Paleoecology and paleoenvironments of the Upper Devonian Martin formation in the Roosevelt Dam-Globe area, Gila County, Arizona
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Authors Meader, Norman Mack, 1951-
Publisher The University of Arizona.
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Link to Item http://hdl.handle.net/10150/566642 PALEOECOLOGY AMD PALEOENVIEONMENTS OF THE
UPPER DEVONIAN MARTIN FORMATION H
THE ROOSEVELT DAM-GLOBE AREA, GILA COUNTY, ARIZONA
by
Norman Mack Meader
A Thesis Submitted to the Faculty of the
DEPARTMENT OF GEOSCIENCES
In Partial Fulfillment of the Requirements For the Degree of
MASTER OF SCIENCE
In the Graduate College
THE UNIVERSITY OF ARIZONA "
1 9 7 7 STATEMENT BY AUTHOR
This thesis has been submitted in partial fulfillment of re quirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.
Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judg ment the proposed use of the material is in the interests of scholar ship. In all other instances, however, permission must be obtained from the author.
SIGNED , /Vk stj .
APPROVAL BY THESIS DIRECTOR
This thesis has been approved on the date shown below:
DIETMAR SCHUMACHER Date Assistant Professor of Geosciences ACKNOWIEDGMENTS
In completing this thesis I would like to thank the members of
ngr committee, Drs. Joseph F. Schreiber Jr., Richard F. Wilson, and
Dr. Dietmar Schumacher for their direction and assistance. I would
especially like to thank Dr. Schreiber for his moral support and
Dr. Schumacher for his patience in the difficult times preceding its
completion. I would also like to thank Professor Terah Smiley for
accommodating me in the technical aspects of my degree.
Special thanks go to my sister Sally for her companionship in
the field and suggestions on shortening the time and energy required to
complete this degree. I would also like to thank Don Witter for his
enthusiasm and discussion concerning the Devonian of Arizona.
I thank the Union Oil Company Foundation for financial assist
ance in this study.
I lastly would like to thank my mother, Mrs. Ruth Header Foster,
for her encouragement in completing this degree and steadfast support in
troubled times.
iii TABLE OF CONTENTS
Page
LIST OF ILLUSTRATIONS...... vi
LIST OF T A B L E S ...... ix
ABSTRACT ...... x
1. INTRODUCTION ...... 1
1.1 The Problem and. the Objectives 1.2 Location ......
1.3 M e t h o d s ...... to to H 1.4 Previous Work •— Stratigraphy
1.5 Previous Work — Paleo ecology -ovn
2. STRATIGRAPHY-...... 10
2.1 Nomenclature ...... 10 2.2 Age of Strata ...... 12 2.3 Beckers Butte Member ...... 12 2.4 Jerome M e m b e r ...... 13
3. PALE O N T O L O G Y ...... ' ...... 16
3*1 Introduction...... 16 3*2 B i a s e s ...... 16 3*3 Faunal Assemblages at Roosevelt D a m ...... 18 3*3-1 Stromatolite Assemblage ...... 18 3*3-2 Arthrodiran Assemblage ...... 21 3*3-3 Crinoid-Schizophoria and Fenestrate Bryozoan- Stropheodonta Assemblages ...... 21 3*3-4 Coenites-Spiriferid Brachiopod Assemblage .... 25 3*4 Faunal Assemblages at Pinal Creek ...... 25 3*4-1 Ostracode-Algal Assemblage ...... ••••• 26 3*4-2 Stropheodonta-Schizophoria Assemblage '...... 26 3*4-3 Atrypa-Cyrtospirifer Assemblage ...... 2? 3*4-4 Atrypa-Theodosia Assemblage...... 29 3*5 Faunal Assemblages at Globe H i l l s ...... 29
4. SEDIMENTARY ENVIRONMENTS ...... 35
4*1 Introduction...... 35 4.2 Beckers Butte Member ...... 39
iv V
TABLE OF CONTENTS— Continued
Page
4*3 Fetid Dolomite Unit ...... 41 4.4 Aphanitic Dolomite Unit — Roosevelt D a m ...... 41 4*5 Aphanitic Dolomite Unit — Pinal Creek ...... 47 4.6 Upper U n i t ...... 49 4*6-1 Upper Unit at Roosevelt D a m ...... 51 4.6-2 Upper Unit at Pinal Creek ...... 55 4*7 Problems...... 60
5* PAIEOECOLOGY ...... 6l
5*1 Introduction...... 6l 5*2 Associations...... 63 5*2-1 Stromatolite "Association" ...... 63 5*2-2 Ostracode-Algal Association ...... 65 5*2-3 Coenites-Spiriferid Brachiopod Association * * . 65 5*2-4 Crinoid-Schizophoria Association ...... 65 5*2-5 Fenestrate Bryozoa-Stropheodonta Association * . 66 5*2-6 Stropheodonta-Schizophoria Association . * . * * 66 5*2-7 Disphyllum-Massive Stromatoporoid Association . . 67 5*2-8 Atrypa-Cyrtospirifer Association ...... 68 5*2-9 Atrypa-Theodosia Association ••*••...... 68 5*3 Lateral Relationships ...... 69 5*4 Comparison with Other Studies ...... •.*•• 72 5*5 Comparison of Martin and Percha Associations...... * 89 5*6 Summary and Conclusions ...... 92
6. CONCLUSIONS AND PROBLEMS FOR FURTHER INVESTIGATION...... 94
6.1 Conclusions • • • ...... 94 6.2 For Further Investigation ...... 97
APPENDIX: MEASURED STRATIGRAPHIC SECTIONS ...... 98
REFERENCES CITED ...... 120 LIST OF ILLUSTRATIONS
Figure Page
1. Location Map ...... 3
2. Stratigraphic Nomenclature for the Devonian of Central A r i z o n a ...... 11
3» Vertical Distribution of Rock Types, Sedimentary Structures, and Fossil Occurrences at Roosevelt Dam and Pinal Creek ...... in pocket
4» General Stratigraphic Position of Fossil Assemblages in Units of the Martin Formation...... 19
5* Algal Laminae in the Fetid Dolomite Unit at Roosevelt Dam • 20
6. Large Head Shield Plate of Dinichthys sp. from the Aphanitic Dolomite Unit at Roosevelt D a m ...... 22
7* Large Undetermined Plate of Dinichthys sp. from the Aphanitic Dolomite Unit at Roosevelt D a m ...... 23
8. Arthrodiran Plate, Smaller Genus from the Aphanitic Dolomite Unit at Roosevelt Dam ...... 23
9* Cruziana Trails and Cross Sections of Inclined Burrows, Upper Unit at Roosevelt Dam ...... 24
10. Brachiopod Slab, Mostly Schizophoria with Pedicle Valves Convex-up, Upper Unit at Globe Hills ...... 32
11. Abundant Crinoid Columnals Associated with the Stropheodonta- Schizophoria Assemblage • ...... 32
12. Disphyllum Colony in Growth Position, Upper Unit at Globe H i l l s ...... 33
13. Environmental Distribution of Organic Structures...... 37
14. Shaw (1964)-Irwin (1965) Model ...... 38
15. Interbedded Shale and Dolomite in the Upper Unit of the Beckers Butte Member at Roosevelt Da m ...... 40
vi VIO
LIST OF ILLUSTRATIONS— Continued
Figure Page
16. Laminations in the Fetid Dolomite Unit at Roosevelt Dam • • 42
17• Mudcracks in the Aphanitic Dolomite Unit at Roosevelt D a m ...... 43
18. Intraformational Breccia, Aphanitic Dolomite Unit at Roosevelt Dam ...... 43
19* Acetate Peel of Intraformational Conglomerate, Aphanitic Dolomite Unit at Roosevelt D a m ...... 44
20. Channels in the Lower Part of the Aphanitic Dolomite Unit at Roosevelt D a m ...... 46
21. Rounded Intraclasts, Birdseye Structure, and Burrow Remnants in the Aphanitic Dolomite Unit at Pinal Creek ...... 48
22. Crossbedding in Lower Part of Upper Unit at Roosevelt Dam • 52
23. Close-up of Vertical Burrow in Lower Part of Upper Unit at Roosevelt Dam ...... * 52
24. Close-up of Crossbedding in the Upper Unit at Roosevelt D a m ...... 53
25. Horizontal Burrows in the Upper Unit at Roosevelt Dam • • • 54
26. Grazing Traces (Chondrites) in the Upper Unit at Roosevelt Dam ...... 54
27* Convolute Bedding in the Upper Part of the Upper Unit (Unit 27) at Roosevelt D a m ...... 56
28. Laminations and Crossbedding in the Upper Part of the Upper Unit (Unit 27) at Roosevelt Dam ...... 56
29* Characteristics of the Upper Unit at Pinal Creek ...... 58
30. Lateral Relationships of Faunal Associations...... 70
31. Placement of Associations in Anderson*s (1971) Scheme . . . 71
32. Biofacies and Environments of the Middle Devonian Cedar Valley Formation ...... 77 VXli
LIST OF ILLUSTRATIONS— Continued
Figure Page
33« Comparison of Communities, Associations, Biofacies, and Assemblages from Epeiric Carbonate Environments • • • • • 79
34» Comparison of Communities, Associations, Biofacies, and Assemblages from Miogeosynclinal and Deltaic Environments . . 80
35* Sonyea, Genesee, and Foreknobs Depositions! Environments and Communities • • • ...... 84
36. Guilmette Environments ...... 87
37* Associations and Environments of the Percha Formation • • • 91 LIST OF TABLES
Table Page
1. Characteristics of Carbonate Depositions! Environments • • • 36
2. Taxonomic Composition, Relative Abundance of Taxa, Trophic %rpe, and Relationship of Organisms to Substrate • • • • 64
3* Characteristics of the Middle Devonian of Northwestern Europe ...... 75
ix ABSTRACT
The Martin Formation in the Roosevelt Dam-Globe area of central
Arizona contains a broad spectrum of paleoenvironments, from fluvial nearshore to offshore below wave base. These environments succeed each other vertically in a complete sequence. The Martin at Roosevelt
Dam is characterized by dolomitized lime muds and faunas of low diver sity, while sections near Globe contain well developed skeletal sands
(biosparites) and diverse faunas. The faunas and lithologies present suggest a more nearshore environment for the Roosevelt Dam area.
Five fossil assemblages are recognized in the Martin Formation at Roosevelt Dam. In ascending stratigraphic order, they are:
1) stromatolite assemblage, 2) arthrodiran assemblage, 3) crinoid-
Schizonhoria assemblage, 4) fenestrate bryozoa-Stropheodonta assemblage, and 5) Coenites-spiriferid brachiopod assemblage. These are all consid ered ecological associations, with the exception of the arthrodiran assemblage.
Five faunal assemblages are also identified from the Globe area, but they do not correspond well with those at Roosevelt Dam.
These are all considered ecological associations, and they are as fol lows, in ascending stratigraphic order: l) ostracode-algal assemblage,
2) Stropheodonta-Schizophoria assemblage, 3) Disphyllum-massive stro- matoporoid assemblage, 4) Atrypa-Gyrtospirifer assemblage, and
5) Atrypa-Theodosia assemblage.
x CHAPTER 1
INTRODUCTION
1.1 The Problem and the Objectives
The depositional history of the Martin Formation in central
Arizona has been studied on a general regional basis by Teichert (1965) and Fine (1968). Teichert1s study of Devonian rocks and paleogeography in central Arizona resulted in observations and conclusions concerning depositional environments and fossil "communities" within the Martin
Formation.
In recent years a better understanding of carbonate deposition al environments has evolved. Paleocommunity studies have increased and paleoecological techniques have become more standardized, allowing re finement of previous interpretations. Comparison of the Roosevelt Dam section and sections near Globe revealed striking differences in faunas, faunal successions, and rock types. These two sections are well suited to a detailed paleoecological study because of distinct lithofacies, faunas, and their rapid lateral change. The well-developed vertical
succession of faunas and sedimentary structures is also reason to use these sections. Combining these features in a paleoecological approach provides a better understanding of depositional environments and their vertical and lateral change.
Comparison with other paleoecological studies was undertaken to
document similarities and differences between Upper Devonian communities
1 2 elsewhere in the world. Unlike other lower Paleozoic paleocommunities, those of the Upper Devonian are highly variable in composition from one region to another. In this study new as well as equivalent communities are recognized.
1.2 Location
The study area lies between Roosevelt Dam and Globe, Arizona
(Fig. l). The Roosevelt Dam and Pinal Creek sections were redescribed, and the stratigraphic position of faunas and sedimentary structures were accurately noted. These sections were also sampled for petrograph ic studies. A third section at Globe Hills was visited to record vertical distribution of sedimentary structures and fossils, but was not redescribed or sampled other than for fossils. Other sections visited include Superior, approximately twenty miles west of Globe, and
Windy Hill, four miles east of Roosevelt Dam. The three primary sec tions are as follows:
1. Roosevelt Dam: SE5- NWj- SWj- sec. 29, T. 4N, R. 12 E . , Theodore Roosevelt Dam Quadrangle, Gila County, Arizona.
2. Pinal Creek: W%r NW|- NW^- sec. 10 T. IN., R. 15 B . , Globe Quadrangle, Gila County, Arizona.
3. Globe Hills: S& NW&- sec. 13, T. IN., R. 15 E . , Globe Quadrangle, Gila County, Arizona.
1.3 Methods
Detailed stratigraphic studies of the Roosevelt Dam section and two sections near Globe were undertaken to place sedimentary structures, rock types, and fossil occurrences in their vertical sequence. Figure 1. Location Map. 4
Measurement of the Roosevelt Dam and Pinal Creek sections was done (in
standard procedure) with a Jacob staff and Brunton compass. Every five
feet was marked with paint, and at every ten feet (or at the most oppor
tune interval) the footage above the base of the section was written.
Dips on beds were frequently measured and the inclinometer on the Jacob
staff reset. . This was not so crucial at Pinal Creek, where dips range
from 21° to 27°» but at Roosevelt Dam dips range from 25° to 45°» and
this procedure was essential. Care was also taken to compensate for
faults in these sections. All fossils, sedimentary structures, and
hand samples were referred to the appropriate footage along this line of
section.
Fossils collected in place were labeled as to footage and their
orientation noted. Fossils collected from float were labeled according
to the unit or horizon from which they were weathering. Hand samples were acquired from each unit of unique lithology, or at regular intervals
in thicker units, and their orientation marked. The color of hand
samples was keyed to the standard Rock Color Chart (Goddard and others,
1948) in the laboratory. Bedding terminology is that of McKee and Weir
(1953)• The rock classification used is that of Folk (1959)• Most
lithologies are dolomite, and their crystal size was determined in thin-
section and referred to Folk’s (1968) scale.
Approximately 90 thin-sections were made to accurately ascertain
rock types and mode of fossil preservation. Slabs were cut from hand
specimens to make polished sections and acetate peels. This revealed
some sedimentary structures not recognized in the field. Thin-sections 5 were stained to differentiate calcite from dolomite using the procedure
of Dickson (1965).
All fossils were identified utilizing the best literature
available. Orientation, disarticulation, preservation, and other fac
tors were noted in the field and the laboratory in accordance with
Ager’s (1963) questionnaire. At times it was advantageous to collect
slabs for study in the laboratory where one could give them closer
scrutiny. Trace fossils are also included in this study and treated in
the same manner. From this information faunal associations were defined
and their stratigraphic sequence established.
1.4 Previous Work — Stratigraphy
Ransome (1903) recognized Devonian strata in the Globe area and
correlated Devonian sections in central Arizona with the aid of the
paleontologist Henry Williams. Williams identified nine species of
brachiopods from the Pinal Creek section and noted that many of the forms
were the same as those from the lime Creek Formation of Iowa. Ransome
(1915) recognized Devonian strata at Roosevelt Dam. He correlated these
with the Martin Limestone, which he had described earlier (1904) at
Bisbee. The Pinal Creek section and its fauna were described in some
detail by Stauffer (1923), who referred to these strata as Martin Lime
stone. Stoyanow (1930) proposed the name Jerome Formation for Devonian
strata at Jerome on the basis of lithologies distinct from those of the
Martin Limestone, and this designation has been extended to the
Roosevelt area by some workers. Stoyanow measured and described the
lower part of the Devonian section at Windy Hill in 1925 before the 6 waters of Roosevelt Lake inundated it, and he returned in 1929 to describe the upper part of the section (Stoyanow, 1936). He also coined the term "Mazatzal Land" for a Devonian high in central Arizona in the same publication. Several later researchers of the Devonian debated its actual existence, including McKee (1951), Huddle and Debrovolny
(1952), and Elston (i960). Teichert (1965), after conducting research for the United States Geological Survey, agreed with McKee’s interpre tation that it did not exist. He studied the Roosevelt Dam section and other sections in central Arizona and used them as control points to argue against Stoyanow*s Mazatzal Land. He showed there to be an increase in clastic content between Roosevelt Dam and Windy Hill and suggested an eastern rather than a western source for these elastics.
He also noted a marked concentration of brachiopod shells in the middle of the upper unit in the Jerome Member at both Windy Hill and Roosevelt
Dam. Teichert proposed the stratigraphic nomenclature used in this study.
Tahmazian (1964) conducted petrographic studies on the Troy and
"Martin" clastic sequence at Roosevelt Dam, concentrating on mineralogi— cal content and provenance. Ethington (1965) established an early Late
Devonian age for the Martin Formation of central and southern Arizona on the basis of conodonts. Pine (1968) extended Teichert*s study to the south, with the Globe area as the northernmost extent of his investiga tion. He redescribed the Pinal Creek section and described several other sections in the Globe area, including the Globe Hills section. He focused on paleogeography and petrology and did not document taxa or faunal assemblages. 7
Schumacher and others (1976) proposed the name Percha Formation for strata previously included within the Martin Formation and demon strated that the Percha Formation forms a lithologically distinct, mappable unit which unconformably overlies the Martin Formation. In recent paleomagnetic studies at Roosevelt Dam, Elston and Dressier (in press) have concluded that some of the basal elastics of the Martin
Formation should be assigned to the Gambian Tapeats Sandstone.
1.5 Previous Work — Paleoecology
Teichert’s work (196$) is the most extensive study of the
Devonian in central Arizona. He studied lithologies and faunas and assigned depositional environments to the units of the Martin Formation.
His faunal listings and identifications are the best available, and he ventured paleoecological interpretations, recognizing three or four distinct faunal assemblages.
Paleoecological investigations of the Upper Devonian elsewhere in the United States and the world are expanding. Community paleoeco logical studies in the eastern United States include those of Sutton,
Bowen, and McAlester (1970), Bowen, Rhoads, and McAlester (1974)»
Thayer (1974), and McGhee (1976). The first two papers define and reconstruct faunal communities in the Upper Devonian Sonyea Group of
New York. A similar study has been conducted on the overlying Genesee
Group by Thayer. McGhee discusses the paleoecology of the Four Knobs
Formation along the Allegheny Front in the central Appalachians. All of these studies encompass faunas of the "Catskill Delta" and associated marine environments and relate lateral community succession to them. 8
Because these works involve clastic rather than carbonate regimes, their
applicability to the present study is somewhat limited.
Hoggan1s (1975) study of the paleoecology of the Upper Devonian
Guilmette Formation in eastern Nevada and western Utah is perhaps the
most relevant to this investigation. This formation is of Frasnian age
and is primarily a carbonate sequence. Although it is miogeosynclinal
rather than epeiric in nature, it contains many shallow water environ
ments and faunas similar to those of the Martin Formation.
Because epeiric marine environments persist or recur through
time, similar communities, although of different taxonomic composition,
evolve to occupy those environments. For this reason communities and
their distribution as defined in other Paleozoic studies have relevance
to this investigation. Copper (1966) studied the ecological distribu
tion of Middle Devonian atrypid brachiopods in the Netherlands.
