The Late Middle Devonian (Givetian) Global Taghanic Biocrisis in Its

Home , Acadian orogeny, Eldredgeops, Goniatite, Goniatitidae, Hamilton Group, Middlesex Shale

The Late Middle Devonian (Givetian) Global Taghanic Biocrisis in its Type Region (Northern Appalachian Basin): Geologically Rapid Faunal Transitions Driven by Global and Local Environmental Changes

A dissertation submitted to the Graduate School University of Cincinnati In partial fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

Department of Geology McMicken College of Arts and Sciences August 9th, 2011 by James Joseph Zambito IV M.S., University at Buffalo, 2006 B.S., SUNY College at Brockport, 2004

Dissertation Committee Dr. Carlton E. Brett, Chair Dr. Arnold I. Miller Dr. David L. Meyer Dr. Thomas J. Algeo Dr. Gordon C. Baird Dr. Alex J. Bartholomew

Abstract

The late Middle Devonian Global Taghanic Biocrisis marks the onset of extinction and a loss of faunal endemism that culminated in the subsequent Frasnian-Famennian extinction. Global environmental changes recognized at this time include increased warming and aridity, as well as rapid eustatic sea level fluctuations. In the type region, the northern Appalachian Basin, the biocrisis is recorded within the deposits of the uppermost Hamilton, Tully, and lowermost

Genesee Groups over an interval of ~0.5 million years. A high-resolution stratigraphic framework reconstructed along a complete onshore through offshore gradient has resulted in the recognition of three main pulses (bioevents) of faunal transition in the type region: 1) the incursion of the tropical Tully Fauna into eastern Laurentia and temporary loss of the endemic

Hamilton Fauna; 2) Tully Fauna extermination and replacement by a recurrent Hamilton Fauna; and, ultimately, 3) extinction of large portions of the Hamilton Fauna and the beginning of cosmopolitan Genesee Fauna. Similar faunal patterns of incursion, recurrence, and cosmopolitanism have also been noted for other regions, albeit with somewhat different regional characteristics.

Global environmental changes during the biocrisis are recognized in the type region through reconstruction of δ18O(conodont apatite) and δ13C(carbonate) records. However, regional faunal incursion, replacement, and recurrence patterns during the first and second bioevents, as well as corresponding sedimentological observations, are best explained by basinal-scale water mass changes in response to the global environmental changes. During the third bioevent, eustatic sea- level rise was accentuated regionally by renewed Acadian tectonic activity. Quantitative paleoecological analysis demonstrates that Hamilton Fauna survivors of this bioevent were those taxa adapted to nearshore, siliciclastic-dominated settings. Persistence of these taxa was a direct

ii result of the persistence of their preferred habitat through the biocrisis and subsequent tectonically-driven expansion of this facies. Similar, multi-disciplined studies of the Taghanic

Biocrisis in other regions will increase our understanding of regional response to global change on geologic timescales.

iii

Acknowledgements

Thanks to Dr. Carl Brett for his guidance in the field and classroom, the many research opportunities he has included me in beyond my dissertation, and the freedom to take my research in unexpected directions. I am grateful to Dr. Arnie Miller 'due to' his advice on my dissertation and life itself, his encouragement throughout my time at UC, and for helping me to find out the hard way that brightly colored liquors don't mix well... I would like to thank Dr. Dave Meyer for sharing with me his excitement for all things paleontological, guidance in fossil preparation techniques, and reminding me of the importance of the work done by my predecessors. Thank you to Dr. Tom Algeo for teaching me geochemical techniques and for very helpful discussion of my dissertation. I am very much indebted to Dr. Gordon Baird for all of his assistance and instruction in the field, for sharing his tremendous wealth of locality and stratigraphic knowledge with me, and for great discussions. Thanks to Dr. Alex Bartholomew for assisting with fieldwork in the early phases of my dissertation.

Thank you to Dr. Michael Joachimski and Daniele Lutz for training me in the oxygen isotopic analysis of conodont apatite, discussion of my research, and for taking me to the

Bergkirchweih. I am also grateful to Dr. Jed Day, Dr. Jeff Over, Dr. Ted Williams Jr., Dr.

Charles Thayer, and especially Dr. Bill Kirchgasser for helpful discussion and sharing of samples and data. Thanks to Dr. Susan Butts and the staff at the Yale Peabody Museum for providing access to, and assistance in working with, the Thayer collections. Fieldwork was assisted, at various times, by Nick Bose, Sara Oser, Ian VanDonkelaar, and Joe Sullivan.

I am extremely grateful for all of the financial support and opportunities provided to me by the UC Department of Geology.

Thanks to my family, and in-laws, for all of their support throughout graduate school.

I am eternally indebted to Sarah, my amazing wife and best friend, for helping with

fieldwork, discussion of my research, assistance with data analysis, and putting up with me these

past four years. I could not have done this without you.

Funding for this dissertation was provided by the National Science Foundation,

Deutscher Akademischer Austauschdienst (German Academic Exchange Service), the American

Museum of Natural History (Theodore Roosevelt Memorial Fund), the American Association of

Petroleum Geologists, the Evolving Earth Foundation, the Geological Society of America, the

Paleontological Society, the Schuchert and Dunbar Grants in Aid Program (Yale Peabody

Museum), the Paleontological Research Institute, the Society for Sedimentary Geology, Sigma

Xi, the Mid-America Paleontology Society, the UC Department of Geology, the UC Graduate

Student Governance Association, the UC University Research Council, and the UC Graduate

School.

Table of Contents:

Chapter 1: Introduction (p. 1-16)

Chapter 2: Depositional Sequences and Paleontology of the Middle – Upper Devonian Transition

(Genesee Group) at Ithaca, New York: A Revised Lithostratigraphy for the Northern

Appalachian Basin (p. 17-76)

Chapter 3: The Late Middle Devonian (Givetian) Global Taghanic Biocrisis in its Type Area

(Northern Appalachian Basin): Geologically Rapid Faunal Transitions Driven by Global and

Local Environmental Changes (p. 77-151)

Chapter 4: Reconstruction of Isotopic Changes for the Late Givetian (Middle Devonian) Global

Taghanic Biocrisis in its Type Region (Northern Appalachian Basin) (p. 152-192)

Chapter 5: Quantitative Paleoecological Analysis of the Post-Taghanic Genesee Fauna and its

Relationship to the Pre-Biocrisis Hamilton Fauna (p. 193-230)

Chpater 6: Conclusions (p. 231)

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Chapter 1

Introduction

During the Global Taghanic Biocrisis (GTB), approximately 385 million years ago,

Middle Devonian faunas worldwide underwent a major extinction in apparent conjunction with global warming and aridity, eustatic sea level rise (known as the Taghanic Onlap), and decreased oxygenation of epicontinental seas (Johnson, 1970; House, 2002; Aboussalam, 2003; Joachimski et al., 2004, 2009; Aboussalam and Becker, 2011; and Marshall et al., 2011). In fact, the

Middle-Upper Devonian Boundary was originally defined at this stratigraphic level because of the abrupt faunal changes observed in a number of taxonomic groups globally (Klapper et al.,

1987). Studies of marine invertebrate global biodiversity trends at various taxonomic scales through the Phanerozoic recognize the GTB interval as the beginning of a period of protracted extinction lasting to at least the Frasnian-Famennian extinction, the prolonged duration of which has likely prevented this biocrisis from being recognized as a major mass extinction (Raup and

Sepkoski, 1982; Alroy et al., 2008). A growing body of work suggests, however, that these lesser studied and more frequent events that involve in faunal restructuring and replacement at regional to global scales may have a greater aggregate effect on the evolution of life (Walliser,

1990; Brett and Baird, 1995; Brett et al., 1996; Miller, 1998).

Johnson (1970) and Boucot (1988) describe this time as the end of a period of established

Devonian faunal provinciality related to latitudinal climatic (temperature) gradients, resulting in a world-wide cosmopolitan fauna that persists until the late Frasnian extinction (McGhee, 1996, and references therein; and Sandberg et al., 2002). Indeed, global analyses of sea-surface temperature variation before and after the GTB interval based on oxygen isotopic composition of apatite in conodonts and carbonate in brachiopods have shown a period of global warming, but,

the stratigraphic resolution of these analyses is too coarse to compare with the faunal changes

observed in the type-area during the biocrisis, and, furthermore, samples from the type-area have

never been isotopically examined (Joachimski et al., 2004, 2009). In the type-area of the GTB,

the New York Appalachian Basin, a high-resolution stratigraphic framework has allowed detailed qualitative and quantitative paleoecological study of the pulsed faunal migrations, replacements, recurrence, and extinctions comprising this biocrisis (Heckel, 1973; Baird and

Brett, 2003, 2008; reviewed in Zambito et al., in press). Comparatively, the only paleoenvironmental reconstructions using geochemical proxies in the type-area to date lack the stratigraphic resolution for which paleoecological changes have been described, as the studies were conducted on successions in which a majority of the strata recording the faunal transitions was removed by intra-Devonian erosion (Murphy et al., 2000; Sageman et al., 2003).

Geologic Setting

The northern Appalachian Basin (NAB) deposits found in New York State comprise the

type-area of the GTB (Figs. 1 and 2, see also House, 1985, 2002). At this time, the NAB was

located approximately 30 degrees south latitude (Fig. 1). Regional strata were deposited in a

foreland basin that formed during the Acadian Orogeny, as the Laurentian and Avalonian

terranes converged obliquely (Ettensohn, 1985; Ettensohn et al., 1988; and Ver Straeten and

Brett, 1995, 1997). Erosion of the collisional highlands produced the classic progradational

complex known widely as the “Catskill Delta”, which advanced in a generally westward

direction and largely filled the foreland basin by the early Mississippian. The GTB occurs during

the transition between the second and third collisional tectophases of the Acadian Orogeny

(Ettensohn, 1985; Ettensohn et al., 1988; and Ver Straeten and Brett, 1995, 1997). During each

tectophase, orogenic activity occurred along the eastern seaboard of North America (Laurentia),

causing subsidence of the Appalachian Basin in response to tectonic loading on the crust, and, a

resultant influx of sediment into the basin from the erosional weathering of these mountains.

In the NAB, the GTB is recorded primarily in the sediments of the Tully Group, however,

immigrations and extinctions related to the GTB can be observed first within the upper Hamilton

Group, and continue into the lower Genesee Group (Baird et al., 2003; Baird and Brett, 2003,

2008; and Zambito et al, 2007, 2009, in review). These deposits can be observed in an east-west

trending outcrop belt across New York State that is relatively stratigraphically complete due to

near continuous subsidence during this time, and, furthermore, represent a complete onshore-

offshore gradient as the outcrop belt is normal to depositional strike (Fig. 2).

The Tully Group has received detailed investigation through the years, and is interpreted as being deposited during a period of relative tectonic quiescence, when the second tectophase was waning and sediment input to the basin was relatively minimal, and further, almost entirely precluded in most of the basin by a fault-controlled “clastic trap”, which resulted in carbonate deposition offshore, and siliciclastic deposition onshore (Fig. 2; see discussion in Heckel, 1973;

Baird et al., 2003; and Baird and Brett, 2003, 2008). With the onset of the third tectophase and coincident with a global sea-level rise (Taghanic Onlap), the basin once again subsided, migrated westward, and input of siliciclastic sediment into the western NAB resumed and greatly intensified, as manifested in the deep-water deposits of the Geneseo black shale, subsequent shelf and slope progradation, and preclusion of carbonate depositional settings (Johnson, 1970;

Baird and Brett, 2003, 2008; and Zambito et al., 2009, in press).

The Global Taghanic Biocrisis in the NYAB – Faunal Affinities

Devonian faunas have been divided globally into biogeographic “realms”, the distribution

of which was inferred to be controlled by climatic gradients between the equator and poles

(Boucot et al., 1969; Johnson, 1970; Boucot, 1975, 1988; Koch and Boucot, 1982). At the onset

of the GTB these realms consisted of the equatorial, warm-water ‘Old World Realm’ (OWR), and the higher latitude, slightly cooler-water, ‘Eastern Americas Realm’ (EAR). As illustrated schematically in Figure 1B, prior to the GTB, genera that comprised the ‘Tully Fauna’ (a subset of the OWR) occurred in what is now the western United States and western Canada, in settings more equatorial than the Appalachian Basin. At the same time, the NAB was occupied by the diverse ‘Hamilton Fauna’ (a subset of the EAR) for a period of approximately 5-6 million years

(Brett and Baird, 1995; Brett et al., 1996; Baird and Brett, 2003, 2008).

In the NAB, the GTB has been extensively documented at high-stratigraphic resolution as a series of three bioevents (Fig. 3). These bioevents include faunal migrations and replacements resulting ultimately in the extinction of numerous ammonoid, coral, trilobite, and brachiopod taxa through an interval of approximately 500,000 years: 1) the nearly complete replacement of the endemic ‘Hamilton Fauna’ with the previously equatorial ‘Tully Fauna’; 2) the subsequent extermination of the ‘Tully Fauna’ and return of the ‘Hamilton Fauna’; and 3) extinction of much of the ‘Hamilton Fauna’, at least locally, speciation within some ‘Hamilton’ genera, the return of a few ‘Tully’ taxa, and the further incursion of additional OWR, all of which compose the "Genesee Fauna' (Fig. 3; Baird and Brett, 2003, 2008; reviewed in Zambito et al., in press).

This new combination of taxa constitutes the generalized cosmopolitan fauna that is observed globally until the extensive Frasnian-Fammenian Extinction, approximately 8 million years later

(Fig. 4D; McGhee, 1996; and Sandberg et al., 2002). The dysaerobic communities of the

'Genesee Fauna' have been described recently by Boyer and Droser (2009; see also references therein). Thayer (1974) was the first to describe the nearshore portions of the Genesee Fauna

4 from eastern New York State in detail, although, since his study the stratigraphic framework has been substantially refined (Baird and Brett, 2008; Zambito et al., 2009).

Dissertation Research

This dissertation focuses on four aspects of the Global Taghanic Biocrisis in its type region:

In Chapter 2, I investigate reports in the literature of a 'recurrent Hamilton Fauna' in the

Upper Devonian Ithaca Formation, well after the Global Taghanic Biocrisis and the supposed extinction of the 'Hamilton Fauna'. These chapter focuses on developing a lithostratigraphic framework and documenting the biostratigraphic ranges of taxa and their paleoecological associations in the Ithaca Formation to determine the origin of the anachronistic Hamilton taxa.

In Chapter 3, I qualitatively describe biofacies spectrums and review lithologic and tectonic changes through the Global Taghanic Biocrisis. Within the framework of inferred global warming and aridity for this interval, I investigate watermass circulation models that best explain the combined paleontological and sedimentological observations in the type region.

13 18 In Chapter 4, I reconstruct changes in δ Ccarb and δ Oapatite through this biocrisis for the type region. I compare the record from the type region to records from other regions to recognize global patterns versus local changes. Furthermore, I compare temperature changes inferred from this dataset to faunal changes to investigate the role of warming on latitudinal distribution of faunas.

In Chapter 5, I focus on the paleoecology of the post-biocrisis Genesee Fauna. I expand upon previous investigations by using a more quantitative analytical protocol and a higher- resolution stratigraphic framework, focusing in particular on the nearshore assemblages of the

Genesee Fauna to better understand the post-extinction fauna. Specifically, I reconstruct biofacies for this fauna and investigate its relationship to the pre-biocrisis Hamilton Fauna.

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Group) at Ithaca, New York: A Revised Lithostratigraphy for the Northern Appalachian

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Figure 1: Paleogeographic reconstruction of the globe (A) and study area before (B) and after

represented by ‘star’) that record this biocrisis were deposited approximately 30 degrees south of the paleo-equator. OWR and EAR denote the positions of ‘Old World Realm’ and ‘Eastern

Americas Realm’ faunas, respectively; note the position of the Trans-Continental Arch

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Figure 2: Outcrop belt for the Hamilton, Tully, and Genesee groups in the Appalachian Basin of

New York State. Line labeled ‘a’ represents the position of the shoreline during deposition of the Tully Group. ‘Star’ denotes type locality of the Global Taghanic Biocrisis.

Figure 3: Composite stratigraphic column for Hamilton, Tully, and Genesee groups in the

Appalachian Basin deposits of New York State. Faunas, and representative taxa, are shown for reference. Adapted from (Baird and Brett, 2003) with additional data (Zambito et al., 2009, in press; and Zambito, unpublished data).

Figure 1

Figure 2

Figure 3

Chapter 2

ZAMBITO, J.J., IV, BAIRD, G.C., BRETT, C.E., and BARTHOLOMEW, A.J., 2009, Depositional

Sequences and Paleontology of the Middle – Upper Devonian Transition (Genesee

Group) at Ithaca, New York: A Revised Lithostratigraphy for the Northern Appalachian

Basin; Chapter 3, in Studies in Devonian Stratigraphy: Proceedings of the 2007

International Meeting of the Subcommission on Devonian Stratigraphy and IGCP499,

edited by D. Jeffrey Over: Paleontographica Americana, v. 63, p. 49-69.

James J. Zambito IV1, Gordon C. Baird2, Carlton E. Brett1, and Alexander J. Bartholomew3

1: University of Cincinnati, Dept. of Geology, 500 Geology/Physics Bldg., Cincinnati, OH

45221-0013

2: State University of New York, College at Fredonia, Dept. of Geosciences, Fredonia, NY

14063

3: State University of New York, College at New Paltz, Dept. of Geology, 1 Hawk Dr., Wooster

Science Bldg, New Paltz, NY 12561

Running Title: Genesee Group Stratigraphy at Ithaca, New York

Key Words: Taghanic, Hamilton, Geneseo, Sherburne, Renwick, Ithaca, Genundewa, West

River, Givetian, Frasnian

ABSTRACT

The Genesee Group at Ithaca, New York is a thick succession of predominantly turbiditic siltstones and shales that accumulated at the shelf margin and fore-slope of the Catskill Delta in the northern Appalachian Foreland Basin of New York. Deposition occurred during the transition between the Middle (Givetian) and Late (Frasnian) Devonian, and therefore, its benthic faunas record important stages in the Global Taghanic Biocrisis, one of the great faunal turnovers of the Phanerozoic. The Genesee Group in this area has seen many stratigraphic revisions since the Ithaca Formation (then including parts of the Renwick) was first described over 150 years ago. While past researchers have named stratigraphic units within the Renwick and Ithaca formations, the subdivisions have never been precisely defined and few have been shown to be traceable across the type area around the city of Ithaca at the south end of Cayuga

Lake. A succession of coarsening upward sequences are used to revise the lithostratigraphy of the type Renwick and Ithaca formations; these have been correlated using distinct beds of condensed shell material. The Genesee Group at Ithaca: the Lodi Limestone Member, Renwick

Formation, Cornell Member, Ithaca Formation, Cascadilla Member, Treman Member,

Triphammer Member, and Cayuga Heights Member are revised or proposed, as well as the

Ithaca Falls Limestone Beds, Fall Creek Limestone Beds, University Quarry Sand and Limestone

Beds, Beebe Limestone Beds, Forest Home Sandstone Beds, and the Coy Glen Limestone Bed.

The faunal successions recognized in the strata of the southern Cayuga Lake area are described in relation to the preliminarily placement of the lithostratigraphic framework in a sequence stratigraphic framework. Furthermore, a review of the current state of goniatite and conodont biostratigraphy for the interval studied and outline of possible correlations with the more basinal sections of western New York are presented.

INTRODUCTION

Correlation of the lower Frasnian strata in New York State has been ongoing for over 150 years

(see Kirchgasser, 1985; Kirchgasser et al., 1994, for summary). While recent work has recognized key temporal horizons (e.g., sequence boundaries, condensed sections, and flooding surfaces) in western New York sections, correlation of such horizons into the vicinity of Ithaca,

New York is unfinished (Kirchgasser 2000, Baird et al., 2006). This study focuses on detailed examination of the Ithaca Formation and surrounding strata in its type area, which has not been studied in any detail in over two decades (Kirchgasser, 1985). These strata include fossil-rich calcareous siltstone and shell-rich limestone beds, within sparsely fossiliferous turbiditic successions, that appear to record episodes of siliciclastic sediment starvation associated with both small- and large-scale transgressions. We outline the position of these beds within repeated coarsening upward depositional sequences that form the basis for the lithostratigraphic revision described below and present a preliminary sequence stratigraphic interpretation of these sequences and condensed beds.

Previous studies of the Genesee Group at Ithaca, New York include observations of a variety of coquinitic lenses that were thought to be only local, and therefore could not be correlated between sections (Caster, 1933a,b; deWitt & Colton, 1978; W.H. Hass in Huddle, 1981).

However, recent mapping has revealed numerous previously known and some newly recognized condensed horizons and coarsening upward sedimentary successions that can be traced throughout the study area (Text-figs. 1 and 2). We believe that the variability observed within the marker beds discussed below, associated with shifting depocenters at and near the delta-front, is what led to problems with attempts of earlier workers to produce a high-resolution stratigraphic framework. Our correlations are further supported by stratigraphic stacking order, faunal

19 epiboles, sedimentological characteristics, and general faunal incursions into the study area.

