and non-mollusc curves. The
diversity index curves are rather nondescript and, used alone, are mis-
leading. The stillstand occurs within Sample 5. The diversity index
curves show a slight inflection at the stillstand, which is in agreement
with a low equitability value. These low values at the stillstand are
explained by an uneven taxonomic frequency spread caused by the
dominance of Cyclogyra, a planispiral foraminifer of the family Fischer-
inidae, and Tolypammina, a tubular encrusting foraminifer of the family
Ammodiscidae.
There is a diversity index high and corresponding equitability high
at the Sample 2 position, which is readily explained by the presence of
only seven taxa that are evenly distributed. This equitable frequency
distribution among the seven taxa pumps up the diversity indices regard-
less of the number of taxa present (Table 7).


TABLE 7.-SUMMARY OF DIVERSITY AND EQUITABILITY VALUES FOR LOCALITY 9,
GLADE CITY, PENNSYLVANIA.

Sample Number Molluscs Without S-W1 S Equita-
Number Interval of Taxa Only Molluscs Diversity Diversity ability
8 2.5-3.5' above limestone 6 4 2 1.42 2.21 .37
7 1.5-2.5' above limestone 16 7 9 2.05 2.81 .18
6 10.0-14.0" above limestone 24 13 11 2.05 2.63 .11
5 5.0-10.0" above limestone 26 16 10 2.31 2.84 .11
4 0-5.0" above limestone 23 13 10 2.06 2.43 .11
3 0-1.0' below limestone 9 4 5 1.67 2.38 .27
2 1.0-2.0' below limestone 7 4 3 1.99 3.30 .47
1 2.0-3.0' below limestone 5 3 2 1.04 1.96 .39
1 S-W=Shannon-Wiener
2 S=Simpson


The faunal succession is markedly asymmetrical with a gradual
transgressive phase composed of a few eurytopic taxa, peaking at the
stillstand, and degrading relatively rapidly in the regressive phase.
Qualitatively, the limestone is of low diversity and probably was de-
posited in a brackish restricted environment. The limestone was formed
during transgression.


Vol. 19, No. 2







feet
12


sample t

11 -







9\
10 -





6



8- /

limestone


7-


7 / C j
3














DIVERSITY INDICES NUMBER OF TAXA EQUITABILITY
Shannon-Weiner -- total fauna -
Simpson - molluscs only - -
without molluscs
TD
FIGURE 7.-Summary of sample locations, diversity indices, number of taxa, and equitability
for Locality 9, Glade City, Pennsylvania.







feet sample








4


/
/ I
/ I


/ I

/


0 1 2 3 4
DIVERSITY INDICES
Shannon-Weiner
Simpson


0 5 10 15 20
NUMBER OF TAXA
total fauna
molluscs only - -
without molluscs- -


25 0 .05 .10 .15 .20
EQUITABILITY


FIGURE 8.-Summary of sample locations, diversity indices, number of taxa, and equitability for Locality 2,
Shelocta, Pennsylvania.


I

I
I


limestone



2







SHAAK: BRUSH CREEK


Low DIVERSITY MOLLUSCAN FAUNAS

LOCALITY 2, SHELOCTA, PENNSYLVANIA.-Brant (1971) presented a
very detailed interpretation of the faunal succession of this locality. He
used species diversity, equitability, and geochemical data for the pur-
pose of zoning the section into communities. Brant defined 12 zones, of
which zones 1 through 6 were classified as transgressive and zones 11
and 12 regressive. He did not indicate the position of the stillstand, but
stated: "the position of the stillstand in this section does not appear
meaningful" (Brant 1971:72).
Although the data curves for this locality (Fig. 8) are relatively
flat, two diversity index highs are shown. These curves have a near-
perfect fit with the equitability curve which, is explained by an "even-
ness" of spread of the frequencies within the various taxa for the highs
and a dominance factor for the lows.
The stillstand is judged to occur within Sample 3. Molluscs com-
prise 43 percent of the total number of taxa. Absolute high diversity
index values of 2.5 and 3.1 also occur within this sample (Table 8).

TABLE 8.--SUMMARY OF DIVERSITY AND EQUITABILITY VALUES FOR LOCALITY 2,
SHELOCTA, PENNSYLVANIA.
Sample Number Molluscs Without S-W' S' Equita-
Numbi r Interval of Taxa Only Molluscs Diversity Diversity ability
5 2.0-3.5' above limestone 22 10 12 1.78 2.09 .095
4 1.0-2.0' above limestone 21 8 13 1.83 2.29 .11
3 0-1.0' above limestone 23 10 13 2.46 3.13 .14
2 0-1.0' below limestone 21 9 15 1.39 1.70 .07
1 1.0-3.0' below limestone 20 8 12 2.16 2.76 .14
SS-W=Shannon-Wiener
2 S=Simpson

The diversity high at Sample 1 may represent a transgressive or oppor-
tunistic faunal patch that is controlled by eurytopic non-molluscs, in-
cluding 10 taxa (50 percent) of foraminifers. Although surprisingly
mature for an opportunistic fauna, Sample 1 does not reach the succes-
sional maturity of Sample 3 (stillstand).
These observations indicate that diversity index data alone can be
misleading. The refinement of the raw faunal assemblage data of the
"reflection" of standing crop provides the basis for the interpretation of
this outcrop.
The limestone is qualitatively judged to be of low diversity, con-
taining Kegelites (an amphissitid ostracod with a pitted shell) and
chonetid brachiopods. Brant (1971: 52) gave a Shannon-Wiener aver-
age index for the limestone of 1.25, which is in agreement with a quali-









feet
11 r


sample


4




3 (limestone)




2




1


\ \

\.




7/

7/

.,, ./
/


I i I i I
0 1 2 3 4
DIVERSITY INDICES
Shannon -Wiener
Simpson -


0 5 10 15 20
NUMBER OF TAXA
total fauna
molluscs only - -
without molluscs -


25 .1 .2 .3
EQUITABILITY


FIGURE 9.-Summary of sample locations, diversity indices, number of ttaxa, and equitability for Locality 3, Barton,
Pennsylvania.


'N












7


7
7


.4 .5 .6


_ _1







SHAAK: BRUSH CREEK


tative guess of low diversity in this study. However, he claimed that
the limestone is diagenetic (secondary) in origin (Brant 1971: 9), based
on its variable thickness and the localized gradational contact with the
subjacent and suprajacent shales. This interpretation is in disagreement
with that of the present study. The Brush Creek limestone is laterally
persistent and in several localities (3 and 7) contains a stable mature
fauna. Local lithologic variations, such as those at this locality, reflect
different limestone lithotopes within the various limestone facies. The
limestone at this locality is interpreted as a transgressive limestone de-
posited in a marginal but restricted environment. The restricted nature
is evidenced by the absence of stenotopic organisms.
The transgressive-regressive phases are asymmetrically distributed
above and below the stillstand.
LOCALITY 3, BARTON, PENNSYLVANIA.-FiVe trench samples were
taken within a 7.5 foot stratigraphic interval. The diversity index curves
(Fig. 9) for this locality are controlled by extreme fluctuations in equi-
tability. The stillstand is judged to occur within Sample 3, the limestone
unit, as evidenced by the species diversity curves. The lack of agree-
ment between the diversity index curves and species diversity curves at
the level of the stillstand is explained by the corresponding equitability
low (0.15). This equitability low is a function of dominance by two
taxa, Cyclogyra and Glabrocingulum (the latter a small pleurotomari-
acean gastropod). The stillstand, or stable-mature, fauna represents a
relatively short stillstand duration, as evidenced by the lack of an inflec-
tion in the diversity index curves. The stillstand fauna failed to reach
a high level of ecosystem maturity or biological accommodation even
though the number of taxa increased to an absolute high of 25 (Table 9).