Fraunfelter (196?) defined eight biofacies in the Middle Devonian Cedar
Valley Formation of east-central Missouri. Johnson and Flory (1972)
described a new Middle Devonian community from Nevada, and Johnson
(1974b) discussed Lower and Middle Devonian communities of western and
Arctic North America. Walker and Alberstadt (1975) investigated eco
logical succession in the Frasnian Lime Creek Formation of north-central
Iowa. Boucot (1975) discussed Silurian and Lower-Middle Devonian com
munities from several localities in the world. Meader (1976) has
conducted paleoecological analysis of Famennian strata in south-central
Arizona, encompassing some of the environments encountered in the
present study. 9
For a better understanding of current paleoecological thinking and concepts one is referred to Ziegler and others (1974) and Scott and
West (1976). CHAPTER 2
STRATIGRAPHY
2.1 Nomenclature
The stratigraphic nomenclature in this work is that of Teichert
(1965) with modifications from Schumacher and others (1976) and Elston and Bressler (in press). Teichert divided the Martin Formation in central Arizona into the basal Beckers Butte Member and the overlying
Jerome Member. He further subdivided the Jerome Member into three in
formal "members," the fetid dolomite unit, the aphanitic dolomite unit, and the upper unit. Elston and Bressler (in press) have proposed new nomenclature based upon paleomagnetic studies of the basal elastics of the Devonian in central Arizona. They have referred the greater part
of these elastics to the Cambrian Tapeats Sandstone and have thus greatly reduced the thickness of the overlying Beckers Butte Member.
They also have recognized a disconformity between the Beckers Butte
Member and the overlying Jerome Member. It has been shown by Schumacher
and others (1976) that the uppermost shale and carbonate units in the
Martin Formation represent a lithologically distinct, mappable unit which can be recognized over much of central and southern Arizona. This
unit unconformably overlies the Martin Formation and is assigned to the
Percha Formation, a recommendation followed in this text. Teichert’s
upper unit is abbreviated by this change. This nomenclature is illus
trated in Figure 2.
10 SCHUMACHER TEICHERT (1965) Bothers (1976) THIS PAPER carbonate carbonate member member
upper shale shale member member PERCH A FM. A PERCH unit FM. PERCHA upper Unit
aphanitic aphanitic dolomite dolomite unit unit JEROME MEMBER fetid fetid dolomite dolomite unit JEROME MEMBER unit MARTIN FORMATION Beckers Beckers
MARTIN FORMATION Butte Butte Member Member
Figure 2. Stratigraphic Nomenclature for the Devonian of Central Arizona. 12
2.2 Age of Strata
Williams (in Ransome, 1903) recognized the close association of brachiopod faunas of the upper unit at Pinal Creek to the Upper Devonian
Lime Creek Formation of Iowa and the Ithaca fauna of New York. Stauffer
(1928) corroborated this age designation. The lower part of the
Devonian section in central Arizona lacks diagnostic fossils and is not easily dated. Teichert and Schopf (1958) dated a psilophyton flora from the Beckers Butte Member at the Salt River Canyon and assigned an
Early to Middle Devonian age to it. A considerable hiatus was postu lated between the Beckers Butte Member and the Jerome Member on this basis. A review of this flora by Canright (1968) established it as latest Givetian (late Middle Devonian) or earliest Frasnian in age on the basis of brachiopod and coral assemblages. On the basis of cono- donts the Martin Formation was established as early to late Frasnian by Ethington (1965), Witter (1976), and Schumacher and others (1976).
Schumacher and others have also dated the overlying Percha Formation as late Famennian on the basis of conodonts and brachiopods.
2.3 Beckers Butte Member
The Beckers Butte Member of the Martin Formation at Roosevelt
Dam is separated into two units, a basal sandstone unit 18.0 feet (5.5 meters) thick overlain by 3*5 feet (l.l meters) of very thinly inter- bedded aphanitic dolomite and shale. This member is not present in the Globe area. The clastic unit is weakly resistant and rests upon the cliff-forming upper unit of the Tapeats Sandstone. This contact is easily recognized. The clastic unit is composed of coarse to very 13 coarse, poorly sorted sandstone that displays some trough crossbedding at its base and contains thin, micaceous siltstone partings. Its contact with the overlying unit is poorly exposed. This overlying unit contains some small, sandy chert nodules near the top and is marked by discrete hematitic stains two to three centimeters in diameter. Its contact with the resistant overlying fetid dolomite unit of the Jerome
Member is somewhat undulatory but sharply defined.
2.4 Jerome Member
Teichert (1965) divided the Jerome Member into three units, in
ascending stratigraphic order, the fetid dolomite unit, the aphanitic dolomite unit, and the upper unit. The fetid dolomite unit was origi
nally named for its fetid odor. At Roosevelt Dam it is medium to coarse crystalline dolomite, strongly laminated, very porous, and
stromatolitic throughout. The base of the unit is quite resistant and
its lower contact easily defined. Its contact with the overlying
aphanitic dolomite unit is gradational. The unit is approximately 15.0
feet (4*5 meters) thick at Roosevelt Dam.
The base of the formation at Pinal Greek is not exposed, and
the nature of the basal units could not be ascertained there. At the
Globe Hills locality approximately two miles to the east-southeast, it
was discovered that Pine (1968) did not realize that the base of the
Devonian section was in fault contact with the Troy Quartzite, assuming
the contact to be depositions!. In the present study a full complement
of the aphanitic dolomite unit of the Jerome Member was discovered in a
separate fault block to the north-northeast. The base of the Devonian 14
section is a chert pebble and cobble conglomerate several feet thick resting upon Precambrian Mescal Limestone(?). Rare quartzite pebbles were also noted in this conglomerate. The basal ten feet of the
aphanitic dolomite unit contain subangular chert pebbles and sand-size debris that decreases in abundance upward, and the contact between the
conglomerate and the aphanitic dolomite unit is somewhat gradational.
The Beckers. Butte Member (unless one wishes to equate it with this
conglomerate) and the fetid dolomite unit are absent at this locality.
The aphanitic dolomite unit was so named for its aphanocrystal- line fabric and is a recognizable unit throughout central Arizona. At
Roosevelt Dam it is approximately 115 feet (35*1 meters) thick, thin- bedded with shale intercalcations, and displays desiccation features
such as mudcracks and birdseye structure. Near Globe the unit attains
a comparable thickness but is massive, bioturbated in intervals, and
contains pelletal dolomites near its base.
The contact between the aphanitic dolomite unit and the overly
ing upper unit is sharply defined throughout central Arizona by a
silica-cemented, trough-crossbedded quartzarenite ten or more feet in
thickness. The upper unit varies considerably in lithology and faunal
content between Roosevelt Dam and the Globe area. At Roosevelt Dam it
contains a much greater component of coarse sand and is composed essen
tially of medium-crystalline dolomites and dolomitic sandstones. The
upper unit at Pinal Greek and Globe Hills is much less sandy, contains
several intervals of well developed skeletal sands (biosparites), and is
much more fossiliferous. It is also much thinner. The basal shale of the Percha Formation is distinctive, and the contact with the under lying dolomites of the Jerome Member is easily recognized in all
sections. For a more detailed stratigraphic description one is referred to the appendix. CHAPTER 3
PALEONTOLOGY
3.1 Introduction
In order to elucidate the origin of the remarkable differences in fossil abundance, composition of assemblages, and fossil diversity in the Martin Formation between Roosevelt Dam and Globe, sections were measured at each locality, fossil occurrences noted, and the vertical succession of assemblages ascertained. Most fossil samples were col lected in place because they did not weather free of their matrix. An exception to this was in unit 26 at Pinal Creek, where specimens in float were fairly abundant and well preserved. Slabs or blocks were collected for closer study and identification of fossil content in the laboratory. Fenton and Fenton’s (1924) study of the lime Creek fauna of north-central Iowa was the primary reference used in identification of specimens.
In this study, "association" and "assemblage" are applied to faunal occurrences. For clarification of their usage here, an associa tion refers to taxa that existed together in life, while an assemblage refers to all taxa brought together after death.
3.2 Biases
There are some very important biases in this study, principally the degree of exposure of fossils on the outcrop and the quality of
16 17 preservation. Those intervals that exhibited fossiliferous bedding planes and those from which fossils were easily weathered were naturally
given more intense scrutiny. Faunal lists were thus longer for these units. In many intervals one could do little more than view fossils in
cross-section and identify silicified specimens that projected a few millimeters from the rock's surface. Although the two or three most
dominant constituents in an interval could be determined in this manner,
less abundant taxa may have been missed.
The quality of preservation was also a factor in this study.
Four types of preservation were noted: l) silicif ication;
2) dolomite-hematite replacement; 3) external molds; and 4) original
hard parts. Diagenesis appears to have been more extreme at Roosevelt
Dam, as many fossil horizons in the road cut are represented only by
external molds and dolomite-hematite replacement. Some silicification
of brachiopods does occur on the adjacent hillslope exposure. Fish
bones and plates are, however, preserved as original apatite. The poor
quality of preservation at Roosevelt Dam has obscured the presence of
less abundant taxa. Dominant faunal constituents, however, could be
recognized well enough to indicate major faunal changes in the section.
Brachiopods at Pinal Creek and Globe Hills were preserved as
original shell material in certain intervals, aiding identification
greatly. Conclusions concerning diversity were more valid because of
this. Silicification was more common in resistant units where fossils
were not well exposed. Dominant fossil constituents could be recognized
in these units, but less abundant taxa were missed. The detailed occurrence of fossil assemblages in these sections is illustrated in Figure 3 (in pocket).
3.3 Faunal Assemblages at Roosevelt Dam
Although fossil preservation at this locality was rather poor, the succession of faunas is of considerable significance. The follow ing fossil assemblages are recognized, in ascending stratigraphic order:
fetid dolomite unit: 1) stromatolite assemblage (algal mats)
aphanitic dolomite unit: 2) arthrodiran assemblage (Dinichthys and a second unidentified genus)
upper unit: 3) crinoid-Schizophoria(?) assemblage 4) fenestrate bryozoan-Stropheodonta assemblage 5) Coenites-spiriferid brachiopod assemblage
Their stratigraphic occurrence is illustrated in a general manner in Figure 4* Vertical burrows, grazing burrows, and two or three types of horizontal burrows were noted in the upper unit. The
Beckers Butte Member is unfossiliferous at this locality.
3.3-1 Stromatolite Assemblage
The fetid dolomite unit is comprised, for the most part, of algal stromatolites (Fig. 5)» No associated invertebrate or trace fossils were recognized, although diagenesis has transformed the rock into a porous, medium- to coarsely-crystalline dolomite and may have destroyed any invertebrates that were originally present. The 19
ROOSEVELT PINAL CREEK DAM
Atrvoa-Theodosia A ssem .
Coenites-Spiriferid Brachiopod Assem. z 3 Atrvoa-CvrtosDlrlfer A s s e m .
Fenestrate Bryozoa- Strooheodonta Assem. UPPER Crinoid-SchizoDhoria A s s e m . Strooheodonta- Schizophoria Assem.
H Z 3 J O Arthrodiran Q A ssem . Ostracode- Algal
a ph A s s e m . I APR DOL. UNIT UPPER UNIT
Stromatolite F. D.U. = Fetid Dolomite Unit
F.D.U. A ssem . Beckers Butte Member B.B.M.
Figure 4» General Stratigraphic P of Fossil Assemblages in Units of the Martin Formation 20
Figure 5* Algal Laminae in the Fetid Dolomite Unit at Roosevelt Dam. 21
stromatolites are planar to somewhat fenestral in form and are inter
preted to be of an "algal mat" origin.
3*3-2 Arthrodiran Assemblage
Plates of Dinichthys up to 15 inches in length (38 centimeters)
occur in the upper part of the aphanitic dolomite unit at Roosevelt
Bam. Their large size indicates that they were probably disarticula
ted upon decay of the organism and experienced minimal transport
afterward. The plates of a smaller associated genus are very thin and
fragile, yet large, and indicate little transport also. Their associa
tion with mudcracks suggests that they were transported to the area of
decay and final burial by storms or tides. These are illustrated in
Figures 6, 7» and 8.
3*3-3 Crinoid-Schizophoria and Fenestrate Bryozoan-Stropheodonta Assemblages
The crinoid-Schizophoria assemblage occurs in interbedded
unfossiliferous and crinoidal dolomite. Schizophoria occurs near the
base of this interbedded sequence on the adjacent hillslope in a
brachiopod coquina. In the same exposure a Stropheodonta coquina is
found near the top of these beds (unit 17) and recurs just above and
possibly with the abundant fenestrate bryozoa occurrence in unit IB.
Because these coquinas could be readily placed in the road cut section,
they were employed to define assemblages 3 and 4> respectively.
Assemblage 3 also contains rare cystoid plates and Aulopora. and
assemblage 4 contains rare Flatyrachella, rare to common Cruziana
trails, and inclined burrows (Pig. 9)* I
22
Figure 6. Large Head Shield Plate of Dinichthys sp. from the Aphanitic Dolomite Unit at Roosevelt Dam. 23
Figure ?• Large Undetermined Plate of Dinichthys sp. from the Aphanitic Dolomite Unit at Roosevelt Dam.
Figure 8. Arthrodiran Plate, Smaller Genus from the Aphanitic Dolomite Unit at Roosevelt Dam. Figure 9» Cruziana Trails and Cross Sections of Inclined Burrows Upper Unit at Roosevelt Dam. 25
Although the shells in these coquinas lie in various orienta tions, their original matrix was lime mud, and most shells in cross- section appear to be of entire valves, although they are disarticulated.
Therefore, post-mortem transport was probably minimal. Teichert (1965) suggests that such coquinas were derived from ”shell banks.” They could also represent storm lags (Sutton and others, 1970).
The interval between the Stropheodonta-fenestrate bryozoa assemblage and the Ooenites-spiriferid brachiopod assemblage contains a few horizons of brachiopods and fenestrate bryozoa. Some spiriferids were noted, but most brachiopods were preserved as unidentifiable external molds.
3*3-4 Coenites-spiriferid Brachiopod Assemblage
The Coenites-spiriferid assemblage represents the highest faunal occurrence in this section. These two taxa are dolomitized and occur as hematitic ghosts that are easily missed as fossils. Coenites is abundant and appears to lie horizontal with respect to bedding. No other taxa were observed in this assemblage.
Other fossils in the section include fish bone fragments, which first occur in the middle of the aphanitic dolomite unit and are present in the remainder of the section. Ptychtodont tritors (pavement teeth) occur sporadically in the upper unit.
3.4 Faunal Assemblages at Pinal Creek
Four faunal assemblages were recognized in this section. In ascending stratigraphic order, they are as follows: 26
aphanitic dolomite unit: 1) ostracode-algal assemblage
upper unit: 2) Stropheodonta-Schizophoria assemblage 3) Atrypa-Cyrtospirifer assemblage 4) Atrypa-Theodosia assemblage
Their stratigraphic occurrence is illustrated in Figure 4*
This section also contains several crinoidal biosparite horizons, indicating high energy conditions that were not developed in the
Roosevelt Bam area. In comparison to the Roosevelt Bam section, this section displays a marked increase in faunal abundance and diversity.
Faunal assemblages are different, although Schizophoria and Stropheo- donta do occur at Roosevelt Bam below spiriferid brachiopods and pos sible atrypids.
3.4- 1 Ostracode-Algal Assemblage
The ostracode-algal assemblage is recognized only in thin- section in the basal beds of the aphanitic dolomite unit. The ostra- codes are unomamented, and the algae is preserved as borings in fecal pellets. These taxa are associated with interbedded pelletal and aphanitic dolomites. This assemblage is marked by very low diversity.
The remainder of the aphanitic dolomite unit is unfossiliferous, although bioturbation is evident in several intervals.
3.4- 2 Stropheodonta-Schizophoria Assemblage
The first assemblage encountered in the upper unit is a
Stropheodonta-Schizophoria assemblage in unit 18. Its elements are
listed below: 27
Taxa Abundance
Brachiopoda: Stropheodonta sp. common Schizophoria iowensis rare Schuchertella(?^ sp. rare
Bryozoa: massive trepostome rare/common small, branching rare
Echinodermata: round crinoid columnals common/abundant pentagonal crinoid columnals rare cystoid plates rare
Gastropoda: Diaphorostoma(?) sp. rare
Anthozoa: Disphyllum(?) sp. (fragments only) rare zaphrentid corals rare/common
Most of the fossil debris noted was concentrated in thin, poorly- sorted biosparite horizons. The massive trepostome bryozoa ranges up to three centimeters thick and twenty centimeters across, and occurs in growth position. The larger Stropheodonta are fragmented in these horizons, indicating possible transport, although compaction could be a factor here. Associated crinoidal sands and possible Disphyllum fragments suggest some transport. The associated dolomites are much less fossiliferous. The assemblage is diverse, but much less so than the Atrypa-Cyrtospirifer assemblage higher in the section.
3.4-3 Atrypa-Cyrtospirifer Assemblage
The third major assemblage occurs in unit 26, is dominated by two species of Atrypa, and displays a high diversity. Its constituents and their abundance are as follows: 28
. Taxa Abundance
Brachiopoda: Atrypa devoniana abundant Atrypa sp. (finely plicated) abundant Atrypa owenensis common Atrypa planosolcata(?) (one .specimen) rare Camerotoechia sp. (one specimen) rare Cyrtospirifer whitneyi common Devonoproductus sp. common Nervostrophia sp. common Productella(?) sp. common SchizophoriaC?) sp. (one specimen) rare Spinatrypa sp. rare/common Tenticospirifer sp. (one specimen) rare
Gastropoda: Bellerophon sp. (one specimen) rare Floydia cf. F. concentrica (one specimen) rare StraparoHus sp. (two specimens) rare
Bryozoa: massive trepostome rare/common fenestrate bryozoa rare
Echinodermata: pelmatozoan columnals . rare/common
Anthozoa: lamellar stromatoporoid (one fragment) rare zaphrentid corals rare/common Aulopora sp. rare
Annelida: Spirorbis sp. (attached to brachiopod) rare
The massive trepostome bryozoan, the rare Floydia cf. F. concentrica, and the lamellar stromatoporoid were collected at the top
of this interval and lower occurrences of them were not observed. The interval that was collected was several feet thick, and if studied in 29 greater detail one might document faunal succession within it. If one considers this a true paleocommunity, it would certainly be a time- averaged one (Walker and Bamback, 1971)•
Both adult and juvenile specimens of Atrypa are present. The massive trepostome bryozoan is in growth position, and most brachiopod valves are still articulated, indicating very quiet water and no trans port after death. The enclosing matrix was originally a lime mud, supporting this conclusion.
3*4-4 Atrypa-Theodosia Assemblage
The third recognized assemblage is of very low diversity and caps the upper unit at this locality. It is comprised of two common species of Atrypa with rare to common Theodosia cf. T. hungerfordi.
The specimens collected are very large adults, and no other fossils were associated with them. The valves of a n brachiopods present are still articulated, and they occur in what was originally a lime mud, indicating a quiet environment of deposition.
The biosparites in the section are composed essentially of crinoidal debris, but do contain brachiopod fragments and zaphrentid corals. Also present in the upper unit are horizontal burrows, which
consistently occur in more arenaceous intervals.
3*5 Faunal Assemblages at Globe Hills
The upper unit here contains the same faunal assemblages as
Pinal Greek and in the same vertical sequence, but shows a marked increase in brachiopod abundance and diversity in beds equivalent to 30 those containing the Stropheodonta-Schizophoria assemblage at Pinal
Greek. Massive stromatoporoids and Disphyllum colonies occur in this interval also. Many of the additional taxa are rare and may well have been overlooked at Pinal Creek. The brachiopod-rich beds are at the very base of the section in fault contact with the Troy Quartzite.
This unit is equivalent to unit 3 of Pine (1968). The stromatoporoid-
Disphyllum association occurs ten feet above the base of this contact but is not in direct association with these brachiopods. The basal beds contain the following constituents:
Taxa Abundance
Brachiopoda: Cranaenella cf. C. calvini rare Crytospirifer(?) sp. (one specimen) rare Orbiculoidea sp. (inarticulate brachiopod) common Platyrachella sp. rare Schizophoria iowensis abundant Schuchertella(?) sp. rare/common Stropheodonta sp. abundant Strophonella(?) sp. rare
Bryozoa: round, button-like trepostome common branching bryozoa, very small rare
Echinodermata: large, round crinoid columnals abundant pentagonal crinoid columnals common star-shaped crinoid columnals rare
Anthozoa: Alveolites (?) sp. rare
Vertebrate: fish spine, bone fragments rare 31
Taxa Abundance
Ichnia: short (5 cm.), stubby horizontal burrows abundant large horizontal burrows rare borings on Schizophoria valves common
The brachiopod fauna (Fig. 10) is overwhelmingly dominated by
Schizophoria and Stropheodonta. Some of the Stropheodonta have been fragmented and crushed by compaction, but others still possess unbroken alae. Most brachiopods lie parallel to the bedding with pedicle valves convex-up. The Schizophoria are much more robust, have withstood com paction, and are less fragmented. Some of them are bored on their pedicle valves and some juvenile specimens are present. A number of
Schizophoria are orientated with the brachial valve up, and a few specimens lie discordant to the bedding. These two species are associa ted with large crinoid columnals (Fig. 11), and these three faunal ele ments dominate this assemblage. The enclosing matrix was originally lime mud (although there are some interbedded biosparites). The preservation and orientation of these brachiopods suggests little
transport after death.