Additionally, we summarize the current goniatite and conodont biostratigraphic framework for the study area; the result being a working hypothesis of high-resolution stratigraphic correlation for the Genesee Group from basinal sections in western New York to the delta-front deposits near Ithaca.

GEOLOGIC SETTING

The Devonian strata of the Appalachian Basin of New York were deposited within a foreland basin that resulted from the Acadian Orogeny; during which oblique convergence occurred between the Laurentian and Avalonian terranes (Ettensohn 1985; Ver Straeten & Brett 1995;

Ettensohn et al., 1988). Erosion of the collisional highlands produced the classic progradational complex known widely as the “Catskill Delta”, which advanced in a generally westward direction and largely filled the foreland basin by the early Carboniferous. This study focuses on the Ithaca Formation, a portion of the delta progradation that followed the third collisional tectophase of the Acadian Orogeny which involved craton-ward emplacement of overthrusts that depressed the lithosphere to deepen the foreland basin (see Ettensohn, 1998).

Following deposition of the Tully Limestone, orogenic activity caused major basin subsidence which was coincident with a global sea level rise (Johnson et al., 1985). This deepening resulted initially in the deposition of the black Geneseo Shale, and its equivalents, over much of the Appalachian Basin, i.e., the Taghanic Onlap of Johnson (1970). Furthermore, these basinal changes and associated global warming may have caused the global Taghanic

Biocrisis, which resulted in the demise of Middle Devonian faunas worldwide (House, 1985;

Becker & House, 2000; Aboussalam et al., 2001; Aboussalam, 2003). Interestingly, some elements of this Middle Devonian fauna returned anachronistically to the Appalachian Basin

during deposition of the Ithaca Formation, and subsequently, in younger strata (Williams, 1913).

During the time of deposition of the Geneseo Shale, offshore portions of the foreland basin were

for the most part devoid of benthos, except for organisms adapted to a dysoxic sea floor, such as

the rhynchonellid brachiopods Camarotoechia (Hall and Clarke, 1894) and Leiorhynchus (Hall,

1860, p. 75; Hall and Clarke, 1894), rare chonetid brachiopods, and the bivalves Pterochaenia

sp. (Clarke, 1904) and Buchiola sp. (Barrande, 1881). The stratified water column was

punctuated episodically by times of slightly better bottom-water conditions, resulting in the

deposition of the Fir Tree and Lodi limestones and their associated faunas, including the

brachiopods Pseudoatrypa devoniana (Webster, 1921), Ambocoelia umbonata (Conrad, 1842),

and assorted chonetids (Baird et al., 1988). During and following this interval, progradation of

the Catskill Delta resulted in the deposition of the coarser-grained Sherburne and Ithaca formations. Between the time of deposition of the Sherburne and Ithaca formations, which are primarily comprised of turbiditic sequences, another sea-level deepening resulted in the deposition of the black Renwick Shale. It is during the shallowing phase following this sea level rise associated with the basal Renwick Shale transgression that the ‘recurrent Hamilton Fauna’ comprised of many Middle Devonian forms (Williams, 1884, 1913) is first observed.

METHODS

We obtained a high-resolution stratigraphic framework for the Genesee Group in the vicinity of Ithaca, New York, by examining in detail eight fairly continuous sections, as well as many smaller sections, around the southern edge of Cayuga Lake within an area of approximately 50 square kilometers (18 square miles; Text-fig. 2). All sections are located on the Ithaca East and

Ithaca West 7.5 minute USGS quadrangles. The sections were measured bed-by-bed with tape measure and hand level. In particular, we focused on the documentation of relatively condensed,

fossiliferous beds that occur within the otherwise sparsely fossiliferous, turbiditic strata of the

Genesee Group (Text-fig. 3). Correlations between sections were largely based on the

recognition that each section contains a series of widely spaced shell beds that contain

taphonomic and compositional characteristics that act as distinguishing fingerprints, allowing

correlation. Our correlations were tested by relative stacking order, detailed pattern matching,

and faunal epiboles (cf. Brett et al., 2003).

Within this stratigraphic framework we then recognized a series of coarsening-upward successions that we used to define stratigraphic subdivisions within the Renwick and Ithaca formations (Text-fig. 2); additional sections are represented graphically in Zambito et al. (2007).

The coarsening upward successions observed typically proceed from silty shale, to interbedded silty shale and siltstones, to stacked siltstones, and finally to large-scale, channelized, silt and sandstones (Text-fig. 3). We place the boundary between members at the top of the youngest sandstone channel, or, at the erosional base of the overlying condensed shell bed when the coarsening succession is truncated. We also designate reference sections that help to fully encompass the lithological heterogeneity observed in the study area. The stratigraphic nomenclature of the Renwick and Ithaca formations has a long and varied history (Text-fig. 1).

Whenever possible we attempt to use the first name given to a stratigraphic unit, synonymize the names used by past researchers, and redefine names proposed in the past that have overlapping boundaries. Finally, we tentatively placed our stratigraphic framework within a generalized sequence stratigraphic model, allowing us to discuss the relationships between sedimentary successions and faunal change to relative sea level.

GENESEE GROUP STRATIGRAPHY IN THE STUDY AREA

BACKGROUND

Correlation of the thin, basinal deposits of western New York into the eastward-thickening and coarsening delta-front succession around Cayuga Lake has long been plagued by a variety of factors, including: misunderstanding of intertonguing facies relationships, under-estimation of the rate of stratal thickening and within-bed lithological variation, and biostratigraphic misidentifications (see discussions in Williams, 1951; Kirchgasser 1985; and Zambito et al.,

2007 for a complete summary and previous stratigraphic schemes; also, Text-fig. 1).

The rocks exposed in the vicinity of Ithaca, New York were initially described by Hall (1839,

1843) and given the name Ithaca Group (Vanuxem 1840, 1842). These strata were placed in various ways within the Portage and Chemung groups of older stratigraphic terminology during this time (see Prosser, 1897; Rickard, 1964, 1975). Clarke (1898) also summarized these early works. The first detailed bed-scale litho- and biostratigraphic work on the Ithaca Formation was carried out by H.S. Williams (1881, 1884, 1906, 1913), Williams et al. (1909), and Kindle (1896,

1906). Examination of the Ithaca strata by the present authors has not only confirmed, but also reinforced the importance of the work of H.S. Williams and E.M. Kindle. Chadwick (1933,

1935) was the first to realize that the Genesee, Portage, and Chemung units were better described as time-transgressive facies belts rather than unique periods of time and that their spatial relationships represent an offshore to onshore gradient (Genesee to Portage to Chemung facies).

Around this same time, Caster (1933a, 1933b) focused on Ithaca area sections and attempted to divide the Ithaca Formation into traceable units. However, he apparently disregarded a number of the stratigraphic terms and correlations of previous workers, specifically those of H.S.

Williams and E.M. Kindle. Subsequently, G.Q. Williams (1951) expanded upon Caster’s work,

23 adding the greatly needed type localities and graphic sections. Next, the tracing of the

Middlesex and Rhinestreet black shales into the area of Cayuga Lake by Sutton (1959, 1963),

Sutton et al., (1962), deWitt and Colton (1959, 1978), and finally, Rickard (1964, 1975, 1981) placed both the Sherburne, Renwick, and Ithaca formations within the Genesee Group; previously these formations were correlated with much younger strata in the western, more basinal deposits.

The process of building a high-resolution biostratigraphic framework for the basinal through pro-delta deposits of the Genesee Group was begun with the documentation and revision of

Genesee Group goniatites by House (1962), Kirchgasser & House (1981), Kirchgasser (1985,

2000), and House & Kirchgasser (1993, 2008), and also conodonts (see below). For the goniatites, identification of the “Linden Horizon” and the ammonoid Koenenites styliophilus styliophilus (Clarke, 1898) in the Cayuga Lake succession provided a datum from which other marker beds of the western succession could be located in the Cayuga Valley (Kirchgasser,

1985). Subsequently, high-resolution lithostratigraphic correlation was undertaken when Baird et al. (1988) traced the Fir Tree and Lodi horizons from the west into the vicinity of Cayuga Lake and beyond. Huddle (1981) attempted biostratigraphic correlation of the Genesee Group using conodonts, but his efforts were focused mostly in western New York and likely need some taxonomic revision in order to be applied to the more recent zonations provided by Klapper &

Johnson (1990, also, see references therein; Kralick, 1994). Kirchgasser (1994) and Over et al.

(2003) have expanded on this conodont work, but mostly in sections west of the current field area.

STRATIGRAPHY OF THE GENESEO AND SHERBURNE FORMATIONS

The lowermost Genesee Group strata in the study area are the Geneseo and Sherburne formations

(Text-figs. 1 and 2). The Geneseo Formation is a black shale that was deposited under dysoxic conditions as part of the Taghanic Onlap event representing a substantial eustatic sea level rise

(Johnson, 1970; Baird & Brett, 2003, 2008). Brief excursions of more oxic conditions, associated with shallowing and subsequent siliciclastic starvation during relative sea level rise, resulted in the deposition of the auloporid-rich Fir Tree and Lodi Limestone submembers (Baird et al.,

1988). From Seneca Lake eastward, the upper portion of the Geneseo Formation and the gray shales of the Penn Yan Formation, including the Fir Tree and Lodi Limestone intervals, begin to interfinger with the turbiditic siltstones facies of the Sherburne Formation (Vanuxem 1840,

1842; Boekenkamp, 1963), and in the vicinity of Ithaca, the Penn Yan Formation has completely lost its identity in the siltstone facies of the Sherburne Formation (Baird et al., 1988). de Witt and

Colton (1959) designated the exposures at Glenwood Creek on the western side of Cayuga Lake north of Ithaca as a reference section for the Sherburne Formation.

We further designate the succession at the southern gully of Twin Glens as a reference section for the Sherburne Formation, where this formation attains a total thickness of approximately 37 meters, with the lowest 4.5 meters correlating to the Lodi Limestone submember of northern and western sections and herein elevated to the stratigraphic level of

“member” in the immediate study area (Text-fig. 2). We designate the base of the Lodi

Limestone Member as the sharp contact of fossiliferous siltstone with the underlying unfossiliferous turbiditic-facies of the Hubbard Quarry submember of Baird et al. (1988). The lowest traceable marker bed above the Lodi Limestone Member is the Cornell Member of the basal Renwick Formation, the sharp base of which marks the uppermost boundary of the

Sherburne Formation in the study area. In the study area the Sherburne Formation above the

Lodi Limestone Member generally coarsens upward from interbedded shales and turbiditic

siltstones to more densely packed siltstones. The siltstone beds are thin- to thick bedded.

Commonly structure-less, and rarely, internally planar-laminated to rippled at their top. The siltstone beds have scoured bases with tool-marks, and somewhat gradational tops.

Kindle (1896) reports the following fossils from the interval of the Lodi Limestone Member: the brachiopods Ambocoelia umbonata, Schuchertella chemungensis (Conrad, 1842),

Sinochonetes lepidus (Hall, 1867), the bivalves Glyptocardia speciosa (Hall, 1843), Nuculites oblongatus (Conrad 1841), Paleoneilo constricta (Conrad, 1842), P. filosa (Conrad, 1842),

Pterochaenia fragilis, the gastropod Glyptotomaria (Dictyotomaria) (Knight, 1945; Rollins et al., 1971) sp., auloporid corals, and crinoid ossicles. Though unconfirmed by the present authors, Kindle (1896, 1906) also reports the presence of Warrenella laevis (Hall, 1843) either slightly above or in the uppermost part of the Lodi Limestone Member.

STRATIGRAPHY OF THE RENWICK FORMATION

The Renwick Member of the Ithaca Stage was originally proposed by Caster (1933a) in an

abstract and discussed in a fieldtrip guidebook (1933b), but no specific type locality was selected

(Text-fig. 1). Synonymous with Caster’s Renwick is the “Ithaca Lingula Shale” of Williams

(1906), the “Lingula complanatum Zone” of Williams et al. (1909), and the zone of channel fillings described by Williams (1881). G.Q. Williams (1951) described its thickness at about 30 m, but gave only an arbitrary lithological upper boundary. Boekenkamp (1963) cited a much lower thickness of this unit in his description of the strata in the Ithaca area, but his definition of the unit was not followed by later workers. Sutton et al. (1962) included the Renwick in his

Ithaca. A type section was later designated for the exposures along Renwick Brook, to the

26 northeast of Ithaca (deWitt & Colton 1959, 1978). In doing so, deWitt and Colton (1959, 1978) also removed the Renwick from the Ithaca, giving it ‘equal’ stratigraphic status (Text-fig. 1).

As a lower boundary for the Renwick, Williams (1951) used the top of the “Warrenella (also called Spirifer laevis or Reticularia laevis) Zone” of Williams (1884), Kindle (1896, 1906), and

Williams et al. (1909). Prior to G.Q. Williams (1951), but subsequent to the work of H.S.

Williams, Kindle, and Caster, this zone was formally named the Cornell Member by Smith

(1935), who suggested for it equal stratigraphic rank to the Sherburne and Ithaca (Text-fig. 1).

The type section is Fall Creek in Ithaca, downstream of the Cornell University campus at the base of Ithaca Falls at approximately 400 feet above sea level. The Cornell Member consists of approximately 5 meters of dark silty shale and interbedded siltstones that sit sharply upon the unfossiliferous turbiditic facies of the underlying Sherburne Formation. Because of its lithological and paleontological similarity to the overlying Renwick Formation, we assign the

Cornell Member to the lowest portion of the herein revised Renwick Formation. We also designate the exposures in the southern gully of Twin Glens as a reference section. We interpret the Cornell Member to represent a transgressive facies relative to the underlying, progradational siltstones and shales of the Sherburne Formation. The occurrence of a rather diverse and more aerobic fauna within the Cornell Member compared to the overlying Lingula-rich shales also supports this interpretation.

The fauna of the Cornell member includes: the brachiopods Warrenella laevis,

Camarotoechia mesacostales (Hall, 1843, 1867), Cyrtina hamiltonensis (Hall, 1867),

Sinochonetes lepidus, the bivalves Glyptocardia speciosa, Lunulicardium ornatum (Hall, 1843),

Pterochaenia fragilis, Paleoneilo filosa, P. constricta, Pseudoaviculopecten sp. (Newell, 1938),

Modiomorpha subalata (Conrad, 1841), Grammysioidea subarcuata (Hall, 1883, 1884),

Nuculoidea corbuliformis (Hall, 1883, 1885), the gastropod Glyptotomaria capillaria, the crinoid

Eutaxocrinus ithacensis (Williams, 1882), the goniatite Ponticeras perlatum (Hall, 1874), the hydrocoral Plumalina plumaria (Hall, 1858), and orthocones; plant and wood fragments are also present (see Williams, 1884, and Kindle,1896, for a more complete species list). Warrenella laevis is an immigrant brachiopod from the Old World Realm fauna of western North America that entered the Appalachian Basin at or before the time of deposition of the Lodi Limestone based on the observations of Kindle (1906). A reasonable hypothesis is that Warrenella laevis first entered the Appalachian Basin during the Taghanic Onlap of Johnson (1970); this would be the West Brook Coral Bed and overlying deposits of Baird and Brett (2003, 2008).

Renwick Formation strata overlying the Cornell member represent a coarsening upward succession. The Cornell Member is overlain by an interval of Lingula-rich shales and siltstone channel fillings previously described by Williams (1881, 1906) that ranges in thickness from 15 to 30 meters. These channel fillings are lenticular silt to fine-grained sand channels with scoured bases within the surrounding dark gray silty shale. These deposits are interpreted as forming in response to a decrease in the rate of sea-level rise and corresponding progradation of coarser sediment. The fauna of this interval includes various forms of the inarticulate brachiopod

Lingula, as well as the articulate brachiopods Truncalosia truncata (Hall 1867), Cupularostrum eximum (Hall, 1867), Camarotoechia mesacostalis, Productella speciosa (Hall, 1867), the bivalves Pterochaenia fragilis, Glyptocardia speciosa, and the gastropods Glyptotomaria

(Dictyotomaria) capillaria and Paleozygopleura delphicola (Hall, 1897) (see also Williams,

1884).

Above the interval of channel fillings the succession continues to coarsen upward and the

‘recurrent Hamilton Fauna’ as described by Williams (1884, 1913) is observed. This interval

consists of interbedded pyritic silty shale and siltstones and, when present, by meter-scale silt

and sandstone channel deposits and ranges in thickness from 3 to 12 meters. Siltstone beds have

similar characteristics to those described for the Sherburne Formation. The top of the Renwick

was originally defined as the contact with the Sixmile Creek Member of Caster (1933a),

however, this name was not used in Caster (1933b) or subsequently by other researchers.

Williams (1951), deWitt and Colton (1978), and Grasso et al. (1986) recognized the upper

boundary of the Renwick arbitrarily at the top of the youngest siltstone-filled channel in the

sequence of dark shale and intercalated siltstone that composes the Renwick, by. We place the

top of the Renwick Formation stratigraphically higher, at the top of the coarsening upward

succession, which sometimes occurs at the erosional base of the Ithaca Falls Limestone Beds

(Text-figs. 1 and 2), and formally abandon any use of the name Sixmile Creek Member for the

Ithaca Formation. Within the Ithaca area, the Renwick Formation as defined herein varies in thickness from 30 to 45 m. Our study of the section at Renwick Brook failed to locate the Ithaca

Falls Limestone Beds with confidence. This bed is observed to ‘pinch and swell’ within outcrop from 0 to 34 cm at other localities, which may be the reason it has not been located yet at

Renwick Brook. We designate as reference sections the successions exposed at Twin Glens, Fall

Creek, and Cascadilla Creek.

The ‘recurrent Hamilton Fauna’ of the uppermost Renwick Formation is similar to the

‘Lingula’ shales below, but with the addition of the brachiopods Ambocoelia umbonata, Elyta

fimbriata (Conrad, 1842), “Mediospirifer” angusta (Hall, 1867), Tylothyris mesacostales (Hall,

1843), Tropidoleptus carinatus (Conrad, 1839), Rhipidomella vanuxemi (Hall, 1867), and the

trilobite Eldredgeops rana (Green, 1832) (formerly Phacops rana; Williams 1884, 1913; Kindle

1896; Zambito et al., 2007). Although more work is necessary, this may be interpreted as a

slightly more aerobic version of the fauna of the Lingula-rich shales and both faunas may be

considered ‘Hamilton-like’. Faunal lists from the literature, and our preliminary paleoecological

data suggest that the ‘recurrent Hamilton fauna’ are generalistic forms that survived the Taghanic

Biocrisis, and subsequently became intermixed within the Upper Devonian biofacies spectrum

that first occurs in the Northern Appalachian Basin following the Taghanic Onlap (Williams,

1884; Kindle, 1896; Prosser, 1897; Clarke, 1898; and Thayer, 1974).

STRATIGRAPHY OF THE ITHACA FORMATION

The type section for the Ithaca Formation was designated by deWitt and Colton (1959) at Coy

Glen, south of Ithaca, for the strata between the Renwick and West River formations. We

restrict the Ithaca Formation to the strata between the Renwick Formation and the newly

described Forest Home Sandstone Beds (see below; Text-figs. 1 and 2), reducing the Ithaca

Formation by approximately 40 meters at Coy Glen; by doing so, giving the Ithaca Formation a more discrete upper boundary. We designate the following as reference sections: Fall Creek,

Williams Brook, and the NY Rte. 13 roadcuts at Cayuga Heights. In general, the Ithaca

Formation comprises four, coarsening upward sedimentary successions that can be correlated around the study area. Each succession includes silty shales, turbiditic siltstones, and channelized sandstone beds.

Cascadilla Member

The name Cascadilla was proposed by Caster (1933a, 1933b) presumably for the exposures

along Cascadilla Creek, but no boundaries for this unit or a type section were specified. G.Q.

Williams (1951) subsequently defined this unit from the top of his Renwick to a level above

Caster’s Williams Brook Limestone at Williams Brook. Synonymous units include, in part, the

“Paracyclas lirata Zone” of Williams et al. (1909; Text-fig. 1). The Cascadilla Member as

30 revised herein commences with the top of the coarsening upward sequence of the Renwick

Formation, or in some cases, at the erosional base of the newly described Ithaca Falls Limestone

Beds. The youngest bed of this coarsening upward succession or in some cases the erosional base of the Fall Creek Limestone Beds marks the upper boundary (Text-fig. 2). The type section is designated at Cascadilla Creek, between Linn Street and College Avenue, with reference sections designated at Twin Glens, Fall Creek, and Coy Glen. The Cascadilla Member ranges in thickness from 15 to 25 meters.

The Ithaca Falls Limestone Beds are best developed in the cliff face at the level of the tunnel associated with the old Ithaca Gun Factory above the lip of Ithaca Falls, for which they are named, as well as in the reference sections of the southern gully of Twin Glens, and at Coy Glen.