TABLE 9.-SUMMARY OF DIVERSITY AND EQUITABILITY VALUES FOR LOCALITY 3,
BARTON, PENNSYLVANIA.

Sample Number Molluscs Without S-W1 S-' Equita-
Number Interval of Taxa Only Molluscs Diversity Diversity ability
5 0.5-1.5' above limestone 8 3 5 0.86 1.43 .18
4 0-0.5' above limestone 18 6 12 2.37 3.73 .21
3 limestone 25 11 14 2.18 3.65 .15
2 0-0.5' below limestone 8 2 6 2.09 3.50 .44
1 0.5-1.5' below limestone 3 1 2 1.00 1.63 .54
1 S-W=Shannon-Wiener
2 S=Simpson


Because it contains a stable-mature fauna, the limestone at this lo-
cality is unique. Lithologically the limestone is very argillaceous and
poorly cemented, thus very friable. The fossils are exquisitely preserved


1975







BULLETIN FLORIDA STATE MUSEUM


and readily removed from the matrix by the Amine 220 technique. This
particular limestone perhaps represents a true pro-delta basinal organic
limestone with minor but continuous terrigenous influx. The terrigenous
fraction is probably the cause of the friable nature of the limestone and
perhaps was the limiting factor in the low level of biological accommoda-
tion.
The transgressive-regressive phases are distributed asymmetrically
around the stillstand, with a relatively rapid transgressive faunal bloom
peaking at the stillstand. The regressive phase is less pronounced, with
a gradual biological winnowing of the stenotopic components of the
weakly developed stable-mature fauna.
LOCALITY 4, SEWICKLEY, PENNSYLVANIA.-Six trench samples were
taken within a 5.5 ft. interval, including the lower 0.5 ft. of the 1.5 ft.
thick limestone unit (Table 10). The resultant data and associated

TABLE 10.-SUMMIARY OF DIVERSITY AND EQUITABILITY VALUES FOB LOCALITY 4,
SEWICKLEY, PENNSYLVANIA.
Sample Number Molluscs Without S-W1 S2 Equita-
Number Interval of Taxa Only Molluscs Diversity Diversity ability
6 1.0-2.0' above limestone 14 7 7 1.12 1.68 .12
5 0.5-1.0' above limestone 22 10 12 1.25 1.64 .07
4 0-0.5' above limestone 17 5 12 1.20 1.58 .09
3 lower 0.5' of limestone 19 10 9 1.10 1.59 .08
2 0-1.0' below limestone 19 11 8 0.86 1.33 .07
1 1.0-2.0' below limestone 19 10 9 1.45 1.79 .09
1 S-W=Shannon-Wiener
2 S=Simpson

diversity curves (Fig. 10) at first appearance were rather non-descript
and difficult to interpret. However several subtle faunal trends pro-
vided an insight into the faunal succession.
The values along all of the data curves are quite low compared with
the other localities. The equitability scale has been exaggerated to show
inflections that normally would be masked at a more reduced scale.
The diversity index curves deviate only slightly from a straight line
owing to a marked dominance in all samples by two foraminifer genera,
Cyclogyra and Tolypammina.
The successional interpretation is derived for this locality from data
other than the diversity index curves. The key to the interpretation is
in the inverse relationship between the molluscs and non-molluscs in
the number of taxa or species diversity curves (Fig. 10). Going up-
section, the number of molluscan taxa is greater than the number of non-
molluscan taxa. Within the limestone the two curves intersect and the


Vol. 19, No. 2







feet
7 c

sample


6 6 r


5 6



\ \

4 limestone


3 -
3 /


S\ *
2

2 '

1 \ 1I


0 .5 1.0 1.5 2.0 0 5 10 15 20 25 0 .05 .06 .07 .08 .09 .10 .11 .12
DIVERSITY INDICES NUMBER OF TAXA EQUITABILITY
S hannon-Wiener-- total fauna
Simpnon -Wi r molluscs only
without molluscs -

FIGURE 10.-Summary of sample locations, diversity indices, number of taxa, and equitability for Locality 4, Sewickley, S
Pennsylvania.






102 BULLETIN FLORIDA STATE MUSEUM


non-molluscan taxa become dominant, suggestive of an increase in water
depth (Stevens 1971). A molluscan low and a non-molluscan high are
reached within Sample 4. This probably represents the maximum trans-
gression (thus deepest water) at this locality. These data correspond
to an equitability high of .09. The foraminiferal dominance is still para-
mount; however Sample 4 is more equitable than the subjacent and
suprajacent samples. The ornamented ostracods and the crinoids reach
an absolute high for the outcrop within Sample 4. Astartella reaches an
absolute low in this sample. This is all suggestive of deeper water.
Thus, the stillstand is judged to have occurred within Sample 4, based
on relative water depths.
On visual inspection only, the species diversity curves would indicate
that the stillstand occurred within Sample 5. The key to this interpreta-
tion is again the mollusc and non-molluse relationship. The molluscs
reach a taxonomic frequency low within Sample 4 and increase from 5
to 10 taxa (Table 10) at Sample 5. The non-molluscan number of taxa
remains unchanged from Sample 4 to 5 (12 taxa). This phenomenon re-
flects a molluscan diversity pumping resulting from shoaling effects.
Even though five molluscan taxa are added to the fauna, their frequen-
cies are so low that with the increase of the dominant foraminifers (be-
cause of shoaling) the equitability value decreases drastically. The
reduction of ornamented ostracods by a factor of five and the threefold
increase of Astartella are further suggestive of shoaling conditions (Fig.
10). Thus Sample 5 reflects a very diverse relict-mature fauna.
There is an alternative explanation for the increase in the number
of taxa within Sample 5. The fauna of Sample 5 may reflect an ecotone
or a transition between two communities. The increase in the number
of taxa from Sample 4 to 5 is entirely molluscan. This increase might
be explained by the "edge effect" (Odum 1971: 1957) in which there is
often a greater faunal diversity and density in the ecotone than in the
adjoining communities. This edge effect may represent the junction zone
between the early relict-mature fauna and an adjacent shoal water mol-
luscan fauna. Unfortunately, this concept cannot be documented with
the data available from this investigation.
There is another peculiar attribute of this locality that warrants an
explanation. The lower .75 ft. of limestone is so poorly consolidated
and friable that the fossils were removed from the matrix with ease and
treated with the standard data recovery techniques. The upper .75 ft. of
limestone is argillaceous, but less friable and more highly consolidated
than the lower .75 ft. This suggests increased terrigenous influx during
the deposition of the upper segment of the lime, and might explain the
decrease in the number of molluscs through the limestone, peaking at a