The massive stromatoporoids and Disphyllum colonies (Fig. 12)
are in growth position, although fragments of both are found in various
orientations in the same horizon, indicating considerable turbulence.
They are associated with crinoid columnals and brachiopod fragments.
One of the difficulties in studying this section is the struc
tural complexity of the area, with different intervals of section
exposed in adjacent fault blocks. The part of the section that was 32
Figure 11. Abundant Crinoid Columnals Associated with the Stropheodonta-Schizophoria Assemblage. 33
Figure 12. Disphyllum Colony in Growth Position, Upper Unit at Globe Hills. studied was that measured by Pine (1968). Brief exploration in the area to the east revealed the presence of the aphanitic dolomite unit and a better exposure of the Atrypa-Cyrtospirifer assemblage noted in the Pinal Greek section* At Globe Hills this assemblage contains a greater abundance of Cyrtospirifer. CHAPTER 4
SEDIMENTARY ENVIRONMENTS
4.1 Introduction
By noting the occurrence and association of lithologies,
sedimentary structures, and invertebrate fossils, one can make environ
mental interpretations and reconstructions of depositional history.
Lists of these features and their environment of occurrence are given
in Table 1. Trace fossils are also environmentally dependent and
comprise several facies, as illustrated in Figure 13. More detailed
discussions of them are given in Laporte (1969) and Heckel (1972).
In this study the Shaw (1964)-Irwin (1965) model for clear
water sedimentation in epeiric seas (Fig. 14) is used. In this model,
three energy zones are recognized and thus three basic environments of
deposition: l) a nearshore, low energy zone above wave base, charac
terized by lime mud deposition; 2) offshore, high energy zone at and
just above wave base, characterized by skeletal sands; and 3) an off
shore, low energy zone below wave base, characterized by lime muds.
Low, moderate, and high faunal diversity are respectively associated
with these three environments (Bretsky and Lorenz, 1970). These envi ronments can be further subdivided into supratidal, intertidal, restric
ted subtidal above wave base, subtidal above but near wave base, wave
wave base, subtidal below but near wave base, and deep subtidal
35 36
Table 1. Characteristics of Carbonate Depositional Environments. From Laporte (1969).
FACIES FACIES SUITES CHARAC Tidal Shallow Deep Organic TERISTICS Flat Subtidal Subtidal Build-ups
Mud cracks typical — — — and birdseye Scour and f i l l w/ pebble cgls typical — — — Laminations typical — — — Early dolomite typical — — • — Sparite/micrite variable high-low low variable
X-stratification small-scale medium-scale — sometimes present Burrow-mottling rare common abundant rare Oolites — often present — — Bedding thin-medium medium-thick thick,massive unbedded,massive
Algal structures stromatolites oncolites — typical in Burrows vertical vertical and horizontal rare horizontal Fossil abundance low very high variable very high Fossil diversity low medium usually high medium-high Major taxa trilobites and/ calc.algae,pel- bracks,trilobites, tabulate,rugose, or ostracodes matozoafbrachsf ectoprocts,and and stromatopo- and ectoprocts pelmatozoa roid corals Vertical facies sharp and transitional very gradual complex variations frequent and common and infrequent Areal facies outcrop scale relatively basinal scale outcrop scale to variations persistent several miles Facies strike variable parallel to parallel to variable basin margin basin axis MARINE MARGINAL NONMARINE s h a llo w deep to slope below wave base above littoral to tidal flat
GENERAL BIOTURBATION
DEPTH OF BURROWING
VERTICAL TUBES (SIMPLE TO U-SHAPED) ^-""Skolithos* facies OBLIQUE TO HORIZONTAL U-TUBES ^.generally 'Cruiiona* facies vertical
RESTING MARKS
FEEDING MARKS FROM FIXED POINT
MEANDERING & SPIRAL g e n e r a lly GRAZING MARKS h o r i z o n t a l
UNIDIRECTIONAL CRAWLING MARKS unrestricted os to feci CERTAIN DIGITATE FEEDING MARKS
LAND ANIMAL & BIRD TRACKS <3
Figure 13'# Environmental Distribution of Organic Structures. — From Heckel (1972). DEEPER WATER SHALLOW WATER V. SHALLOW WATER LAND
SEDIMENT BELOW SEDIMENT ABOVE WAVES, CURRENTS NON WAVE BASE WAVE BASE DAMPED MARINE
MUDS TO SANDS MUDS, SANDY MUDS (some abraded, sorted)j SOME SANDY
biota diverse biota diverse biota restricted
j SUPRA-! INTERTIDAL^ n TIDAL-I
...... 'i i'lu| in x 1 'LAMINATED ( j REEFS(locolly) p E L UETED \ CALCILUTITE eff. wave base SKELETAL CALCILUTITE SHELLY CALCARENITE (some shells) EVAPORITES I CALCILUTITE (when climate arid)
(theoretical) after Heckel, 1972
Figure 14. Shaw (1964)-Irwin (1965) Model. — Modified from Heckel,(1972). 39 regimes. In the following discussion, the paleoenvironments of the
Martin Formation are discussed in ascending stratigraphic order, utilizing Teichert's (1965) stratigraphic subdivisions as guidelines.
4*2 Beckers Butte Member
The Beckers Butte Member of the Martin Formation has been dis cussed in some detail by Teichert and Schopf (1956) and Teichert (1965).
Elston and Bressler (in press) have subdivided the member into two units, and these are discussed here.
The basal sandstone unit contains low-angle trough crossbedding and is somewhat conglomeratic at its base. The remainder of the unit is composed of coarse-grained, immature sandstone with some silt stone partings. At the Salt River Canyon the overlying aphanitic dolomite unit contains a psilophyfcon flora in interbedded shales (Teichert and
Schopf, 1956). Although these interbedded dolomites and shales are present at Roosevelt Dam (Fig. 15), no plant remains have been found in them. This member, as defined by Elston and Bressler (in press) is a persistent unit not confined to channels as is the underlying Tapeats
Sandstone. On the basis of trough crossbedding and the immaturity of the elastics present, these units are considered to represent fluvial or deltaic plain sediments capped by nearshore marine deposits that may be lagoonal in origin. The thinness yet the widespread distribu tion of the unit, coupled with its nearshore aspect, suggest that its
origin is related to the transgression represented so convincingly by
the overlying Jerome Member. 40
Figure 15• Interbedded Shale and Dolomite in the Upper Unit of the Beckers Butte Member at Roosevelt Dam. a
4«3 Fetid Dolomite Unit
The fetid dolomite unit at Roosevelt Bam is composed of porous, dolomitized a l g a stromatolites and is approximately 15 feet (4*5 meters) thick. This unit was originally assigned by Teichert (1965) to an offshore.environment below wave base on the basis of its hydro
carbon content. He envisioned a plain south of the Defiance Uplift
covered by 100 to 150 feet (30.5 to 45 meters) of water, possibly in a large embayment. Beus (1973) followed Teichertfs interpretation for
this unit in the Jerome area. Pine (1968), however, recognized its
stromatolitic nature and assigned it to a supratidal or intertidal
environment following the interpretation of Laporte (196?) for such
occurrences in the Lower Devonian Manlius Formation of New York. I
concur with Pine's interpretation. The unit is strongly laminated
(Fig. 16) and contains the undulatory fenestra! texture inherited from
an algal mat. The unit also contains abundant birdseye structure, a
feature characteristic of supratidal or intertidal environments (Shinn,
1968). This unit was not observed in sections near Globe.
4.4 Aphanitic Dolomite Unit — Roosevelt Dam
The contact of the fetid dolomite unit and the aphanitic dolo
mite unit is gradational and its placement rather arbitrary. The
aphanitic dolomite unit is aphanocrystalline in its lower part, grading
to finely crystalline near its top. At Roosevelt Dam I encountered
seven horizons of mudcracks (Fig. 17), five horizons of birdseye struc
ture, and two horizons of intraformational breccias (Figs. 18 and 19).
The unit is laminated throughout and contains small channels at bedding 42
Figure 16. Laminations in the Fetid Dolomite Unit at Roosevelt Dam. — (Glove for Scale). 43
Figure 18. Intraformational Breccia, Aphanitic Dolomite Unit at Roosevelt Dam. 44
Figure 19. Acetate Peel of Intraformational Conglomerate, Aphanitic Dolomite Unit at Roosevelt Dam. 45 contacts, especially in its lower part (Fig. 20). All of these structures are criteria for the tidal flat environment. The aphanitic dolomite unit is 109 feet (33*2 meters) thick at this locality, and these structures are found throughout the basal 85 to 90 feet (26 to
27.5 meters). Near the top of this interval, arthrodiran plates are present (Figs. 6, 7 and 8). The upper 20 feet of the unit lacks these features, and this may indicate a transition to a shallow subtidal environment. These structures have been noted in the aphanitic dolo mite unit by other workers throughout its area of occurrence, and the unit has been assigned to an intertidal or very shallow subtidal envi ronment by them (Teichert, 1965; Pine, 1968; Beus, 1973). The evidence for a supratidal-intertidal origin for most of the aphanitic dolomite unit at Roosevelt Dam is overwhelming.
Shale partings are common in the aphanitic dolomite unit at the
contacts of many beds at Roosevelt Dam and may reflect periodic clastic influx or times when water chemistry was not amenable to carbonate - precipitation (Heckel, 1972). Floating quartz grains are abundant and
probably aeolian in origin, an interpretation suggested by both Teichert
(1965) and Pine (1968).
Although the stromatolites, birdseye structures, and mudcracks
here indicate periodic subaerial exposure, they are not related to a
complete evaporation of a standing body of water, for evaporite minerals
such as gypsum and halite are absent from these rocks. This precludes
these rocks from forming and accumulating in a sabkha-type environment. 46
Figure 20. Channels in the Lower Part of the Aphanitic Dolomite Unit at Roosevelt Dam. 47
4<>5 Aphanitic Dolomite Unit — Pinal Creek
In comparing the aphanitic dolomite unit at Roosevelt Dam with that at Pinal Creek, some striking differences are noted. At Pinal
Creek the aphanitic dolomite unit is massively bedded and lacks mud- cracks, channeling, or intraformational breccias. Dessication features such as mudcracks may be present, but bedding plane exposures are few.
Midway through the unit an erosional-solutional surface occurs, with two to three feet (0.6 to 0.8 meters) of relief. Two units of pelletal dolomites occur near the base of the section, and in some intervals bioturbation has created rounded, unsorted intraclasts associated with some small, vertical burrows (Fig. 21). Pellets are interpreted by
Laporte (196?) as being characteristic of supratidal or intertidal environments. They also are common in nearshore restricted marine environments such as lagoons. The smooth-shelled ostracodes and algal borings of pellets in these lower beds also suggest such an environment.
Unit 7, 25 to 32 feet (7.6 to 9*8 meters) above the base of the
section, contains abundant birdseye structure. The overlying unit
contains an urisorted, non-stratified dolomite pebble conglomerate or
conglomeratic dolomite near its top. Its base appears to be brecciated, but it displays no transport. This unit maintains a consistent thick ness, and it occupies the. same stratigraphic position throughout the entire outcrop. It is difficult to conject an origin for it, but it may reflect subaerial processes.
The top of unit 10 along the erosional surface and unit 11 just above it are composed of round, unsorted intraclasts (Fig. 21). 48
Figure 21. Rounded Intraclasts, Birdseye Structure, and Burrow Remnants in the Aphanitic Dolomite Unit at Pinal Creek. — (From Acetate Peel). 49
These intraclasts are associated with birdseye structure, suggesting
intense bioturbation. In certain intervals, small coalescing vertical burrows occur where the sediment was not entirely broken up. This mode
of burrowing suggests a restricted subtidal or intertidal environment
(Heckel, 1972) ♦ The lack of distinct sedimentary structures in the
remainder of the aphanitic dolomite unit may indicate a transition to
a shallow subtidal environment. At the top of unit 13, four feet
(1.2 meters) below the top of the aphanitic dolomite unit, more biotur bation and birdseye structure were noted.
Again, the evidence strongly supports the interpretation that
most of the aphanitic dolomite unit is intertidal and supratidal in
origin — the pelletal dolomite, the birdseye structures, the solution
surfaces, and vertical burrowing.
4.6 Upper Unit
The upper unit contains a variety of subtidal environments. At
Roosevelt Dam it contains a much greater percentage of coarse clastic
debris interspersed with dolomite than at Pinal Creek. Only a few
horizons of biosparite occur, 95 to 113 feet (29 to 34*5 meters) above
its base. The remainder of the unit is dolomite. Although diagenesis
has been more extreme at Roosevelt Dam, faunal diversity and abundance
of taxa genuinely appear to be lower. At Pinal Creek coarse clastic
debris is minimal, except in the beds capping the aphanitic dolomite
unit. Faunas are more diverse, and their dominant constituents more
abundant. Within the upper unit at Pinal Creek there are four or five 50 horizons of well developed skeletal sands (biosparites), which suggest a more offshore environment for the area.
The basal beds of the upper unit are comprised of quartz- cemented, trough-crossbedded quartzarenite with dip angles up to 20°.
This is a consistent relationship in most Devonian sections throughout central Arizona. This quartzarenite was noted at all five localities visited in this study, and most sections described by Teichert (1965) and Pine (1968) contain it. This quartzarenite varies in thickness and grain size, but it is commonly ten or more feet thick. It occupies the same stratigraphic position as the "arthrodiran sandstone” of
Stoyanow (1936) at Jerome and Payson. At Pinal Greek this quartzare nite, based on cross stratification, displays a dominant component of westward transport complemented by a lesser eastward component. It contains horizontal burrows in one horizon, is ripple marked on top, and is capped by a thin, coarse chert-quartzite pebble lag containing ptychtodont fish tritors (pavement teeth). At Roosevelt Dam the base of the quartzarenite contains quartzite pebbles, suggesting a discon- formity between the aphanitic dolomite unit and the upper unit. This quartzarenite is interpreted to be a shallow subtidal sand body such as an offshore or barrier bar, but could alternatively have been a beach deposit. It was laid down seaward of the restricted environment
of the aphanitic dolomite unit or upon a scoured surface, reflecting an erosional interval. 51
4.6-1 Upper Unit at Roosevelt Dam
Above these basal clastic units the upper unit varies markedly between Roosevelt Dam and final Creek, and thus they will be discussed separately. The vertical distribution of sedimentary structures, rock types, and fossil contents is illustrated in Figure 3 (in pocket). At
Roosevelt Dam, the basal quartzarenites are overlaid by siltstone and ultimately a troughr-crossbedded, very sandy, laminated dolomite to dolomitic quartzarenite that contains three or four horizons of intra clasts and large, rare to common vertical burrows (Figs. 22, 23, and
24). The unit is unfossiliferous. Its base is more strongly cross- bedded and intraclastic. The overlying two units lack such features and are unfossiliferous, with the exception of rare spiriferid brachio- pods. These units are considered to have formed in a shallow, subtidal environment above wave base. Trough and planar crossbedding, the lack of fossils, and the presence of vertical burrows are character istic of such an environment (Heckel, 1972).
Above this there is a transition from ripple-marked, dolomi- tized lime mud containing abundant horizontal burrows and grazing traces, Chondrites, (Figs. 25 and 26) to dolomitized biosparites con taining brachiopods, indicating a transition from a subtidal above wave base environment to an offshore environment that frequently was
in a zone of agitation above or at wave base. These dolomitized
skeletal sands may represent a transgressional maxima in the section.
The overlying 60 feet (18.1 meters) is comprised of sandy,
sparsely fossiliferous dolomites. No biosparites are present and Figure 22. Crossbedding in Lower Part of Upper Figure 23# Close-up of Vertical Burrow in Unit at Roosevelt Dam. — Note Lower Part of Upper Unit at Vertical Burrows in Upper One-half. Roosevelt Dam. vn K> Figure 24. Close-up of Crossbedding in the Upper Unit at Roosevelt Dam. 54
Figure 25. Horizontal Burrows in the Upper Unit at Roosevelt Dam.
Figure 26. Grazing Traces (Chondrites) in the Upper Unit at Roosevelt Dam. 55 faunal diversity is low. This interval contains a horizon of oscilla tion ripple marks and is bioturbated. The predominance of dolomitized lime muds and low faunal diversity indicates that these units were laid down in a shallow subtidal environment above wave base.
The upper 50 feet (15.3 meters) of the upper unit is comprised of unfossiliferous dolomites or dolomitic sandstones containing hori zontal burrows in rare horizons. Unit 27 is a very fine-grained dolomitic quartzarenite 20 feet (6.1 meters) thick, uniform in texture, and gently trough-crossbedded at its base. It is strongly laminated and contains some convolute bedding (Fig. 27)» small scale tabular- planar and wedge-planar crossbedding (Fig. 28), and appears to be stromatolitic in certain horizons (Fig. 28). These features are com monly associated with tidal flat environments. Due to the absence of fossils and the nature of these lithologies and sedimentary structures, these units are presumed to have been laid down in an increasingly shallow subtidal environment above wave base.
4.6-2 Upper Unit at Pinal Creek
Fluctuations of sea level probably occurred during deposition of the upper unit at Roosevelt Dam, but they cannot be recognized with the certainty that they can be at Pinal Creek. In the Globe area the upper unit is composed of three basic lithologies: l) barren dolomite or siltstone (originally muds); 2) fossiliferous dolomite (originally lime mud); and 3) biosparites (originally skeletal sands). These units tend to be stratigraphically distinct. Their vertical Figure 27. Convolute Bedding in the Upper Part of the Upper Unit (Unit 2?) at Roosevelt Dam. 57 distribution, interpreted environment of deposition, and energy levels are illustrated in Figure 29#
Immediately overlying the basal trough-crossbedded quartza- renite is an arenaceous dolomite containing horizontal burrows, ripple laminations, and rare crinoid columnals# The overlying unit contains the Stropheodonta-Schizophoria assemblage, which is moderately diverse, and a few thin biosparite horizons# On the basis of these characteris tics, these units are interpreted to have formed in a deepening sub- tidal environment above wave base, approaching it very briefly at times, resulting in the formation of these skeletal sands. The succeeding barren unit was originally a silty lime mud, and its unfos- siliferous nature indicates a shallowing of seas and sedimentation in a nearshore, above wave base environment# It does contain horizontal burrows near its top.
In the overlying 10 feet (3.1 meters) of section, a sequence from l) a ripple-laminated, fine-grained quartzarenite, to 2) a calcar- enite, 3) a fossiliferous dolomite, 4) a biosparite, 5) an unfossilif- erous dolomite with horizontal burrows in an arenaceous horizon at its top, and 6) a return to a barren siltstone or shale is present.
This may represent a rapid transgressive-regressive pulse that reached wave base at the transgres sional maxima.
The latter barren interval becomes increasingly dolomitic upward and is capped by an Atrypa-bearing dolomite that grades into a crinoidal biosparite. Above this crinoidal biosparite is a thick (21 feet, 6.4 meters) fossiliferous dolomite containing a diverse fauna 58
S e d im e n t E n e rg y D iv e rs ! Environment w ave deep s u b tid . s u b tid .
Figure 29. Characteristics of the Upper Unit at Pinal Creek 59 dominated by two species of Atrypa (Atrypa-Cyrtospirifer assemblage).
This sequence of units as well as faunal content suggests a trans gressive pulse or basin subsidence with a succession of environments from l) shallow, restricted subtidal environment above wave base,
2) subtidal environment above wave base but somewhat deeper and with better circulation, 3) an environment at and just above wave base, and
4) a below wave base environment.
Above this latter unit is a thin (6.5 feet, 2.1 meters)
sequence of l) calcarenite, 2) fossiliferous dolomite dominated by
small Atrypa sp., 3) a crinoidal biosparite, and 4) a barren, very
thin-bedded dolomite. This suggests a reversal of environments in a
regressive pulse. The upper three units (25 feet, 7*6 meters) over-
lying this barren interval comprise the following sequence: l) very
sparsely fossiliferous dolomitej 2) fossiliferous dolomite, dominated
by atrypid brachiopods; 3) a poorly sorted, dolomitic crinoidal bio
sparite which contains vertical living(?) burrows at its upper contact;
and 4) a sparsely fossiliferous dolomite with low diversity, containing
two species of Atrypa and Theodosia cf. T. hungerfordi. This indicates
a transgressive-regressive pulse resulting in the following succession
of environments: l) very shallow, restricted subtidal above wave base;
2) deeper subtidal environment above wave base with better circulation;
3) at and just above wave base; and 4) shallow subtidal above wave base.