These beds are typically a composite of fossil hash lenses with a sharp erosional base, cross- bedding, and are sometimes interbedded with siltstones. These beds can be observed in outcrop

(Coy Glen) to pinch-and-swell from 0 to 34 cm. At Cascadilla Creek, the Ithaca Falls Limestone

Beds are apparently less than 1 cm thick. The fauna of these beds is dominated by the bivalve

Paleoneilo sp., and nuculid clams, the bryozoan Sulcoretopera cf. incisurata (Hall and Simpson,

1887), the brachiopods T. mesacostalis, C. hamiltonensis, the gastropod Glyptotomaria

(Dictyotomaria) capillaria, and abundant crinoid material, and commonly yields undeformed clams and gastropods that have calcite replaced shells. The overlying portions of the Cascadilla member contain interbedded silty shales and turbiditic siltstones coarsening upward to more abundant siltstones and channelized silt and sandstones, and contains a similar ‘recurrent

Hamilton Fauna’ to that observed in the underlying Renwick Formation.

Treman Member

The interval herein named the Treman Member was originally proposed for all strata between the

Renwick and Middlesex of Sutton et al. (1962), which included the Cascadilla and Triphammer of Caster (1933b) and Williams (1951). In an attempt to simplify the stratigraphic nomenclature of the study area, we revise the Treman Member to consist of the coarsening upward sequence between the Cascadilla and Triphammer Members (Text-figs. 1 and 2). The Treman Member is therefore delineated at its lower boundary by the top of the Cascadilla Member sequence and has as its top the youngest bed in its coarsening upward sequence, or in some cases the erosional base of the University Quarry Sand and Limestone Beds of the Triphammer Member (Text-figs.

1 and 2). The original type section for the Treman Member was designated by Sutton et al.

(1962) as the exposures along Buttermilk Creek, south of Ithaca. Though we have not examined this section in detail, local stratal dip, as well as graphic sections in Williams (1951) and data from deWitt and Colton (1978) suggest that this interval is exposed there. Furthermore, we designate the successions exposed at NY Rte. 13 at Cayuga Heights, Fall Creek, Coy Glen, and

Cascadilla Creek as reference sections.

Near or at the base of the Treman Member is the Fall Creek Limestone, named for exposure capping the waterfall immediately downstream of the suspension bridge and the Cornell Power

Plant at Fall Creek. This bed is also well developed at Coy Glen, as a series of closely-spaced fossiliferous, calcareous siltstone lenses comprised almost entirely of fossils of Cupularostrum eximum and ranging in thickness from 30 cm to up to 2 meters in the study area. This condensed unit was previously recognized by Williams (1884, station No. 37), Kindle (1896, sample 3), and

Kirchgasser (1985). These beds can be traced to slightly below the strata on which the Power

Plant foundation is built. The succession of the Treman Member is similar to that of the

Cascadilla Member: silty shales with a few interbedded siltstones coarsen upward to more

abundant siltstones, which are overlain by packages of lenticular siltstones and sandstones. Fossil

assemblages of the Treman Member are also similar to those below, with the addition of the

brachiopods Cranaena eudora (Hall, 1867), and Orthospirifer mesastrialis (Hall, 1843), and the

pyritization of the bryozoan Sulcoretopera cf. incisurata (Hall and Simpson, 1887), particularly

in the coarsest deposits. The Treman Member ranges locally in thickness from 8 to 17 meters.

Triphammer Member

The name Triphammer Member was first introduced by Caster (1933a, 1933b) presumably for

exposures at Triphammer Falls, below Beebe Lake, on Fall Creek, yet no upper or lower bounds

were specified. G.Q. Williams (1951) placed this interval from a level above the Williams Brook

Limestone of Caster (1933a) to the base of the Enfield Formation; an older stratigraphic name

that included units presently assigned to the Ithaca and West River formations, as well as the

Middlesex Formation and even higher portions of the Sonyea Group (Text-fig. 1). The

Triphammer Member is the most studied and referred to unit in the Ithaca Formation and has the most varied nomenclature. The unit records the first incursion of the ‘Ithaca Fauna’ (Williams,

1884) into the area of study.

Herein the lower boundary of the Triphammer Member is designated as the top of the coarsening upward sequence of the Treman Sequence, or, in most cases, with the erosional base of the revised University Quarry Sand and Limestone Beds, an interval first described by

Williams (1884) (Text-figs. 1 and 2). Synonymous with the upper, typically sandier portion of the University Quarry Beds is Caster’s (1933a) “Marathon Sandstone”, apparently named for the strata quarried near Marathon, east of Ithaca, and the ‘Spirifer mesastrialis Zone’ and the

‘mesastrialis sands’ of Williams et al. (1909) and Williams (1913), respectively. This interval

was so named because it was formerly quarried by Cornell University for building stone (circa

1890); the former quarry, long since filled, is thought to have been along the edge of the Fall

Creek Gorge near Stewart Avenue (Williams et al., 1909; W.T. Kirchgasser, pers. comm., 2006).

The term “Firestone Beds” was applied by Kirchgasser (1985, figure 5), for an interval in the

lower portion of the University Quarry Sand and Limestone Beds that is more fossiliferous, and

therefore more calcareous, than the rest of the unit. This term was used informally by Williams

(1884) and Kindle (1896) to describe these beds and others like them, in which the high

carbonate content rendered the rock resistant to breakage during heating.

As described above, the uppermost, coarsest intervals of the Treman Member were likely also quarried, but we herein restrict the University Quarry Beds to the interval above the channelized sandstone lenses, in which more planar-bedded sandstones and fossiliferous and pyritic, sandy pack- and grainstones are present, i.e., the “Firestone Beds” and the ‘mesastrialis

sands’. In some sections there is an intervening, approximately .5 meter thick package of silty

shale showing pseudo-hummocky cross-bedding between the channelized lenses of the Treman

Member and the “Firestone Beds”, as is seen at the NY Rte. 13 roadcut at the Cayuga Heights cloverleaf; but more commonly, the erosional base of the “Firestone Beds” of the Triphammer

Member sits directly on the channelized sandstone beds of the Treman Member.

Williams et al. (1909) also identified the interval of the University Quarry Sand and

Limestone Beds at: 1)Fall Creek (behind the Cornell University Power Plant); 2) at Cascadilla

Creek approximately half-way up the gorge; and, among other places, 3) at Williams Brook between 600 and 650 feet elevation and therefore synonymous with Caster’s Williams Brook

Limestone. This is but one example of the recognition by H.S. Williams and E.M. Kindle that the fossiliferous units within the Ithaca Formation are indeed traceable in the area.

The “Firestone Beds” at the old University Quarry and equivalents on South Hill, Ithaca are the source of the goniatite Chutoceras nundaium (Hall, 1874), a form previously referred to as

Ponticeras cf. regale (Holzapfel, 1899; Kirchgasser & House, 1981; House & Kirchgasser,

1993) and misidentified by Hall as Manticoceras (Goniatites) sinuosum (Hall, 1843) of the post-

Genesee Sonyea Group (Kirchgasser, 1985). Kirchgasser (1985; see also Kirchgasser & House,

1981) also identified the “Linden Horizon” near the top of the interval herein referred to as the

University Quarry Sand and Limestone Beds. This horizon is recognized as a sharp contact at the top of a black shale, a flooding surface on which the goniatite Koenenites styliophilus styliophilus is abundant. This goniatite marker bed can be correlated westward from Cayuga

Lake to its type section in the Penn Yan Shale at Linden, NY, Genesee County. At its westernmost localities, the “Linden Horizon” is a condensed bed of styliolinid limestone with the goniatite Koenenites styliophilus styliophilus; it splays eastward across the Wyoming Valley-

Honeoye Valley region into a thicker bundle of thin limestone beds yielding Styliolina fissurella

(Hall, 1843) and Koenenites.

Following on the work of Kirchgasser, Baird et al. (2006) mapped the Genesee Group in the area surrounding Linden, NY, and their observations suggest the possibility that Kirchgasser’s

(1985) “Linden Horizon” on Fall Creek may correspond to the erosive/corrosive flooding surface discontinuity that both caps and oversteps the condensed “Linden Horizon” in the type Linden area (Kirchgasser and House, 1981; Kirchgasser, 1985). Given that the “Linden Horizon” has been observed to thicken eastward (Baird et al., 2006), it appears likely that the University

Quarry Beds, including the “Firestone Beds” succession, may be a greatly thickened eastern equivalent of the “Linden Goniatite Horizon”. A goniatite specimen found within the Caster collections at the University of Cincinnati has been identified as Koenenites styliophilus

35 styliophilus (W.T. Kirchgasser, pers. comm., 2007). This specimen was labeled as “cascade at

Power House Falls,” which would place it below Kirchgasser’s “Linden Horizon” on Fall Creek, further substantiating the possibility that Koenenites entered the succession during the time represented by the initial transgressive “Firestone Beds” interval of the University Quarry Beds, and was concentrated at the sediment-starved flooding surface lag represented by the “Linden

Horizon”. The Chutoceras horizon in the “Firestone Beds” is believed to pre-date the levels with

Koenenites styliophilus styliophilus.

While the entire transgressive interval (“Firestone Beds” and “Linden Horizon”) is included within the University Quarry Beds, we find it useful to keep both of these names as mappable, informal marker units. This is particularly important in westernmost New York, where styliolinid- and Koenenites- bearing grainstone nodules are reworked on a corrosional discontinuity surface of the Linden Horizon at all localities west of Murder Creek (Baird et al.,

2006). These clasts of styliolinid grainstone may be correlative with the “Firestone Beds” in the

Cayuga Lake section. Conversely, in eastern sections near Ithaca, the “Firestone Beds” appear to be more easily mapped than the “Linden Horizon” (Zambito et al., 2007). Furthermore, although the Williams Brook Limestone, which correlates with the “Firestone Beds” interval of the

University Quarry Sand and Limestone Beds, is an impressive- three-plus meter thick shell-rich encrinite that shows internal channelization and cross-bedding, it is atypical compared to all other area sections. The Williams Brook Limestone is retained herein as an informal name to represent this facies of the “Firestone Beds” at Williams Brook. Typically, the “Firestone Beds” interval of the University Quarry submember is comprised of a complex of up to 4 meters of fossil-rich sandstones and pack- and grainstone lenses, commonly containing rip-up clasts and phosphatic pebbles reworked from underlying horizons. With inclusion of the “Linden

Horizon”, the University Quarry Beds reaches a thickness of up to almost 9 meters. The succession beginning at the base of the Cornell University Power Plant to above the power plant cascade is designated the principle reference section for the University Quarry Sand and

Limestone Beds (see Kirchgasser, 1985, figure 5).

The upper boundary of the type Triphammer Member is placed at the top of the coarsening upward sequence observed in the face of Triphammer Falls on Fall Creek and in the inlet gorge to Beebe Lake on Fall Creek for which we designate the type section. In some cases, the upper boundary for the Triphammer Member can be found at the erosional base of the next higher condensed bed, the Beebe Limestone Beds of Caster (1933a,b) and deWitt and Colton (1978)

(Text-fig. 2). Reference sections include the roadcut at the NY Rte. 13 cloverleaf at Cayuga

Heights and Williams Brook. The thickness of the Triphammer Member, as described herein, varies greatly, from about 10 to 40 meters. The strata of the Triphammer Member are thickest to the southeast of the study area (Text-fig. 2), which agrees with deWitt and Colton (1978) and indicates that the source of sediment was from that direction. This may suggest locally shifting depocenters, but more likely is attributable to the abrupt shallowing and influx of sandy sediment into the study area during and just prior to the deposition of the University Quarry Beds. In general, this succession coarsens upward from the “Linden Horizon” to silty shales and interbedded siltstones and silty shales, to heavier-bedded siltstones, and eventually silt and sandstone channel deposits.

The University Quarry interval marks the appearance of the ‘Ithaca Fauna’ as defined by

Williams (1884) in this succession, characterized by the first occurrence of the brachiopods

Schizophoria impressa (Hall, 1843), Pseudoatrypa devoniana, Spinatrypa cf. hystrix (Hall,

1843), Nervostrophia nervosa (Hall, 1843), “Pugnoides” pugnus (Martin, 1809), Douvillina

cayuta (Hall, 1867), the bivalves Eoschizodus chemungensis (Conrad, 1842), Pterinopecten

erectus (Hall, 1884), zaphrentid corals (Heterophrentis cf. simplex (Hall, 1876)), and the

gastropod Platyceras sp. (Conrad, 1840) (Williams, 1884; Kindle, 1896). ‘Ithaca Fauna’ forms

first seen below the University Quarry Beds, such as Orthospirifer mesastrialis, Cranaena

eudora, Productella speciosa, Plumalina plumaria and Tylothyris mesacostales, can be found

throughout, and in most cases range above the University Quarry Beds. Some aspects of the

‘recurrent Hamilton fauna’ also continue through the University Quarry interval from below,

including the gastropods Glyptotomaria (Dictyotomaria) capillaria and Paleozygopleura

delphicola, and the bivalves Cypricardella bellistriata (Conrad, 1842) and Modiomorpha

subalata (Conrad, 1841), the brachiopod Cyrtina hamiltonensis, and auloporid corals. Oddly, the

brachiopod Strophodonta demissa (Conrad, 1842) is found within the University Quarry interval.

This long-ranging taxon occurs in rocks as old as the Lower Devonian Schoharie Formation and prior to its appearance in the University Quarry Beds, is last observed in the Appalachian Basin

of New York in the uppermost Hamilton Group Windom Shale, where it is exceedingly rare.

Cayuga Heights Member

The Cayuga Heights Member, so named for exposures along the Cayuga Heights cloverleaf

interchange of NY Rte. 13 and Cayuga Heights Road to the northeast of Ithaca, is a relatively

thin sequence of condensed, fossiliferous strata through silty shales, to thick-bedded siltstones

and sandstones. Fall Creek and Williams Brook serve as reference localities. The base of this

unit is the top of the coarsening upward Triphammer Sequence, or in some cases the erosional

base of the Beebe Limestone Beds of Caster (1933a, 1933b), which has been correlated across

the study area (Text-fig. 2). Like the University Quarry Beds, the Beebe Limestone Beds also

display dramatic thickness (20 cm to 1 meter) and lithological variation over small geographic

38 distances (Zambito et al., 2007, figure 3)). Caster probably meant for exposures at Beebe Lake, along Fall Creek, to serve as the type locality.

The Beebe Limestone Beds were not located by Williams (1951) in his study of the type

Ithaca Formation. deWitt and Colton (1978) describe the Beebe Limestone Beds as occurring in the cliffs of Fall Creek west of Beebe Lake. Huddle (1981) describes the bed as occurring in the top of the Fall Creek Gorge near the Thurston Avenue bridge as well as in float blocks at the bottom of the gorge. The present authors have located the float blocks, but have been unable to locate the Beebe Limestone Beds in place west of Beebe Lake. The base of the Thurston Avenue bridge is currently inaccessible due to ongoing construction, but its elevation is where the Beebe

Limestone Beds would project based on observation of the horizon upstream from the bridge.

We have located what we understand to be the Beebe Limestone in situ on the northeast side of the inlet gorge to Beebe Lake, and designate this as the type section. While the float pieces within the gorge are a dense coquina with reworked phosphate pebbles and rip-up clasts, the

Beebe Limestone Beds on the northeast side of Beebe Lake is a fossiliferous calcisiltite. We have observed both lithofacies, as well as intermediates, at similar stratigraphic levels throughout the study area (Zambito et al., 2007). The Cayuga Heights Member, approximately 5 to 7 meters thick, has as its upper boundary the top of its coarsening upward sequence, or in some cases the erosional base of the Forest Home Sandstone Beds; this boundary also marks the top of the

Ithaca Formation as defined in this study (Text-fig. 2). The Beebe Limestone Beds contain an

‘Ithaca fauna’ similar to that of the University Quarry Beds, and is observed to be the last occurrence of Orthospirifer mesastrialis in the study area. This is the ‘recurrent Ithaca fauna’ of

Caster (1933b) (Text-fig. 1).

STRATIGRAPHY OF THE UN-NAMED UNIT

The depositional sequence overlying the Ithaca Formation is currently left un-named. This sequence is underlain by strata containing the Ithaca Fauna (Cayuga Heights Member), and overlain by strata that faunally can be placed within the West River Formation. Furthermore, based on the biostratigraphic information and the comparison to western sections presented below this interval, or part of it, is likely a correlative for the Genundewa Formation of western sections. The lower boundary of this sequence is the top of the Ithaca Formation as described above.

The type section of the Forest Home Sandstone Beds is the exposure on Fall Creek upstream of the Caldwell Road Bridge in Forest Home. These beds have been located at Coy Glen and at approximately 10 meters above the Williams Brook Limestone of the University Quarry Beds at

Williams Brook; these are designated as reference sections. This interval consists of thin- to thick-bedded fossiliferous siltstones and sandstones, with a thickness of up to 8 m. Based on observations at Fall Creek and Williams Brook (Text-fig. 2), what we herein name the Forest

Home Sandstone Beds may contain several smaller cycles. The succession above these beds coarsens upward from silty shales to fine-grained sandstone channel lenses; the upper boundary of the un-named unit is the top of the coarsening upward sequence. The only complete section measured in this study is at Coy Glen, where the Un-named unit reaches a thickness of approximately 30 meters.

The fauna of this bed is composed of the brachiopods Pseudoatrypa devoniana, Schizophoria impressa, Schuchertella chemungensis, the Hamilton-form Mucrospirifer mucronatus (Conrad,

1841), Tylothyris mesacostalis, large productids, and auloporid corals. The Forest Home

Sandstone Beds also contain abundant Melocrinus sp. (Goldfuss, 1826) and small crinoid

ossicles. Although not observed by the present authors, Kindle (1896) reports Warrenella laevis from near this horizon at Fall Creek.

STRATIGRAPHY OF THE WEST RIVER FORMATION

At Coy Glen, there is a 0-25 cm thick, channelized, crinoid- and brachiopod-rich grainstone,

which is likely the equivalent of deWitt and Colton’s horizon 6791-SD (1978, plate 3; Huddle,

1981). We herein name this the Coy Glen Limestone Bed. Commonly observed fossils include

Spinatrypa sp., diminutive spiriferids, chonetids, and productid brachiopods. A sandy, spiriferid

shell hash bed is found approximately 5 meters higher on Coy Glen and may possibly represent

an overlying small-scale depositional cycle. Similar condensed intervals have also been observed

near this level at Williams Brook (Text-fig. 2). Above the Coy Glen Limestone Bed, the

succession is lithologically and faunally distinct from any of the Ithaca strata already described.

Foremost, the succession is observed to be sparsely fossiliferous compared to the underlying

Ithaca Formation. Typical fossils present include Lingula sp. (Brugiuére, 1791), Ambocoelia

umbonata, Paleoneilo sp. (Hall, 1870), Buchiola sp., Pterochaenia sp., and Leptodesma sp.

(Hall, 1883, 1884), which we interpret as a deeper water fauna than the Ithaca (Williams et al.,

1909). These strata are comprised of irregularly alternating packages of gray shale, black shale,

and wave-marked or soft-sediment deformed siltstones. The Locality/Horizon I-3/1 of

Kirchgasser and House (1981) occurs approximately 15 m above the Coy Glen Limestone and

contains the Koenenites aff. lamellosus (Sandberger and Sandberger, 1851) goniatite fauna (now

Koenenites beckeri (House and Becker, 2008), representing the cycle below the Bluff Point

Siltstone of the West River Formation west of the study area (see Text-figs. 1 and 2). We

recognize an almost 1 m thick zone of deformed siltstones about 1 meter above this and

tentatively correlate this with the Bluff Point Siltstone of western sections. For these lithological

and biostratigraphic reasons, we consider the strata overlying the Coy Glen Limestone to belong

to the West River Formation.

PRELIMINARY SEQUENCE STRATIGRAPHIC INTERPRETATION

The recurrent nature of facies associations presented above suggests some over-arching control on changes in accommodation; we interpret this as the result of relative sea-level oscillation. The general characteristics of this repeating pattern are considered as a relatively condensed interval overlain by a generally coarsening-upward succession. Generalized sequence stratigraphic models suggest that as relative sea-level initially rises, progradation slows and may stop completely depending on the rate and magnitude of transgression. During this time, sediment is sequestered in bays and estuaries, and delayed from reaching the basin. Alternatively, progradation and increased supply of sediment to the basin is predicted during intervals of sea level fall. Text-figure 4 outlines the preliminary model we apply to the coarsening upward sedimentary successions observed in the study area; ideally, before applying the sequence stratigraphic model a three-dimensional Model of surfaces and enclosed packages of strata along the complete onshore-offshore gradient would be undertaken. Under this model, we have developed the preliminary sequence stratigraphic framework for the strata in this study (Text-fig.

5). The reader is referred to Van Wagoner et al. (1990), Posamentier and Allen (1999),

Catuneanu (2002, 2006), and McLaughlin and Brett (2007) and references therein for further

discussion of sequence stratigraphic models. In particular, we use a slightly modified version of

‘Depositional Sequence Model IV’, as outlined in Catuneanu (2002, fig. 29).