Vol. 19, No. 2







SHAAK: BRUSH CREEK


low in Sample 4. The increased terrigenous influx would have affected
the various feeding types (esp. filter feeders) and could have caused a
decline in the number of taxa (Purdy 1964: 243). However the maxi-
mum density of the crinoids and fenestrate ectoprocts within this sample
negates any strong sedimentologic influence.
The distribution of the transgressive-regressive phases around the
stillstand is asymmetrical within the confines of the sampling design.
Unfortunately the initial taxonomic buildup of the transgressive phase
is lower in the section than the sampled interval. The highest and low-
est samples have relatively high equitability values, as is common in
early transgressive and late regressive phases.
LOCALITY 5, GLENSHAW, PENNSYLVANIA.-This locality is unique be-
cause it shows an extremely rapid transgression to the stillstand from
non-marine, or near non-marine conditions within a stratigraphic interval
of only 13 inches (Fig. 11). Six trench samples were taken within a 6.0
ft. stratigraphic interval. The basal unit of the sequence is a massive
black mudstone at least 10 ft. thick (the basal coal is not exposed),
which is capped by a six-inch bed of limestone. The sample interval
extended two feet into the mudstone. Only two taxa of ostracods (one
smooth and one ornamented) were recovered from the matrix. A second
outcrop several hundred yards to the southwest also is barren of fossils
below the limestone and lithologically is composed of interbedded shale
and ironstone nodules. The black mudstone represents a restricted en-
vironment at the extreme end of the physical accommodation and mem-
ber of Sanders' stability-time hypothesis. The physiological stress condi-
tions were so great that the resultant environments were beyond the
adaptive means of most marine animal taxa.
The marine transgression was initiated with the deposition of the
limestone which, on a qualitative inspection, is very low in diversity.
The diversity index and species diversity curves peak within Sample 3
(Fig. 11), indicating the stillstand. The stillstand peak occurs within
13 inches of stratigraphic section; thus the transgression was nearly in-
stantaneous geologically. The high diversity index value of 6.0 for the
Simpson equation is a result of the rapid increase in the number of taxa
from 1 in Sample 2 to 21 in Sample 3 (Table 11). These peaks corre-
spond to an intermediate equitability value of 0.28, which is intermediate
because of dominance by Shansiella, a large turbiniform pleurotomaria-
cean gastropod.
The species diversity curves show a second inflection (Sample 5)
in the regressive or relict-mature fauna. The mollusc and non-mollusc
curves are nearly parallel through Sample 4, but in Sample 5 the curves





















/
/


limestone



2


0 1 2 3 4
DIVERSITY INDICES
Shannon-Wiener
Simpson -


\ \



\ \


//


5 6 0 5 10 15 20 25
NUMBER OF TAXA
total fauna
molluscs only - -
without molluscs -


FIGURE 11.-Summary of sample locations,
Pennsylvania.


diversity indices, number of taxa, and equitability for Locality 5, Glenshaw,


feet
14
sample


13


12-


11l


10-


0 .25 .50 .75 1.0
EQUITABILITY







SHAAK: BRUSH CREEK


TABLE 11.-SUMMARY OF DIVERSITY AND EQUITABILITY VALUES FOR LOCALITY 5,
GLENSHAW, PENNSYLVANIA.

Sample Number Molluscs Without S-W1 S2 Equita-
Number Interval of Taxa Only Molluscs Diversity Diversity ability
6 2.0-3.0' above limestone 8 3 5 2.39 4.91 .61
5 1.0-2.0' above limestone 15 9 6 2.26 3.86 .26
4 0.5-1.0' above limestone 16 7 9 2.29 2.80 .18
3 0-0.5' above limestone 21 10 11 3.03 5.96 .28
2 0-1.0' below limestone 1 0 1 0.00 1.00 1.00
1 1.0-2.0' below limestone 2 0 2 1.00 2.00 1.00
1 S-W=Shannon-Wiener
2S=Simpson

have reversed position, with the molluscs becoming dominant with re-
spect to the number of taxa for the first time in the sequence. This
molluscan increase corresponds to an increase in equitability and di-
versity index values, especially the Simpson function.
An abnormally high Simpson index of 4.9 occurs in Sample 6, late in
the regressive phase or relict mature fauna. This peak is not controlled
by the number of taxa, but by an equitability high (.51) that reflects
an even distribution of the frequencies within the eight recorded taxa.
The distribution of the transgressive-regressive sequence around the
stillstand is markedly asymmetrical, with a rapid transgressive phase and
an accompanying rapid buildup of the opportunistic fauna. The regres-
sive phase was more irregular than the transgressive phase. The still-
stand and accompanying stable-mature fauna was relatively shortlived,
as the number of taxa increased, peaked, and decreased within a seven-
inch stratigraphic interval.
The lack of agreement between the lower portion of the diversity
index curves and the equitability curve warrants an explanation. Samples
1 and 2 have a value of 1.0 perfect equitability. However, the corre-
sponding diversity index values of the Shannon-Wiener value is 0.0,
compared with the perfect equitability of 1.0. The Shannon-Wiener
function is strongly influenced by equitability, and in this case the di-
versity index should be high. However a perfectly equitable distribu-
tion (one taxon) represents a totally inequitable distribution in the
Shannon-Wiener function because of total (100 percent) dominance.
Thus, because of total dominance, the Shannon-Wiener index is zero.
The corresponding Simpson value is 1.0 which, except for infinity, is the
lowest calculable value for the equation, again because of total domi-
nance.
LOCALITY 6, MURRYSVILLE, PENNSYLVANIA.-Six trench samples were
taken within a 5.5 ft. stratigraphic interval. The diversity index curves













feet
7 -


sample
6
6 \



/ c

4 /



S limestone
(channel) .\
-- \ ,




limestone
1 \. //

0 1 2 3 4 5 6 7 0 15 20 25 0 .1 .2 .3 .4 .5 .6 .7
DIVERSITY INDICES NUMBER OF TAXA EQUITABILITY
0 Shannon -Weiner total fauna
Simpson - molluscs only -
without molluscs -