The sequence at Globe Hills is similar, although it does con
tain a massive stromatoporoid-Disphyllum association that probably
thrived near wave base. This association is present above the basal
quartzarenite of the upper unit. As faunas and unit sequence are 60 similar to the Pinal Creek section, the succession of environments for
Globe Hills will not be discussed here.
4.7 Problems
A major problem to be discussed here is that at Roosevelt Dam the upper unit is dominated by shallow, nearshore marine environments, yet it is considerably thicker than sections near Globe, which were undoubtedly deposited in a more offshore position. This may be attrib uted to greater subsidence in the Roosevelt Dam area, accompanied by a greater depositional rate that maintained relatively shallow water environments. Alternatively, sedimentation may have begun earlier in this area and/or ceased later. It is possible that this transgression occurred upon a surface of some relief, and that the Globe area was topographically higher. This is supported by the absence of the
Beckers Butte Member and fetid dolomite unit there. Post-Martin, pre-
Percha erosion may also have removed a greater part of the upper unit
near Globe, but this seems a less viable explanation. Displacement
of the Globe-Roosevelt Dam areas by faulting in post-Martin time is a
possibility also. CHAPTER 5
PALEQE OOLOGY
5.1 Introduction
As stated by Watkins and Boucot (1975» P* 244), MA solid paleo- ecological synthesis depends on a solid framework of taxonomy and strat igraphic geology.” The previous two chapters have dealt with these topics. In this chapter these two aspects are synthesized to determine which assemblages represent paleocommunities or associations (taxa that lived together) and what the lateral relationships of those associations were on the sea floor. The taxa of these associations may be classified on the basis of their mode of food gathering and a community’s tropic structure partially reconstructed. Morphology may be utilized to postu late living habits. Literature helpful In this endeavor is compiled in
Ziegler and others (1974) and Scott and West (1976). Basic paleoeco- logical techniques are discussed and specific examples of recent and fossil communities are given in the former. Further discussion, classi fication and recognition, and specific examples of paleocommunities are presented in the latter.
As discussed in Chapter 3» an assemblage refers to all organisms brought together after death and preserved together. An association
refers to organisms that existed together in life. The biological and
geological definitions of a community necessarily differ. The tremen
dous loss of biotic information in taphonomy— the events affecting
61 62
organisms between their death and eventual discovery— destroy many
elements of a living community, including most producers and all soft- bodied organisms. Kauffman and Scott (1976) have designated this
living community an holistic community, comprised of all interacting
organisms that are restricted in distribution by environmental pararo-
eters. As this holistic community is impossible to reconstruct from
the rock record, we must employ recurring fossil assemblages as the
basis of paleocommunity definition. Biofacies is a larger paleoeco-
logical unit and may encompass more than one community or fossil
association.
In community paleoecology there are two basic approaches, a
quantitative approach and a qualitative approach. The first relies upon
statistical analysis of large numbers of taxa. From this, percentage
composition of assemblages are calculated, diversity coefficients
derived, etc. This approach is much more applicable to units from
which large numbers of specimens can easily be removed or in which
large expanses of fossiliferous bedding planes are exposed. A qualita
tive approach utilizes relative abundance of taxa, and abundance of
these taxa within an interval— are they rare, common, or abundant? The
mode of occurrence and preservation of assemblages in this study does
not allow a quantitative analysis in all instances, and thus the quali
tative approach is employed.
Transport is a primary factor in masking paleocommunity recogni
tion. Those assemblages considered to represent communities are those
that have undergone little or no transport. Thus, enclosing sediment 63 type, fragmentation or abrasion of fossils, and their orientation must. be noted in order to determine if an assemblage has been transported.
By this method associations are determined. Once certain associations and their succession are recognized, they may be compared with other studies in time-equivalent units elsewhere. To these ends this chapter is devoted.
$.2 Associations
Most of the assemblages encountered in this study may be termed associations because of the minimal transport they experienced. The exception to this is the arthrodiran assemblage, which occurs in an intertidal environment, a habitat that it could not have lived in.
Taxonomic composition, relative abundance of taxa, trophic type and
relationship of organisms to the substrate (epifaunal or infaunal) for
the associations are listed in Table 2 and are discussed in the follow
ing sections on the basis of ecological similarity and increasing dis
tance from shore.
5.2-1 Stromatolite "Association"
This association is composed solely of algal stromatolites.
The algal mat that created it was a primary producer and the stromato
lites were formed in place. These stromatolites occur with abundant
birdseye structure and occupied a supra- or intertidal environment, as
stated earlier. Laporte (196?) has noted such an occurrence in the
supratidal facies of the Lower Devonian Manlius Formation of New York. Table '• Taxonomic Composition, Relative Abundance of Taxa, Trophic T^rpe, and Relationship of Organisms to Substrate.
.1
sus. 2 1 10 pi TAZON §1
tn low-level sus. scavenger deposit feeder deposit predator passive grazer-browser active active predator stromatolite ASSOCIATION ostracode-algal brae] Coenites-spir. ml Ihigh-level IIIg1 SchizoDhoria iownsis X X e a Strocheodonta X X c a Elatvrachella X X r r Sclmchertella? X X 3 Crmnaenella calvlni X X r Orbiculoidea X X c Strochonella? X X r Atrypa devonlana X X a c Atrypa sp. X X a c Atrypa owenensls X X c Atrypa planosulcata X X r Camarotoechla X X r Cyrtosnlrifer whitnayi X X c "spiriferid brack." X X 96 Devonooroductua X X c Mervoatrophia X X c Producteila X X c Spinatrvm X X Tenticospirifer X X r Iheodosia X X gastropods X X‘ r c crinoid X X a a c r fenestrate bryozoa X X a r massive trepostome X X /c: : branching trepostome X X r button-like trap, c zaphrentid corals 11 X X r Disphvllum X X r c : Coenites X X q/a Aulopora X X r r Alveolites X X r massive strom. X X c lamellar strcm, X XI? r Spirorbis X X'? r fish bone X 1i X r r stranatolites X [Prociuc263 a algal filaments X If rocfan263•i ostracodes X X c Cruziana trails X X c horizontal burrows X X a vertical burrows X X c inclined burrows X X c 65
5*2-2 Ostracode-Algal Association
The ostracode-algal association present at Pinal Creek was not observed at Roosevelt Dam* It is comprised of smooth-shelled ostracodes and algal filaments, which are preserved as borings in associated fecal pellets. This association is constituted of epifaunal grazers (ostra codes) and primary producers and has a low diversity. The pellets indicate that possible presence of molluscs, such as gastropods, which are epifaunal grazers, predators, or scavengers. The habitat is inferred to have been lagoonal or tidal flat based upon the rock types and sedimentary structures discussed in the previous chapter.
5*2-3 Coenites-Spiriferid Brachiopod Association
The Coenites-spiriferid brachiopod association is unique to the
Roosevelt Dam section, although spiriferids occur in sections near
Globe. Coenites occurs in various orientations, as do the scattered,
rare brachiopods. However, the enclosing matrix was originally a silty lime mud, and post-mortem transport was probably minimal. This associa
tion is dominated by a passive benthonic predator in association with
a low-level, epifaunal suspension feeder. It has a very low diversity,
suggesting a restricted, above wave base habitat.
5.2-4 Crinoid-Schizophoria Association
The crinoid-Schizophoria association contains the greatest
concentration of pelmatozoan debris in the Roosevelt Dam section. It
is of moderate diversity and dominated by high- and low-level epifaunal 66
suspension feeders. The interbedded dolomitized skeletal sands and lime muds indicate that the association inhabited an environment at to
above wave base.
5*2-5 Fenestrate Bryozoa-Stropheodonta Association
The fenestrate bryozoa-Stropheodonta association contains one
of the greatest concentration of fenestrate bryozoa within the Martin
Formation. This association is comprised of low- to intermediate-
level suspension feeders. Cruziana trails and inclined burrows indicate
the presence of possible scavengers and deposit feeders. Both the
Stropheodonta and fenestrate bryozoa are in various orientations, but
the entombing sediment was originally a lime mud, and little post
mortem transport probably occurred. This association occurred in a
subtidal environment above wave base, inferred from its moderate diver
sity and the nature of the enclosing sediment. Together with the
crinoid-Schizophoria association theysresemble the Stropheodonta-
Schizophoria association in the Globe area, which occupied a comparable
environment. The taxa between the fenestrate-bryozoa-Stropheodonta
association and the Coenites-sprirferid brachiopod association at
Roosevelt Dam may represent a recurrence of the fenestrate bryozoa—
Stropheodonta association— fenestrate bryozoa are present— but preser
vation is too poor to allow valid paleoecological inferences.
5*2-6 Stropheodonta-Schizophoria Association
The Stropheodonta-Schizophoria association is better developed
at Globe Hills than at Pinal Creek, but is present in both sections. 67
It contains abundant crinoidal debris associated with these two dominant brachiopod genera. They occur with a number of rarer brachio- pods and bryozoans. Some fish bone fragments are present also. They are associated with a few horizons of biosparite, indicating wave base conditions, but most of the enclosing sediments were originally lime muds.
This association is dominated by high- to low-level, epifaunal suspension feeders, with rare nektonic predators or scavengers.
Abundant horizontal burrows indicate the presence of deposit feeders such as annelids. The skeletal sands and the moderate diversity of the association demonstrate that these organisms thrived in a subtidal habitat above wave base with periodic agitation near it. As discussed earlier, these brachiopod faunas have experienced little transport.
5*2-7 Disphyllum-Massive Stromatoporoid Association
A Disphyllum-massive stromatoporoid association occurs 10 feet
(3 meters) above the previous association at Globe Hills. It is domina ted by passive benthonic predators in association with rare high- and low-level suspension feeders, as evidenced by brachiopod and crinoidal debris. The Disphyllum colonies and massive stromatoporoids are in growth position, but fragments of them are found in the same horizon, suggesting a turbulent environment at or near wave base. This associa tion may have lived with the brachiopod association, forming energy buffers that created habitats for them to colonize. 68
$.2-8 Atrypa-Cyrtospirifer Association
The Atrypa-Cyrtospirifer association occurs in strata inferred to have formed below wave base. It occurs in what were originally lime muds, and the fauna is quite diverse. It contains a rich brachiopod fauna composed of abundant Atrypa devoniana and Atrypa sp. (finely plicated) with five other common brachiopod species and five rare species. It also contains common gastropods and rare fenestrate and massive bryozoa. The massive trepostome is in growth position and in the form of pads as large as 0.5 meters across. Crinoid debris is rare rather than abundant, indicating an environment with little agitation.
The association is strongly dominated by low-level suspension feeders.
The gastropods were presumably algal grazers or scavengers. Also noted were common zaphrentid corals, which are passive benthonic predators.
Rare Spirorbis. a calcareous test-producing annelid, was found on a few brachiopod valves, possibly in a commensal relationship.
5*2-9 Atrypa-Theodosia Association
The Atrypa-Theodosia association at the top of the section is comprised of three or four brachiopod species and no other taxa. It contains two common species of Atrypa associated with Theodosia cf.
T. hungerfordi. The enclosing sediment was originally lime mud. The
specimens present are all large adults, and the association is composed
of solely low-level suspension feeders. It is of low diversity and may
have inhabited an above wave base habitat. It seems logical, however,
that it would not have been separated from the Atrypa-Cyrtospirifer
association by the radically different Stropheodonta-Schizophoria 69 association, and thus it is placed adjacent to the Atrypa-Crytospirifer association and below wave base in the illustrations. The relationship
of these associations may be complicated by the evolution of a differ
ent sequence of environments in transgressive and regressive phases.
5.3 Lateral Relationships
The relationships of associations and environments are illus
trated in Figure 30, employing the Shaw (1964)-Irwin (1965) Model.
Anderson (1971) has utilized the low-high-low energy scheme of this
model and has recognized five environmental categories: l) tidal flat;
2) restricted subtidal; 3) open shelf above wave base, with regular wave, current action; 4) open shelf near wave base with occasional wave
and current action; and 5) open shelf below wave base, with only
organic reworking. He then correlates five communities with these
environments, which he feels is a consistent pattern throughout the
Paleozoic. The associations in the present study are correlated with
Anderson’s scheme in Figure 31.
These divisions are roughly equivalent to Boucot’s (1970) six
benthic assemblages, although Boucot does not relate them to environ
ments in this manner. In tectonically active areas with high clastic
influx, this pattern is reduced to three lateral communities (Anderson,
1971), a pattern characteristic of the Sonyea and Genesee Groups of
New York and the Fourknobs Formation of the Allegheny Front of the
Central Appalachians.
The fossil associations present are asymmetrical with respect
to transgressive-regressive cycles; lower faunal occurrences in more PINAL CREEK
Subtidal Subtidal Intertidal Supratidal below wave base above wave base
T O s tra c o d e 1 Stropheodonta- A lg a l Association Atrvpa- ' AtryBS” Schizophoria Cvrtospirlfer Theodosia Association Association Association
ROOSEVELT DAM
Fenestrate Bryozoa- Association Strooheodonta Associations
Figure 30. Lateral Relationships of Faunal Associations. ENVIRONMENT ROOSEVELT DAM PINAL CREEK 8 GLOBE HILLS
Stromatolites TIDAL Ostracode-Algal FLAT Arthrodiran Association Assemblage RESTRICTED Coenites-Spiriferid SUBTIDAL Brachiopod Association
Strobheodonta-Fenestrate Strooheodonta-Schizoohoria OPEN SHELF Bryozoa Association Association NEAR WAVE . BASE Crinoid-Schizophoria Disphvllum- Massive (reg. current action) Association Stromotoporoid„ Association OPEN SHELF AtrvDa-Theodosia NEAR WAVE Association BASE (occasional cur. act.) Atrvog-Cvrtospirifer Association OPEN SHELF BELOW WAVE BASE
Figure 31. Placement of Associations in Anderson’s (1971) Scheme 72 nearshore environments do not recur in the upper part of the section.
From this one may assume that l) rates of transgression and regression influence the type of community developed and its distribution, 2) the sequences of environments that evolve in a transgressive interval differ from those in a regressive interval, or 3) evolution has caused the occupation of similar niches by different organisms, resulting in new community composition and structure (community replacement).
In this study the latter hypothesis is probably invalid. One would assume that, barring biological catastrophe, later communities occupying recurrent environments in a continuous depositional sequence would be composed of organisms derived from stock from earlier communi ties that had adapted to those environments. For this reason, the first two hypotheses seem more valid. Bowen and others (1974) and
Thayer (1974) have documented a similar phenomena in the Upper Devonian
(Frasnian) Sonyea and Genesee Groups of New York. The controls there, however, were a function of progradation rates of the "Catskill Delta.”
5.4 Comparison with Other Studies
Between Frasnian and Famennian time, mass extinctions occurred in marine benthic organisms. The sustained Frasnian transgression was
terminated by a rapid regression that eliminated many environments,
and hence, many brachiopod genera (Johnson, 1974a)• Many genera of « other marine invertebrates, such as stromatoporoids, also became extinct
at this time (McLaren, 1970). For this reason, Middle Devonian taxa
and assemblages have more in common with Frasnian assemblages than do 73 succeeding Famennian assemblages. Thus, studies of earlier or contemporaneous fossil assemblages are more relevant to the present investigation than studies of later ones.
Although Stauffer (1928), Stoyanow (1936) and Beus (1973) described the paleontology of the Martin Formation (or Jerome Formation) they did not speculate on paleoecology or paleocommunities. Teichert
(1965) discussed the.paleoecology of the Martin Formation in central
Arizona in a very general manner. Although refusing speculation on communities and their lateral relationships, he discussed two types of brachiopod assemblages, l) a "mixed assemblage," with a diverse fauna, and 2) a "restricted assemblage," generally coquinas dominated by one
or two genera. He also mentioned 3) a biostromal "facies" composed of
stromatoporoids and/or corals, and 4) an ostracode-calcisphere associa
tion.
Teichert*s (1965) mixed assemblage contains several brachiopod
genera (e\g., Schizophoria, Atrypa. Spinatrypa, Cyrtospirifer, and
others) that are generally associated with corals such as Pachyphyllum
and Thamnopora. It is variable in composition. Although the Atrypa-
Cyrtospirifer assemblage at Pinal Greek has a diverse brachiopod fauna,
corals are not present. Teichert*s "restricted assemblages" are com
prised of atrypids, Schizophoria, Theodosia, or Camarotoechia, but are
limited to one or two genera. Stropheodonta and Schizophoria coquinas
were noted at Roosevelt Dam in the present study, but such concentra
tions cannot be labeled paleo communities. Teichert*s biostromal
"facies" consists of massive stromatoporoids associated most commonly 74 with tabulate corals such as Thamnopora and Alveolites. Pachyphyllum
is the most commonly associated rugose coral, but Hexagonaria may be
present also. The Disphyllum-massive stromatoporoid association at
Globe Hills is the best correlative association noted in this study,
but it did not develop into biostromal proportions. Teichert’s
ostracode-calcisphere association is very widespread and occurs most
commonly in the upper part of the aphanitic dolomite unit. Although
calcispheres were not noted in the present study, this association is
similar to the ostracode-algal association at Pinal Creek. It is evi
dent from Teichert’s work and Stoyanow (1936) that elsewhere in the
Martin Formation a variety of other distinct fossil assemblages occur.
Copper (1966) discussed Middle Devonian atrypid "biotopes” of
central Europe, showing them to occupy a restricted marine environment
behind a seaward mud mound or organic build-up and succeeding each
other perpendicular to the shore line. These "biotopes" he related to
four magnafacies. These magnafacies and associated environments and
organisms are listed in Table 3» In comparison to Martin environments,
the Old Red magnafacies is similar to environments of the Beckers Butte
Member. The Rhenish magnafacies is restricted marine and contains
locally abundant pelecypods, gastropods, and some brachiopods.
Stoyanow (1936) described a molluscan assemblage from the Island Mesa
beds in Arizona, which may have inhabited environments similar to those
of this magnafacies. The Eifel magnafacies contains an association of
brachiopod and coral genera similar to Teichert’s (1965) mixed assem
blage, especially the association of Atrypids and Thamnopora. The Table 3. Characteristics of the Middle Devonian of Northwestern Europe
Old Red magnafacies Rhenish magnafacies Eifel magnafacies Hercynian magnafacies Lithology conglomerates,sand sandstones,siltstones, calcareous shales, massive,light coloured, stones, fresh water noncalcareous shales Buddy limestones, *'pure"limestones, limestones and shales rare dolomites black-purple sterile or ammonoid bearing shales Dominant fish remains,fresh plant remains, rare rich in rugose and stromatoporoids,large megafauna water molluscs,plant fish remains, locally tabulate corals, knoll-block tabulates, remains abundant pelecypods, stromatoporoids, cerioid rugosans(hom gastropods,primitive brachiopods, corals absent), ammonoids brachiopod stocks, crinoids abundant, brachiopods rare crinoids (no ammonoids) locally abundant
Corals — rare horn and cylindrical stromatoporoids dominate, corals,phaceloid and then colonial corals cerioid rugosana, abundant small tabulates like Itiamnopora, Favoaites. Heliolites,Alveolites, Aulopora Brachiopods inarticulate s( Lingula). varied, multispecific small,smooth-shelled strongly ribbed,long- groups mainly atrypids, pentamerids,meristellids, hinged spiriferids spiriferids,rhynchonellids, atrypids or large Uncites, Of/sterolites group), athyrids but also gypidulids, Stringocephalus.Meganteris, schuchertellids,orthids, meristellids Rensselarviia rhynchonellids# Atrypid rare,some primitive Atrypa(sg.I,sg.P), Himatrypa,Karpinskta, brachiopods Atrypa(gp.reticularis) De squama tia , Spinatrypa, Carinatina.Vagrania of Spina trypina, Atryparia, larger,coarse ribbed type Gruenewaldtia* Carinatina rare. and small,smooth Cryptatrypa, Kerpina locally abundant Glassia.Dubaria• l&ivironment c ontinental(deltaic, brackish water,shallow shallow,sheltered marine open marine, turbulent fluviatile,lacus marine,pericontinental (mainly back-red, lagoonal?) (fore-reef zone?) trine ), non-marine 76
Hercynian magnafacies is dominated by massive stromatoporoids associated with colonial corals and brachiopods. Although brachiopod genera differ, it is similar to Teichert’s biostromal facies and the
Disphyllum-massive stromatoporoid association of the present study.