We recognize five traceable depositional sequences within the strata of the Renwick and

Ithaca formations (Text-fig. 5). At this time, we speculate that these are 4th-order cycles,

although the sequences beginning with the Lodi Limestone Member and the University Quarry

Beds may represent 3rd-order cycles. Ongoing research in the area of the Tioughnioga Valley to

the east of the Ithaca suggests that equivalent strata continue to splay open up-ramp, such that

higher-order cycles are preserved. Correlation of these two meridians is therefore necessary to placing temporal context on the recognized sequences. Although not all sections display the ideal sequence as outlined in Text-fig. 4, the general patterns observed support the inference that these depositional sequences are in part controlled by relative sea-level changes. We further suggest

that proximity to the source of sediment and locally shifting micro- and macro-scale depocenters

can alter these sequences from the ‘ideal model’, even at the scale of the study area, due to

proximity to the delta-front. In general, we interpret the condensed intervals at the base of each

succession as forming during the Transgressive Systems Tract (TST), the coarsening upward

turbiditic facies to have formed during the Highstand Systems Tract (HST), and the stacked

siltstones and channelized sandstones to have formed during the Falling Stage Systems Tract

(FSST). Where not reworked into the overlying TST deposits, the Lowstand Systems Tract

(LST) is represented by a silty interval that is somewhat fossiliferous and contains storm-

influenced sedimentary structures.

Because these depositional sequences correspond to the coarsening upward successions

described above (i.e., the Renwick Formation and the members of the Ithaca Formation) we

apply the names of the lithostratigraphic units to their depositional sequences; ideally, such

coarsening upward successions should be recognizable in both up- and down-ramp directions of

the study area and can serve as a tool in future stratigraphic work in the northern Appalachian

Basin when the lithologic character of a given marker bed undergoes facies-change. Although

not traced locally in this study, we also recognize a number of sequences in the Geneseo,

Sherburne, and post-Ithaca strata.

REVIEW OF CURRENT BIOSTRATIGRAPHIC FRAMEWORK

Although sparse relative to western sections, the biostratigraphic data available in the study area

provide a framework for correlations within the Genesee Group westward across New York

(Text-fig. 5).

GONIATITES

The Middle-Upper Devonian (Givetian-Frasnian) boundary is based on conodont zones and does

not correspond to a goniatite zone-boundary. However, its position in the Ithaca-area succession

can be approximated. The highest Givetian goniatite zone represented in the area is the New

York Regional Zone of Ponticeras perlatum (House and Kirchgasser, 1993). The nominate

species first appears in the Hubbard Quarry Shale submember at the top of the Geneseo

Formation and ranges upward to the Cornell Member of the basal Renwick Formation. There are

also a few unconfirmed records of Ponticeras in the Cascadilla and Treman members. The next

known level is the occurrence of Chutoceras nundaium (formerly referred to Ponticeras cf.

regale) in the “Firestone Beds” in the lower part of the University Quarry Beds of the

Triphammer Member of the Ithaca Formation; the precise horizon of this species in Fall Creek is

unknown (Kirchgasser & House, 1981; Kirchgasser, 1985; House & Kirchgasser, 1993, 2008).

Koenenites styliophilus styliophilus first appears within the “Firestone Beds,” probably in an

interval that post-dates that of Chutoceras, and is also concentrated in the “Linden Horizon” at the top of the University Quarry Beds. Goniatites indicative of the Genundewa Limestone of western sections, and the overlying goniatite zone, including Koenenites aff. styliophilus (House and Kirchgasser, 1993; now Koenenites styliophilus kilfoylei (House and Kirchgasser, 2008)) and

Manticoceras contractum (Clarke, 1898), are unknown in the study area with any stratigraphic certainty; although the only known specimen of Manticoceras simulator (Hall, 1874), comes

from an unknown horizon in the Ithaca area. The next regional zone, represented by the

occurrence of Bluff Point Siltstone goniatite fauna, and including Koenenites aff. lamellosus (G.

and F. Sandberger), is placed around some of the highest exposures at Coy Glen (Text-figs. 2 and 5; Locality/Bed I-3/1 of Kirchgasser & House, 1981). The zone with Sandbergeroceras syngonum (Clarke, 1897) would begin at the base of the Sonyea Group, within the Middlesex

Formation.

CONODONTS

The conodont biostratigraphic zonation in the study area is still poorly known (Text-fig. 5). The

conodont age of the strata immediately above the Lodi Limestone Member is fairly well

constrained with Montagne Noire (MN) Zone 1, marking the base of the Upper Devonian. The

block that contained the single specimen of C. nundaium yielded a single specimen of the

conodont Ancyrodella rotundiloba (early form) (Bryant, 1921), the index species of MN Zone 1

(Kirchgasser, 1994). Conodonts of MN Zone 2, represented by Ancyrodella rotundiloba (late

form), are yet unknown in the Ithaca sections, but to the west they occur in the “Linden

Horizon”, the level with Koenenites styliophilus styliophilus recognized at Ithaca at the top of the

University Quarry Beds of the Triphammer Formation. The University Quarry Beds is thus the

likely position of the MN 1-2 boundary in the Ithaca area succession. The University Quarry

submember is therefore a key biostratigraphic interval, marking changes in both the goniatite and

conodont faunas. The Coy Glen Limestone Bed (Horizon 6791-SD of deWitt and Colton, 1978;

Huddle 1981) has a fauna indicative of MN Zone 3 [which is recognized as the first occurrence

of Ancyrodella alata (late form) (Glenister and Klapper, 1966) and Ancyrodella rugosa (Branson

and Mehl, 1934); Huddle, 1981]. However, based on regional thickening patterns observed in

Text-fig. 6, this is likely not the base of this biozone (W.T. Kirchgasser, pers. comm., 2007). MN

Zone 4 begins just below the Middlesex Formation, within the Beard’s Creek interval based on the first occurrence of Palmatolepis transitans (Müller, 1956) (see Over et al., 2003; Text-fig. 6).

CORRELATIONS WITH WESTERN SECTIONS

Both the Fir Tree and Lodi Limestones are traceable from western to central New York State

(Baird et al. 1988). The Lodi Limestone is seen at the base of Twin Glens, just above the level of

Cayuga Lake. Between the Lodi Limestone and the “Linden Horizon,” which caps the

University Quarry Beds, correlations are less certain. Kirchgasser (2000) suggests that the

Renwick may be correlative to, or just below, the Schumacher Bed (SB), which is a thin, conodont-rich black shale above the Lodi level, and low in the Penn Yan Shale in western New

York. Two fossil-bearing gray shale bands, informally termed the “Abbey Beds” are observed to overlie the Schumacher Bed at some Genesee Valley meridian sections (Text-fig. 6); these may correlate with the Ithaca Falls and Fall Creek Limestone Beds in the Ithaca sections. The Starkey

Black Bed of deWitt and Colton (1978), or more appropriately the base of this unit, is another possibly correlative bed to one of these limestones, but has not been studied by the present authors.

The “Crosby Sandstone” (Fox 1932, Torrey et al., 1932) is a bed of resistant, sparsely fossiliferous, but bioturbated silt- to sandstone known from sections in the Keuka and Seneca valleys (deWitt and Colton, 1978). At Mill Creek in the Seneca Valley, this bed occurs above the

“Linden Horizon” and University Quarry Beds correlatives (Kirchgasser and House 1981). It has not yet been confidently linked to Genesee Valley or Ithaca area localities, although it appears to be correlative with a bed of partially exhumed and truncated concretions slightly below the

Genundewa Formation in the Canandaigua Valley (Baird, 1976). This same horizon may also be

46 composited with the “Linden Horizon” at the Canandaigua Valley as proposed by Kirchgasser

(1985).

In the Ithaca area, deWitt and Colton (1978) placed the Crosby Sandstone at 20 m (70 to 80 feet) above the Williams Brook Limestone at the section on Williams Brook. This corresponds well with the lower portion of a unit we have traced, and called the Forest Home Sandstone

Beds. This is also the basal Enfield Member as designated by Williams et al. (1909, see references therein), and also for the most part by Williams (1951). Huddle (1981) sampled the

Forest Home Sandstone Beds equivalent at Fall Creek for conodonts, and the absence of

Ancyrodella rugosa, unless due to facies restriction, suggests that this bed is older than the Upper

Genundewa Limestone. Based on these conodont observations, both the Forest Home Sandstone

Beds and the Beebe Limestone Beds should be below the Genundewa Limestone in western sections. This is particularly troubling because the only known traceable, condensed unit between the “Linden Horizon” and the Genundewa Limestone is the Crosby Sandstone.

Our composite section, with the upper Ithaca strata based on the section at Coy Glen may help to explain this (Text-fig. 5). The conodonts observed by Huddle (1981) in the Coy Glen

Limestone Bed include Ancyrodella rugosa and A. alata, placing this bed within MN Zone 3.

The identification of A. rugosa was been confirmed by Kralick (1994); however, the identification of A. alata needs review as this species has been mistaken for the earlier

Ancyrodella recta (Kralick, 1994) of the Upper Genundewa. Comparison with the positioning of the Bluff Point Siltstone goniatite fauna by Kirchgasser and House (1981) at Coy Glen and the general thickening pattern observed across New York State (Text-fig. 6), suggests correlation of the Coy Glen Limestone Bed with the conodont- and glauconite-rich Huddle Bed of Genesee

Valley sections is likely. This tentative correlation then suggests correlation of the Crosby

Sandstone with the Beebe Limestone Beds and places the Genundewa between the Beebe

limestone Beds and the Coy Glen Limestone Bed at the Ithaca meridian (Text-figs. 5 and 6). The

only condensed shell rich zone in this interval is the Forest Home Sandstone Beds. Although the

conodont evidence, or more appropriately lack thereof, provided by Huddle (1981) argues

against this latter correlation, the MN Zone 2-3 boundary is documented as occurring within the

Genundewa Limestone in western sections. Therefore, the absence of A. rugosa in the Forest

Home Sandstone Beds may simply be a matter of sampling and failure to obtain conodonts from

the appropriate level within the interval. Moreover, Kralick (1994) has shown that some of the

conodont identifications of Huddle (1981) need revision, and a detailed study of the Ithaca

Formation conodonts is therefore a necessary next step in order to test the hypothesized

correlations. Interestingly, the elevation at which Williams et al. (1909) describes the termination

of the ‘Ithaca Fauna’ at Coy Glen corresponds with the Forest Home Sandstone Beds, and may

further indicate a correlation between this level and the Genundewa Limestone. Furthermore,

the abundance of Melocrinus sp. ossicles within the Forest Home Sandstone Beds also suggests a

Genundewa correlation.

DISCUSSION

The apparent relationship between benthic faunal, biostratigraphic changes and the preliminary sequence stratigraphic surfaces in the Genesee Group suggests that the biota may be in part controlled by water mass conditions, as biotic changes are occurring during transgressions and possibly at flooding surfaces when the possibility of extra-basinal influences would be greatest. Alternatively, these changes could be artifacts of unconformities, sensu, Holland

(1995). However, the apparently near-conformable nature and inferred position below storm wave base of the tentative sequence boundaries in the study area argues against this.

The appearance of the ‘recurrent Hamilton Fauna’ long after most of its taxa had apparently

become extinct in the Appalachian Basin suggests not only that a refugium existed, but also that

during the Taghanic Onlap, this refugium may have been in other areas of the Appalachian Basin

during the time when bottom conditions were relatively inhospitable (Geneseo/Burkett black

shale). Additionally, the interval of the University Quarry Beds contains the first appearance of

diagnostic pelagic index fossils, incursion of the Upper Devonian ‘Ithaca Fauna’ into the study

area, and a turnover in rhynchonellid brachiopods as reported by Harrington (1972) and noted by

Kirchgasser (1985). This is further suggested by previous, but unconfirmed, reports of these taxa

initially occurring in possibly correlative beds east of the present study area (Prosser 1897;

Clarke, 1898; and Thayer, 1974), thereby precluding a facies-based, and therefore apparent,

faunal transition. These observations may suggest a linkage of previously isolated faunas through

sea level rise, and also possibly a change in water-mass conditions at this time; the possibility of

an ‘Ithaca Bioevent’ is a current focus of our research. Finally, the repeated incursion of

Warrenella laevis further suggests such intra-basinal biotic exchanges may have occurred repeatedly during transgressions in the Genesee Group; this study area is an ideal place to test such hypotheses.

CONCLUSIONS

The results of this lithostratigraphic revision of the type Renwick and Ithaca formations near

Ithaca, New York and their correlations with western sections can be summarized as follows:

1) The Renwick Formation represents a coarsening upward depositional sequence,

beginning with the transgressive Cornell Member. We tentatively correlate the

Renwick with the Schumacher Bed (SB) of the Genesee Valley.

2) The Ithaca Formation is comprised of four depositional sequences: the Cascadilla,

Treman, Triphammer, and Cayuga Heights members. Each of these sequences

coarsens upward, with the following condensed intervals near their base: the Ithaca

Falls Limestone Beds, Fall Creek Limestone Beds, University Quarry Sand and

Limestone Beds, and the Beebe Limestone Beds, respectively. We correlate the

above beds with the two ‘Abbey Beds’, the “Linden Horizon”, and the Crosby

Sandstone, respectively, of western sections.

3) We recognize a herein un-named depositional sequence between the Ithaca and West

River formations that represents a distinct transition between the faunas of these

formations. We tentatively correlate this unit with all, or part of, the Genundewa

Formation of western sections; this and the above hypothesized correlations should be

confirmable with detailed study of the conodont biostratigraphy of the study area.

ACKNOWLEDGEMENTS

The authors are extremely indebted to W.T. Kirchgasser for extensive discussion, comments on the initial draft, and the use of past field notes and stratigraphic collections. P.I. McLaughlin offered valuable insight into defining and interpreting the litho- and sequence stratigraphy of these strata. We are also grateful for the time and effort of D.J. Over for editing this volume. S.E.

Kolbe assisted with photography and in editing the final draft. Fieldwork was supported through student grants from The Paleontological Society, The Mid America Paleontology Society, The

Geological Society of America, The American Museum of Natural History, The American

Association of Petroleum Geologists, The Society for Sedimentary Geology, and the Department of Geology at the University of Cincinnati; awarded to JZ.

REFERENCES

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Text-figure 1

History of the stratigraphic nomenclature for the Genesee and Sonyea Group strata exposed near

Ithaca, New York from selected references. In some cases, taxonomy of faunal zones of past literature have been updated. (full page width and over half page length)

Text-figure 2

Correlation of fossiliferous marker beds around the vicinity of Ithaca, New York (see inset for

section locations). Numbering scheme on left of stratigraphic columns represents key reference

points in sections. Southern Gully of Twin Glens: 1) Level of NY Rte. 34; 2) Level of Cayuga

Heights Road. NY Rte. 13 at Cayuga Heights: 1) Section below Cayuga Heights Road; 2)

Section at entrance ramp of Cayuga Heights Road onto NY Rte. 13 eastbound. Williams Brook:

1) Level of NY Rte. 89; 2) Level of NY Rte. 96. Fall Creek: 1) Base of Ithaca Falls; 2) Lip of

Ithaca Falls; 3) Approximate level under suspension bridge; 4) Foundation level of Cornell

University Power Plant; 5) upper lip of Power Plant Falls; 6) “Linden Horizon” of Kirchgasser

(1985); 7) Lip of Triphammer Falls; 8) Level of Beebe Lake; 9) Section under Caldwell Road

Bridge. Coy Glen: 1) Base of section exposed at rear of Calvary Cemetery; 2) Level of Elm

Street Extension Bridge; 3) Locality/Horizon I-3/1 of Kirchgasser and House (1981). Cascadilla

Creek: 1) Section exposed below Linn Street Bridge; 2) Level of footbridge; 3) Section exposed below College Street Bridge. (full page portrait)

Text-figure 3

Characteristic facies of the strata observed in this study. A) Channelized sand and siltstone occurring at Fall Creek in the upper Cascadilla Member. B) Turbiditic succession observed at

Fall Creek near the middle of the Cascadilla member. C) Beebe Limestone Bed from Sixmile

Creek (see Zambito et al., 2007 for graphical section). Note abundant shells, crinoid ossicles, and reworked silt clast (arrow). D) Auloporid ‘thicket’ and Pseudoatrypa devoniana from the

“Firestone Beds” at NY Rte. 13. E) Reworked concretion at the base of the Beebe Limestone

Bed at Sixmile Creek. (full page portrait)

Text-figure 4

Idealized sequence stratigraphic model for this study. A) Relative sea-level curve over a general

large-scale transgression showing position of systems tracts along curve. (adapted from Coe et

al., 2003) B) Idealized depositional sequence and sequence stratigraphic interpretation for the

study area. HST: Highstand Systems Tract, FSST: Falling Stage Systems Tract, SB: Sequence

Boundary, LST: Lowstand Systems Tract, TST: Transgressive Systems Tract, PB: Precursor Bed

(i.e., forced regression surface), MSS: Maximum Starvation Surface; and MFS: Maximum

Flooding Surface. Scale is approximate. (single column width and less than half page length)

Text-figure 5

Preliminary biostratigraphic and sequence stratigraphic interpretation of the Genesee Group near

Ithaca, New York. Section is a composite adapted from on Text-fig. 1 Relative sea-level curve is

based on faunal lists from Williams (1884), Williams et al. (1909), Kindle (1896), and Zambito

et al. (2007). BA stands for benthic assemblage. T-R Cycles (transgressive-regressive) are

presented for reference and are based on the North American Cratonic Devonian T-R Cycles of

Day et al. (1996). ‘?’ within biostratigraphic columns represent uncertainty in the location of a given boundary. Goniatite biostratigraphy is based on Kirchgasser and House (1981), House and

Kirchgasser (1993), and W.T. Kirchgasser, pers. comm. (2007). Conodont biostratigraphy is based on Kirchgasser (1994), Kralick (1994), and Over et al. (2003). MN zones is in reference to the Montagne Noire reference section of Klapper and Johnson (1990). See figure 2 for lithologic key. (single column width and full page length)

Text-figure 6

Correlations of marker beds in composite sections within the Genesee Group across western and central New York State. MBR: Member, FM: Formation, GRP: Group. Adapted from

Kirchgasser (1985). Correlations are based on data from Over et al. (2003), Baird et al. (2006),

Zambito et al. (2007), and this study. Note that stratigraphic columns are to scale, but some beds are not. (full page, landscape)

Text-figure 1

Text-figure 2

Text-figure 3

Text-figure 4

Text-figure 5

Text-figure 6

Chapter 3

ZAMBITO, J.J., IV, BRETT, C.E. AND BAIRD, G.C., in press. The Late Middle Devonian (Givetian)

Global Taghanic Biocrisis in its Type Area (New York State Appalachian Basin):

Geologically Rapid Faunal Incursion, Replacement, Recurrence, and Extinction as a

Result of Global and Local Environmental Changes. UNESCO/International Year of

Planet Earth volume entitled ‘Global Biodiversity, Extinction Intervals and

Biogeographic Perturbations through Time’ Edited by John Talent.

The Late Middle Devonian (Givetian) Global Taghanic Biocrisis in its Type Area (Northern

Appalachian Basin): Geologically Rapid Faunal Transitions Driven by Global and Local

Environmental Changes

Key Words: New York, Hamilton, Tully, Genesee, Geneseo

James J. Zambito IV1, Carlton E. Brett1, Gordon C. Baird2

1: University of Cincinnati, Department of Geology, Cincinnati, OH 45221-0013

2: SUNY College at Fredonia, Department of Geosciences, Fredonia, NY 14063

email: [email protected]

Abstract

Large mass extinctions have long been recognized in the fossil record; however, the lesser

studied and more frequent events that still result in faunal restructuring and replacement at

regional to global scales may have a greater aggregate effect on the evolution of life. The late

Middle Devonian “Taghanic (Pharciceras) Event” was originally named by M. House for

goniatite turnovers in the New York Appalachian Basin during the deposition of the Tully

Limestone; subsequently it has been associated with extinction of most of the long-lasting

‘Hamilton Fauna’ in this region. Detailed stratigraphic and paleoecological research of the

Taghanic Biocrisis in the type area has revealed at least three main faunal transitions, that are recognized as the following bioevents: 1) replacement of much of the endemic ‘Hamilton Fauna’

(a subset of the Eastern Americas Realm) with the previously equatorial ‘Tully Fauna’ (a subset of the Old World Realm) during the Lower Tully Bioevent; 2) subsequent extermination of most of the ‘Tully Fauna’ and the recurrence of the ‘Hamilton Fauna’ during the Upper Tully

Bioevent, coincident with the eustatic sea level rise referred to as the ‘Taghanic Onlap’; and, 3) extinction of much of the ‘Hamilton Fauna’ and return of some ‘Tully’ taxa along with further incursion of Old World Realm taxa during continued rise in global sea level during the Geneseo

Bioevent. The Taghanic Biocrisis is now recognized globally as a series of pulsed biotic transitions and extinctions, ultimately resulting in an end to previous faunal provinciality and the appearance of a global cosmopolitan fauna.