FIGURE 12.-Summary of sample locations, diversity indices, number of taxa, and equitability for Locality 6, Murrysville,
Pennsylvania. Z


ho







SHAAK: BRUSH CREEK


TABLE 12.-SUMMARY OF DIVERSITY AND EQUITABILITY VALUES FOR LOCALITY 6,
MURRYSVILLE, PENNSYLVANIA.
Sample Number Molluscs Without S-W1 S2 Equita-
Number Interval of Taxa Only Molluscs Diversity Diversity ability
6 2.0-3.0' above limestone3 5 4 1 1.55 2.77 .55
5 1.0-2.0' above limestone 9 4 5 2.35 4.36 .49
4 0-1.0' above limestone 15 7 8 1.93 2.84 .19
3 0-7.5" below limestone 23 12 11 2.16 3.21 .14
2 7.5-15" below limestone 23 12 11 2.62 4.62 .19
1 21.0-27.0" below limestone 10 6 4 2.91 6.44 .64
1 S-W=Shannon-Wiener
2 S=Simpson
3 =datum-channel limestone
(Fig. 12) alone are meaningless in the interpretation of species diversity
and faunal succession. The diversity index curves peak in two samples
(1 and 5), both of which are relatively equitable samples representing
no marked dominance by any one taxon. Sample 1 is represented by 10
taxa, with a very high Simpson index of 6.4 (Table 12). As previously
explained, the equitability factor is derived by diving the Simpson index
(6.4) by the number of taxa (10), resulting in an equitability index of
.64. The equitability value for this sample is an excellent guide in the
understanding and interpretation of diversity-equitability data in general.
Knowing what the equitability value represents allows one to look ob-
jectively at the diversity values. The Simpson index of 6.4 is controlled
either by number of taxa (species diversity) or equitability. Also, the
question of adequacy of sample size must be taken into consideration.
The data from Sample 1 clearly define this relationship. If the Simpson
index is compared with the equitability value (6.4 versus 0.64) within
the framework of sample size adequacy test as described earlier, the
values minus decimal are equal (in this case to five digits). If the
sample-size test is valid, this sample is adequate, removing the question
of incomplete data retrieval. Knowing that the sample size is adequate,
the diversity index curves can be interpreted. Sample 1 contains only
10 taxa, thus the diversity index value is not controlled by the number of
taxa but by the evenness of spread of the frequencies within the 10 taxa.
Again, the high equitability value of Sample 1 controls the high diversity
index value. An almost identical condition occurs within Sample 5,
where the diversity index peak is a function of high equitability rather
than the number of taxa.
Sample 1 was taken through a six-inch carbonaceous shale interval
between the basal coal and the overlaying limestone (Appendix A).
There is no non-marine sequence on top of the coal as 10 taxa were
accounted for within this basal sample. The overlying limestone is
quantitatively low in diversity and represents a transgressive limestone.






108 BULLETIN FLORIDA STATE MUSEUM


The stillstand occurs within Sample 2, a 7.5 inch interval immediately
suprajacent to the limestone. Samples 2 and 3 have identical number of
taxa values, and trends in the faunal succession. Sample 2 has a higher
equitability value and correspondingly higher diversity index values than
does Sample 3. Sample 2 has a more equitable frequency distribution
among its taxa than Sample 3, which fits better within the definition of a
stable-mature fauna. If Sample 2 represents a stillstand and Sample 3
an early regressive phase, Sample 3 should reflect shoaling trends. This
is the case, especially in faunal composition. One of the more reliable
shoal-water indicators is Astartella, which increases by a factor of 14
(36,115 to 489,365) from Sample 2 to Sample 3. Of 19 molluscan taxa
recognized from Samples 2 and 3, eight taxa are common to the two
samples. Six of these taxa increase in frequency in Sample 3; a further
suggestion of shoaling conditions, or initiation of the regressive phase.
The number-of-taxa curves graphically depict the asymmetrical dis-
tribution of the transgressive-regressive phases around the stillstand.
The transgressive phase was of relatively short duration, with a rapid
buildup of the opportunistic fauna. The stillstand was achieved in
Sample 2, with the accompanying degradation of the stable-mature fauna
quite regular with respect to the transgressive phase.
A channel limestone is exposed at this locality (Appendix A), which
on general inspection is devoid of fossils. Although very interesting with
respect to sedimentation and depositional environments, the channeling
removed six inches of the regressive phase deposits and associated fossils
from the section. The channel has masked another important relation-
ship in which there is a reversal in the number-of-taxa-curves from a
molluscan to a non-molluscan dominance within Samples 4 and 5. With
shoaling conditions resulting from regression of the sea, the molluscs
should remain dominant with respect to the number of taxa. This non-
molluscan dominance is only of the order of one taxon in each of the
two samples and is judged to be relatively insignificant as the trend re-
verts to a molluscan dominance in the highest sample (Sample 6).

THE LIMESTONE PROBLEM
All nine outcrops were trench sampled, and the total samples were
broken down by the Amine 220 technique. All of the washed residues
were split with a standard sample splitter. Thus, from outcrop to micro-
scope, these data are sound with respect to randomness. Every fossil
within the samples had a chance of being identified and included in the
frequency counts.
The limestone members of the Brush Creek interval present a worri-
some drawback to an otherwise credible data recovery system. The


Vol. 19, No. 2






SHAAK: BRUSH CREEK


limestones are not amenable to the Amine 220 technique. Several lime-
stone samples were reduced in a jaw crusher and subsequently treated
with the Amine 220 technique, but the sample pieces fractured across
fossils and only fossil fragments were recovered in the washed residues.
Possible alternatives to the system are qualitative analysis of either
whole-hand samples or polished slabs. Some hand samples have whole
fossils standing out in positive relief, which allows taxonomic identifica-
tion but cannot provide adequate frequency data. Polished sections
record all taxa in contact with the plane of the cut. Unfortunately the
fossils may have any orientation with respect to the plane, thus taxo-
nomic identifications are most difficult and very time consuming.
The limestone problem was alleviated somewhat by comparison of
the various limestone lithologies. Seven of the nine localities have well
consolidated limestones that are unbreakable by the Amine technique.
The remaining two localities (Loc. 3, Barton, Pennsylvania; and Loc. 4,
Sewickley, Pennsylvania) have poorly consolidated, friable limestones
from which the fossils were readily retrieved. The entire limestone unit
from the Barton locality was broken down and quantitatively is judged
to represent the stillstand. The lower 0.5 ft. interval of the 1.5 ft. lime-
stone from the Sewickley locality broke down and quantitatively is in-
termediate in values between those of the subjacent and suprajacent
samples within the transgressive phase. The limestones at the remaining
localities, with the exception of the ironstone-limestone horizon at the
Uniontown locality, are well consolidated and judged qualitatively to be
of low diversity. The ironstone-limestone interval at the Uniontown
locality is inferred to represent the standstill on the basis of a subjective
quantitative analysis of the well preserved and very rich molluscan fauna
that was retrieved from well-weathered float samples. Also, the esti-
mated diversity index and number of taxa values are substantially greater
than in the sub- and suprajacent samples. Thus there appears to be a
trend within the limestones, whether real or diagenetic, of an increase
in diversity with a decrease in the level of consolidation.
A second trend is perhaps more obvious. The limestone unit at two
of the nine localities is judged to contain the stable-mature fauna, repre-
sentative of the marine stillstand. The limestone unit at the remaining
seven localities is judged to contain a segment of the opportunistic fauna,
representative of the transgressive phase. At no locality studied in this
investigation does the limestone occur above the stillstand position. Two
of the localities have the limestone unit between two quantitatively
analyzed samples within the transgressive phase and qualitatively show
corresponding intermediate number of taxa and diversity index values.
The remaining seven localities have the limestone subjacent to the still-


1975






BULLETIN FLORIDA STATE MUSEUM


stand samples and qualitatively appear to be in accord with the pre-
dicted intermediate values.
These two trends, though subjective, are considered clear enough as
to not invalidate the placement of the stillstand at the seven localities
where well-consolidated limestones occur.