Fraunfelter (196?) correlated Stainbrook’s (1941) eight faunal zones of the Middle Devonian Cedar Valley Formation of Iowa with eight biofacies in the Middle Devonian of east-central Missouri (Fig. 32).
Schumacher (1976) assigned six of these to certain environments, illus trated in the same figure. These facies represent an onshore-offshore
sequence.
The Turbonopsis Biofacies is characterized by the gastropod
T. providencis and contains no other taxa. This facies occupied an
intertidal to shallow subtidal environment, but has no corresponding
association in the present study. The Hexagonaria profunda, Atrypa
bellula, and H. lativentra Biofacies occur in a shallow subtidal envi
ronment above wave base. Stoyanow (1936) and Teichert (196$) have
noted the presence of Hexagonaria in the Martin Formation but did not
assign it to a particular environment. In the Cedar Valley Formation,
these are associated with bryozoans and a diverse brachiopod assemblage.
The Atrypa missouriensis facies occurs at to just below wave base, as
does the Atrypa-Cyrtospirifer association of the present study. The
Stropheodonta Biofacies is by far the most diverse (Schumacher, personal
communication). It is dominated by Stropheodonta and is associated
with the tabulate coral Tabulophyl 1nm T trepostome bpyozoans, brachio
pods, and locally a diverse molluscan assemblage. The T-TURBONOPSIS ZONES BIOFACIES HP-HEX AGON ARIA PROFUNDA ML- HEXAGONARIA LATIVENTRA CEDAR VALLEY FORMATION MISSOURI MIDDLE DEVONIAN AB-ATRYPA GELLULA A-ATRYPA MISSOURENSIS STRAPAROLUS ___ STACMYODES SR-STROPHEODOMTA ► x — TA-TADULDPHYLLUU IDIOSTROMA TABULOPHYLLUM SA-STACHYOOES CRANAENA IOV/ENSIS STROPHEODONTA ATRYPA WATERLOOENSIS ATRYPA MISSOURIENSIS
PENTAMERELLA HEXAGONARIA LATIVENTRA | ATRYPA BELLULA ATRYPA BELLULA HEXAGONARIA. PROFUNDA HEXAGONARIA PROFUNDA
ATRYPA INDEPENDENSIS^ TURBONOPSIS GENERAL RELATIONSHIPS OF THE BIOFACIES OF THE MIDDLE CDRRELATIONOF CEDAR VAUJEY AND MISSOURI KWDDLE DEVONIAN DEVONIAN OF CENTRAL AND NORTHEASTERN MISSOURI FAUNAL UNITS
: ■ , Correlation of Cedar Volley and Missouri ^Middle Devonian faunal units. . , . , General relationships of the Biofacies of the Middle Devonian of central end northeastern Missouri.
FORMATION CEDAR VALLEY FORMATION
LIT HOF A C1 E S COOPER CALLAWAY M IN E O l A CALLAWAY
BIOFACIES Hv.:r;;;.'u H,::,u C rr.-.V .v::-
DEPOSITIONAl 1 1D A 1 SHALLOW SUftllOAL DEEP SUBilDAl
ENVIRONMENT P 1 A I L O W ENERG Y HIGH ENERGY LO W ENERGY
IITHOIOGY MIC t i f f LIME MUDSTONE •IOSPARIII LIME MUDSTONE
GENERALIZED
WEST TO EAST
CROSS-SECTION
Figure 32. Biofacies and Environments of the Middle Devonian Cedar Valley Formation. — Top from 1 Fraunfelter (1967); Bottom from Schumacher (1976). 3 78
Stropheodonta-Schizophoria association of the present study contains abundant Stropheodonta. but occurs at to above wave base and is not nearly so diverse. The Tabulophyllum Biofacies occupies the same environment as the Stropheodonta Biofacies, but contains much fewer taxa. The Stachyodes Biofacies is dominated by stromatoporoids, tabu late corals, and brachiopods, most importantly Granaena, and it occurs in a shallow, above wave base habitat. This facies is similar to the biostromal facies of Teichert (1965) and the Disphyllum-massive stromatoporoid association of the present study. These biofacies are compared with other communities and faunal associations in Figures 33 and 34*
Johnson and ELory (1972) described a Spinatrypa-Thamnopora community from the Middle Devonian of Nevada. This community is dominated by the brachiopods Cryptatrypa paracircula and Spinatrypa asymmetrica, and the tabulate coral Thamnopora in association with stromatoporoids. Because of the low diversity, occurrence in growth position, and high abundance of relatively few taxa, the environment of habitation is considered to have been a shallow and protected environ ment such as a "backreef" environment. These two genera are common in the Martin Formation and may correspond to Teichert*s mixed assemblage, which commonly contains atrypid brachiopods and Thamnopora. The
Coenites-spiriferid brachiopod association at Roosevelt Dam may repre
sent it, as it is of low diversity, inferred to have inhabited a simi lar environment above wave base, and contains a similar branching
tabulate coral. CEDAR VALLEY FRASN IAN OF CAN. M A R T IN F M . P E R C H A F M . ENVIRONMENT (Sbhumacher, 1976) (Johnson, 1974b) (this study) (Meader, 1976)
SUPRATIDAL Stromatolites Stromatolites
INTERTIDAL L in g u la O s tra c o d e - Turbonoosis LAGOON C o m m u n ity Algal Association B lo fa c ie s ...... -...... •.. n ...... •...... _ Depauperate Mucrosoirifer RESTRICTED M o llu s c a n Hexaaonaria C o e n ite s - Splrlferid Brach. A s s e m b la g e SUBTIDAL o r o fu n d a C o m m u n ity Association B io f a c ie s
SUBTIDAL Strooheodonta- Hexaaonaria Nervostroohia- Schizoohoria Assoc Paurorhvncha AT TO ABOVE la t iv e n tr a Devonooroductus DisDhvllum-Mass. Association B lo f a c ie s C o m m u n ity W A V E B A S E 9 Strom. Association A tryR a ■------? ...... - A t r y p a - Atrvoa-Theodosla SUBTIDAL missouriensis Enslferites Association B lo fa c ie s Schizophoria NEAR a BELOW Association C o m m u n ity Atrypa-CvrtosDir, W A V E B A S E Strooheodonta Association a Tabuloohyllum DEEP B lo fa c ie s SUBTIDAL
Figure 33. Comparison of Communities, Associations, Biofacies, and Assemblages.from Epeiric Carbonate Environments. M. DEV. NEVADA SONYEA GROUP GENESEE GROUP FOREKNOBS FM. ENVIRONMENT (Johnson ft Flory,l972)|(Sutton ft others,1970) (Thayer, 19 74) (McGhee, 1976)
SUPRATIDAL
INTERTIDAL
LAGOON N u c u lite s Leotodesmo-
c Palaeosolen T y jo th r is RESTRICTED *o Acrospiriferid- L_ 3 i f 0 E F a c ie s C o m m u n ity SUBTIDAL a £ - ? ------? ------Leptocoelid E o a> Q 9 1 2 m o o B io fa c ie s 01 Cyrtospirlfer- SUBTIDAL E o Camorotoechia 13 AT TO ABOVE JC a C o m m u n ity 0 in Figure 34* Comparison of Communities, Associations, Biofacies, and Assemblages from Miogeosynclinal and Deltaic Environments. § 81 Johnson (1974b) recognized an offshore-onshore sequence of brachiopod biofacies in the Lower Devonian of western and Arctic North America. He defined an outer, deep water biofacies of Gipidula-Atrypa- Schizophoria shoreward of a pelagic facies, and an aerospiriferid— leptocoelid biofacies occupying an inner, shallow water environment between the G-A-S biofacies and the tidal flat environment. He believed these biofacies persisted until the end of the Frasnian. Each biofacies includes two or more communities that existed for approxi mately a stage. These are compared with other communities in Figures 33 and 34* The G-A-S biofacies is comprised of two communities and contains certain widespread genera. A community of "small species" (dominated by Dicaelosia nitida and Salopina submurifer)occurs. but Atrypa is the only genus present that occurs in the Martin Formation. A community of "large species" (dominated by Resserella elegantuloides and Dale.lina subfrequens) contains no corresponding genera in the Martin. Of the widespread, unrestricted large genera, Gipidula, Atrypa, and Schizophoria commonly occur together but in varying abundance. Gipidula was not recognized in the present study, but Atrypa and Schizophoria were found to occur in abundance, but not in direct association. These two genera occupied, respectively, a below wave base environment and an environment at to just above wave base, envi ronments relatively equal to those of the G-A-S biofacies. The acrospiriferid-leptocoelid biofacies contains a Spino- plasia zone community characterized by Leptocoelina and Spinoplasia. A Trematospira zone community is recognized also, based upon the lack 82 of the above two genera. Both of these communities lack genera common to the Martin Formation, but may have occupied similar, above wave base environments. Johnson (1974b) feels that the Lower Devonian Ehenish fauna of Europe represents the acrospiriferid-leptocoelid biofacies. In com parison of these communities to Late Devonian communities, Johnson (1974b) states that H. L. Orndston (unpublished work) recognizes four communities in the Frasnian of western Canada, 1) Atrypa-Schizophoria, 2) Nervostrophia-Devonoproductus, 3) Macrospirifer, and 4) Lingula. These communities comprise an off shore-onshore sequence and do contain genera common to the Martin Formation, except that Atrypa and Schizophoria were not found in association in the present study. Atrypa. Nervostrophia. and Devonoproductus commonly occur together in the Atrypa-Cvrtosprifer association of the present study. Mucrospirifer may have occupied niches similar to Cyrtospirifer. No lingulids have been recognized in the Martin. These communities are compared in Figures 33 and 34* Because of insufficient data, however, it is diffi cult to position them with respect to wave base. Mallory (1968) reported the following brachiopod associations from the Frasnian Lime Creek Formation of central Iowa (genera listed in decreasing rank abundance): 1) Sulcato strophia, Strophonella. Douvi 1 ~l Ina 2) Devonoproductus. Cyrtina iowensis, Schizophoria iowensis(?), Cranaella(?), Schuchertella 3) Atrypa devoniana. Cyrtospirifer whitneyi, Spirifer orestes, Theodosia hungerfordi, Tenticospirifer. Spirifer sp. 83 These associations may represent an onshore-offshore sequence (Sulcatostrophia to Atrypa devoniana), but relationships to wave base are not known by the writer. The Atrypa-Cyrtospirifer association of the present study corresponds very well to association 3 above. Association 1 is dominated by strophomenid brachiopods and is inferred to occupy a more nearshore position, as is the Stropheodonta- Schizophoria association of the present study. Devonoproductus of association 2 is common in the Atrypa-Cyrtospirifer association, while Schizophoria. CraeneHa, and Schuchertel la occur in the more nearshore Stropheodonta-Schizophoria association. Mallory*s (1968) associations correspond to those of this study better than do any of the associa tions in the other studies reviewed. Paleoecological studies have been conducted in the Upper Devonian of the eastern United States, encompassing the Frasnian Sonyea Group (Sutton and others, 1970), the Genesee Group (Thayer, 1974), and the Frasnian-Famennian Foreknobs Formation of the Appalachian-Allegheny Front (McGhee, 1976). The first two studies deal with community change in response to progradation rates of the “Catskill Delta.” McGhee (1976) documented paleocommunities in a prograding deltaic sequence. The communities of these studies and their environment of occurrence are illustrated in Figure 35• In Figures 33 and 34 they are illustrated with respect to wave base in comparison with the associations of the present study. No taxonomic correlations of communities can easily be made, although some share certain taxa. Of the four communities recognized [BARRIER WEST. EAST •PRODELTA------BAR (HMca Areal COneonla Ai«al SLOW PROGRADATION >111111! nsii ■Hill SLOW PROGRADATION RAPID PROGRADATION |-prodelta-JBARRbar [-lagoon^ e 2or4 r ^ R A P I D PROGRADATION x * SLOW PROGRADATION Misicmu Nul ifcali SLOW RROORAOATION Environmental model for Foreknobs shelf conditions, combining previous stratigraphic and scdi- mentological Interpretations with evidence from the preserved fauna. Block A precedes block B in time; RAPID both sections are normal to the ancient shoreline. PROGRADATION 1, Ambocoelia-Chonctcs Community; 2, Cyrtospirifer- Camarotoechia Community; 3, Atrypa-Cypricardella Community; 4, Leptodesma-Tylothyris Community. Figure 35. Sonyea, Genesee, and Foreknobs Depositional Environments and Communities. — Left - from McGhee (1976). Right - from Thayer (1974)• in the Sonyea Group, two are respectively dominated by the pelecypod Cyrpicardella and the gastropod Bellerophon, and both occupied near shore environments# No corresponding molluscan assemblages were dis covered in the present study, but Stoyanow1 s (1936) molluscan assemblage from the Island Mesa beds may represent them. The Rhipidomella conn munity is dominated by the brachiopods Camarotoechia, Tylothyris, Chonetes, and Hhipidomella (in decreasing relative abundance). Camaro toechia does occur in abundance elsewhere in the Martin Formation, but only one specimen was found in the present study. Only the Productella community contains brachiopods commonly found in the Martin Formation. It is dominated by Productella, Mucrospirifer, Leiorhynchus. and Atrypa (most to least abundant). Productella is common in the Atrypa- Cyrtospirifer association. The Atrypa of the Productella community are much less common, however, and do not approach the dominant position they hold in this association. These latter two communities of the Sonyea occupied environments at to below wave base. Thayer" (1974) recognized seven biofacies in the Genesee Group, which are shown in Figure 35• Four offshore, below wave base facies are of very low diversity (perhaps due to very poor circulation). They are as follows: l) a Styliolina-brachiopod facies, 2) a Flumalina facies, 3) a Cladochonus facies, and 4) an Ambocoelia facies. None correspond to any Martin faunal associations. Thayer’s Schizophoria-strophemenid brachiopod facies may correspond with the Stropheodonta-Schizophoria association of the present study. It occupied an environment at to above wave base, but it contains many genera not found in the Martin 86 association. The delta platform Bhipidomella-Leiorhynchus facies and the nearshore Nuculites-Palaeosolen facies have virtually no genera in common with Teichert's (1965) or the author’s faunal associations. Four communities were recognized in the Foreknobs Formation by McGhee (1976) (Figure 35)• His Ambocoelia-Chonetes community occupied an offshore environment below wave base, but it corresponds to no faunal associations in the present study. The Cyrtospirifer- Camarotoechia community is overwhelmingly dominated by these two genera, and it is postulated to have occupied a barrier bar-lagoonal environment. Teichert (1965) reported a coquina of similar composition in the Martin Formation in his Limestone Hills section, but it con tains abundant Granaena, with Cyrtospirifer being much less abundant. McGhee’s Atrypa-Cypricardella community does contain abundant Atrypa, common Cyrtospirifer, and common Productella, as the Atrypa- Cyrtospirifer association of this study, and it occurs offshore near or below wave base. It is, however, dominated by the bivalves Leptodesma and Cypricardella. His Leptodesma-Tylothyris community is dominated by the bivalve Leptodesma and again lacks true correspondence to any associations in the Martin Formation. Hoggan (1975) investigated depositional environments and paleo- ecology of the Frasnian Guilmette Formation in Utah and Nevada. His scheme is illustrated in Figure 36, which is similar to Copper’s (1966) reconstruction (not illustrated). The Guilmette is a miogeosynclinal carbonate sequence deposited in a northward trending basin between the Antler foreland and the craton. Shallow marine environments are HIGH ENERGY MODERATE ENERGY LOW ENERGY MODERATE HIGH ENERGY ENERGY Intertidal areas crinoids brqchlopods crinoids massive strom. algal mats tabular strom. tetracorals tetracorals bulbous strom. algal mounds tetracorals Amphipora Stachyodes Thamnopora bulbous strom. tabulate corals calcispheres Stachyodes Stochvodes MSL ffg na £ MUD MOUND NEARSHORE OFFSHORE Figure 36. Guilmette Environments. — After Hoggan.(1975) 3 88 common, and the lower part of the formation contains intertidal or supratidal environments similar to those of the Martin Formation. Stromatolitic horizons commonly occur in these environments of the Guilmette. He did, however, use a different environmental energy scheme, which is illustrated with his environmental reconstruction. He recognized three basic faunal associations: l) a massive stromato- poroid association, occurring in a high energy zone, 2) brachiopod associations in low-energy, deep water, composed predominantly of Atrypa, Spinatrypa, Allenaria, and Stringocephalus(?), and 3) algal mounds and mats in a "high energy" intertidal environment. He defined no specific paleocommunities. In comparison to the Martin Formation in central Arizona, association 1 corresponds to the stromatoporoid-Disphyllum association noted at Globe Hills in this study and the stromatoporoid-coral associa tion (biostromal facies) observed elsewhere by Teichert (196$). Some of Hoggan’s (1975) brachiopod associations may be equivalent to the associations recognized in this study, especially those dominated by Atrypa, but he treated brachiopods in a generalized manner, assigning them to a low energy, "deep water" environment. Although no algal mounds are present in the Martin Formation, algal mats are a common constituent of the fetid dolomite unit. The Guilmette also contains abundant Amphipora and calcispheres, which are described by Teichert as common to abundant in the Martin Formation of central Arizona, although not recognized by the writer in the Roosevelt Dam-Globe area. 5*5 Comparison of Martin and Percha Associations Header (1976) defined two faunal associations from the Famennian Percha Formation of south-central Arizona, l) an Ensiferites (sponge) association, and 2) a Paurorhyncha (rhynchonellid brachiopod) association. The Ensiferites association is very diverse and consi dered to have thrived below wave base. The Atrypa-Qyrtospirifer association of the current study is very diverse and is interpreted to have inhabited the same environment, which suggests that the Ensiferites association may have replaced it. Both are dominated by diverse brachiopod faunas and both contain zaphrentid corals. They share none of the same brachiopod genera, however. The Atrypa-Cyrtospirifer, association contains no large brachiopods that correspond in size or morphology to Syringospira prima, and Schizophoria australis of the Ensiferites association. Of the smaller brachiopods, the spiny Produc- tella of the Atrypa-Cyrtospirifer association is morphologically similar to the spiny Torynifer spinosus of the Ensiferites association. The dominant Atrypa of the Atrypa-Cyrtospirifer association are not correspondingly replaced by abundant rhynchonellids as they should be if Ager (1968) is correct. The massive, pad-like trepostome bryozoa of the Atrypa- Cyrtospirif er association may be represented in the Ensiferites associ ation by smaller, fist-like trepostome bryozoans. Crinoidal debris is common in the Ensiferites association, but rare in the Atrypa- Cyrtospirif er association, a significant difference. The addition of abundant sponges (Ensiferites) is a notable change also. 90 Header (1976) considered the Paurorhyncha association to have occupied an environment at to just above wave base and may correspond to the Stropheodonta-Schizophoria association of this study. The Paurorhyncha association is dominated by Paurorhyncha cooperi, P. endlichi, and Cyrtospirifer kindlei and contains algal fragments, crinoidal debris, echinoid debris, and bryozoan fragments. The Stropheodonta-Schizophoria association is dominated by two species of large brachiopods, occurring with crinoidal debris and less common brachiopods and bryozoa. These associations are both moderately diverse. The thick-shelled Schizophoria may have been replaced by the large, hardy Paurorhyncha and the Stropheodonta by the large Cyrtospi rifer kindlei. These are not morphologically similar, however, and thus do not represent similar adaptive forms. Both associations are domina ted by epifaunal, low-level suspension feeders, although the Stropheodonta-Schizophoria association has a much greater percentage of pelmatozoan debris, indicating abundant high-level suspension feeders. A transitional association equivalent to her Paurorhyncha- Leioproductus-Syringospira association was not noted in the dobe- Roosevelt Dam area, nor a counterpart to her depauperate molluscan assemblage. Associations from her study and their environment of occur rence are illustrated in Figure 37. These observations do not support Ager’s (1968) suggested ecological replacement among Upper Devonian brachiopods, which may indicate faulty environmental interpretations on the part of S. Header or the writer. 