In this paper, we review the current knowledge of these faunal transitions in the type area with respect to geologically rapid global and local environmental changes observed using a high- resolution stratigraphic framework across the entire onshore-offshore environmental gradient to reconstruct biofacies spectrums before, during, and after the biocrisis. Globally recognized

environmental changes, namely temperature increases, changes between arid and humid

intervals, rapid sea level fluctuations, and widespread black shale deposition, account for the

faunal transitions (incursion, replacement, recurrence, and extinction) recognized in the type-

area, but only in the context of regional basin dynamics associated with basin morphology and

the degree to which estuarine-type watermass circulation patterns were operating, resulting in

salinity variation as a dominant control on faunal distribution. Herein, we outline the interplay

between global and local environmental changes that served as driving forces behind the

observed local incursions and extinctions, including the demise of the long-stable Hamilton

Fauna. Finally, we discuss the implications that the observed faunal transitions have for

understanding the cohesiveness of faunas and the role of habitat tracking at the faunal level.

Introduction

During the Global Taghanic Biocrisis (GTB), Middle Devonian faunas worldwide underwent a major extinction in apparent conjunction with eustatic sea level rise, intensified oceanic circulation, increased warming, carbon-cycle changes, reduced oxygenation in epicontinental seas, and increased aridity (Johnson, 1970; Murphy et al., 2000; House, 2002;

Aboussalam, 2003; Joachimski et al., 2004, 2009; Hüneke, 2006, 2007; van Geldern et al., 2006;

Marshall et al., in press; and Aboussalam and Becker, in press). House (2002) estimated that the impact of this biocrisis on biodiversity may have been as great, or greater, than the well-known

Frasnian-Fammenian crisis. Johnson (1970) and Boucot (1988) describe this time as the end of an established Devonian faunal provinciality, resulting in cosmopolitan faunas world-wide.

Moreover, McGhee (1982, 1989, 1996) and Sandberg et al. (2002) describe this interval as a time of faunal crisis, lasting approximately 7 million years and culminating in the Frasnian-

Fammenian extinction. Studies of marine invertebrate global biodiversity trends at various

taxonomic scales through the Phanerozoic recognize the GTB interval as the beginning of a

period of protracted extinction with no clear end until the beginning of the Permian, the duration

of which has likely prevented this biocrisis from being recognized as a mass extinction (Raup

and Sepkoski, 1982; Alroy et al., 2008). Nevertheless, the more frequent events that still result

in faunal restructuring and replacement at regional to global scales may have a greater aggregate

effect on the evolution of life than the ‘Big Five’ (Walliser, 1990; Brett and Baird, 1995; Brett et

al., 1996; Miller, 1998).

The type-area of the GTB, is the Appalachian Basin deposits of New York State (Fig. 1).

The GTB (House, 1985) is named after the Taghanic Onlap of Johnson (1970) which in turn is

named for the exposures along Taughannock Creek, near the Village of Trumansburg in central

New York State (Fig. 2). Taughannock and Taghanic, along with several other variants, have all

been accepted names and spellings for this creek, the waterfalls along it, and the sections

exposed therein (Hall, 1843; Kurtz, 1883; Cooper and Williams, 1935). Interestingly, the GTB

and the Taghanic Onlap were both named for the paleontologic and lithologic changes seen,

respectively, at the base of the Tully Formation; however, as pointed out in Baird and Brett

(2003), the greatest transgression of this interval actually commences with the deposition of the

upper part of the Tully Formation, and continues into the overlying Geneseo Formation (Fig. 2).

In describing the biotic changes observed during the GTB, we prefer the terminology

outlined in Walliser (1996) and refined in Aboussalam and Becker (in press): a biocrisis is a

perturbation interval spanning more than one biozone and comprised of a series of bioevents that

each generally occur within a single biozone, black shale interval, and/or one trans-regressive

couplet. In the type-area of this extinction, the Taghanic Biocrisis has been extensively documented at high-stratigraphic resolution as a series of at least three bioevents involving

faunal incursions, replacements, recurrences, and extinctions, resulting ultimately in the

disappearance of numerous ammonoid, coral, and brachiopod taxa through an interval of

approximately 500,000 years (House, 2002, and references therein; Baird and Brett, 2003, 2008;

Kaufmann, 2006; and Zambito et al., 2007, 2009). These transitions include, in respective

upward-succession: 1) replacement of much of the endemic ‘Hamilton Fauna’ (a subset of the

Eastern Americas Realm) with the previously equatorial ‘Tully Fauna’ (a subset of the Old

World Realm) during the Lower Tully Bioevent; 2) subsequent extermination of most of the

‘Tully Fauna’ and the recurrence of the ‘Hamilton Fauna’ during the Upper Tully Bioevent,

coincident with the eustatic sea level rise referred to as the ‘Taghanic Onlap’; and, 3) extinction

of much of the ‘Hamilton Fauna’ and return of some ‘Tully’ taxa along with further incursion of

Old World Realm taxa during continued rise in global sea level during the Geneseo Bioevent.

The Taghanic Biocrisis is now recognized globally as a series of pulsed biotic transitions and extinctions, ultimately resulting in an end to previous faunal provinciality and the appearance of a global cosmopolitan fauna (Johnson, 1970; Boucot, 1988; Oliver, 1990; Feist,

1991; Day, 1996; Day et al., 1996; Brice et al., 2000; Aboussalam and Becker, 2001, in press;

House, 2002; and Aboussalam, 2003, and references therein). As a globally recognized biocrisis, it is therefore imperative to fully understand the interplay between global and local environmental changes in the type area, where this biocrisis is recorded in a relatively complete stratigraphic succession along an entire onshore-offshore gradient. Only with a complete understanding of the faunal patterns and environmental changes in the type area can we accurately understand this biocrisis at the global scale. Below, we review the faunal transitions observed during the GTB in the type-area by reconstructing biofacies spectrums before, during, and after the biocrisis, outline the interplay between global and local environmental changes

81 driving these transitions, and discuss the implications of these observations for evolutionary paleoecology.

Geologic Setting

The type-area of the late Middle Devonian Taghanic Biocrisis is located in the northern

Appalachian Basin deposits of New York and nearby states, herein referred to as the NAB

(northern Appalachian Basin) (Figs. 1 and 2, see also House, 1985; House, 2002; Baird and

Brett, 2003). At this time, the NAB was located approximately 30 degrees south latitude (Fig.

1). Regional strata were deposited in a foreland basin that formed during the Acadian Orogeny, as the Laurentian and Avalonian terranes converged obliquely (Fig. 1; also see Ettensohn, 1985;

Ettensohn et al., 1988; Ver Straeten and Brett, 1995, 1997). Erosion of the collisional highlands produced the classic progradational complex known widely as the “Catskill Delta”, which advanced in a generally westward direction and largely filled the foreland basin by the early

Mississippian. The GTB occurs during the transition between the second and third collisional tectophases of the Acadian Orogeny (Ettensohn, 1985; Ettensohn et al., 1988; Ver Straeten and

Brett, 1995, 1997). During each tectophase, orogenic activity occurred along the eastern seaboard of North America (Laurentia), causing subsidence of the Appalachian Basin in response to tectonic loading on the crust, and, a resultant influx of sediment into the basin from the erosional weathering of these mountains.

In the NAB, the GTB is recorded primarily in the sediments of the Tully Group, however, immigrations and extinctions related to the GTB can be observed first within the upper Hamilton

Group, and continue into the lower Genesee Group (Sessa, 2003; Baird et al., 2003; Baird and

Brett, 2003, 2008; and Zambito et al., 2007, 2009). These deposits can be observed in an east- west trending outcrop belt across New York State that is relatively stratigraphically complete due

to near continuous subsidence during this time, and, furthermore, represent a complete onshore-

offshore gradient as the outcrop belt is normal to depositional strike (Fig. 3). The Tully

Formation has received detailed investigation through the years, and the reader is referred to the

studies of Grabau (1917), Trainer (1932), Cooper and Williams (1935), and Johnson and

Friedman (1968, 1969). More recent studies of the Tully Formation interpret this time as a

period of relative tectonic quiescence, when the second tectophase was waning and sediment

input to the basin was relatively minimal (Heckel, 1973; Baird et al., 2003; Baird and Brett,

2003, 2008).

Sediment supply to the basin was further controlled by the syn-depositional formation of

a fault-controlled “clastic trap”, which resulted in three distinct, yet concurrent, depositional

facies for the Tully Formation (Fig. 4; Heckel, 1973; Baird et al., 2003; and, Baird and Brett,

2003). This included: 1) a broad epicontinental shelf across the western and central New York

and northwest Pennsylvania region where the anomalous Tully limestone deposit accumulated

under clastic sediment-starved conditions; 2) in east-central New York and in central

Pennsylvania, a structural trough was developed which separated the platform from areas of clastic sediment-supply from the east and southeast, characterized by sparsely-fossiliferous dysoxic facies; and, 3) an eastern shelf area connected to paralic habitats along the paleocoastline that was variably supplied by terrigenous sediments from that coast, which together with the sediments deposited in the trough, has been referred to as the TFCC (Tully Formation Clastic

Correlative) (Figs. 4 and 5; Heckel, 1973; Baird et al., 2003; see also Heckel, 1997, and Ver

Straeten and Brett, 1997 for alternatives views on the ‘clastic trap’ formation).

In comparison, depositional lithofacies during the preceeding upper Hamilton Group were similar to, but much more gradational than, Tully deposits. For example, the upper

Hamilton Group of New York also displays an eastern shelf, centrally-located dysoxic basin, and western carbonate-rich facies; however, during upper Hamilton-times the basin exhibited a

gently dipping ramp profile, resulting in an overall siliciclastic-dominated basin in which marker

beds representing discrete time intervals can be traced along the entire onshore-offshore gradient

(Fig. 5; Brett and Baird, 1985, 1994). With the onset of the third tectophase of the Acadian

Orogeny and coincident with a global sea-level rise (Taghanic Onlap), the basin once again changed drastically, as it subsided, migrated westward, and input of siliciclastic sediment into the western NAB resumed and greatly intensified, as manifested in the deep-water, anoxic deposits of the Geneseo black shale and subsequent formation and progradation of a distinct slope setting

(Fig. 5; Johnson, 1970; Zambito et al., 2007, 2009).

Taghanic Biocrisis in the Type Area: Sequence of Faunal Transitions

Pre-Biocrisis Interval

Boucot et al. (1969), Johnson (1970), Boucot (1975, 1988), and Koch and Boucot (1982)

suggested that brachiopod-dominated faunas of the Devonian could be divided globally into

biogeographic “realms”, inferring that the distribution of realms was controlled by climatic

(temperature) gradients between the equator and poles. At the onset of the GTB these realms in

North America consisted of the equatorial Old World Realm (OWR), and the higher latitude,

slightly cooler-water, Eastern Americas Realm (EAR) (Fig. 1B). Prior to the Taghanic Biocrisis,

genera that comprised the ‘Tully Fauna’ (a subset of the OWR Cordilleran province) occurred in

what is now the western United States and western Canada, in settings more equatorial than the

Appalachian Basin. The ‘Tully Fauna’ that eventually comes to occupy the NAB was a low-

diversity, primarily benthic fauna, dominated by brachiopods and almost entirely devoid of

mollusks (see faunal lists of Cooper and Williams, 1935; and Heckel, 1973). At this same time,

84 the NAB was occupied by the highly diverse ‘Hamilton Fauna’ (a subset of the EAR

Appohimchi province) comprised of various functional forms, conspicuous encrusting biotas, and large trace fossils, for a period of approximately 4-5 million years (Brett and Baird, 1995;

Brett et al., 1996). During this time, the Hamilton Fauna was characterized by a pattern of long- term stability of biofacies associations among fossil communities (coordinated stasis), comprised of species lineages that appear to track their preferred habitat rather than adapt to locally changing conditions (Brett and Baird, 1995; Brett et al., 1996, 2007a, 2007b; Brett et al., 2009;

Ivany et al., 2009). Additionally, detailed morphological studies of various organisms indicate morphological stasis through the Hamilton interval as well (Sorauf and Oliver, 1976; Lieberman,

1994; Lieberman et al., 1995).

Towards the end of this stable interval, pre-biocrisis incursions of OWR taxa are observed within the upper Hamilton Group (Fig. 6). Beginning during the deposition of the

Amsdell Beds and correlative Fisher Gully submember, Emanuella praeumbona (an OWR genus) becomes common in upper Hamilton Group dysoxic dark gray shales and siltstones.

Notably, the upward change from oxic shelf to dysoxic shale facies within the Sheds through

Highland Forest submembers suggests that diverse brachiopod facies typical of the Hamilton

Group occupied shallower, better oxygenated settings, while OWR taxa replaced typical dysaerobic Hamilton biofacies (Baird and Brett, 2003; Sessa, 2003).

Lower Tully Bioevent

The onset of Taghanic biotic instability (Lower Tully Bioevent) is marked by step-wise incursion of ‘Tully Fauna’ taxa into the NAB as observed in the New Lisbon Member

(uppermost Hamilton Group) and the lower Tully Formation (Figs. 6 and 7). The New Lisbon

Member succession is characterized by the first occurrence of the OWR taxa Camarotoechia

mesocostale, Rhyssochonetes aurora, and Tullypothyridina venustula. Although C. mesocostale

is abundant within the dysoxic, flaggy siltstone facies of the New Lisbon succession, R. aurora

and T. venustula occur only rarely, and, furthermore, these OWR associations are gradational

through the upward shallowing New Lisbon succession to generalistic taxa of the ‘Hamilton

Fauna’ in more oxic facies (Fig. 7; Baird et al., 2003; Sessa, 2003; Baird and Brett, 2008).

The incursion of the ‘Tully Fauna’ becomes further pronounced in the overlying lower

Tully Formation where R. aurora and T. venustula become more common, and within the

succeeding TFCC, in which the first appearance of OWR taxa “Nervostrophia” tulliensis,

Schizophoria tulliensis, and Echinocoelia ambocoeloides are observed. By this time, the ‘Tully

Fauna’ is found in oxic, outer shelf facies, and the ‘Tully Fauna’ prominently occupies both the

carbonate and siliciclastic (TFCC) portions of the onshore-offshore gradient (Figs. 6 and 7)

(Cooper and Williams, 1935; Heckel, 1973; Baird et al., 2003; Baird and Brett, 2008).

Upper Tully Bioevent

The second phase of this biocrisis, termed the Upper Tully Bioevent, represents the loss of a majority of the Tully Fauna from the Appalachian Basin and recurrence of the ‘Hamilton

Fauna’ in the NAB (Figs. 6 and 7). To date, there has been little progress in identifying the refugia of the Hamilton during lower Tully times, however, possibilities include since-eroded areas of the Canadian Shield and South America (see discussion below, and Boucot et al., 1986;

Brett et al., 2007a). The Upper Tully Event commences with the deposition of the Taughannock

Falls Bed and correlative TFCC, in which a return of dysoxic to mid-shelf ‘Hamilton Fauna’ is observed (Baird et al., 2003; and Baird and Brett, 2003). Facies occupied by the ‘Hamilton

Fauna’ during this time are observed to grade laterally into low diversity communities of the

‘Tully Fauna’ in more basinal TFCC facies in east-central New York and Pennsylvania (Baird

and Brett, 2008). Therefore, the recurrence of the ‘Hamilton Fauna’, like the incursion of ‘Tully

Fauna’ is step-wise, and, furthermore, rather symmetrical; ‘Tully taxa’ first appear in more

basinal facies relative to ‘Hamilton taxa’ and the ‘Hamilton’ taxa first recur in more proximal

facies relative to ‘Tully’ taxa. Additionally, it is observed that the generalistic taxa of each fauna

are the first to appear with each faunal transition, followed later by more specialized forms.

The most diverse representation of the Hamilton faunal elements that recur in the NAB is

best observed in the Bellona-West Brook Beds, and consists of over 100 species of corals,

bryozoans, brachiopods, mollusks, trilobites, and echinoderms (see Cooper and Williams, 1935;

and Heckel, 1973 for extensive faunal lists). Quantitative paleoecological analysis across

various spatial scales showed taxonomic stability between the recurrent ‘Hamilton Fauna’ of the

upper Tully Formation and older occurrences of diverse coral-brachiopod facies within the

Hamilton Group (Bonelli et al., 2006). This recurrence, while extensive in that almost all

‘Hamilton Fauna’ biofacies are represented, is geologically short-lived as the Taghanic Onlap continued rendering the basin inhospitable to most benthos due to the overspread of near-basin-

wide, post-Tully dysoxia and local anoxia during Geneseo black shale deposition (Figs. 5 and 7).

It is important to note that the most dysoxic portions of the ‘Tully Fauna’ continue to persist

through the interval of the recurrent ‘Hamilton Fauna’, most notably Camarotoechia

mesacostales in place of the typical Eumetabolotoechia multicostatum community of the

Hamilton Group. Additionally, and in a general sense, similar to when the ‘Tully Fauna’

occupies the NAB the recurrent ‘Hamilton Fauna’ also occupies both carbonate and siliciclastic

(TFCC) portions of the onshore-offshore gradient. For example, the Moravia Beds are

dominantly carbonate, but the West Brook Shale (with peak development of the recurrent

‘Hamilton Fauna’) is anomalously shaly. Even the Bellona Bed with its coral fauna is very

impure carbonate at best (Figs. 5 and 6; Heckel, 1973).

Geneseo Bioevent

The third phase of the biocrisis, the Geneseo Bioevent, occurred during the subsequent,

post-Tully, highstand part of the Taghanic Onlap. This resulted in the extinction of most

Hamilton taxa observed in the recurrent ‘Hamilton Fauna’ of the upper Tully Formation (at least locally), as generalistic ‘Hamilton’ taxa replace the diverse biofacies in the transitional Moravia

Beds that occur between the Bellona-West Brook interval and the Geneseo black shale. This was

a time characterized by speciation within ‘Hamilton’ genera (see Linsley (1994) for more

information), and the additional immigration of taxa from the Western US and Canada (OWR)

such as Tylothyris mesacostales, including the reappearance of a few ‘Tully’ taxa (“N.” tulliensis

and E. ambocoeloides); however, these taxa are only observed in shallow settings at this time as the basin was inhospitable to benthos. This was part of a global trend toward faunal cosmopolitanism that is observed until the Frasnian-Fammenian Extinction, approximately 7

million years later (Fig. 7) (Johnson, 1970; McGhee, 1982, 1989, 1996, 1997; Boucot, 1988;

Sandberg et al., 2002). Shown in Fig. 7, the Genesee Group biofacies spectrum is composed of a

cosmopolitan fauna of generalistic taxa with poorly defined biofacies; for example, there were no

Hamilton-like analogs of diverse coral and brachiopod assemblages in the Genesee Group

(Zambito et al., 2007, 2009; J. Zambito, unpublished data).

Post-Biocrisis Interval

The cosmopolitan fauna that resulted from the aftermath of the Taghanic Biocrisis

occupied the NAB until the Frasnian-Fammenian extinction with only minor faunal changes

through that time (see Zambito et al. 2007 and 2009, for some of these changes). Earlier

workers, most notably H.S. Williams and his students, described a recurrent ‘Hamilton Fauna’ in

pro-deltaic deposits of the Frasnian Ithaca Formation near Ithaca, NY long after the ‘Hamilton

Fauna’ was thought to have gone extinct with the deposition of the Geneseo black shale

(Williams, 1884, 1906, 1913; Kindle, 1896; Williams et al., 1909). Recognition of these

anachronous taxa is essentially the observation of generalist ‘Hamilton’ taxa within the

cosmopolitan fauna of the Upper Devonian; we observe these forms to persist in nearshore

settings during the deposition of the Geneseo black shale in offshore portions of the basin. The

‘recurrence’ of Hamilton forms in the Ithaca Formation, therefore, is the result of the survival of

these taxa in nearshore settings while the offshore portions of the basin were inhospitable; hence,

these biotas would later expand back into offshore settings when hospitable conditions returned

(Cooper and Williams, 1935; Zambito et al., 2007, 2009; J. Zambito, unpublished data).

Taghanic Biocrisis in the Type Area: Global and Local Environmental Changes

While at first glance, a change from predominantly siliciclastic, to carbonate, and then

returning to siliciclastic depositional environments (Hamilton, Tully, and Genesee Groups,

respectively) seems like a reasonable explanation for the above noted faunal changes,

reconstruction of a detailed stratigraphic framework along a complete onshore-offshore gradient

shows that both the ‘Hamilton’ and ‘Tully’ faunas occupied comparable onshore-offshore environmental gradients, including both siliciclastic and carbonate depositional settings (Figs. 5 and 7) (Heckel, 1973; Baird and Brett, 2003, 2008). Additionally, stratigraphic ranges of taxa cross large-scale unconformities (sequence boundaries), in particular sequence boundaries that correspond with bioevent commencements, and, onshore-offshore faunal gradients are mirrored in shallowing and deepening depositional sequences in a given outcrop, suggesting that the

observed transitions are not artifacts of a biased preservation of certain environments (sensu

Holland, 2000).