COMMUNITY STRUCTURE

GENERAL STATEMENT
One of the most consistent features of shallow benthic marine envi-
ronments is the recurrence of a particular taxon or taxonomic assemblage.
These ubiquitous taxa may be numerically dominant and may reflect
some observable physical environmental parameter. If these ubiquitous,
numerically dominant, and environmentally sensitive taxa are found in
association with other commonly recurrent species or taxonomic groups,
the definition of a fossil community is met. This definition is in accord
with the organism and habitat communities of Newell et al. (1959) and
the marine level-bottom communities within the framework of marine
biology (Bretsky 1969: 46).
The recurrence of species or taxonomic groups is explained by inter-
specific associations, similar responses to the physical environment, or
chance (Johnson 1964: 128). The chance associations are probably
minimal in level-bottom communities and most commonly are found
among transient species planktonicc or nektonic) that are relatively un-
important at the organizational level of any particular benthic com-
munity. It is commonly accepted that benthic species are quite inde-
pendent, and the resultant communities are associations of species living
together in harmony with the physical environment. The simple organ-
izational level of shallow benthic communities is more amenable to a
community structure analysis than the more diverse communities, such
as coral reef and rocky intertidal regimes.
The most common community analysis tools have been correlation
coefficients and factor analysis of a data matrix. A data matrix (Ap-
pendix B) was prepared for this study to show either presence or ab-
sence of each recognized taxon at all nine localities. Surprisingly, only
eight taxa (Table 13) were found to be ubiquitous within the study
area. The faunal succession was traced through the transgressive-still-
stand-regressive phases, and a relationship between these phases and the
community structure seemed more logical than taxonomic groupings
based on numerical dominance. Thus the transgressive, stillstand, and
regressive sample-adjusted frequencies were averaged for the eight ubi-


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TABLE 13.-SUMMARY OF TRANGRESSIVE-STILLSTAND-REGRESSIVE SAMPLE FREQUENCY
AVERAGES FOR TAXA COSMOPOLITAN TO THE STUDY AREA.

Taxa Transgressive1 Stillstand2 Regressive3
Ostracods (smooth) 3954 3834 2882
Ostracods (ornamented) 98 600 389
Astartella 90507 75190 85065
Clabrocingulum 21904 92502 63829
Ianthanopsis 17040 13181 2189
Aclisina 5714 6564 8968
Plagioglypta 1679 16934 8673
Crinoids 847 1238 423
1 Transgressive values are based on an average of 28 transgressive samples.
2 Stillstand values are based on an average of 9 stillstand samples.
3 Regressive values are based on an average of 24 regressive samples.
quitous taxa to ascertain community trends in parallel with the faunal
succession. If the marine interval can be divided into transgressive,
stillstand, and regressive phases, the corresponding taxa should be sub-
divisible into transgressive, stillstand, and regressive communities. The
frequency averages for the eight ubiquitous taxa adequately support this
premise.

Astartella-Ianthanopsis COMMUNITY
Astartella and lanthanopsis are selected to serve as name bearers for
the transgressive or opportunistic community. Astartella is a small eury-
topic crassatellacean bivalve that was an infaunal non-siphonate suspen-
sion feeder. It is classified as a "filterer-A" within the framework of the
Russian classificatory scheme for marine benthic invertebrates (Turpaeva
1957: 137). The successional trend of Astartella (Table 13) is quite
unique because it peaks numerically within the transgressive phase,
decreases in the stillstand, and increases within the regressive phase.
The frequency low within the stillstand phase is predictable because of
the shallow water preference of this species. Its regressive bloom ap-
proaches, but does not reach, the numerical dominance developed within
the transgressive phase. These marine stage frequencies of Astartella
lead one to speculate on the successional maturity of the stillstand or
stable-mature fauna for the study area as a whole. Although the still-
stand frequencies are reduced, they are still relatively high. The still-
stand values for Astartella, as well as any eurytopic organism, would
continue to be reduced with more pronounced biological accommodation
(Levinton 1970). However the modest frequency deduction in the still-
stand phase suggests a relatively low level of community maturity and
an accompanying low level of biological accommodation. In terms of the
stability-time hypothesis, this trend is also suggestive of an average short
stillstand duration.


1975







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lanthanopsis, the second name bearer of the opportunistic com-
munity, was a globular to high-spired fusiform gastropod of the family
Subulitidae. It was an epifaunal vagrant browser and deposit feeder
of the "collector" group of marine benthic invertebrates (Turpaeva
1957). This taxon peaks numerically within the transgressive or oppor-
tunistic phase and reaches a low within the regressive or relict-mature
phase (Table 13). Thus, lanthanopsis is a eurytopic component of the
community, and after transgressive bloom never again regained its nu-
merical dominance. The trend of lanthanopsis clearly delimits this
species as opportunistic, even more so than Astartella. Further suggestive
of a natural transgressive community among the ubiquitous taxa are the
unornamented ostracods, which also peak numerically within the trans-
gressive phase and decline through the stillstand and regressive phases.
The Astartella-lanthanopsis community is dominated by epifaunal
and infaunal vagrant deposit feeding organisms ("collectors" of the Tur-
paeva classification). This mode of life dominance in conjunction with
the paucity of sessile benthonic filterers ("filterers A and B" of Tur-
paeva), such as crinoids and bryozoans, is suggestive of an unstable
substrate in a high energy regime in shoal water environments. These
conditions are predictable for the opportunistic community as the fauna
is the product of the extremes of physical accommodation.