90 Header (1976) considered the Faurorhyncha association to have occupied an environment at to just above wave base and may correspond to the Stropheodonta-Schizophoria association of this study. The Faurorhyncha association is dominated by Faurorhyncha cooperi, F. endlichi, and Cyrtospirifer kindlei and contains algal fragments, crinoidal debris, echinoid debris, and bryozoan fragments. The Stropheodonta-Schizophoria association is dominated by two species of large brachiopods, occurring with crinoidal debris and less common brachiopods and bryozoa. These associations are both moderately diverse. The thick-shelled Schizophoria may have been replaced by the large, hardy Faurorhyncha and the Stropheodonta by the large Cyrtospi rifer kindlei. These are not morphologically similar, however, and thus do not represent similar adaptive forms. Both associations are domina ted by epifaunal, low-level suspension feeders, although the Stropheodonta-Schizophoria association has a much greater percentage of pelmatozoan debris, indicating abundant high-level suspension feeders. A transitional association equivalent to her Faurorhyncha— Leioproductus-Syringospira association was not noted in the GLobe- Roosevelt Dam area, nor a counterpart to her depauperate moHuscan assemblage. Associations from her study and their environment of occur rence are illustrated in Figure 37* These observations do not support Ager*s (1968) suggested ecological replacement among Upper Devonian brachiopods, which may indicate faulty environmental interpretations on the part of S. Header or the writer. Subtldal Subtldal Intertidal Supratidal below wave base above wave base WAVE BASE Depauperate Paurorhvncha Molluscan Ensiferites Association Association Assemblage Figure 37• Associations and Environments of the Percha Formation. — After Header (1976). Subtldal Subtldal Intertidal Supratidal below wave base above wave base WAVE BASE Depauperate Ensiferites Moiluscan Association Assemblage Figure 37* Associations and Environments of the Percha Formation. — After Header (1976). 92 5«6 Summary and Conclusions Of the faunal assemblages encountered in this study, the following ecological associations were recognized: 1. Stromatolite Massociation" 2. Ostracode-algal association 3. Coenites-spiriferid brachiopod association 4» Crinoid-Schizophoria association 5. Stropheodonta-fenestrate bryozoan association 6. Stropheodonta-Schizophoria association 7* Disphyllum-massive stromatoporoid association 8# Atrypa-Theodosia association 9» Atrypa-Cyrtospirifer association These occupied the following respective environments: 1. supratidal, intertidal 2. tidal flat-lagoon 3. restricted subtidal, above wave base 4« at to above wave base 5. subtidal, just above wave base 6. at to above wave base 7. at to above wave base 8. subtidal above (?) wave base 9. subtidal below wave base The stromatolite "association" is of very low diversity and is comprised solely of primary producers. The ostracode-algal association is also of very low diversity, and is composed of deposit feeders, primary producers, and possible grazers or scavengers (gastropods possibly), as inferred from associated fecal pellets. The Coenites- spiriferid brachiopod association is of low diversity and is comprised of a passive benthonic predator and an epifaunal, low-level suspension feeder. The crinoid-Schizophoria, fenestrate bryozoa-Stropheodonta, and Stropheodonta-Schizophoria associations are of moderate diversity 93 and are dominated by high- and low-level suspension feeders. The Disphyllum-massive stromatoporoid association is comprised of passive benthonic predators and appears to be closely associated with the Stropheodonta-Schizophoria association above. The Atrypa-Theodosia association is of low diversity and is constituted entirely of epi- faunal, low-level suspension feeders. The Atrypa-Cyrtospirifer associ ation has a high diversity and is composed essentially of epifaunal, low-level suspension feeders. These communities are not easily compared to communities from the deltaic environments of the M Cat skill Delta,” but they do share affinities with associations of the Guilmette Formation of Utah and Nevada, the Frasnian of Canada, and the lime Creek Formation of central Iowa. Faunal associations from Lower and Middle Devonian strata correspond (in a general manner) taxonomically and environmentally with those of the Martin in some regions, and in others not at all. The mass extinctions at the end of the Frasnian caused new and radically . different communities to evolve in the Famennian, a change marked by the replacement of strophomenids by productids, atrypids by rhynchonellids, and pentamerids by spiriferids (Johnson and Boucot, 1971)• In the present study, it appears that orthids and strophomen ids have been replaced by Paurorhyncha (rhynchonellid), which contra dicts this. Errors in environmental interpretation may underlie this ”anomaly.” CHAPTER 6 CONCLUSIONS AND PROBLEMS FOR FURTHER INVESTIGATION 6.1 Conclusions The Martin Formation in central Arizona contains a full spec trum of environments, from fluvial nearshore to subtidal below wave base. The majority of the units were deposited during a transgression that allowed accumulation of the thick supra- and intertidal sediments of the fetid and aphanitic dolomite units. These grade upward into the shallow subtidal, wave base, and ultimately below wave base beds of the upper unit. Fluctuations of sea level, water depth, and energy are reflected in repeated lithologies and faunas. The lithological and faunal differences between Roosevelt Dam and Pinal Creek indicate that the Roosevelt Dam succession was deposi ted in a more nearshore, restricted marine environment. The Pinal Creek section contains a much greater abundance of skeletal sands, reflecting high energy environments at or near wave base. Although the upper unit at Pinal Creek is much more fossilifer- ous and presumably deposited in a more offshore, "basinward" environ ment, the upper unit at Roosevelt Dam is much thicker. Based upon the absence of the Beckers Butte Member and the fetid dolomite unit in the Globe Hills section, a pre-Upper Devonian high may have existed in the area with deposition beginning later and ending earlier than at 94 95 Roosevelt Dam. Post-Martin, pre-Percha erosion may have been greater in the Globe area, but there is no evidence for it. Alternately this "anomaly" could indicate that subsidence was greater in the Roosevelt Dam area and sedimentation was rapid enough to maintain shallow marine environments. Four fossil associations are recognized at Roosevelt Dam. In ascending stratigraphic order they are: l) a stromatolite "associa tion," 2) a czdnoid-Schizophoria association, 3) a fenestrate bryozoa- Stropheodonta association, and 4) a Goenites-spiriferid brachiopod association. These occupied the following environments: 1) supra- or intertidal, 2) sub tidal, near and above wave base, 3) subtidal, just above wave base, and 4) shallow subtidal, above wave base. An arthro- diran assemblage was also encountered in the intertidal to subtidal beds in the upper part of the aphanitic dolomite unit. In contrast, the Pinal Greek section contains the following associations: 1) ostracode-algal association, 2) Stropheodonta- Schizophoria association, 3) Atrypa-Cyrtospirifer association, and 4) Atrypa-Theodosia association. These occupied the following respec tive environments: l) intertidal, lagoonal, 2) subtidal above or near wave base, 3) subtidal below wave base, and 4) shallow restricted subtidal above wave base. A massive•stromatoporoid-Disphyllum associa tion occurs just above and with the Stropheodonta-Schizophoria assemblage at Globe Hills. This association lived at or just above wave base in a turbulent environment. 96 Teichert's (1965) four faunal assemblages correlate in a general manner with associations encountered in this study. His assem blages are, however, of variable composition, depending upon locality, and they have not been defined qualitatively or quantitatively. Although many of the taxa encountered in faunal associations of the Martin Formation are present in associations from the Guilmette Forma tion of Utah and Nevada and the clastic deltaic sequences of the eastern United States, they are present in different ratios and no direct correlations can be made. They best correspond with associations from the lime Greek Formation of Iowa, as determined by Mallory (1968), and Frasnian associations from Canada, which were briefly discussed in Johnson (1974b). The variability of Upper Devonian associations (or communities) contrasts with the more consistent recurrence of spe cific level bottom communities and community patterns in Silurian strata independent of substrate type or locality. In the Percha Formation the Schizophoria-Stropheodonta associa tion occurring near and above wave base appears to have been replaced by the Paurorhyncha association of S. Header (1976), and the Atrypa- Cyrtospirifer association appears to have replaced the Ensiferites association. These replacements, however, contradict those suggested by Ager (1968) and Johnson and Boucot (1971)» implying that the envi ronmental interpretations of the writer or S. Header could be in error. No counterpart to her depauperate molluscan assemblage was encountered in the present study, and conversely, no counterpart to the Disphyllum- massive stromatoporoid association in this study was encountered in her investigations. 97 6.2 For Farther Investigation As is evident from Teichert’s (1965) work, a much broader spectrum of faunal associations is present in the Martin Formation at other sections in central Arizona. He classified them in a general manner, not upon relative abundance of taxa or dominant genera for each case. Studies of other sections in central Arizona would allow the recognition of other faunal associations and communities. One also should encounter the associations noted in this study, perhaps in a better state of preservation, which would allow better determination of their faunal composition and serve as a check upon the validity of conclusions presented herein. Quantitative studies of fossil exposures on bedding planes, such as at Globe Hills, would allow calculation of percentage composition of communities and other paleoecological para meters, such as diversity indices. A statistical analysis would refine community definition. This approach could possibly be applied to the Atrypa-Qyrtospirifer association also, as specimens weather free of their matrix. A foot by foot sampling in this interval might reveal subtle community changes as those documented by Mallory (1968) in the Lime Greek Formation of Iowa. There are still some unanswered ques tions concerning the abrupt faunal changes at the Frasnian/Famennian boundary also. This study supplements Witter1s (1976) study of conodont bio stratigraphy of the Martin and Percha Formations and Meader’s (1976) paleoecological study of the Percha Formation of south-central Arizona. APPENDIX MEASURED STRATIGRAPHIC SECTIONS Roosevelt Dam SEj- NW&- SW^- sec. 29, T. AN., R. 12 E., Theodore Roosevelt Dam Quad rangle. Section measured and described in readout and quarry on east side of Roosevelt Dam. Devonian: Percha Formation (unmeasured and undescribed): Martin Formation: Jerome Member: •’upper unit” : Unit Cumulative Thickness Thickness Unit no. Description Ft. (M.) Ft. (M.) 29 Dolomite, very silty, light-brown (5 YR 6/4), weathers same; medium- crystalline; thin- to thick-bedded; . slightly hematitic; unfossiliferous 5«5 (1.7) 379*0 (115*6) 28 Dolomite, sandy, calcitic, pale-brown (5 YR 5/2) to light-brown (5 YR 6/4), weathers same; dolomite is medium crystalline; sand is coarse-grained, subrounded; thin- to thick-bedded; resistant ...... 4.5 (1.4) 327*5 (113*9) 27 Quartzarenite, dolomitic, light-brown (5 YR 6/4), weathers same; very fine grained, well-sorted, angular; thin- to thick-bedded; strongly laminated; resistant; low-angle trough cross- bedding at base of unit; convolute bedding 17.0 ft. above base of unit; low-angle tabular-planar crossbedding 98 99 Unit Cumulative Thickness Thickness Unit no. Description Ft* CM.) Ft* (M.) 18.0 ft. above base of unit; textur- ally uniform throughout ...... 20.0 (6.1) 369*0 (112.5) 26 Quartzarenite, dolomitic, to very sandy dolomite, calcitic, pale-brown (5 YR 5/2) to pale-red (10 R 6/4), weathers light-brown (5 YR 6/4) to pale-brown (5 YR 5/2); dolomite is medium crystalline; sand is medium to coarse grained, rounded, well- sorted; thick-bedded; lacks lamina tions; unfossiliferous; upper 3*5 ft. of unit is much less sandy; top of unit marked by a shale parting and a thin (cm.’s thick), very coarse grained, hematitic quartzarenite that contains long horizontal burrows 0.5 to 1.0 cm. in diameter ...... 19.0 (5.8) 349*0 (106.4) 25 Dolomite, very silty, light-brown (5 YR 6/4), weathers slightly lighter; medium-crystalline; thick-bedded; fossiliferous in basal 2.0 ft., 5*0 ft. above base of unit, and in upper 2.0 ft. of unit; these horizons con tain poorly preserved Coenites and spiriferid brachiopods; hematitic re placement of fossils; patchy hematitic stains throughout unit; voids filled with coarsely crystalline calcite • 9*0 (2.7) 330.0 (100.6) 24 Quartzarenite, dolomitic, to sandy dolomite, light-brown (5 YR 6/4), weathers pale-yellowish-brown (10 YR 6/2); dolomite is medium crystalline; sand is coarse grained, moderately sorted, rounded; thick-bedded; clastic content varies greatly in unit; sand fines upward; unit contains some scattered quartz granules; styolites in more dolomitic intervals; disrup tion of bedding by bioturbation towards top; contains rare unidenti fiable brachiopods ...... 6.0 (1.8) 321.0 (97.9) 100 Unit Cumulative Thickness Thickness Unit no. Description Ft. CM.) Ft. (M.) 23 Dolomite, very silty, slightly sandy, grayish orange-pink (5 YR 7/2) to pale- red (10 R 6/2), weathers light-brown (5 YR 6/4) to pale-reddish-brown (10 R 5/4)? medium-crystal line; very thick- bedded (massive)j cliff-forming; slightly hematitic; lower 1.0 ft. contains scattered spiriferid brachio- pods and other fossil debris; directly overlying this the unit contains intraclasts generated by bioturbation (lack orientation); 13.0 ft. above base of unit are two sets of oscilla tion ripple marks (seen in cross sec tion) 8 cm. apart with a wave length of approximately 12 cm.; the interval from 14.0 to 17.0 ft. above base of unit contains fossil debris in linea- tions, predominantly poorly preserved brachiopods and fenestrate bryozoa; remainder of unit is bioturbated- bedding destroyed, creating uneven distribution of sand content; styo- lites 22.0 ft. above base of unit; hematitic blotches throughout, in lineations somewhat parallel to bedding ...... 26.0 (7.9) 315.0 (96.1) 22 Dolomite, slightly sandy, yellowish- brown (10 YR 5/2), weathers same; coarsely crystalline; very thick- bedded (massive); no remnants of fossils or sedimentary structures; styolites 0.5 ft. above base of unit; top of unit marked by shale parting; unit slightly hematitic ...... 9.5 (2.9) 289.0 (88.1) 21 Dolomite, silty, calcitic, grayish- orange (10 YR 7/4) to pale-brown (5 YR 5/2), weathers light-brown (5 YR 5/6); medium-crystalline; very thick- bedded (massive); strongly laminated, laminations slightly undulatory; shale partings between beds; upper 1.0 ft. contains fish bone fragments and abundant brachiopod molds, some 101 Unit Cumulative Thickness Thickness Unit no Description Ft. (M.) Ft. (M.) of which are spiriferids; in 3 to 4 ft. laterally the fossil debris is replaced by thin, tabular intraclasts up to 5 cm. in length; bioturbation possible origin; some hematitic staining of unit ...... 6.5 (2.0) 279*5 (85.2) 20 Dolomite, slightly silty, yellowish- brown (10 YR 6/4), weathers grayish- orange (10 YE 7/4); medium-crystal line; one bed; contains abundant, poorly preserved brachiopods (Atrypa??); some hematite replacement of them • • • 1.0 (0.3) 273*0 (83*3) 19 Dolomite, calcitic, light-brown (5 YR 6/4) with light-grayish-orange (10 YR 7/4) laminations, weathers same; medium-crystalline; thin-bedded; strongly laminated; small diameter horizontal burrows at base of unit; well developed inclined burrows (?) 2.0 to 3*0 ft. above base of unit; very sparsely fossiliferous .... 6.0 (1.8) 272.0 (83*0) 18 Dolomite, calcitic, pale-yellowish- brown (10 YR 6/2) to yellowish-brown (10 YR 6/4), weathers same; medium- crystalline; thin- to thick-bedded; contains abundant fenestrate bryozoa, especially in lower 2.0 ft.; associa ted with Schizophoria (?) on hillslope outcrop; hematite replace ment of fossils; unit grades into overlying laminated dolomite • • • 4*0 (1.2) 266.0 (8l.l) 17 Interbedded silty dolomite and crinoidal dolomite (crinoidal bio- sparite originally?); silty dolo mite is yellowish-brown (10 YR 5/4) 1 weathers same; crinoidal dolomites are light-brown (5 YR 6/4) to pale- yellowish-brown (10 YR 6/2), weathers same; both are coarsely crystalline; thin-bedded; interbedded in cyclic fashion, beds 8 to 10 inches (20 to 25 cm.) thick; silty dolomite is 102 Unit Cumulative Thickness Thickness Unit no. Description Ft. (M.) Ft. (M.) strongly laminated; unit lacks sand; crinoidal dolomites are calcitic, contain fish bone fragments, intra clasts, and brachiopods; gently undulatory contacts between the crinoidal dolomites and the under lying laminated dolomites; crinoidal dolomite is resistant, laminated dolomite is not; some primary defor mation— crinoidal dolomites forced into underlying laminated dolomites; short (3 to 4 cm.) horizontal burrows (?) abundant 4.0 ft. above base of unit; top bed in unit is massive, planar-laminated dolomite 3.0 ft. thick; styolites near" top of unit; shale parting at upper contact • • 22.0 (6.7) 262.0 (79*9) 16 Dolomite, very slightly silty, pale- yellowish-brown (10 YR 6/2), weathers grayish-orange (10 YR 7/4); medium- crystalline; thin-bedded; weakly resistant; coarsely laminated; base is coarse to very coarse grained quartzarenite 7 to 8 cm. in thick ness, strongly hematitic; radiating • grazing burrows common in basal 20.0 ft.; branching horizontal burrow 17.0 ft. above base of unit ...... 24.0 (7*3) 240.0 (73.2) 15 Dolomite, very silty, very slightly sandy, pale-yellowish-brown (10 YR 6/2), weathers same; medium- to coarsely-crystalline; thin- to thick- bedded; calcite-filled vugs throughout; base marked by coarse-grained quartz arenite containing quartz granules, grades rapidly upward into sandy dolo mite; unit contains burrows (?) 