Widely recognized, global environmental changes during this interval that could be

responsible for the faunal transitions in the type-area include: 1) sea level rise and intensified

oceanic circulation (Johnson, 1970; Hüneke, 2006, 2007); 2) reduced oxygenation in

epicontinental seas (Murphy et al., 2000; Aboussalam, 2003); 3) Carbon cycle changes, and

increased nutrient influx (Aboussalam and Becker, in press), 4) increased warming (Joachimski

et al., 2004, 2009; van Geldern et al., 2006), and 5) increased aridity and rapid climate shifts

(Marshall et al., in press). Below, we place the faunal transitions and extinctions outlined in the

reconstructed biofacies spectrums (Fig. 7) in the context of these global environmental changes.

Eustatic Sea Level Rise and Faunal Incursion

The first appearance (incursion) of ‘Old World Realm’ genera in the NAB occurs prior to the GTB and concurrently with ‘Hamilton Fauna’, during the deposition of dysoxic dark shales during the uppermost part of the Hamilton Group succession when the generalistic genus

Emanuella is first observed in the NAB (Fig. 6). The uppermost Hamilton Group strata probably record the second highest sea level conditions for the biocrisis interval, followed only by the later post-Tully (Genesee) part of the Taghanic Onlap (Johnson et al., 1985; Baird and Brett, 2003).

The rise in sea level during the latest Hamilton Group deposits, and continuing throughout the

GTB, likely resulted in increased linkage between the NAB and western North America, thereby facilitating the immigration of the OWR taxa. The scenario of transgression induced immigration has been invoked for numerous Devonian Laurassian benthic immigrations

(Johnson, 1970; Racki, 1993; Brice et al., 1994; May, 1995; Day, 1996, 1998). During the

Lower Tully Bioevent, further incursion of OWR taxa occurs, and these incursions are also likely

90 due to increased basin linkage (Figs. 1 and 6). While increased sea level explains the migration pathways of the faunal incursions, it cannot alone explain the replacement of the ‘Hamilton

Fauna’ by the ‘Tully Fauna’ in the NAB, which suggests that a major paleoenvironmental control was driving this change.

Basin Eutrophication (Reduced oxygenation and Enhanced Nutrient Flux)

Globally, it has been observed that with many Paleozoic transgressions in epeiric seas, bottom-water stagnation occurs and low oxygen conditions prevail in offshore settings, often associated with biotic crises (Walliser, 1996; Hallam and Wignall, 1999). In the NAB, deoxygenation of bottom waters could be further enhanced by the increased input of organic matter to the basin as a result of the terrestrial colonization of plants as seen in the first appearance of the Gilboa fossil forest during the latest part of the Hamilton Group (Fig. 6;

Bridge and Willis, 1994; Bartholomew, 2002, and references therein). In fact, it is during this time that plant material first becomes common in basinal settings, continuing for the remainder of the Devonian. Furthermore, it is associated with relatively organic-rich, dysaerobic, and relatively nearshore facies (Prosser, 1899; Cooper and Williams, 1935; J. Zambito, unpublished data). Therefore, the increased nutrient flux to marine settings as a result of enhanced physical and chemical soil weathering by vegetation may have resulted in enhanced burial of organic carbon and resultant increases in bottom water oxygen depletion observed at this time in the

NAB (Algeo et al., 1995; Algeo and Scheckler, 1998).

During the Lower Tully Bioevent , we observe a step-wise replacement of offshore portions of the Hamilton fauna, leading to the near-exclusion of all but some generalistic

“Hamilton” taxa in nearshore settings (Fig. 6). This pattern of replacement suggests there was some environmental change occurring in deeper water that was precluding occupation by

Hamilton forms and promoting incursion of the ‘Tully Fauna’, while, simultaneously, not affecting shallow-water habitats to the same degree. That these immigrants were generalistic

OWR taxa would be expected, as generalistic taxa are typical of dysoxic settings, and would have an easier time tolerating any differences between the NAB and their endemic area, as has been shown in studies of migrations through the Late Devonian (Rode and Lieberman, 2004).

This pattern of replacement, though, suggests that low-oxygen conditions alone could not explain these incursions. This is because any explanation for this initial incursion and subsequent establishment of OWR taxa must account for the predominance of similar dysoxic shale facies in the Hamilton Group that were occupied by dysaerobic biofacies of the ‘Hamilton

Fauna’ prior to this incursion for a period of 4-5 million years (Figs. 5 and 7). While eustatic sea level rise and increased nutrient influx likely led to bottom water oxygen deficiency in the NAB, some other aspect of these settings must have allowed for ‘Tully Fauna’ incursion, while simultaneously resulting in ‘Hamilton Fauna’ exclusion. Furthermore, at the peak of Lower

Tully Bioevent, ‘Tully’ taxa are observed in oxic settings, and, during the onset of the Upper

Tully Bioevent dysaerobic ‘Hamilton’ biofacies are more proximal than dysaerobic ‘Tully’ biofacies; both of these observations suggest an additional environmental control on faunal distribution than oxygen deficiency alone. Additionally, carbon-cycle changes during the GTB are seen as a positive carbon isotope excursion beginning with the Upper Tully Bioevent in sections from Morocco representing ocean-facing settings (Aboussalam, 2003; Aboussalam and

Becker, in press); assuming these changes are global, this would suggest that increased carbon burial, and therefore possibly lower oxygen conditions was more prevalent beginning with the recurrence of the ‘Hamilton Fauna’, and after the occupation of the ‘Tully Fauna’ in the NAB.

Obviously, application of these ocean-facing environmental patterns to the NAB epeiric setting

92 should be done cautiously, though, and suggests that reconstruction of a carbon isotopic curve for the type-area is necessary.

It therefore appears that some other environmental change, possibly in conjunction with reduced oxygenation of the NAB is responsible for the observed faunal transitions during the

Lower and Upper Tully Bioevents; however, as suggested by previous studies and discussed in detail below, the pervasive dysoxic/anoxic settings associated with the Geneseo Bioevent did have an effect on the faunal patterns observed during the GTB.

Global Warming

Recent reconstructions of temperature changes through the Taghanic Biocrisis have depicted this event as a period of global warming, but no study to date has produced a high- resolution temperature curve during the Taghanic Biocrisis interval that can be directly compared to the faunal changes seen in the Tully Formation type-area, given that current temperature reconstructions are based on oxygen isotopic changes within conodont apatite from areas other than the NAB that are much less stratigraphically complete (Joachimski et al., 2004, 2009). The position of the OWR in more equatorial settings prior to and during the biocrisis, and the subsequent immigration of these taxa into the NAB immediately before and during the Lower

Tully Biocrisis, supports the hypothesis that changes in climatic gradients, specifically the warming of the NAB, could have driven these incursions (Johnson, 1970; Boucot, 1988). In particular, an episode of global warming, coupled with transgressive connecting of basins, would have expanded the ranges of equatorial taxa into higher latitudes thereby increasing cosmopolitanism.

As outlined in Figure 7, during the Lower Tully Bioevent the offshore portions of the

‘Hamilton Fauna’ were replaced in the NAB by the ‘Tully fauna’ and, additionally, the diverse

93 coral and brachiopod assemblages of the ‘Hamilton Fauna’ are absent from the NAB altogether.

If these portions of the ‘Hamilton Fauna’ were forced to emigrate from the NAB due to warming, then one might expect that higher latitude (cooler) locations would be an ideal location for the Hamilton Fauna to find refuge. As shown in Figure 1, possible locations of higher latitude refugia include South America and Africa. Unfortunately, correlative rocks in South

America have either been eroded away or represent non-marine environments, so that there is no record of marine faunas at high latitudes in the Americas during the GTB, and, faunal lists from the same age rocks in Africa do not contain the emigrated Hamilton taxa (Barrett, 1988; Barrett and Isaacson, 1988; de Melo, 1988; Isaacson and Sablock, 1988, Brice and Latréche, 1998; P.E.

Isaacson, pers. comm. 2008; Racheboeuf et al., 2001, 2004).

Although the predicted high-latitude refugia have yet to be identified for the ‘Hamilton

Fauna’, the hypothesis of shifting latitudinal climatic gradients is nonetheless supported by the temperature reconstructions of a period of warming as well as latitudinal affinities of taxa

(Boucot, 1988; Joachimski et al., 2004; 2009; though, see Brand et al., 2008); however, a higher resolution temperature reconstruction, preferably from the type-area, is needed to demonstrate the corresponding hypothesis that a brief return to cooler temperatures allowed the recurrence of

Hamilton taxa during the Upper Tully Bioevent. It should be noted, that the most recent temperature reconstruction (Joachimski et al., 2009) indicates that the entire Hamilton Group- through-Frasnian succession, inclusive of the Taghanic interval, was a period of almost steady temperature increase, and, also, that the ‘Hamilton Fauna’ occurred during some of the coolest times in all of the Devonian. This suggests that, if a reduction in the climatic gradient associated with warming did indeed drive the faunal transitions of the GTB, some temperature threshold must have been reached during the latest Hamilton Group that allowed for the faunal incursions

and replacements. If global warming is driving the OWR incursions, though, there would also

need to be an explanation for why ‘warm’ water occurs more in deeper water settings, as would

be suggested by the distribution of ‘Tully’ taxa in offshore settings, down-ramp of generalistic

‘Hamilton’ taxa, during the Lower and Upper Tully Bioevents (Fig. 7).

Increased Aridity and Rapid Climate Shifts

Previous studies have suggested that the GTB interval was a period of generally increased aridity (Day et al., 1996; Witzke and Bunker, 1997; Marshall et al., in press). Marshall and others (in press), in their work on the Old Red Sandstone, also suggested that during this overall arid interval the GTB was a period of rapidly fluctuating cool arid and hot pluvial events, corresponding with times of intra-Tully erosion (unconformities) and carbonate deposition, respectively. Based on the correlation of these climate changes with the depositional sequences of the Tully Group and faunal transitions, they speculated that OWR incursions were driven by these hot pluvial events. This agrees well with the hypothesis that OWR incursions are driven by shifts in climatic gradients associated with warming, and basin linkage resulting from sea level rise; however, under this model, the recurrent ‘Hamilton Fauna’ would occur during an inferred hot pluvial event.

Aridity, in the form of increased marine salinity, may have some control on faunal distribution and migration. The work of Boucot (1988) suggests that OWR taxa were adapted to higher salinity environments, as he places these taxa within an arid belt containing evaporate deposits (see also discussion in Boucot (1975, pgs. 269-282, 346)). Additionally, within the

EAR, the “Hamilton Fauna has been a problem ever since it was first described”, (Boucot, 1975, pgs. 320-321) as it contains an admixture of earlier faunas (see also Brett et al., 2009).

Presumably, this suggests that the Appalachian Basin “Hamilton Fauna” therefore requires some

unique environmental setting; we suggest that relatively low salinity, as a function of the

proximity to fresh water sources (Acadian Hinterlands) and restricted nature of the Northern

Appalachian Basin, is a likely characteristic of “Hamilton” times (Boucot, 1975; Algeo et al.,

2007).

Watermass Circulation Patterns

If salinity is a controlling factor, it would be useful to model the influence of freshwater influx on the relatively restricted NAB. The most appropriate model for the NAB is that of estuarine-type circulation (sensu Algeo et al., 2007). Due to the restricted nature of the NAB

marine embayment, oceanic water influence was rather minimal (Fig. 1); therefore, we have

adapted the super-estuarine model of marine anoxia, presented by Algeo et al. (2008; see also

Witzke, 1987). Our model (Fig. 8) differs because the super-estuarine model invokes a

connection to ocean settings, which the NAB did not have, so the NAB was not influenced by

the oceanic thermocline. Applied to the NAB, this model of estuarine-type circulation would

have operated as a result of influx of higher-salinity water from the lower latitude portions of the

North American craton, where evaporitic settings were intermittently developed throughout the

GTB interval, such as within the Iowa-, Elk Point-, and Great Basin-successions (Day et al.,

1996; Witzke and Bunker, 1997). The higher-salinity watermass would have been denser than the overlying lower-salinity watermass resulting from freshwater runoff of the Acadian hinterlands. This layered structure would have supported a halocline which, in turn, would have enhanced the oxycline, already strengthened by enhanced nutrient influx. Upwelling, commonly associated with estuarine circulation, would also have been possible. The resulting pycnocline would have acted more like a boundary layer, where salinity and oxygen levels are constantly fluctuating (Fig. 8).

Under this model, the ‘Hamilton Fauna’ would have been relegated to shallower, less

saline waters, and the ‘Tully Fauna’ to deeper more saline and possibly warmer waters, which

explains the facies distribution and step-wise replacements observed during the GTB.

Furthermore, the distribution of these faunas would be expected to overlap in biofacies

composed of generalistic taxa, which is what is observed during the Upper Tully Bioevent.

Additionally, this model is compatible with the observed global warming, sea level rise, and aridity observed at this time, as all of these changes would result in decreased barriers to migration between basins, as well as influx of a cratonic watermass into the NAB. While epeiric seas, and, in particular the NAB, were subject to large deviations from normal marine conditions because of their restricted nature (Witzke, 1987; Algeo et al., 2007, 2008), it should be noted that both the ‘Hamilton’ and ‘Tully’ faunas contain what are considered to be fully marine taxa, such as trilobites, echinoderms, brachiopods, and corals. This suggests that each fauna was comprised of a spectrum of taxa adapted to different salinity levels; alternatively, this might suggest that absolute deviation in salinity from normal marine conditions was rather small. This model may also be applicable to times of OWR incursion into the EAR areas during the Late Eifelian and prior to the appearance of the ‘Hamilton Fauna’, during which basinal facies underwent OWR incursion and turnover (Appalachian and Michigan basins), yet shallow water settings did not experience the same level of incursion and turnover, such as the platform settings in Ohio and

Ontario described in Desantis et al. (2007). During Hamilton-times prior to the GTB, rare

incursion of OWR ambocoeliid brachiopods also occurs in biofacies composed of generalistic

taxa that occupy basinal settings (Goldman and Mitchell, 1990).

Environmental Changes Superimposed on Local Basin Dynamics

As noted above, we suggest that the presence OWR and EAR taxa in the NAB was

controlled mainly by salinity and nutrient flux, and that the distribution of these taxa along an

onshore-offshore (shallow-deep) environmental gradient would suggest that some form of

watermass stratification was in place, such as an estuarine-type circulation model. Application

of this model to the NAB can be tested by placing it in the context of the geologically rapid

changes in Appalachian Basin morphology that occurred during the GTB. In Figure 9 (see also

figures 4 and 5), we outline these major changes in basin dynamics: A) during Hamilton times,

the basin displayed a gently sloping, ramp-style morphology; B) coincident with the onset of the

Lower Tully Bioevent, a fault-bound ‘clastic trap’ formed in nearshore portions of the basin with associated development of a sediment-starved and nutrient-poor carbonate bank setting offshore from it to the west; C) by the time of maximum development of the recurrent ‘Hamilton Fauna’, during the Upper Tully Bioevent, the clastic trap had been filled and the basin once again resembled the ramp-style morphology typical of the Hamilton Group; and, D) with the onset of the third tectophase of the Acadian Orogeny, the basin rapidly subsided and was filled with detrital sediments derived from the rejuvenated Acadian hinterlands. For the first time since the initial appearance of the “Hamilton Fauna”, the NAB took on a shelf-slope profile due to these

increased sedimentation and progradation rates (see Fig. 5; Rogers et al., 1990).

Below, we outline how the changes in NAB morphology might amplify the effects of the

estuarine-type watermass circulation model, the supporting lithologic observations for this amplification, and correspondence of hypothesized watermass circulation patterns to the faunal transitions. Application of the estuarine-type circulation model with regards to changes in basin

morphology is shown in Figure 10. Inferred as a generally arid time undergoing increasing

global warming and sea level rise, the lower Tully Group would be deposited under relatively

reduced riverine influx, and relatively high input of watermass influx from cratonic settings. A

pycnocline would develop between these two watermasses, and would be further enhanced by

the ‘silled’ basin formed as a result of the placement of the ‘Sherburne High’ (Fig. 4 and 10A;

see for reference Witzke, 1987; Algeo et al., 2008). The position of the pycnocline in this model

provides two differing depositional settings that correspond to the onshore-offshore (Hamilton-

Tully) biofacies distributions (Fig. 7). It is further possible that anti-estuarine circulation, due to

increased aridity and evaporation and low riverine influx, may also have developed at this time

(sensu Witzke, 1987, and references therein).

The model shown in Figure 10A is further supported by the unique lithological

characteristics observed in strata containing the ‘Tully Fauna’ (Baird and Brett, 2003, 2008).

Chamosite, which is rare in the Hamilton Group, is observed at numerous horizons in the New

Lisbon Member and lower Tully Formation. It characteristically occurs as mud-supported, sand-

size, discoidal, black grains within intensely bioturbated thin layers in association with

diagenetic siderite. It is most concentrated in the Smyrna Bed, both along and east of the

“Sherburne High” (see Figs. 4, 5, and 6) (Heckel, 1973; Baird et al., 2003; Baird and Brett,

2008). Tully chamosite beds generally contain very few fossils, which are often highly corroded.

The Smyrna Bed appears to record only moderate to low energy conditions, despite its

designation as the “Tully oolite” in literature (Cooper and Williams, 1935; Heckel, 1973; Baird and Brett, 2003). While the origin of chamosite bearing beds is poorly understood, some generalizations about its depositional requirements can be made. In particular, sediment-

starvation, reducing conditions, warm humid climates, and high sea level events have all been

implicated as conditions favoring this type of deposit (Huber and Garrels, 1953; Maynard, 1986;

Kim and Lee, 2000; Baird et al., 2003). These reconstructions accord well with the model

presented in Fig. 10A, especially when considering that the Tully Group is inferred to have been

deposited during warm humid periods during an overall aridity event. Synchronous reduced

sediment input, high sea level conditions, and development of a ‘mixing front’ between the two

watermasses at or near the ‘Sherburne High’ would explain the unique chamositic character of

the Smyrna Bed (Baird et al., 2003; Baird and Brett, 2008; Marshall et al., in press). Originally,

Baird and Brett (2003) modeled the development of numerous, repeated, eutrophication-driven

oxygen minimum zone events impinging the top and east flank of the “Sherburne High” in a

sediment-starved, warm water regime to explain the Smyrna Bed “oolite”. However, the stratified water mass model, advanced herein, is similarly suited as an explanation for the chamosite texture and distribution.

Additionally, the Smyrna Bed also contains stromatolites and syneresis cracks, which are not observed in the intervals before or after the GTB (Baird et al., 2003). The most commonly held view is that syneresis cracks are the result of contraction of the swelling clay lattices due to salinity changes in pore waters, possibly associated with mat structures (Jüngst, 1934; White,

1961; Burst, 1965; Plummer and Gostin, 1981; Pflueger, 1999, however see Pratt, 1998, for alternate interpretation). Modern stromatolites form in physically-stressed environments, such as

hypersaline, high-energy, with shifting oolitic sand substrates, and can be found in both shallow or deepwater settings (Monty, 1971; Hofmann, 1973; Logan et al., 1974; Playford, 1980; Dravis,

1983; Böhm and Brachert, 1993; George, 1999). Again, placement of a mixing front within proximity to the ‘Sherburne High’ would provide an environment conducive to stromatolite and syneresis crack formation.

100

Finally, the Tully limestone is itself a dramatic, lithologic anomaly within the overall

Catskill Delta siliciclastic succession. Tully Group carbonates differ drastically from Hamilton and Genesee Group carbonates in that the former are dominantly calcilutites and micrites with dilute concentrations of well preserved fossils, and in the latter consist of local shell accumulations during siliciclastic sediment starvation (Heckel, 1973; Brett and Baird, 1994;

Zambito et al., 2007, 2009). Heckel (1973) also observes that carbonate grains within the Tully

Group are polycrystalline, with various shapes and sizes, and suggested that these grains are possibly pieces of skeletal grains that have undergone extreme comminution. However, no algal structures were observed within the Tully carbonates and, furthermore, skeletons are typically non-abraded. Due to these observations, Heckel (1973) could not rule out physiochemical precipitation of at least some of the Tully carbonate grains, sensu whiting events (Cloud, 1962;

Wells and Illing, 1964; Shinn et al., 1989). We suggest that physiochemical precipitation of at least some of ‘Tully’ carbonate occurred, and was facilitated by, the watermass mixing front at the interface of the higher salinity watermass from cratonic areas and the lower salinity freshwater runoff of the Acadian hinterlands (Fig. 10A). Under extreme aridity, the possible formation of anti-estuarine circulation during Tully deposition may also have occurred. Anti- estuarine circulation would have resulted in carbonate-rich, nutrient-poor conditions, which are typical of the Tully (Witzke, 1987; Heckel, 1973; Baird et al., 2003).