Glabrocingulum-Plagioglypta COMMUNITY
Glabrocingulum is a turbiniform, gradate to conically-spired gas-
tropod of the family Eotomariidae. Plagioglypta is a scaphopod of the
family Dentaliidae marked by distinct circular wrinkles generally
throughout the shell. These two genera are selected as standard bearers
for the stable-mature, or stillstand community because of their cosmo-
politan nature and their frequency trends through the faunal succession.
Glabrocingulum was a eurytopic vagrant epifaunal browser and de-
posit feeder of the "collector" benthic group of Turpaeva. The eurytopic
nature of this taxon is out of phase with the stable mature concept of
community succession. The eurytopic components theoretically are re-
duced in frequency, if not entirely removed, as the fauna trends toward
biological accommodation. With increasing biological accommodation,
the stenotopic components trend toward a state of equilibrium. If the
succession goes unchecked as a result of environmental stability over a
lengthy stillstand, the opportunistic species would be relatively rare
(Levinton 1970: 69). However, because of the relatively low level of
successional maturity and relatively short duration of the stillstand, the
stenotopic organisms did not have enough time to develop a dominance
over the eurytopic organisms. Deeper water conditions and increased


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substrate stability provided suitable habitats for the stenotopic organism
blooms, thus pumping up the diversity of the fauna but without exclu-
sion of the eurytopic components. It is quite possible for an explosive
opportunist to numerically peak within the stillstand or stable-mature
fauna if the limiting factor of that phase is temporal brevity.
Glabrocingulum peaks numerically within the stable-mature phase
and tails off in the relict-mature phase to a level intermediate between
the transgressive and stillstand phases (Table 13). The intermediate re-
gressive value further supports the contention that Glabrocingulum is
eurytopic.
Plagioglypta was a sublittoral benthic infaunal animal ("collector"),
living partly embedded in the substrate with only the posterior extremity
projecting into the water (Ludbrook 1960: 137). Because of its restric-
tion to keep (sublittoral) water, it is an excellent stillstand indicator.
The frequency trend of Plagioglypta through the faunal succession is
similar to that of Glabrocingulum, because its peak is within the still-
stand and the regressive average is intermediate in value (Table 13).
However the transgressive frequency is increased by 100 percent in the
stillstand, whereas the regressive frequency is reduced 50 percent from
that of the stillstand. This pronounced stillstand frequency peaking is
a further indication of the stenotopic nature of this animal.
There currently is marked controversy as to the exact biological
affinity of Plagioglypta. The large forms ( +10 or coarser) probably are
true scaphopods. The smaller forms, many of which pass through a
number 100 sieve, may represent polychaete worm tubes. However the
characteristic concentrically wrinkled shell is discernible on all size
specimens. Regardless of their biological affinity they are recognizable,
and their frequency trends place them within the stillstand or stable-
mature fauna.
Further supportive of a stillstand community is the frequency trend
of the ornamented ostracods. The frequency averages of the orna-
mented ostracods peak within the stillstand, with the transgressive and
regressive frequency averaging significantly lower (Table 13). Addi-
tional support is provided by crinoid frequencies, which also peak within
the stillstand.
The successional maturity of the Glabrocingulum-Plagioglypta com-
munity is quite low, as evidenced by the abundance of eurytopic com-
ponents. Increased water depth and near-normal marine conditions
existed, even if only temporarily. The Glabrocingulum-Plagioglypta
community is dominated by epifaunal deposit feeders of the "collector"
group, as is the case of the transgressive Astartella-lanthanopsis com-
munity. The most notable changes are in the sessile benthonic suspen-







114 BULLETIN FLORIDA STATE MUSEUM


sion feeders. The crinoids, ramose and fenestrate bryozoans, and brachi-
opods reach their frequency peaks within this community. Environ-
mentally, this community is farthest from shore, in the deepest water
(with reference to the study area), and in a low terrigenous influx re-
gime as is required by the sessile benthonic suspension feeders ("Fil-
terers" A and B). The substrate is more stable than in the transgressive
environments, as evidenced by the marked increase in the rooted and
cemented benthos.


Aclisina COMMUNITY

The Aclisina community represents the regressive phase and the cor-
responding relict-mature fauna. Aclisina is a high-spired snail with
distinct spiral ornamentation of the family Murchisoniidae. It was prob-
ably eurytopic, as evidenced by the similar frequencies throughout the
marine event. However the frequencies increase gradually through the
transgressive and stillstand phases and peak within the regressive phase
(Table 13). Aclisina is selected as name bearer for the relict mature
community because it is cosmopolitan to the study area and is the only
taxon of the cosmopolitan taxa that has its frequency peak within the
regressive phase.
The Aclisina community is the highest stratigraphically (thus young-
est) of the three laterally persistent benthic communities within the
bounds of the study area.
Environmentally, the Aclisina community is interpreted as indicating
a return nearer to shore and shoal water conditions. It is the relict-
mature community of the regressive phase, composed of the more eury-
topic components left over from the Clabrocingulum-Plagioglypta still-
stand community. The stenotopic components are biologically win-
nowed from the fauna during the entirety of the regressive phase. Thus
the environment shifts from a low level of biological accommodation
to pronounced physical accommodation. The opportunistic community
is the product of aggradation, whereas the relict mature community is
the product of degradation. The stable-mature community was marked
by deeper water, offshore environments, and a decrease in terrigenous
influx that allowed the more stenotopic sessile suspension feeders (cri-
noids and bryozoans) to increase in density. This process is reversed
in the regressive phase. The only noticeable differences between the
transgressive and regressive phases are in the vagaries of the faunal suc-
cession. The explosive opportunists such as Astartella and lanthanopsis
never regain their prominence in the regressive phase.


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SHAAK: BRUSH CREEK


Rhombopora-Septopora COMMUNITY
The cosmopolitan communities are easily recognized and can be
readily documented. However, one laterally restricted unique faunal
association occurs within the study area and warrants discussion. The
use of community in this instance is a convenient abstraction. Although
this restricted faunal assemblage is a real three dimensional unit, it is a
small scale one that cannot be recognized on a basin-wide level.
The marine transgressive phase at Loc. 4, Sewickley, Pennsylvania,
yielded an exquisite bryozoan fauna composed of the genera Septopora
and Rhombopora. Septopora is a very distinctive cryptostomatous
bryozoan of the family Acanthocladiidae. The genus is recognized by its
distinctive branch-bifurcation network and associated dissepiments.
Also, each branch is divided by a medial carina separating the laterally
adjacent zooecial rows. Rhombopora is a rhabdomesid cryptosome
found as ramose zoarial fragments displaying irregularly spaced bifurca-
tions. The most striking structures are large blunt spines that are the
surficial expressions of megacanthopores (Huffman 1970: 675).
The Rhombopora-Septopora community developed within the trans-
gressive or opportunistic phase, culminating in the limestone subjacent
to the stillstand sample. This community represents the highest bryo-
zoan density within the study area. The locality itself is classified in the
low diversity molluscan group of localities characterized by offshore,
deeper water environments. Macroscopically the community is domi-
nated by bryozoans, which occur as thick mats exposed on shale and
limestone bedding planes. However, microscopically the community is
numerically dominated by chonetid brachiopods, agglutinated forams,
and pleurotomariacean and bellerophontacean snails. The community
perhaps developed in a bryozoan garden or biostrome; thus the actual
find was by chance, as the community probably represents just an areal
patch. The community formed offshore in relatively deep water. The
bryozoans are classified as "Filterers B" in the Turpaeva classificatory
scheme and require deep offshore turbid waters under conditions of low
terrigenous influx on a moderately stable subtrate. The bedding plane
occurrence of the bryozoans perhaps represents alternating periods of
silting and quiescence.

DIvERSITY INDICES AS PALEOECOLOGIC TOOLS

GENERAL STATEMENT
Paleoecological and ecological research in recent years has shown
a trend toward quantification of data. This quantification is applicable






BULLETIN FLORIDA STATE MUSEUM


to animal communities because of their inherent feature of diversity.
Because animal diversity can be quantified, critical community features
such as structure, stability, and evolution can be synthesized. One of
the more informative methods of quantification is the derivation of
numerical species diversity.