2.5 to 5 cm. in length ...... 10.5 (3.2) 216.0 (65.9) 14 Dolomite, very slightly silty, light er angish-br own (5 YR 7/4), weathers same, with sharply defined moderate reddish-brown (10 R 4/6) hematitic blotches; medium-crystalline; thin- 103 Unit Cumulative Thickness Thickness Unit no. Description Ft. Ft. CM.) to thick-bedded; non-landnated; sub- conchoidal fracture; base of unit marked by striking aphanitic dolomite 7 to 15 cm. thick, which is laminated, hematitic; base of unit rests on thin, coarse-grained quartzarenite of under lying unit; small fragments of fish bone in associated siltstone; calcite- filled vugs in basal 3«0 ft.; from 8.5 to 10.0 ft. above base of unit the unit is thin-bedded and contains shale partings; one poorly preserved spiri- ferid brachiopod was collected near the top of unit ...... 11.5 (3*5) 205*5 (62.7) 13 Dolomite, very silty and very sandy, to dolomitic quartzarenite/siltstone, grayish-orange-pink (5 YR 7/2), weathers grayish-orange (10 YR 7/4)? dolomite medium crystalline; elastics are bimodal sand and silt mixture; sand is medium to coarse grained; very thick-bedded (massive); cliff forming; pelletal and intraclastic; intraclastic horizons at base of unit and 8.0, 22.0, and 25.0 ft. above base of unit; several horizons contain coarse sand lags; strongly laminated at base, with low-angle trough crossbedding; slight contor tions of bedding at intraclastic horizons; shale partings separate massive beds; sand grades finer up ward in cyclic fashion; less sandy in upper part of unit; hematitic blebs throughout unit; glauconitic in thin-section; contains vertical burrows in hill-slope exposure; top of unit marked by coarse-grained quartzarenite 5 cm. thick ...... 26.0 (7*9) 194*0 (59*2) 12 Siltstone, calcitic, dusky-red (5 R 2/6) in lower 2*5 ft., weathers darker; upper 2.5 ft. is dark greenish gray (5 G 6/l), weathers same; very thin-bedded; slope-forming; contains 104 Unit Cumulative Thickness Thickness Unit no. Description Ft. (M.) Ft. CM.) dense nodules of quartzarenite; glauconitic in thin section . • • • $.0 (l.$) 168.0 (51#2) 11 Quartzarenite to sandy silt stone, slightly calcitic, yellowish-brown (10 YR 6/2), weathers same; bimodal, contains medium-grained sand and quartz silt; poorly sorted; thin- to thick-bedded; resistant; cliff- forming; silica cement (obscures roundness); strongly hematitic at base and top ...... 5.0 (1.5) I63.O (49#7) 10 Interbedded quartzarenite, siltstone and shale; quartzarenite and silt- stone are grayish-red (5 R 4/2), weather yellowish-brown (10 YR 6/4)» shale is greenish-gray (5 GY 6/l), weathers same; quartzarenite is lenticular, medium-grained, hema titic, up to 1.0 ft. thick; unit is very thin bedded; slope-forming • . 10.5 (3.2) 158.0 (48.2) 9 Quartzarenite, grayish-red (10 R 4/3)» weathers yellowish-brown (10 YR 6/4); fine-grained overall; medium- to coarse-grained at base, with quartzite fragments and quartz granules; thin- to thick-bedded; laminated; resistant; cliff-forming; silica cement; undulatory contact with underlying dolomite; contains low-angle trough cross-bedding; strongly hematitic at base • • . • 2.5 (0.8) 147.5 (45*0)] Total of upper u n i t ...... 231.5 (70.6) Aphanitic dolomite unit: 8 Dolomite, slightly calcitic, slightly sandy, base of unit is light- brownish-gray (5 YR 6/l), weathers yellowish-brown (10 YR 6/4); top of unit is pale-red (10 R 6/2), weath ers yellowish-brown (10 YR 6/4); 105 Unit Cumulative Thickness Thickness Unit no. Description Ft. Cm .) Ft. (M.) unit aphanocrystalline except for the upper part of the unit, which is finely crystalline; thinr-bedded, bed ding irregular; large-scale ripples or small tidal channels (?) form most of contacts, especially in lower part of unit; unit is finely laminated, but much less so in upper part of unit; slope-forming; conchoidal frac ture; hematitic at certain horizons; chert lenses in lower part of unit, dark gray (N3) on fresh surface, weathers lighter; thin shale partings at contacts between many beds; part ings increase to 10 to 15 cm. in thickness in upper part of unit; contains floating sand grains; sand content increases upward also; con tains fish remains and sedimentary structures as follows (all footages above base of this unit): arthro— diran fish remains noted at 20.0 ft., one external mold of a plate approxi mately 10 cm. in length, with spine; birdseye structure from 23.0 to 24.0 ft., overlain by an intraclastic dolomite with angular clasts derived from this horizon; associated scour surface; mudcrack polygons approxi mately 12 to 15 cm. on a side noted in float at 30.0 ft., birdseye struc ture at 30.0 ft., appears to be associated with small diameter hori zontal to vertical burrows; mudcracks at 36.O ft., polygons 5 to 8 cm. on a side; birdseye structure at 36.5 ft.; mudcracks at 42.0 ft., polygons 5 to 8 cm. on a side; fish plates at 51#0 ft.; large external mold of arthro- dire plate (Dihichthys) at 54#0 ft., approximately 25 cm. across; intra clasts from 45#0 to 45#5 ft.; birdseye structure from 45#5 to 46.0 ft.; dessication "pillows'1 at 56.0 ft.; mudcracks at 67.0 ft., polygons 5 to 8 cm. on a side; mudcracks at 70.0 ft., 106 Unit Cumulative Thickness Thickness U n it no. D escrip tio n F t. CM.) F t. (M .) polygons 15 cm. on a side; large plate of Dinichthys (35 to 40 cm. in length) at 74*5 ft.; siltstone from 87.0 to 88.0 ft., base of which is moderate-red (5 E 4/6)f grades upward to greenish-gray (5 G 6/l) .... 92.0 (28.1) 145*0 (44*2) 7 Dolomite, moderate-brownish-gray (5 YR 5/1)> weathers yellowish-brown (10 YR 5/2); grades from medium- crystalline at base to very finely crystalline at top; thin-bedded; undulatory bedding contacts as in "unit 6; finely laminated with possible birdseye structure; contains rare, rounded, floating quartz grains; chert in certain horizons, more abundant in upper part of unit; some silicification in very small dimensions (mm. Is); top of unit marked by laterally continuous chert h o r i z o n ...... 17.0 (5.2) 53.0 (16.2) Total of aphanitic dolomite unit . 109.0 (33.2) Fetid dolomite unit: 6 Dolomite, calcitic, brownish-gray (5 YR 4/l)» weathers same; coarsely crystalline; thin-bedded; laminated; less resistant than remainder of fetid dolomite unit; grades upward into fenestra! texture of an algal mat; con tains abundant siliceous particles (2 to 4 mm. in size); calcite partially fills porosity; upper part of unit is irregularly bedded, similar to very large oscillation ripple marks; top 1.0 ft. has shaly appearance on out crop; unit contains partings of less resistant carbonate ...... 5.0 (1.5) 36.0 (11.0) 5 Dolomite, calcitic, yellowish-brown (10 YR 6/2), weathers same or slightly lighter; coarsely crystalline; 107 Unit Cumulative Thickness Thickness U n it no. D escription F t. CM.) F t. (M .) thin- to thick-bedded; strongly planar-laminated, possibly algal in origin; very porous ...... 4.0 (1.2) 32.0 (9.8) 4 Dolomite, calcitic, yellowish-brown (10 YE 5/2), weathers pale-yellowish- brown (10 YE 6/2); coarsely crystalline; thin-bedded; planar- to fenestral-lanrLnated (algal mat); base marked by irregular chert masses, lenticular, up to 15 cm. in length; some silicification along algal laminations; calcite partially fills porosity (birdseye)...... 2.5 (0.8) 27.0 (8.2) 3 Dolomite, calcitic, pale-yellowish- brown (10 YE 6/2), weathers slightly darker; coarsely crystalline; thin- to thick-bedded; resistant; strongly planar-laminated; some thin, mottled chert nodules at base of unit; very p o r o u s ...... 3.0 (0.8) 24.5 (7.5) Total of fetid dolomite unit . . . 14«5 (4*4) Total of Jerome M e m b e r ...... 357*5 (109.0) Becker's Butte Member: Aphanitic dolomite unit: 2 Interbedded dolomite and shale; dolomite is pale-yellowish-brown (10 YE 6/2), with moderate-reddish- brown (10 E 6/2) hematitic stains in discrete patches 2.5 to 5 cm. in diameter; shale is greenish-gray (5 G 6/l), weathers same; dolomite is aphanocrystalline; unit is very thin- bedded; poorly exposed; contact with overlying resistant unit is undula- tory, but s h a r p ...... 3.5 (1.1) 21.5 (6.6) 108 Unit Cumulative Thickness Thickness Unit no. Description Ft. (M.) Ft. (M.) Lower unit: 1 Quartzarenite, moderate-brown (5 YR 4/4)» weathers light-brown (5 YR 6/4); base very coarse-grained, contains quartz granules, grades rapidly up ward to coarse-grained; moderately sorted, subrounded; thin- to thick- bedded; slope-forming; poorly exposed; hematitic; contains micaceous shale/ siltstone partings; trough crossbedded at base (low-angle); lenticular chert nodules at top of unit, 5 cm. thick, 15 cm. in length, contain discrete sand grains ...... 18.0 (5.5) 18.0 (5.5) Total of Becker*s Butte Member. • • 21.5 (6.6) Total of Martin Formation...... 379.0 (11$.6) Cambrian: Tapeats Sandstone (undescribed): 77.0 (23.5) J 109 Pinal Creek Vfc NW|- SE|- sec. 10, T. 1 N., R. 15 E. Located on northerly and north easterly facing slopes on the south side of Pinal Creek. Devonian: Percha Formation (unmeasured and undescribed): Martin Formation (incomplete): Jerome Member: Upper unit: Unit Cumulative Thickness Thickness Unit no. Description Ft. (M.) Ft. (M.) 33 Dolomite, light-brown (5 YR 6/4), weathers pale-yellowish-brown (10 YR 6/2); finely to medium crystalline; thick-bedded; homogeneous texture, no pockets or lineations of concentrated fossil debris; Atrypa and Theodosia common; valves articulated in almost all cases; some Atrypa are as large as 2.5 cm. in length; these two brachiopods predominate to the ex clusion of all other fossil types; brachiopods are silicified • • • • 11.0 (3.4) 235*0 (71*1) 32 Dolomite, calcitic, to dolomitic crinoidal biosparite; fossiliferous dolomite grades upward into crinoidal biosparite; dolomite is light-brown (5 YR 6/4). weathers grayish-orange (10 YR 7/4)i biosparite is medium- gray (N5), weathers somewhat lighter; dolomite is medium crystalline; thin- to thick-bedded; resistant; cliff forming; very abundant atrypid brachiopods in basal 2.0 ft., poorly preserved; Cyrtospirifer possibly present also; fossils silicified; both rock types contain crinoidal segments as large as 1 cm. in diameter, 7*5 cm. in length— much more abundant in upper part of unit; no Unit Cumulative Thickness Thickness Unit no. Description Ft. Cm .) Ft. (M.) biosparite not w e n washed in certain horizons, is poorly sorted, contains patches of dolomite; contains rare brachiopods, senary rugose corals, and fenestrate bryozoa; large crinoid stem fragments have project ing spines; horizontal burrows at top of unit; upper part of unit con tains resistant, irregular, sdla- ceous, moderate yenowish-brown (10 YR 5/4) lineations; non-resistant interval at top of unit • ...... 9.0 (2.7) 224.0 (68.3) Dolomite, snghtly snty, grayish- orange (10 YR 7/4)i weathers pale- yenowish-brown (10 YR 6/2); medium-crystainne; thin-bedded, but somewhat resistant; laminated; unfo ssinf erous with the exception of one thin horizon in center of unit that contains crinoidal debris; grades into overlying fossil i.ferous unit; chert at base of unit is 5 to 7*5 cm. thick, medium-gray (N5), laterally continuous for tens of feet • • • ...... 5.0 (1.5) 215.0 (65.6) Dolomite, silty, calcitic, dark- yeUowish-orange (10 YR 6/6), weathers pale-yellowish-brown (10 YR 6/2); medium-crystalline; thinly laminated to very thin-bedded; poorly exposed; slope-forming; unfossiliferous ...... 12.5 (3.8) 210.0 (64.0) Biosparite, sandy, medium-gray (N5), weathers same; well-sorted calcarenite composed of crinoidal debris; one bed; no brachiopods observed; sandier horizons are cemented by silica giving appearance of chert; small chert nodules in upper 1.5 ft. . . 2.0 (0 .6) 197.5 (60.2) Dolomite, fossiliferous, to dolomitic biomicrite, slightly silty, mottled medium light-gray (N6)/grayish-orange in Unit Cumulative Thickness Thickness Unit no. Description Ft. (M.) F t. (Mo) 10 YR 7/4)« weathers grayish-orange (10 YR 7/4)i dolomite is medium- crystalline ; thin-beddedj base and top are weakly resistant; dominated by very small brachiopods; Atrypa present; fossils silicified • • . • 3.0 (0.9) 195-5 (59-6) 27 Biosparite, crinoidal, medium light- gray (N6), weathers lightr-gray (N7); composed of medium-grained, well-sorted calcarenite; one bed ...... 1.5 (0.5) 192.5 (58.7) 26 Dolomite, slightly silty, medium dark- gray (N4) t weathers grayish-orange (10 YR 7/4)1 medium-crystalline; thin- to thick-bedded; moderately resistant; weathers rounded rather than angular; fossiliferous through out except in basal 2.0 ft., which contain horizontal burrows (in arenaceous intervals); uppermost 3-0 to 4*0 ft. is silty, weakly resistant, contains few fossils; brachiopods weather free of matrix; original shell preserved; Atrypa sp. over whelmingly dominant; associated with common Cyrtospirifer and several other less common brachiopods; solitary rugose corals, 1 cm. in diameter, 2 to 3 cm. in length; rare gastropods; crinoidal debris; rare fenestrate bryozoa ...... • ...... 21.0 (6i4) 191-0 (58.3) 25 Biosparite, very sandy, dolomitic, crinoidal, pale-brown (5 YR 5/2) matrix, medium-gray (N5) crinoidal debris, weathers orangish-brown (10 YR 6/4); sand medium-grained; thin-bedded; resistant; crinoid coluranals up to 1 cm. in diameter; some scattered indeterminant brachiopod fragments; sand decreases in abundance upward; silica cement in sandy intervals— patches stand out in relief • • • . 3-0 (0.9) 170.0 (51-8) 112 Unit Cumulative Thickness Thickness U n it no. D escrip tio n F t. CM.) F t. (M .) 24 Quartzarenite, dolomitic, to sandy dolomite, moderate yellowish-brown (10 YR 6/6), weathers orangish-brown (10 YR 6/4); arenaceous horizons weather pale-yellowish-brown (10 YR 5/4)i medium-crystalline dolomite; base is thii>-bedded, top is thick- bedded; very resistant— stands as one cliff face with overlying biosparites; large, sandy, lenticular chert nodules at base, as large as 12 cm. thick, 1 m. in length; sand at base is very fine-grained, grows patchier, very coarse upward; interval 3*5 to 5»0 ft. above base of unit contains common to abundant silicified atrypid brachio- pods; uppermost 1 ft. contains rounded coarse quartz sand with coarse calcaren- ite in roughly equal parts; this interval also contains small lenticular chert nodules up to 6 cm. thick, 20 cm. long, as well as crinoid columnals as large as 1 cm. in diameter; brachiopod interval is in coarse-grained dolomite; irregular lineations of sand in center of unit look as if algal bound . o r i g i n a l l y ...... 6.0 (1.8) 167.0 (59.9) 23 Dolomite, very silty, to dolomitic siltstone, orangish-brown (10 YR 6/4), weathers pale-yellowish-brown (10 YR 6/2); fine- to medium-crystalline; • grades from thinly laminated at base to very thin-bedded at top; poorly exposed; slope-forming; unfossili- f e r o u s ...... 16.0 (4.9)161.0 (49.1) 22 Dolomite, very silty, dark-yellowish- orange (10 YR 6/6), weathers somewhat lighter; medium-crystalline; thin- to thick-bedded; unfossiliferous; top of unit marked by resistant quartzarenite horizon containing abundant horizontal burrows approximately 1 cm. in width, 113 Unit Cumulative Thickness Thickness Unit no. Description Ft. (M.) Ft. (M.) and as long as 20 cm. (on upper bedding-plane surface only); similar to burrows in unit 17 ...... 3.0 (9.9) 145*0 (44*2) 21 Biosparite, crinoidal, dolomitic, medium-gray (N5), weathers same; contains bed 15 to 20 cm. thick of sparsely fossiliferous dolomite; basal 1.5 ft. is medium-grained calcarenite, well-sorted; upper part of unit much coarser, crinoidal biosparudite; unit thin-bedded, bedding somewhat nodular; moderately resistant; crinoidal bio sparudite contains crinoid columnals to 1 cm. in diameter, small solitary rugose corals as large as 1 cm. in diameter, 2 to 3 cm. in length (common); indeter minant brachiopod fragments; low-angle trough crossbedding at base of unit 4*5 (1*4) 142.0 (43*3) 20 Quartzarenite, dolomitic, orangish- brown (10 YR 6/4), weathers somewhat lighter; very fine-grained, well-sorted; thin-bedded; strongly laminated; very resistant; silica cement; ripple- laminated ...... 2.5 (0.7) 137*5 (41*9) 19 Dolomite, very sandy, calcitic, orangish- brown (10 IB 6/4), weathers same; dolo mite is medium-crystalline; sand is very fine grained; very thin-bedded; poorly exposed; slope-forming; unfossili- ferous; upper 1.0 ft. contains small horizontal burrows 2 to 3 mm. across, some rarer large horizontal burrows 1 cm. across ...... 10.0 (3*1) 135*0 (41*2) 18 Dolomite, silty, with very thin biosparite horizons, pale-yellowish- brown (10 YR 6/2), weathers grayish- orange (10 YR 6/4); medium-crystal line; biosparite horizons are medium dark- gray (N4), weather medium light-gray (N6); thin-bedded, nodular bedding; base weakly resistant, rests on ’’bench" formed by underlying unit; contains 114 Unit Cumulative Thickness Thickness Unit no* Description Ft* (M.) Ft* CM.) crinoid columnals up to 1 cm. in diameter, common to abundant in biosparite horizons; contains rare Schizophoria, common Stropheodonta, rare gastropods, possible cystoid plate; biosparite 7.0 ft. above base of unit contains massive trepostome bryozoa as large as 3 cm. thick, 20 cm. in diameter, in growth position; small solitary rugose corals rare to common, 1 cm. in diameter, 2 to 3 cm. in length; small, rare branching bryozoa, top of unit marked by hori zontal burrows, approximately 1 cm. in diameter, several cm. in length; arenaceous' at top with undulatory laminations that follow nodular bedding; biosparite horizons at base of unit, 7.0, 14*5» and 16.5 ft. above base of unit ...... 16.5 (5.0) 125.0 (38.1) 17 Interbedded dolomitic quartzarenite and sandy dolomite, pale-yellowish- brown (10 YR 6/2), weathers moderate yellowish-brown (10 YR 5/4); dolomite is medium-crystalline; sand is very fine-grained, well-sorted, angular (from solutioning); contains coarse sand stringers; thin-bedded; base weakly resistant; siliceous cemented sand forms irregular nodules; upper 2.0 ft. is sacchroidal dolomite, some what gnarly, contains rare crinoid columnals, 3 to 4 mm. in diameter most common, as large as 1 cm., rare gastropods; abundant horizontal burrows from 3*0 to 5*0 ft. above base of unit, as large as 1 cm. across, 3 cm. in length; top of unit is ripple- laminated ...... 9.0 (2.7) 118.0 (32.9) 16 Quartzarenite, white (N9) to very light gray (NS), weathers grayish- orange (10 YR 7/4); three depositional units, basal sand in each is very coarse-grained to granule in size; 115 Unit Cumulative Thickness Thickness Unit no. Description Ft* (M«) Ft. (M.) grades finer upward until next deposi- tional unit encountered; sand is bimodal, roundness obscured by silica * cement; finer intervals are micaceous; thick-bedded; resistant; cliff-forming; ripple-marked at top of unit; coarser intervals strongly through crossbedded; sets dip up to 20°; individual sets approximately 1.0 ft. in thickness, comprise a depositions! unit 3.0 to 4«0 ft. in thickness; transport trend predominantly westward, although an easterly trend is fairly common; top of unit is capped by patchy coarse lag with sandstone/quartzite pebbles as large as 4 cm. maximum dimension, quartz chert pebbles (from Mescal Limestone?) as large as 2 cm. in maximum dimension, and ptyctodont fish tritors (pavement teeth); majority of clasts are approximately 5 mm. in diameter (very coarse sand to granule in size); this lag exposed only in patches, is non-resistant, easily eroded; contains horizontal burrows on bedding plane surface in middle of u n i t ...... 