Coincident with the onset of the Upper Tully Bioevent, the ‘clastic trap’ had almost been completely filled with sediment and dysaerobic biofacies of ‘Hamilton Fauna’ are observed up ramp of the ‘Tully Fauna’. This suggests that environmental conditions in shallow settings began to change before those in deeper settings to more Hamilton-like conditions (Figs. 4 and 7)

(Baird and Brett, 2008). We attribute this step-wise recurrence of ‘Hamilton’ biofacies,

101

ultimately culminating in the diverse coral and brachiopod biofacies of the Bellona-West Brook

Beds, to the return of a ramp-style basin morphology and the end of the aridity event (Figs. 9C and 10B; Marshal et al., in press). Though estuarine-type circulation would still have been in

effect, an increase in freshwater runoff and the ramp-style basin would have decreased the elevation of the pycnocline, resulting in a larger habitable area for the ‘Hamilton Fauna’, while still maintaining a mixing front resulting in micrite precipitation which continued until transgressive overspread of regional anoxia associated with post-Tully flexural basin collapse and eustatic highstand, and interbeds with the black shales of the Geneseo Shale as the Taghanic

Onlap progresses. The continued maintenance of the mixing front (pycnocline) and associated watermasses of differing characteristics (namely salinity) is suggested by the persistence of

‘Tully’ taxa in the deepest, most dysaerobic settings well into the Genesee Group; in fact, the

Eumetabolatoechia biofacies of the ‘Hamilton Fauna’ never recurs, and was permanently replaced by the ‘Tully Fauna’ equivalent Camarotoechia biofacies (Fig. 7). The sequence boundary preceding the Taghanic Onlap, at the base of the Bellona-West Brook beds, probably also played a role in the return of diverse ‘Hamilton’ assemblages, as the sequence boundary unconformity essentially ‘leveled the sea floor’ removing any basin topographical remnant of the

‘Sherburne High’ and thereby allowing the low-salinity watermass to reach further into the basin.

However, this relief profile began to return during deposition of the Moravia and Fillmore Glen portions of the uppermost Tully (Fig.4).

With the continuation of the Taghanic Onlap and the onset of the third tectophase of the

Acadian Orogeny, sea level continued to rise, the Appalachian Basin subsided drastically, sedimentation and progradation were greatly increased, and the basin morphology permanently changed to a shelf-slope-basin profile that was present until the Mississippian, when the basin

102 became completely filled (Figs. 5, 9, and 10C). The Geneseo Bioevent is recorded in the transition between the uppermost Tully Group (Moravia and Fillmore Glen Beds) and the lowest

Geneseo Formation (Fig. 5), when black shale deposition takes the place of carbonates in the west and coarser siliciclastics in the east. The Geneseo Shale is interpreted as recording a maximum highstand event for the NAB based on the estimates of Ettensohn (1985). Boyer and

Droser (2007) report minimal bioturbation and low-diversity fossil assemblages for the Geneseo

Shale, indicative of depleted bottom-water oxygen levels. Geochemical analysis of the Geneseo

Shale by Murphy et al. (2000) and Formolo and Lyons (2007) suggests that anoxic, and possibly even euxinic, conditions would have been favored by relatively short-term fluctuations in the position and strength of the pycnocline and upwelling conditions, which may be expected if freshwater runoff and sediment supply was influenced by seasonal or some other climatic oscillation (Figs. 8 and 10C). Witzke (1987) suggests that upwelling may be enhanced under estuarine-type circulation, especially when the basin morphology includes a shelf-slope break, thereby increasing productivity and black shale deposition. The transitional nature of interbedded micritic limestones and black shale of the Moravia Beds into the micrite-free, organic-rich Geneseo black shale likely represents the onset of upwelling conditions and increased nutrient influx to bottom-waters.

Reconstruction of a high-resolution stratigraphic framework along an onshore-offshore gradient during this time suggests that dysoxic conditions extended to at least storm-wave base

(shelf settings) during the initial phases of the Taghanic Onlap as is evidenced in nearshore

Geneseo Formation equivalents by rusty-weathering fossiliferous gutter-casts in otherwise fossil- poor dark gray to black silty shales, and, also, dark gray silty shales containing dysaerobic communities interbedded with swaley cross-bedded sandstones interpreted as shore-zone storm-

103 wave current deposits and containing slightly more diverse and aerobic communities (Fig. 5)

(Johnson and Friedman, 1969; Bridge and Willis, 1994; Zambito, unpublished data).

Additionally, the Taghanic Onlap also increased the linkages between depositional basins, resulting in incursions of OWR taxa, such as Tylothyris mesacostales, and the recurrence of “N.” tulliensis and E. ambocoeloides (Fig. 6). This continued linkage of the NAB with the cratonic watermass following the Taghanic Onlap (Fig. 1C), the rapid subsidence and removal of much of the basin from the mixing effects found above storm wave base, basin morphology induced upwelling, and isolation from oceanic water input, collectively ensured that estuarine-type circulation driven by cratonic watermass influx persisted in the Appalachian Basin throughout the rest its duration see (Algeo et al., 2007).

Sediment input into the basin greatly increased, concurrently with this exceptionally elevated oxycline, precluding low turbidity communities in the NAB such as diverse coral assemblages even when oxygen was available; indeed the extinction rate for rugose corals was higher during the Taghanic than at the Frasnian/Fammenian extinction (Oliver, 1990). With the exception of dysaerobic auloporid communities, the only coral bed known from the Genesee

Group is in the Firestone Beds interval of the Ithaca Formation; however, by this time additional

OWR incursions had occurred and this relatively low diversity coral assemblage had practically no resemblance to the ‘Hamilton Fauna’ (Zambito et al., 2007, 2009). Additionally, only a few coral beds are known from post-Geneseo strata, and all are low-diversity (McLean and Sorauf,

1988). Sediment-input related faunal changes are also seen in the increase in the relative proportion of infaunal bivalves relative to sessile brachiopods at this time (Thayer, 1972, 1974).

These observations suggest that during the Geneseo Bioevent, the amount of available ecospace (both in terms of habitable area and total biofacies spectrum occupancy) in the NAB

104

was greatly reduced by the concurrent elevation of the oxycline and increased sedimentation

input into the basin (Figs. 5 and 7). Furthermore, those biofacies that persisted in the NAB

underwent significant restructuring as a result of the decrease in habitable area and the incursions

of OWR taxa, while a surprising complement of ‘Hamilton’ taxa survived in nearshore settings

only to later reoccupy the basin when hospitable conditions returned to offshore settings

(Zambito et al., 2007, 2009). With continued progradation, the combination of an elevated

pycnocline and high sediment influx left a majority of ‘Hamilton’ taxa with nowhere to go but

extinct.

Conclusions and Implications

The application of watermass circulation models to global environmental changes and

local basin dynamics to understanding the Global Taghanic Biocrisis in the New York

Appalachian Basin provides a relatively simple, plausible, and well-supported explanation for the faunal incursions, replacements, recurrences, and extinctions observed. Under this model, summarized in Figure 11, the incursion and subsequent replacement of the ‘Hamilton Fauna’ by the ‘Tully Fauna’ was driven by the influx of higher salinity waters into the NAB during a time of overall increased aridity, and was facilitated by basin linkage and the breakdown of latitudinal climatic gradients associated with global sea level rise and warming, as well as local basin topography associated with a fault-induced scarp (Lower Tully Bioevent). Subsequently, the end of the aridity event and return to the typical ramp-style basin profile of Hamilton-times, resulted in the recurrence of the ‘Hamilton Fauna’ in the NAB by increasing the amount of the NAB affected by a lower-salinity watermass of riverine runoff origin (Upper Tully Bioevent). Finally, increased subsidence and sediment input into the NAB in conjunction with a highly stratified water column and periodic upwelling resulted in permanent changes to the basin, such that

105

Hamilton-type environments were no longer present, and the ‘Hamilton Fauna’, with the

exception of generalist forms, underwent major extinction (Geneseo Bioevent).

After occupying the Appalachian Basin for approximately 4 to 5 million years during which little ecological change or speciation occurred, the ‘Hamilton Fauna’ underwent extinction as a result of combined global (sea level rise and warming) and local (basin dynamics and watermass circulation) environmental changes. Faunal transitions recognized by reconstructing biofacies spectrums and corresponding changes in basin morphology during the GTB suggest that there was a distinct environmental suite, other than lithofacies, that the ‘Hamilton’ and

‘Tully’ faunas each preferred and tracked temporally. ‘Habitat Tracking’ has been suggested as a mechanism by which communities comprised of species with similar preferred habitats

(biofacies) migrate (through generations) along with a preferred environment (facies belts) rather than adapt to locally changing conditions (Brett et al., 2007a,b). This may be the primary explanation for the pattern of ‘Coordinated Stasis’ in the fossil record (Brett and Baird, 1995;

Brett et al., 1996). The pattern presented here of ‘habitat tracking’ at the faunal level suggests that there is a hierarchical scale at which tracking and the resultant ecological stasis occurs.

An ongoing discussion in the paleoecological literature is whether faunas represent

cohesive communities that are adapted to distinctive environmental conditions, or whether

faunas are comprised of species that are tracking their preferred habitats individually (Brett et al.,

1996; Patzkowsky and Holland, 1999; DiMichele et al., 2004; Brett et al., 2007b). The patterns

observed in the biofacies spectrum during the faunal transitions studied suggest that, indeed,

faunas do represent cohesive communities, but, at the same time, individual species still track

habitats individually. For example, we have suggested from the patterns observed that both the

‘Hamilton’ and ‘Tully’ faunas each consist of cohesive groups of species that had preferred

106 salinity ranges; however, the boundary between these faunas is blurred by the generalistic taxa of each fauna that are commonly observed to overlap in space and time, i.e., during the initial

‘Tully Fauna’ incursions in the latest Hamilton Group, and the initial ‘Hamilton Fauna’ recursions during the middle Tully Group (Figs. 6 and 7).

Following the Geneseo Bioevent, the resultant ‘Genesee Fauna’, which can be considered a subset of global cosmopolitan fauna, is, for the most part, comprised of generalist ‘Hamilton’ and ‘Tully’ taxa, species originating from ‘Hamilton’ genera, and a few, new OWR incursions.

At this point, it is evident that the elevated extinction and origination rates observed at this time are related to the habitat contraction associated with the pycnoclinal rise and increased sediment input that was followed by habitat expansion as progradation allowed progressive portions of the basin to be colonized; one of our current goals is to quantify these evolutionary rates, both temporally and spatially through the extinction and subsequent recovery.

The patterns described suggest that the demise of the recurrent ‘Hamilton Fauna’ during the Geneseo Bioevent was a combination of global and local environmental changes. One thing that remains to be understood is whether, or, to what degree, the local effects of the Acadian

Orogeny were possibly the driving mechanism for the globally observed sea level rise and warming. As a next step, we must compare our observed faunal and environmental patterns to those in Taghanic successions described elsewhere, particularly, where contextual paleolatitude, tectonic, and water circulation parameters are clearly different. This approach should be the best way for us to assess the importance of the Taghanic Biocrisis as a global event.

107

Acknowledgements: We’d like to thank the editor, J. Talent, for his patience with us in getting this manuscript completed. Comments by reviewers, R. Feist and A. Simpson, greatly enhanced the readability of this manuscript and conveyance of ideas therein. Various discussions with

R.T. Becker, and J.E.A. Marshall greatly improved our understanding of the Taghanic Biocrisis at the global scale, in both marine and terrestrial settings. We are also indebted to T.J. Algeo for greatly enhancing our understanding of carbonate depositional environments and watermass circulation models. Our research into the type area of the Taghanic Biocrisis has been supported, at various times, by student grants to JJZ from the American Association of Petroleum

Geologists, the American Museum of Natural History, the Evolving Earth Foundation, the

Geological Society of America, the Mid America Paleontological Society, the Paleontological

Society, the Schuchert and Dunbar Grants in Aid Program at the Yale Peabody Museum, Sigma

Xi, the Society for Sedimentary Geology (SEPM), and the University of Cincinnati, Department of Geology; CEB has been supported by NSF EAR 9219807, EAR 9996178, and the USGS

STATEMAP program; GCB has been supported by the Pennsylvania Department of Natural

Resources (Geological Survey).

108

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WITZKE, B.J., and BUNKER, B.J., 1997, Sedimentation and stratigraphic architecture of a Middle

Devonian (late Givetian) transgressive-regressive carbonate-evaporite cycle, Coralville

Formation, Iowa area, in Klapper, G., Murphy, M.A., and Talent, J.A., eds., Special

Paper - Geological Society of America: Paleozoic Sequence Stratigraphy,

Biostratigraphy, and Biogeography: Studies in Honor of J. Granville ("Jess") Johnson,

volume 321, Boulder, Colorado, p. 67-88.

ZAMBITO, J.J. I.V., BAIRD, G.C., BARTHOLOMEW, A.J., and BRETT, C.E., 2007, Re-examination

of the type Ithaca Formation; correlations with sections in western New York: Guidebook

- New York State Geological Association, Meeting, v. 79, p. 83-105.

ZAMBITO, J.J. I.V., BAIRD, G.C., BRETT, C.E., and BARTHOLOMEW, A.J., 2009, Depositional

Sequences and Paleontology of the Middle – Upper Devonian Transition (Genesee

Group) at Ithaca, New York: A Revised Lithostratigraphy for the Northern Appalachian

Basin, in, Over, D.J., ed., Studies in Devonian Stratigraphy: Proceedings of the 2007

International Meeting of the Subcommission on Devonian Stratigraphy and IGCP 499:

Paleontographica Americana, 63: 49-69.

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Figure 1: Paleogeographic reconstruction of the globe (A) and study area respectively before (B) and after (C) the Taghanic Biocrisis. The Appalachian Basin strata of New York State (type area, represented by ‘star’) that record this biocrisis were deposited approximately 30 degrees south of the paleo-equator. OWR and EAR denote the positions of ‘Old World Realm’ and

‘Eastern Americas Realm’ faunas, respectively; note the position of the Trans-Continental Arch

(‘Continental Backbone’ of Johnson (1970)) relative to these faunas. Abbreviations NA, SA,

and AF stand for North America, South America, and Africa, respectively. Paleomaps adapted

from Blakey (2008).

Figure 2: Type section of the Global Taghanic Biocrisis, Taughannock (Taghanic) Falls,

Trumansburg, Tompkins County, New York (represented by ‘star’ on inset figure of Tully Group

outcrop belt). Lower falls is approximately 6 meters high. Lip of upper falls is approximately

66 meters above plunge pool; top of Tully Group is slightly below level of plunge pool in picture

of upper falls. See text for details of bioevents shown and informal divisions within Tully Group

(i.e., upper and lower).

Figure 3: Outcrop belt for the Hamilton, Tully, and Genesee groups in the Appalachian Basin

deposits of New York State. Line labeled ‘a’ represents the approximate position of the

shoreline during deposition of the Tully Group. ‘Star’ denotes type locality (see Figure 2).

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Figure 4: Regional cross-section of the Tully and basal Genesee Group across east-central New

York State showing inferred correlations of Tully Group divisions with equivalents in the Tully

Formation Clastic Correlative succession (TFCC). Location of section along outcrop belt is shown in inset figure. The underlying Hamilton Group is not shown for ease of Tully unit visualization. The transect shows the rapid eastward thickening of the Tully clastic correlative succession across a possible growth fault east of Sherburne, New York; the sediment-starved, western (structurally upthrown) side of this structure (“Sherburne High”), bounded a local, structurally downthrown, basinal trough which served as a clastic trap. Note the prominent disconformable nature of the mid-Tully sequence unconformity (c) and the upper Tully sequence unconformity (d). Note also the striking thinness and uniformity of thickness of the Bellona

Bed/West Brook Shale (e) relative to underlying and overlying units (see text). The Tully-

Genesee contact (f) is unconformable across part of the region as shown. Lettered features include: a, DeRuyter Bed; b, chamositic-sideritic bed believed to be equivalent to DeRuyter Bed; c, Smyrna Bed floored by mid-Tully sequence disconformity; d, upper Tully sequence disconformity; e, Bellona Bed/West Brook Shale; and f, black shale-roofed corrosional discontinuity with associated detrital pyrite marking Tully-Geneseo contact. Figure adapted from Baird and Brett (2003).

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Figure 5: A) Time-stratigraphic chart for the strata of New York that record times prior to, during, and following the Taghanic Biocrisis, including strata of the Onondaga (On), Hamilton,

Tully (Tul), Genesee, and Sonyea (Son) groups. For the most part, stratigraphic divisions within groups are at the level of formation. B) Environments of deposition overlain on the chronostratigraphic framework of part A of this figure. Note that slope and pro-delta slope environments did not exist prior to the Genesee Group, and diverse coral biofacies (for the most part) do not occur following the Taghanic Biocrisis. Figure is adapted from Rogers et al. (1990) using data and information from the following references: Cooper and Williams (1935), Rickard

(1975, 1981), Brett et al. (1986), Grasso (1986), Brett and Baird (1985, 1994), Bridge and Willis

(1991, 1994), House (2002), Baird and Brett (2003, 2008), Baird et al. (2006), Desantis et al.

(2007), Zambito et al., (2007, 2009), and J. Zambito (unpublished data). For a complete list of diverse coral and brachiopod horizons of the Hamilton Group, see Fig. 4 of Brett et al. (2007a).

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Figure 6: Time-stratigraphic chart showing the ranges of ‘Old World Realm’ taxa in the New

York State Appalachian Basin during the Global Taghanic Biocrisis. Bioevents (i.e., Lower

Tully, Upper Tully, and Geneseo) are marked at the respective horizons for which each bioevent commences; however, the effects of each bioevent (migrations) are seen over a given interval.

SB stands for sequence boundary. Note that, for a number of taxa, ranges cross sequence boundaries (dashed lines), suggesting that the faunal transitions observed are real, and not an artifact of unconformities. Lettered units in ‘white’ represent diverse coral-brachiopod communities of Hamilton taxa. Lettered units include: a) Amsdell Bed, b) Gage Gully submember, c) Sheds submember, d) Highland Forest submember, e) nonmarine (red bed) tongues extending westward into nearshore marine deposits (Gilboa Fossil Forest), f) Vesper

Bed, g) Smyrna Bed (chamosite), and h) the “Taughannock Falls Chamosite Bed” of Heckel

(1973). Diagonal lines represent areas of syn-depositional (intra-Devonian) erosion.

Stratigraphy based on Baird and Brett (2008), Brett and Baird (1994), and Zambito et al. (2007,

2009). Conodont zonation based on summary in Klapper (1981) and House (2002). Faunal information compiled from Williams (1884, 1890), Kindle (1896, 1906), Prosser (1899), Cooper and Williams (1935), Heckel (1973), Baird et al. (2003), Brett and Baird (2003;, 2008), Sessa

(2003), Bonelli et al. (2006), Zambito et al. (2007, 2009), and J. Zambito (unpublished work).

Stratigraphic succession adapted from Baird and Brett (2008). Fossil pictures adapted from

Linsley (1994) and Baranov and Alkhovik (2006).

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Figure 7: New York Appalachian Basin biofacies spectrum through the Taghanic Biocrisis.

Abbreviations include: EAR, ‘Eastern Americas Realm’; and OWR, ‘Old World Realm’.

Portions of the spectrum denoted by ‘?’ indicate unknown biofacies, which is the result of non- deposition, erosion, or lack of outcrop for that facies. Note, selective, depth/salinity-controlled diachroneity respectively for OWR biota, recurrent ‘Hamilton Fauna’, and key Genesee Fauna elements indicated by spectral color shading. Fossil plates are used to illustrate representative taxa of the faunas and are adapted from Linsley (1994). The biofacies spectrum of the

“Hamilton Fauna” was first proposed by Brett et al. (1990), and demonstrated quantitatively by

Brett et al. (2007). The biofacies spectrum for the lower and upper Tully Group is based on observations from Baird et al. (2003), Baird and Brett (2003, 2008), and Baird (unpublished data). The lower Genesee Group biofacies spectrum is based on observations from Boyer and

Droser (2007), Zambito et al. (2007, 2009), and J. Zambito (unpublished data).

Figure 8: Generalized model of estuarine-type watermass circulation pattern for the Appalachian

Basin, after Witzke (1987) and Algeo et al. (2007, 2008). Riverine discharge (white arrow) from the Acadian Hinterlands provides freshwater sources to the foreland basin, which forms a low- salinity surface watermass. Shallow water evaporitic settings on the North American craton (see

Fig. 1) would provide a denser, more saline watermass (gray arrow) to the foreland basin.

Together, these watermasses would be expected to form a pycno(halo)cline, which, upon interacting with the oxycline of the epeiric sea, might result in a ‘boundary layer’ of fluctuating oxygen and salinity.

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Figure 9: Basin dynamics through the Taghanic Biocrisis. Basin profile models represent the

extent of the basin observed along the Tully Group outcrop belt from the paleoshoreline to the

western-most extent of outcrop (see Figure 3); vertical dimension of model is approximately 60

meters for A,B, and C, and 125 meters for D. ‘TO’ represent the initiation of the Taghanic

Onlap, and ‘TP3’ signifies the onset of the third tectophase of the Acadian Orogeny (see text for references). Relative sea level curve is adapted from Brett and Baird (2003), Brett and Baird

(2008), and Zambito et al. (2009). Stratigraphic labels are outlined in Figure 5. A) During the majority of the Hamilton Group, the New York Appalachian Foreland Basin was a gently sloping ramp. B) With the onset of syn-depositional faulting during the lower Tully Group, a

‘clastic trap’ is formed as a result of the ‘Sherburne High’ and a carbonate platform-type setting forms to the west (Heckel, 1973; Baird and Brett, 2003). C) By the time of initial onset of the

Taghanic Onlap (Bellona-West Brook beds - interval), the ‘clastic trap’ has been been filled with sediment and the basin once again exhibits a ramp-profile similar to Hamilton Group times (see

Fig. 7A). D) With a drastic increase in subsidence and progradation due to the onset of the third tectophase of the Acadian Orogeny, a well-defined shelf and slope is formed. For further discussion, see Figure 8.