COMPARISON OF THE SHANNON-WIENER AND SIMPSON DIVERSITY FUNCTIONS

The Shannon-Wiener information function is sensitive to both the
number of taxa present and the degree of evenness by which the number
of individuals are distributed among the taxa. Stable values are rapidly
reached and maintained when a population size of about 200 individuals
for high stress environments and about 400 individuals for low stress
environments per sample is achieved (Sanders 1968: 279). With the
recovery methods used in this investigation, minimum frequencies in
most samples have been greatly exceeded. Therefore within the frame-
work of this investigation the Shannon-Wiener function is relatively
sample-size independent. There is, however, a very strong influence re-
sulting from the evenness of spread of the individuals among the various
taxa.
The Simpson function is markedly influenced by sample size and
less by the evenness of spread of the individuals among the various taxa.
As more individuals are added to the samples, there is a corresponding
increase in diversity values. This relationship stems from the fact that
individuals are added at a constant arithmetic rate, whereas taxa are
added at a decreasing logarithmic rate.
Because these two diversity indices are influenced by several vari-
ables, both were used for all samples in the calculation of diversity
values. A comparison of the two diversity index curves for each locality
(Fig. 3 to 11) shows a remarkable closeness of fit or parallelism.
The index curves at localities 2 and 4 (Shelocta and Sewickley) are
practically congruent. The remaining localities show a close parallelism
between the diversity index peaks. The Simpson index values are nu-
merically higher than the Shannon-Wiener values, and the diversity
value highs for the Simpson function are markedly more peaked than
the corresponding Shannon-Wiener values. This pumping up of the
Simpson peaks over the Shannon-Wiener peaks leads to the conclusion
that these particular samples represent an increase in the number of taxa
over those from the subjacent samples. This is not always true, however.
Because of the individual frequencies evenness of spread in several
sample analyses, the Simpson high peaks are controlled by high equi-
tability values. As expected, the Shannon-Wiener peaks, except under


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SHAAK: BRUSH CREEK


conditions of low sample frequencies, are controlled by the equitability
factor.
The number of taxa retrieved with corresponding high numerical
frequencies in this investigation generally average out the differences
between the Simpson and Shannon-Wiener functions. Even though in-
flections in the curves for the Simpson function are more pronounced
than in Shannon-Wiener, the Simpson index values and curves, if used
alone, are less reliable. This unreliability results from the dual influence
of both equitability and taxonomic frequencies.

RESTRICTIONS IN THE USE OF DIVERSITY INDICES
A review of the data plots (Figs. 3 to 11), including the diversity
index, number of taxa, and equitability curves, supports the contention
that the diversity index values and curves cannot safely be used alone to
define communities or their trends. The diversity index curves range
from peaked to flat, and the general shape of the curves can be con-
trolled by masked subtleties in the faunal distribution. Two very real
situations that are difficult to detect are patchiness, as previously de-
scribed, and faunal aggregations. Faunal aggregations are a function of
sampling if these aggregates are not due to taphonomy. Two distinct
vertical faunal assemblages might be grouped within a single sample.
An ectone might be sampled, showing combined effects of two adjacent
communities. Unfortunately these vagaries generally cannot be detected
in the outcrop. A faunal aggregation or ecotone commonly will cause
an inflection on the diversity index curves that could go unexplained
without further investigation.
Shallow benthic marine communities, in general, are controlled by
the density and diversity of the molluscs. Molluscan densities and di-
versities increase towards shore, whereas the remaining faunal elements
increase offshore (Stevens 1971: 406). Thus the relationship of the
molluscan species diversity curves to non-molluscs and total fauna quite
often are as informative, or more informative, than the diversity index
curves. Inflections on some diversity index curves can be interpreted by
molluscan faunal changes from the subjacent sample.
A third tool, in addition to diversity index and number of taxa, is
equitability. Some of the anomalous inflections on the diversity index
curves, especially the Shannon-Wiener index curves, can be interpreted
by inflections on the equitability curves.
Thus a careful study of the relationship among diversity index,
species diversity, and equitabilty curves can provide a relatively sound
interpretation of faunal succession and community structure. If the






BULLETIN FLORIDA STATE MUSEUM


diversity index curves were smooth, with the only inflection due to still-
stand, sea level history would be easy to interpret. However the many
factors that influence faunal distributions make this type of investigation
very rewarding, because these factors can be reasonably interpreted by
these combined techniques.

CONCLUSIONS
The classical interpretation of marine cycles places the stillstand and
accompanying maximum diversity faunas at the position of the limestone
unit. However this investigation shows that the limestone unit generally
represents a transgressive stage. At only two places, within the limits
of the study area does it occur at the stillstand position. Also, there is
a marked asymmetrical faunal distribution above and below the still-
stand.
Faunal successions, recurrent fossils, and suites of fossils were used
to reconstruct laterally persistent fossil communities. The transgressive
phase includes the Astartella-Ianthanopsis community, the stillstand
phase supports the Glabrocingulum-Plagioglypta community, and the
regressive phase includes the Aclisina community.
Communities are named for the dominant genus or genera that occur
in each. The structure of each community is inferred from recent ma-
rine benthic communities of similar substrates, as well as presumed
habitat and feeding preferences of the extinct animals.
One localized exotic community, the Rhombopora-Septopora com-
munity, is interpreted as a faunal garden or biostrome within the trans-
gressive phase at one of the deep-water localities.
This investigation also shows that the use of a diversity index as the
primary interpretive tool in a paleoecological study can be misleading.
A combination of diversity indices, equitability, and faunal composition
provides an excellent system for a relatively sound interpretation of not
only faunal succession but also community structure.
This investigation shows that the limestones with a high terrigenous
content generally are more friable than the low terrigenous limestones.
Limestone terrigenous content also appears to be one of the limiting
factors in the level of biological accommodation reached by the faunas
recovered from limestone samples.
One of the more significant results of this investigation is the mollusc,
non-mollusc relationship. Molluscan faunas increase in both density and
diversity nearshore, whereas the non-molluscan faunas increase offshore.
Thus, not only the faunal succession but also the relative water depths
for each locality throughout the marine event can be inferred from
mollusc, non-molluse trends.


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BULLETIN FLORIDA STATE MUSEUM


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Vol. 19, No. 2









1975 SHAAK: BRUSH CREEK 123




APPENDIX A.-MEASURED SECTIONS SHOWING SAMPLING INTERVAL AT SAMPLE SITES1


feet KITTANNING LOCALITY
55



50



45


shale
40



35


S siltstone
30


limestone coquina
25
nodular siltstone
sample
limestone interval

S20 -bedded nodules




15 siltstone



-10


shale
5



0 coal

LOCALITY 1.-Stratigraphic section and sample interval at Kittaning, located along
northside of U.S. 422, 0.7 mi. E. of intersection of U.S. 422 and Pa. 66N, Arm-
strong County (Cadet Drive-In).