10.0 (3.2) 99.0 (30.2) Total of upper unit 146.0 (44.5) Aphanitic dolomite unit: 15 Dolomite, very silty, slightly sandy, grayish-orange (10 YR 7/4)» weathers same; fine- to medium- crystalline; thin-bedded; upper 1.0 ft. is nodular, bedding distorted; lower 1.0 ft. is weakly resistant, has shaly appearance ...... 2.0 (0.6) 89.0 (27.1) 14 Dolomite, very slightly silty, pale- yellowish-brown (10 YR 6/2), weathers grayish-orange (10 YR 7/5); fine- to medium-crystalline; thin-bedded; strongly laminated; resistant; n6 Unit Cumulative Thickness Thickness Unit no. Description Ft. fM«) Ft. (M.) separated from underlying unit by a distinct parting; laminations somewhat undulatory in places; more coarsely crystalline than lower units; lacks sand ...... 2.0 (0.6) 87.0 (26.5) 13 Dolomite, intraclastic, grayish-orange- pink (5 IR 7/2), weathers grayish- orange (10 YH 7/4); finely crystalline; one massive bed; lacks sand; somewhat less resistant than underlying unit; uppermost 2.0 ft. is burrowed/biotur- bated as in unit 11; burrows siliceous (?), stand out in relief ...... 6.0 (1.8) 85.0 (25.9) 12 Dolomite, sandy, pelletal/intraclastic, very pale-orange (10 YR 8/2), weathers grayish-orange (10 YR 7/4); matrix is very finely crystalline, pellets/ intraclasts are aphanocrystalline; thick- to very thick-bedded; more coarsely crystalline than lower units; upper 10.0 ft. contains very coarse sand in lineations, mixed with well-rounded, sand-size intraclasts, no bioturbation noted; slightly laminated on outcrop ...... 18.0 (5*5) 79.0 (24.1) 11 Dolomite, intraclastic, sandy, grayish- orange-pink (10 R 8/2), weathers very pale-orange (10 YR 8/2); aphano- crystalline; unit composed of 2 massive beds; very resistant; upper bed contains abundant very coarse sand; basal 1.0 ft. of unit contains rounded intraclasts, some minor brecciation; contact between the two massive beds is undulatory, possibly erosional; contact has coarse sand/intraclast lag upon it; both beds are strongly bioturbated, contain abundant birds- eye structure and rounded intraclasts; some s t y o l i t e s ...... •• 8.5 (2.6) 61.0 (18.6) 117 Unit Cumulative Thickness Thickness Unit no. Description Ft. (M«) Ft. (M.) erosional/solutional surface 10 Dolomite, grayish-orange-pink (5 YR 7/2), weathers very pale-orange (10 YB S/2); finely- to very finely- crystalline; one massive bed; upper 1.0 ft. of unit contains lineations of darker dolomite that pinch out, have appearance similar to gash fractures in metamorphic rocks; erosional contact with overlying unit, maximum relief approximately 2 to 3 ft., very irregular surface, solutional in nature; unit contains rounded intraclasts in upper 2.0 ft., but show no sorting or stratification . 5«5 (1.7) 52*5 (16.0) 9 Dolomite, very slightly silty, pale- red-purple (5 RP 6/2), weathers same; fine- to medium-crystalline; very thin-bedded; weakly resistant; base forms bench on underlying conglomer ate; base displays fissility; poorly exposed ...... 6.0 (1.8) 47*5 (14*5) 8 Dolomite pebble conglomerate to conglomeratic dolomite; matrix of dolomite is light-brown (5 YR 6/4), weathers grayish-orange (10 YR 7/4)» clasts are light-gray (N7), weather same; matrix is finely-crystalline overall, medium- to coarsely- crystalline in voids; clasts are aphanocrystalline; upward in the unit the clasts increase in size to 5 cm. in diameter, and are sub rounded, unsorted; one massive unit; base contains lenticular fragments 10 to 12 cm. in length, 1 to 2 cm. thick, orientated with bedding, with orangish lineations of matrix sur rounding them; contains chert nodules as large as 20 cm. in maximum dimen sion, has a porous texture, is medium light-gray (N4) with a dark- yellowish-brown (10 YR 4/2) 118 Unit Cumulative Thickness Thickness Unit no. Description Ft. (M.) Ft. CM.) weathering rind; chert crosscuts clast boundaries and surrounds them, anastomosing in places ...... 9*5 (2.9) 41*5 (12.7) 7 Dolomite, light-gray (N7), weathers yellowish-gray (5 Y 8/1); aphano- crystalline; thick- to very thick- bedded; lacks allochems; basal 1.0 ft. contains anastomosing burrows, is bioturbated; birdseye structure throughout; styolites common; grades upward into brecciated/ conglomeratic unit ...... 7*0 (2.1) 32.0 (9*8) 6 Dolomite, very light-gray (N8), weathers grayish-orange (10 YE ,7/4) ? aphanocrystalline; thin-bedded; resistant; bedding uneven with a gnarly appearance; lacks allochems...... 4*0 (1.2) 25.0 (7.6) 5 Dolomite, pelletal, light-gray (N7), weathers yellowish-gray (5 Y 7/2); medium-grained dolomite as cement/ void filler; pellets are aphano crystalline; single massive bed; basal 1.0 ft. much less pelletiferous; contains ostracodes, algal (?) filaments in thin-section; basal 2.0 ft. contains vertical burrows, is bioturbated; burrows up to 1.0 cm. in diameter, most are 2 to 3 mm. in diameter; uppermost 5 cm. contains some rounded intraclasts; basal 2.0 ft. grade laterally into well rounded, unsorted intraclasts that lack stratification and appear as a unit to be folded and d e f o r m e d ...... 3.0 (0.9) 21.0 (6*4) 4 Dolomite, light-gray (N7), weathers yellowish-gray (5 Y 8/l); aphano crystalline; some recrystallization in patches; unit is single bed; small amplitude styolites throughout; some pellets or intraclasts near top of unit; contains rare ostracodes in 119 Unit Cumulative Thickness Thickness Unit no. Description Ft. (M.) Ft. (M.) thin-section, abundant algal filaments (?); unit contains some small scat-. tered, siliceous inclusions . • . . 2.0 (0.6) 18.0 (5-5) 3 Dolomite, pelletal, medium-light-gray (N6), weathers yellowish-gray (5 Y 8/l); pellets fine- to medium-grainedj single bed; resistant; rare silici- fied inclusions; erosional/solutional contact with overlying unit • • • • 3.0 (0.9) 16.0 (4»9) 2 Dolomite, medium-light-gray (N6), weathers yellowish-gray (5 Y 8/l); very finely-crystalline, with son® recrystallization; thin-bedded; poorly exposed, slope-forming; con tains rare ostracode valves in thin- section ...... 6.0 (1.8) 13.0 (4.0) 1 Dolomite, medium-light-gray (N6), weathers very pale-orange (10 YR 8/2); aphanocrystalline with voids filled with finely-crystalline dolomite; thin-bedded; moderately resistant; contains small intraclasts or pellets; contains rare ostracode valves in thin-section; contains some undulatory laminations and styolites...... 7.0 (2.1) 7.0 (2.2) Total of aphanitic dolomite unit (incomplete) ...... •••• 89.0 (27.1) Total of Jerome Member (incomplete) 235*0 (71*7) Total of Martin Formation • • • • • 235*0 (71*7) Base not exposed: REFERENCES CITED Ager, Derek V*, 1963» Principles of paleoecology: McGraw-Hill Book Co., San Francisco, 371 p. , 1968, The Famennian takeover: in Symposium on Devonian floras and faunas, Circ. Palaeont. Assoc., no 54* Anderson, E. J., 19711 Environmental models for Paleozoic Communities: Lethaia, v. 4» P» 287-302. Bens, S. S., 19731 Devonian stratigraphy and paleogeography along the western Mogollon Him, Arizona: Museum of Northern Arizona Bull, no. 491 Northern Arizona Society of Science and Art, Inc., Flagstaff, 36 p. Bowen, Z. P . , Rhoads, D. C., and McAlester, A . , 1974, Marine benthic communities in the Upper Devonian of New York: Lethaia, v. 7, p. 93-120. Boucot, A. J., 1970, Practical taxonomy, zoogeography, paleoecology, paleogeography, and stratigraphy for Silurian and Devonian brachiopods: in Proc. N. A. Paleont. Conv., Chicago, Pfc. F., p. 566-611. ______, 19751 Evolution and extinction rate controls: American Elsevier Publ. Co., New York, 370 p. Bretsky, P. W . , and Lorenz, D. M . , 1970, Adaptive response to environ mental stability: a unifying concept in paleoecology: Proc. N. A. Paleont. Conv., Chicago, 1969, Pt. E . , p. 522-550. Canright, J. E . , 1968, Spores and associated macrofossils from the Devonian of Arizona: Geoscience and Man, v. I. Amer. Assoc, of Stratigraphic Palynologists, Proceedings of the first annual meeting, p. 83-88. ' Copper, P., 1966, Ecological distribution of Devonian atrypid brachio pods: Palaeogeo., Palaeoclimat., Palaeoeco., v. 2, p. 245-266. Dickson, J. A. P . , 1965, Modified staining technique for carbonates in thin-section: Nature, v. 205, p. 587. Elston, D. P., and Bressler, S. L. (in press), Unconformities and the strati graphic and paleomagnetic correlation of basal Cambrian and Devo nian strata of central and northern Arizona: U.S. Geol. Survey. 120 121 Elston, W# E e , i960, Structural development and Paleozoic stratigraphy of Black Mesa Basin, northeastern Arizona, and surrounding areas: Am. Assoc. Petrol. Geologists Bull., v. 4 4 1 P« 21-36. Ethington, R. L., 1965, Late Devonian and early Mississippian conodonts from Arizona and New Mexico: Jour. Paleo., v. 39, p. 566-389. Fenton, G. L . , and Fenton, M. A . , 1924, The stratigraphy and fauna of the Hackberry Stage of the Upper Devonian: The McMillian Co., New York, 260 p. Folk, R. L . , 1959, Practical classification of limestones: Am. Assoc. Petrol. Geologists Bull., v. 43, P» 1-38* ______, 1968, Petrology of sedimentary rocks: Hemphill*s, Austin, Texas, 170 p. Fraunfelter, G. H., 1967, Middle Devonian biofacies of central and northeastern Missouri: in Oswald, D. H., ed., International Symposium on the Devonian System, Calgary, Alberta: Alberta Soc. Petrol. Geol., v. II, p. 1043-1060. Goddard, E. N . , Trask, Parker D . , DeFord, Ronald K., Rowe, Olaf N . , Singewald, Joseph F., and Overbeck, R. M . , 1948, Rock Color Chart: Mans ell Color Company, Baltimore, Maryland. Heckel, P., 1972, Recognition of ancient shallow marine environments: in Rigby, J. K . , and Hamblin, Wm. K., eds., Recognition of ancient sedimentary environments: Soc. of Econ. Paleontologists and Mineralogists, Tulsa, Oklahoma, Spec. Pub. no. 16, p. 226- 286. Hoggan, R. D . , 1975, Paleoecology of the Guilmette Formation in eastern Nevada and western Utah: Brigham Young University, Geology Studies, v. 22, p. 141-197* Huddle, J. W., and Dobrovolny, E . , 1952, Devonian and Mississippian rocks of central Arizona: U. S. Geol. Survey Prof. Paper 233-D, p. 67-112. Irwin, M. L . , 1965, General theory of epeiric clear water sedimentation: Am. Assoc. Petrol. Geologists Bull., v. 49, p. 445-459. Johnson, J. G., 1974a, Extinction of perched faunas: Geology, v. 2, p. 479-482. ______, 1974b, Early Devonian brachiopod biofacies of western and arctic North America: Jour. Paleo., v„ 48, p. 809-819. 122 Johnson, J. G*, and Boucot, A. J., 1971, Devonian brachiopods: in Hallam, A., ed., Atlas in paleobiogeography, Elsevier Scientific Pub. Co., New York, p. 89-96. Johnson, J. G., and ELory, R. A., 1972, A Rasenriff fauna from the Middle Devonian of Nevada: Jour. Paleo., v. 46, p. 892-899. Kauffman, E. G., and Scott, R. W., 1976, Basic concepts of community ecology and paleoecology: in Scott, R. W., and West, R. W., eds., Structure and classification of paleocommunities, Dowden, Hutchinson, and Ross, Inc., p. 1-28. Laporte, R. F., 1967, Carbonate deposition near mean se-level and re sultant facies mosaic: Manlius Formation (Lower Devonian) of New York State: Am. Assoc. Petrol. Geologists Bull., v. 51, p. 73-101. ______, 1969, Recognition of a transgressive carbonate sequence within an epeiric sea: Heldeberg Group (Lower Devonian) of New York State: in Friedman, Gerald M., ed., Depositional environments in carbonate rocks, a symposium: Soc. Econ. Mineralogists and Paleontologists, Spec. Pub. No. 14, p» 98-119. Mallory, B. F., 1968, Paleoecologic study of a brachiopod fauna from the Cerro Gordo Member of the Lime Creek Formation (Upper Devonian), north-central Iowa: unpublished Ph.D. dissertation, University of Missouri, 53 P* McGhee, G. R . , Jr., 1976, Late Devonian benthic marine communities from the central Appalachian Allegheny Front: Lethaia v. 9, p. 111- 136. McKee, E. D . , 1951, Sedimentary basins of Arizona and adjoining areas: Geos. Soc. America Bull., v. 62, p. 481-505* McKee, E. D . , and Weir, G. W., 1953, Terminology of stratification and cross-stratification: Bull. Geo. Soc. Amer., v. 64, p* 381-390. McLaren, D. J., 1970, Presidential address: time, life, and boundaries: Jour. Paleo., v. 44, P* 801-815. Meader, S. J., 1976, Paleoecology of the Upper Devonian of south-central Arizona: unpublished M.S. thesis, University of Arizona, 104 P* Pine, G. L . , 1968, Devonian stratigraphy and paleogeography in Gila, Graham, Greenlee, and Pinal Counties, Arizona: unpublished Ph.D. dissertation, University of Arizona, 305 p. 123 Ransome, F. L . , 1903» Geology of the Globe copper district, Arizona: U.S. Geol. Survey, Prof. Paper 12, p. 40-42. , 1904, A description of the Bisbee Quadrangle (Arizona): U.S. Geol. Survey, Geol. Atlas, Bisbee folio 112, 17 p. ______, 19151 The paleozoic section of the Ray Quadrangle, Arizona: Wash. Acad. Sci. Jour., v. 3, p. 380 , 388. Schumacher, D., 1976, Conodont biofacies and paleoenvironments in Middle Devonian-Upper Devonian boundary beds, central Missouri: in Barnes, C. R., ed., Conodont paleoecology, Geol. Assoc, of Canada, Spec. Paper no. 15, p* 159-169* Schumacher, D . , Witter, D. P., Meader, S. J., and Keith, S. B . , 1976, Late Devonian tectonism in southeastern Arizona: in Wilt, J. C. and Jenney, J. P., eds., Tectonic Digest, Arizona Geol. Soc. Digest, v. X, p. 59-70. Scott, R. W . , and West, R. R . , eds., 1976, Structure and classification of paleocommunities: Dowden, Hutchinson, and Ross, Inc., 291 p. Shaw, A. B . , 1964, Time in stratigraphy: McGraw-Hill, Inc., New York, 365 P* Shinn, E. A., 1968, Practical significance of birdseye structures in carbonate rocks: Jour. Sed. Pet., v. 49, p* 928-944* Stainbrook, M. A., 1941, Biotic analysis of Owen’s Cedar Valley Lime stones: Pan-American Geologist, v. 75, P* 321-327* Stauffer, C. R., 1928, The Devonian section of Pinal Creek, Arizona: Ohio Jour. Science, v. 28, p. 253-260. Stoyanow, A. A., 1930, Certain aspects of the Devonian in Arizona: Pan-American Geol., v. 53, P* 316-317* ______, 1936, Correlation of Arizona Paleozoic formations: Geo. Soc. America Bull., v. 47, P* 459-540. Sutton, R. G., Bowen, Z. P., and McAlester, A. L . , 1970, Marine environ^ ments of the Upper Devonian Sonyea Group of New York: Geos. Soc. America Bull., v. 81, p. 2975-2992. Tahmazian, G. A . , 1964, Petrography .of the Troy and Martin clastic sequence at Roosevelt Dam, Gila County, Arizona: unpublished M.S. thesis, University of Arizona, 95.P*. Teichert, C., 1965, Devonian rocks and paleogeography of central Arizona: U.S. Geol. Survey Prof. Paper 464, 181 p. 124 Teichert, Go, and Schopf, J. M«, 1958, A Middle or Lower Devonian psilophyte flora from central Arizona and its paleogeographic significance: Jour. Geol., v. 66, p. 208-217. Thayer, C. W., 1974, Marine paleoecology in the Upper Devonian of New York: Lethaia, v. 7, P« 121-156. Walker, K. R., and Alberstadt, L. P., 1975, Ecologic succession as an aspect of structure in fossil communities: Paleobiology, v. 1, p. 238-357. Walker, K. R . , and Bamback, R. K., 1971, The significance of fossil assemblages from fine-grained sediments: time averaged communi ties: Geol. Soco America, Abstracts with Prog. 3» p. 783-784. Watkins, R., and Boucot, A. J., 1975, Evolution of Silurian brachiopod communities along the southwestern coast of Acadia: Geo. Soc. America Bull., v. 86, p. 243-254* Witter, Do P., 1976, Conodont biostratigraphy of the Upper Devonian in the Globe-Mammoth area, Arizona: unpublished M.S. thesis, The University of Arizona, 99 p« Ziegler, A. M . , Walker, K. R., Anderson, E. J., Kaufftnan, E. G . , Ginsburg, R. N., James, N. P., 1974» Principles of benthic community analysis, notes for a short course: Sediments IV, the Comparative Sedimentology Laboratory, The University of Miami, 175 P* 6 V 1 9 2 9 ROOSEVELT DAM PINAL CREEK LU O g K o Z o ZD PERCHA FM. -low-angle tabular-planar crossbedding 3 6 0 - LU convolute bedding; unit strongly O laminated h- g 3 5 0 - gentle trough crossbedding o Z coarse sand lag, horizontal burrows o / ZD Li. 7" 3 4 0 - 1 y- / / / PERCHA FM. 240--3- 3 3 0 - / / /../. COENI TES-SPI RIFERI D BRACHI0P0D ASSEMBLAGE l v v 3 2 0 2 3 0 - y7 bioturbation >ATRyPA-THEODOSIA ASSEMBLAGE ■ • "7 ..a Jo -horizontal burrows, vertical living burrows (?), Atrypa 310- ,/; / bioturbation le ® ® crinoidal biosparite z / / / / 32 2 2 0 - ^ ® i Z) fenestrate bryozoa, indeterminant brachiopods abundant atrypid brachiopods oscillation ripple marks 3 0 0 - /Z . 210 biot urbation 2 9 0 - 7 f/7 indeterminant brachiopods 200 - — indeterminant brachiopods crinoidal biosparite o: common atrypid brachiopods l u oo crinoidal biosparite 1 9 0 - / / s s STROPHEODONTA-FENESTRATE BRYOZOAN ASSEMBLAGE m z M / with Cruziana trails and inclined burrows 260-1 ^ ATRYPA- CYRTOSPIRIPER ASSEMBLAGE 2 6 1 8 0 - 2 5 0 S CRINOID - SCHI ZOPHORIA ASSEMBLAGE horizontal burrows interbedded barren dolomite and dolomi t ized biosparit e 170 crinoidal biosparite 2 4 0 - y / / -V abundant atrypid brachiopods, crinoid debris or ^ y—y ly LU /-* / CL y 160 - -r CL y 2 3 0 y»y./ / »y ZD / /* / 2 /. horizontal burrows and grazing traces (Chondrites) % ripple marked 220 - m i s 150 - ^1— ~- z horizontal burrows Z 7 crinoidal biosparite quartz granule lag first brachiopod ripple l ami nations horizontal burrows ^ intraclasts X 1 9 0 - f : ***. <>> horizontal , ,1 vertical burrows burrows ## >trough crossbedding 1 80” biosparite /STROPHEODONTA-SCHI ZOPHORIA ASSEMBLAGE Z : 7 ' / - S?!5?. 1: VI Z : horizons intraclasts X z 1 7 0 - -intraclasts I 10 ripple laminations, rare crinoid columnals LU abundant horizontal burrows 2 1 6 0 - trough crossbedding o IOOH granule-pebble lag w. pavement teeth, top of unit is ripple marked q : LU horizontal "D burrows /"large scale trough crossbed ding disconformit y? quartzite pebble lag, trough crossbeddinc 9 0 - i disconformity ? -small vertical burrows-biot urbation-birdseye 80=3 sand-size intraclasts mixed with sand mudcracks 7 0 - r- mudcracks X ARTHRODIRAN ASSEMBLAGE Z z ZD I 10“ birdseye intraclasts 6 0 - mudcracksJ solution surface^small vertical burrows-bioturbation-rounded intraclasts-birdseye ■'Z.vz-Z 100” birdseye -major erosion-solution surface LU 8 K mudcracks 5 0 ” 5 birdseye mudcracks O ■ f e s a i o X o -birdseye 4 0 ” conglomeratic dolomite mudcracks intraclasts birdseye mudcracks brecciation? first fish plate 30 M ^ birdseye < X tidal channels CL pelletal dolomite < 20 - laterally continuous chert horizon solution surface pelletal dolomite 3 > OSTRACODE-ALGAL ASSEMBLAGE .iiiZPp-; 1 0 ” / ripples? 1 / z Z z z 4 0 ” / / // Z 7~ 7 1 z 7~ \STROMATOLITE ASSEMBLAGE BASE NOT EXPOSED r< planar and fenestral laminae, birdseye LEGEND disconformi ty 7- T-T 7 7 ^ /A/*/; LITHOLOGY SEDIMENTARY STRUCTURES FOSSILS z_ / _ / brachiopods dolomite quartzarenite trough crossbedding intraclasts X / / y m bioturbation ©© crinoid columnals i n sandy dolomite shale zy zv ripple lamination /if trough crossbedding E33 horizontal burrows Coenites(tab. coral) UNCONFORMITY pelletal dolomite IH1 siltstone F f ▼ ▼ mudcracks fenestrate bryozoan i n conglomeratic dolomite E 3 chert :v : birdseye structure hi vertical burrows * * * arazina traces(Chondrites) stromatol ites FI biosparite channels FIGURE 3. VERTICAL DISTRIBUTION OF ROCK TYPES, SEDIMENTARY STRUCTURES, AND FOSSIL OCCURRENCES AT ROOSEVELT DAM AND PINAL CREEK r ^ ? / -"777