SAll localities are in Pennsylvania.








124 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 2








feet SHELOCTA LOCALITY
30
-7- -r-

T- mudstone

--- -T-

25 ,







20 _


nodular shale



15 o





sample
10 limestone interval


nodular shale


nodular mudstone
5


shale



S0 O coal
LOCALITY 2.-Stratigraphic section and sample interval at Shelocta, located along
northside of U.S. 422, 0.5 mi. W. of intersection of U.S. 422 and Pa. 156,
Indiana County (adapted from Brant 1971).








1975 SHAAK: BRUSH CREEK 125








feet BARTON LOCALITY
25







-20 interbedded sandstone and shale






shale
-15







S10 -


Interval
S= calcareous shale



5
shale






L railroad bed
LOCALITY 3.-Stratigraphic section and sample interval at Barton, located along
Baltimore and Ohio Railroad cut on eastside of U.S. 119, 1.9 mi. N. of intersec-
tion of U.S. 119 and Pa. 403 (Marion Center, Pa.), Indiana County.








BULLETIN FLORIDA STATE MUSEUM


SEWICKLEY LOCALITY


sample
interval


I-o I

LOCALITY 4.-Stratigraphic section and sample interval near Sewickley, located at
a roadcut along southside of Pa. 51, at south end of Sewickley Bridge, Alle-
gheny County.


Vol. 19, No. 2








SHAAK: BRUSH CREEK


feet GLENSHAW LOCALITY





-20





S- shale


-15





mudstone sample
-'- nodular mudstone interval

-10 limestone





-m--
7--

massive mudstone
5 -r


L. 0 1 X
LOCALITY 5.-Stratigraphic section and sample interval at Glenshaw, located at an
excavation along westside of Pa. 8, at intersection of Pa. 8 and Maple Street,
Allegheny County (Glenshaw Glass Company).


1975








128 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 2



feet MURRYSVILLE LOCALITY





-10 I

cm







nodular siltstone










-5 c J'



ca bedded nodules

shale sample
interval
- limestone (channel)



siltstone


limestone
carbonaceous shale

coal


LO


LocALrrY 6.-Stratigraphic section and sample interval at Murrysville, located at an
excavation on northside of U.S. 22, to immediate east of Allegheny-Westmore-
land County line, Westmoreland County (William Penn Lumber Company).









SHAAK: BRUSH CREEK


feet PICCOLOMINI LOCALITY
60

-T

-55
-


-50 T --
--1- --I"

-Tr --- mudstone
-45
-T- -T

T- T

-40 "-- -T


-T-
-35




-30 siltstone and quartz wackestone




-25




-20




-15
S c. nodular shale 'sample

= s limestone and ironstone interval
10




5 shale



coal
LOCALITY 7.-Stratigraphic section and sample interval near Uniontown, located at
abandoned Piccolomini Brothers strip mine, on eastside of Pa. 51, 5 mi. N. of
Uniontown, Fayette County.








BULLETIN FLORIDA STATE MUSEUM


feet URSINA LOCALITY
30

S sandstone




-25






20 shale






-15






10
10 limestone sample
Interval

nodular shale

5


shale


- 0
LOCALITY 8.-Stratigraphic section and sample interval near Ursina, located along
westside of Jersey Church Road, 0.95 mi. N.W. of intersection of Pa. 53 and
Jersey Church Road, Somerset County (adapted from Flint 1965).


Vol. 19, No. 2









1975 SHAAK: BRUSH CREEK 131

feet GLADE CITY LOCALITY
35

S sandstone






-30








-25 -



siltstone




-20 -








15

shale





-10

channel limestone
S-S-- \ O nodular shale sample
nodula shl interval
SI I I I limestone
shale
nodular siltstone





shale




0coal

LOCALITY 9.-Stratigraphic section and sample interval at Glade City, located along
northside of Western Maryland Railroad, 1.5 mi. E. of Meyersdale, Somerset
County (adapted from Flint 1965).








BULLETIN FLORIDA STATE MUSEUM


TAX


APPENDIX B.-DATA MATRIX OF BRUSH CREEK FOSSILS.

ON LOCALITY
1 2 3 4 5 6 7


Foraminifera
Cyclogyra sp.
Tolipammina sp.
Ammobaculites sp.
Ammovertella sp.
Glomospira sp.
Thurammina sp.
Lituotuba sp.
Ammodiscus sp.
Paleotextularia sp.
Psammosphaera sp.
Reophax sp.
Hemigordius sp.
Bigenerina sp.
Hyperammina sp.
lagenid
Ostracods
Healdia-Bairdia sp.
(smooth)
Amophissitids (pitted)
Hollinella sp. nodosee)
Porifera
Spicules
Coelenterata
Stereostylus sp.
Brachiopoda
Crurithyris sp.
Juresania sp.
Neochonetes sp.
Linoproductus sp.
Composita sp.
Derbya sp.
Antiquatonia sp.
Bryozoa


Ramose X
Fenestrate
Septopora biserialis X
Rhombopora lepidodendroides
Bivalvia


Astartella sp.
Girtyana sp.
Nucula sp.
Culunana sp.
Allorisma sp.
Nuculana sp.
Naiadites sp.
Aviculopecten sp.
Septimyalina sp.
Anthraconaia sp.
Gastropoda
Glabrocingulum sp.
Pseudozygoplieurids


X X
X X
x

x x


X X
x
X X X
X X X

X



X X X


8 9


X X
X X
X X
X X
X X


X X X
X


X X


x x x x x
X X X X


X X


X X
x x
x
x
X X
X

X X X


X X



X
x


x

x x


X



x x x x x
X X X X


x x

x x
x x


X X


x x x x
x x
x x
x x
x x x x
X X
X
x x x x
X
x

x x x x
X X X
X X X


Vol. 19, No. 2








SHAAK: BRUSH CREEK


APPENDIX B.-CONTINUED

TAXON LOCALITY
1 2 3 4 5 6 7 8 9


lanthanopsis sp.
Meekospira sp.
Belleron sp.
Pharkidonatus percarinatus
Euphemites sp.
Retispira sp.
Bulimorpha sp.
Worthenia sp.
Shansiella sp.
Cymatospira sp.
Straparollus sp.
Trepospira sp.
Aclisina sp.


Cephalopoda
Pseudorthoceras sp.
Metacoceras sp.
Scaphopoda
Plagioglypta sp.
Dentalium sp.
Echinodermata
Echinoid debris
Crinoid columnals
Holothurian sclerites
Trilobita
Amc'ura sp.
Condodonts debris
Vertebrates debris


x x x x x x x x x
X X X X X
X


X X

x
X X


X X X
X X

X


X X X X X X X
X X X X X X
X X X X X X

X X X X X X X X


X X
x x


X X X X X X X X


X X X X X
X X X X X X
X


x
X
X X
X X


X X X
X X X
X

X
N


1975







UNIVERSITY OF FLORIDA


3 1262 07055 3853








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