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Figure 10: Watermass circulation models for the New York Appalachian Basin for times during and after the Taghanic Biocrisis. A) Watermass circulation model during the lower Tully

Group, which is inferred to be a period of increased aridity (Marshal et al., in press). Increased aridity would have led to reduced runoff, resulting in a rather shallow, lower-salinity surface layer and an elevated pycnocline. Basin morphology, in the form of a fault-controlled sill, further accentuates the development of contrasting shallow and deep watermasses. B) The upper

Tully Group is inferred to have been deposited toward the end of the arid interval (Marshall et al., in press) which would have resulted in an increased influx of freshwater runoff into the basin that would have forced the pycnocline into deeper settings, accentuated by a basin topography similar to previous Hamilton-times C) By the time of deposition of the Genesee Group, the aridity interval had ended (Marshall et al., in press) and freshwater runoff was further accentuated by the topography of the uplifted Acadian Highlands which also resulted in increased sediment delivery to the basin. The eustatic sea level rise (Taghanic Onlap of Johnson

(1970)) was also in full effect, leading to an influx of higher salinity bottom waters into the basin and resulting in a highly elevated pycnocline. Furthermore, basin topography would have facilitated upwelling.

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Figure 11: Summary of the faunal, climate, and watermass changes discussed in this paper.

Aridity changes from Marshall et al. (in press). Generalized temperature change is from

Joachimski et al. (2009), but has been adapted to represent faunal changes outlined in this study, i.e., the slightly cooler period. See Figure 7 for more detailed description of the faunas. EAR,

OWR, LTB, UTB, TO, GB, and TP3 = Eastern Americas Realm, Old World Realm, Lower

Tully Bioevent, Upper Tully Bioevent, Taghanic Onlap, Geneseo Bioevent, and Tectophase 3 of the Acadian Orogeny, respectively.

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Figure 1

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Figure 2

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Figure 3

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Figure 4

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Figure 5

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Figure 6

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Figure 7

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Figure 8

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Figure 9

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Figure 10

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Figure 11

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Chapter 4

Reconstruction of Isotopic Changes for the Late Givetian (Middle Devonian) Global Taghanic

Biocrisis in its Type Region (Northern Appalachian Basin)

J.J. Zambito IVa,*, M.M. Joachimskib, G.C. Bairdc,1, C.E. Bretta,1, W.E. Davis Jr.d,1, and D.J.

Overe,1 a University of Cincinnati, Department of Geology, Cincinnati, OH 45221-0013 USA b GeoZentrum Nordbayern, Universität Erlangen-Nürnberg, Schlossgarten 5, 91054 Erlangen,

Germany c SUNY Fredonia, Department of Geoscience, Fredonia, NY 14063 USA d Boston University, 23 Knollwood Drive, East Falmouth, MA 02536 USA e SUNY Geneseo, Department of Geological Sciences, Geneseo, NY 14454-1401 USA

1 in alphabetical order

* Corresponding Author: [email protected]

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Abstract

During the Global Taghanic Biocrisis, approximately 385 Ma, Middle Devonian faunas

worldwide underwent a major extinction in apparent conjunction with global warming and

aridity, eustatic sea level rise, and decreased oxygenation of epicontinental seas. In the type

region of this biocrisis, the northern Appalachian Basin, faunal changes have been extensively

documented at high-stratigraphic resolution through the Hamilton, Tully, and Genesee groups as

a series of at least three bioevents that include faunal migrations and replacements resulting

ultimately in the extinction of numerous taxa of the long-lasting (4-5 My) 'Hamilton Fauna' through an interval of roughly 500 Kyr. Carbon isotope record positive excursions have been reported from various regions, but never from the type region. In this study, we reconstruct

13 18 δ Ccarbonate and δ Oapatite changes in the type region of the Global Taghanic Biocrisis and compare these changes to the faunal transitions observed. Isotopic changes apparently reflect

13 both global and local environmental changes. The high-resolution δ Ccarb record shows a ~2‰

positive excursion associated with the semialternans Zone, which is an excursion of global

nature and has utility for chemostratigraphic correlation. δ18O changes reconstructed from

conodont apatite show a period of warming of approximately 4°C concurrent with the biocrisis

and in agreement with previous global reconstructions. In conjunction with faunal

reconstructions in the type region through the biocrisis, the isotopic data suggest that locally,

watermass changes played a large role in the faunal transitions observed. This agrees with

studies of this biocrisis from other regions that, while significant global changes were indeed

occurring at this time, these changes played out differently on regional scales.

keywords: biogenic apatite, warming, biofacies

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1. Introduction

During the Global Taghanic Biocrisis (GTB), approximately 385 million years ago,

The Middle-Upper Devonian boundary was originally defined at this stratigraphic level because of the abrupt faunal changes observed in a number of taxonomic groups (Klapper et al., 1987;

House, 2002). Although not recognized as one of the "Big Five" mass extinctions, studies of marine invertebrate global biodiversity trends at various taxonomic scales through the

Phanerozoic recognize the GTB interval as the beginning of a period of protracted extinction that spans the remainder of the Devonian (Raup and Sepkoski, 1982; Alroy et al., 2008). A growing body of work suggests, however, that these lesser studied, but more frequent events that involve faunal restructuring and replacement at regional to global scales may have had a greater aggregate effect on the evolution of life (Walliser, 1990; Brett and Baird, 1995; Brett et al., 1996;

Miller, 1998).

Johnson (1970) and Boucot (1988) describe the GTB as marking the end of established

Devonian faunal provinciality related to latitudinal climatic (temperature) gradients. The GTB resulted in a world-wide cosmopolitan fauna that persisted until the late Frasnian extinction

(McGhee, 1996, and references therein; and Sandberg et al., 2002). Reconstructions of sea- surface temperature variations before and after the GTB interval indicate global warming, but, the stratigraphic resolution of these analyses is too coarse to compare with faunal changes

(Joachimski et al., 2004, 2009; and Brand et al., 2008).

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A high-resolution stratigraphic framework has allowed detailed qualitative and quantitative paleoecological study of the pulsed faunal migrations, replacements, recurrence, and extinctions during this biocrisis in the type region, the northern Appalachian Basin (NAB)

(Heckel, 1973; Baird and Brett, 2003, 2008; Sessa, 2003; Bonelli, 2008; Zambito et al., 2009, in press; Chapter 4). The only paleoenvironmental reconstruction using geochemical proxies in the type region, to date, lack the stratigraphic resolution for which paleoecological changes have been described, as the studies were conducted on successions in which a majority of the strata recording the faunal transitions was removed by intra-Devonian erosion (Murphy et al., 2000;

Sageman et al., 2003).

Here, we discuss the relationships between the isotopic patterns in carbonate δ13C and apatite δ18O with respect to local and global environmental changes and review the faunal transitions observed in the type region of the GTB in regard to these changes.

2. Geologic Setting of the Type Region

The NAB deposits found in New York and adjacent states comprise the type-area of the

GTB (Figs. 1 and 2, see also House, 1985, 2002). In the Middle Devonian, the NAB was located at approximately 30° S latitude (Fig. 1A, Cocks and Torsvik, 2011). The strata were deposited in a foreland basin that formed during the Acadian Orogeny as the Laurentian and Avalonian terranes converged obliquely; the GTB occurred in the transition from the second to the third collisional tectophases of the Acadian Orogeny (summarized in Ver Straeten and Brett, 1997; and Ettensohn, 2008; see also references therein). During each tectophase, orogenic activity occurred along the eastern seaboard of Laurentia, causing subsidence of the Appalachian Basin in response to tectonic loading on the crust. Erosional weathering of these mountains produced the classic progradational complex in the Appalachian Basin known as the “Catskill Delta”. In

155 the NAB, the GTB is recorded primarily in the sediments of the Tully Group, but, immigration and extinction related to the GTB occur within the underlying uppermost Hamilton Group and the overlying lowermost Genesee Group (Fig. 3; Baird and Brett, 2008, and references therein; reviewed in Zambito et al., in press). The Tully Group has been divided into three informal units that correspond to depositional sequences: the lower, middle, and, upper Tully. These are recognized not only in the type-region, but also globally, and therefore are interpreted to represent eustatic sea level changes (Aboussalam and Becker, 2011; Brett et al., 2011).

The Tully Group has received detailed investigation through the years (Cooper and

Williams, 1935; Heckel, 1973), and is interpreted to have been deposited during a period of relative tectonic quiescence, when the second tectophase was waning and sediment input to the basin was relatively minimal (Ettensohn, 1985). Furthermore, siliciclastic sedimentation was almost entirely precluded in most of the basin by a fault-controlled “clastic trap” resulting in onshore siliciclastic and offshore carbonate deposition (Heckel, 1973; Baird and Brett, 2003).

With the onset of the third tectophase and coincident sea-level rise (eustatic Taghanic Onlap), the basin subsided and migrated westward and siliciclastic sedimentation resumed and subsequently intensified; this was manifested as the deeper-water deposits of the Geneseo black shale, subsequent shelf and slope progradation, and loss of carbonate deposition (Johnson, 1970;

Zambito et al., 2009, in press).

A globally recognized defining feature of the GTB, is eustatic sea level rise, termed the

Taghanic Onlap (Johnson, 1970; Johnson et al., 1985). Subsequently, usage of this term has varied, from the single greatest transgression during the biocrisis (Baird and Brett, 2003), to describing the overall higher sea level observed during the GTB (Aboussalam and Becker, 2011).

We use the term 'Taghanic Onlap' to represent the transgression associated with deposition of the

156 upper Tully (Bellona - West Brook interval) and continued sea level rise through the upper Tully

(latest ansatus to semialternans zones) to the maximum flooding surface at the base of the

Geneseo (hermanni Zone; sensu Baird and Brett, 2003). We prefer a more restricted definition because this reflects the current placement of the Taghanic Onlap in the type region (Brett et al.,

2011), although, a consensus on this designation, in particular, on recognition of a global stratigraphic surface in regards to eustatic sea level change, would greatly increase its utility as a global stratigraphic correlation tool.

3. GTB Recognition and Description

Initially defined by Walliser (1996), and subsequently refined by Aboussalam (2003, see also discussion in Aboussalam and Becker, 2011), a biocrisis is composed of a series of bioevents representing sudden paleooceanographic or biotic turnover. Biocrises should span more than one biozone, and comprise a number of bioevents that themselves occur within single biozones and/or transgressive-regressive cycle. In the GTB type region, at least three bioevents can be recognized and have been studied in detail (Baird and Brett, 2008; see review in Zambito et al., in press). The poly-phased nature of the GTB has also been recognized in other places, including Morocco, Montagne Noire (France), and the Rhenish Massif (Germany), however, each region has somewhat unique changes (Aboussalam and Becker 2011).

3.1 The Global Taghanic Biocrisis in the Type-Region – Faunal Affinities and Changes

Devonian faunas have been divided globally into biogeographic “realms”, the distribution of which is inferred to have been controlled by climatic gradients between the equator and poles

(Johnson, 1970; Koch and Boucot, 1982; Boucot, 1988, and references therein). At the onset of the GTB these realms consisted of the equatorial, warm-water ‘Old World Realm’ (OWR), and the higher latitude, slightly cooler-water, ‘Eastern Americas Realm’ (EAR). As illustrated

157 schematically in Figure 1B, prior to the GTB, genera that comprised the ‘Tully Fauna’ (a subset of the OWR) occurred in what is now the western United States and western Canada, in settings more equatorial than the Appalachian Basin. At the same time, the NAB was occupied by the diverse ‘Hamilton Fauna’ (a subset of the EAR) for a period of approximately 4-5 million years

(Brett and Baird, 1995; Baird and Brett, 2008).

In the NAB, the GTB has been extensively documented at high stratigraphic resolution as a series of three bioevents (Fig. 3). These bioevents were composed of faunal migrations and replacements resulting ultimately in the extinction of numerous ammonoid, coral, trilobite, and brachiopod taxa through an interval of approximately 400 to 600 Kyrs, including:1) the nearly complete replacement of the endemic ‘Hamilton Fauna’ with the previously equatorial ‘Tully

Fauna’; 2) the subsequent extermination of a majority of the ‘Tully Fauna’ and return of the

‘Hamilton Fauna’; and 3) loss of much of the ‘Hamilton Fauna’, at least locally, species turnover within some ‘Hamilton’ genera, the return of a few ‘Tully’ taxa, and the further incursion of additional OWR taxa to form the 'Genesee Fauna' (House, 2002; Baird and Brett, 2008; Zambito et al., in press). This post-biocrisis combination of taxa reflects the cosmopolitan fauna observed globally until the extensive Frasnian-Fammenian extinction, approximately 8 million years later

(Fig. 1C; McGhee, 1996; and Sandberg et al., 2002).

3.2 Environmental Controls on Faunal Biogeography and Faunal Transitions

Importantly, both ‘Hamilton’ and ‘Tully’ taxa occupied comparable onshore-offshore environmental gradients, including both siliciclastic and carbonate depositional settings in the

NAB Tully Group (Heckel, 1973; and Baird and Brett, 2003, 2008; summarized in Zambito et al., in press). Therefore, from an environmental standpoint, the preserved sedimentary record does not record transitions that parallel those observed among the biota. Johnson (1970) and

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Boucot (1988) suggested that instead, changes in (latitudinal) climatic gradients were the

primary drivers of the observed transitions. In particular, an episode of global warming is

thought to have expanded the ranges of equatorial taxa into higher latitudes, and, Johnson (1970)

further suggested that an increase in eustatic sea level, occurring simultaneously, drowned much

of the Trans-Continental Arch and enhanced migration by opening connections between

depositional basins, thereby increasing cosmopolitanism (compare Figs. 1B and C).

If the aforementioned scenario is correct, then one might expect that present-day South

America and Africa (southernmost areas in Figure 1A) would have been suitable refugia for the

‘Hamilton Fauna’, given that a period of global warming should have induced the fauna to migrate out of the Appalachian Basin to higher (cooler) latitudes. Unfortunately, South

American strata in this critical interval have either been eroded or preserve non-marine environments, so that there is no record of marine faunas at high latitudes in the Americas during the GTB, and, faunal lists from coeval strata in Africa do not contain most elements of the

‘Hamilton’ fauna (Barrett et al., 1988; de Melo, 1988; Isaacson and Sablock, 1988; Racheboeuf et al., 2001, 2004; and P.E. Isaacson, pers. comm. 2008).

In addition, the observation of 'Hamilton Fauna' recurrence within the upper Tully Group adds further complexity to understanding the environmental drivers of faunal transition in the type region, especially since global paleotemperature reconstructions during the Taghanic suggest, albeit at a low resolution relative to faunal studies, that warming was continuous through the GTB (Joachimski et al., 2009). Marshall and others (2011), in their study of the Old

Red Sandstone, observed that the GTB interval was an interval of increased aridity. With this in mind, Zambito et al. (in press, also Chapter 2) reviewed the GTB using a combination of biofacies reconstructions, sedimentological observations, and basin morphological models

159

through the GTB and, in combination with previously mentioned climate reconstructions,

hypothesized plausible watermass circulation changes through the biocrisis, as summarized in

Figure 3. In essence, the 'Hamilton Fauna' was present when estuarine-type circulation could be

inferred for the NAB, and the 'Tully Fauna' corresponded to a period when estuarine circulation

weakened, and possibly transitioned to an oligotrophic, anti-estuarine circulation driven by

increased aridity (sedimentological evidence further discussed in detail in Baird et al., in review).

An important aspect of understanding biotic change is determining the way in which

global changes (climate, eustatic sea level, etc.) are manifested regionally and locally. While this

is the type region for the GTB, it is also a tectonically active foreland basin, in close proximity to

siliciclastic sediment supply, and in a rather isolated position relative to fully open-ocean settings

(Fig. 1). Zambito and others (in press; Fig. 3) highlighted that faunal transitions in the type

region were best explained by a combination of global and local environmental changes.

However, the question still remains as to whether the type-region possesses an isotopic record of environmental change similar to those reconstructed for other regions. Against this backdrop, this study will address the following questions: 1) Do isotopic patterns in the type region correspond to records from other areas, and, if so, do these patterns have utility for chemostratigraphic correlation; and 2) what is the relationship between the bioevents and corresponding faunal changes in the type region and environmental changes deduced from isotope records?

4. Materials and Methods

13 The δ Ccarb record is reconstructed from the Cargill Salt Co. Test Core 17 from Lansing,

NY (API: 31-109-13173-00-00), drilled approximately 8 km to the east of the type-section for

the GTB (Taughannock Falls, Trumansburg, New York State; Fig. 2 and Table 1). Carbonate

160 powders were collected using a tungsten carbide drill bit from freshly cleaned core surfaces.

Care was taken to sample only the matrix. Carbon isotope analyses were performed at the

University of Erlangen-Nürnberg, Germany. Carbonate powders were reacted with 100% phosphoric acid at 70°C using a Gasbench II connected to a ThermoFinnigan Five Plus mass spectrometer. All values are reported in per mil relative to V-PDB (Vienna Pee Dee Belemnite) by assigning a δ13C value of +1.95‰ and a δ18O value of -2.20‰ to NBS19. Reproducibility of carbon isotope analyses was monitored by replicate analysis of laboratory standards and was better than ± 0.04‰ (1 std.dev).

18 The δ Oapatite record is reconstructed from conodont apatite collected from the type region (Table 1). The range of localities reflects the availability of material, specifically, the relatively low abundance of conodonts within the Hamilton Group (G. Klapper, pers. comm.; pers. observations). Pre- and post-biocrisis samples came from various localities throughout the type-region, while syn-biocrisis samples (Tully Group) all come from the Long Hill Road cut at

Moravia, NY, from material collected and published on by Davis (1975) as well as from additional samples collected at the same locality. Conodont oxygen isotope ratios were analyzed at the University of Erlangen-Nürnberg, Germany, following the methods outlined by

Joachimski et al. (2009, and references therein). Samples of conodont apatite of ~0.5 to ~1.0 mg

(corresponding to approximately 10 to 20 conodont elements) were dissolved in 2 M HNO3

-3 (nitric acid) and the PO4 within the conodont apatite was chemically converted to Ag3PO4 (see

O'Neil et al., 1994; Joachimski et al., 2009). The Ag3PO4 crystals were extensively rinsed with de-ionized water, dried, and homogenized using an agate mortar and pestle. Recovery rates of

3- PO4 were typically > 93%. The oxygen isotope ratios were measured on CO generated by reducing trisilverphosphate using a high temperature conversion-elemental analyzer (TC-EA)

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connected online to a ThermoFinnigan Delta plus mass spectrometer. Samples were measured in

triplicate. Accuracy and reproducibility was monitored by multiple analyses of

trisilverphosphate prepared from the NIST standard NBS 120c and laboratory standards.

Attention was paid to the taxonomic composition of analysed conodont assemblages. All

18 δ Oapatite values are reported in per mil relative to VSMOW (Vienna Standard Mean Ocean

Water).

5. Results

5.1 Carbon Isotope data

The most striking feature of the carbonate carbon isotope record is that each of the

13 bioevents described in the type region corresponds to a δ Ccarb excursion (Figure 4). Coincident

with the loss of the majority of 'Hamilton Fauna' taxa from the NAB and the incursion of the

'Tully Fauna' (Bioevent 1), a negative excursion of -1.58‰ is observed. The negative excursion

begins the uppermost Hamilton Group shales and continues into the limestones of the lowermost

Tully Group, across a large unconformity within the core. Following this negative excursion,

carbon isotope values gradually return to the apparent baseline of ~1.0‰ through the lower

Tully. Immediately prior to the recurrence of the 'Hamilton Fauna' in the NAB (Bioevent 2), an

13 abrupt shift in δ Ccarb 0.82 to 1.89‰ is observed immediately below the unconformable Smyrna

Bed, a highly condensed chamosite-rich encrinite, within the uppermost Carpenter Falls interval.

The positive excursion continues, across numerous discontinuities, albeit with a relatively large

scatter, to a maximum value of +2.91‰ within the Bellona-West Brook interval. Subsequently, carbon isotope values gradually decreased through the uppermost Moravia and Fillmore Glen intervals to values as low as 0.26‰. The onset of a positive excursion at the top of the studied

162

interval may be recorded, beginning with a trend to more positive values directly below the

Tully-Genesee contact, which is nearly conformable in this core.

5.2 Oxygen Isotope data

The oxygen isotope record profile also shows a broad correspondence between changes in the isotope ratios and faunal transitions (Fig.5). In general, conodonts from the GTB (Tully

18 Group) show lower δ Oapatite values relative to pre-biocrisis times. A shift from values of approximately 17.5‰ to as low as 16.0‰ is observed with the onset of the GTB. Subsequently,

18 δ Oapatite values increase to approximately 16.5‰ just prior to and following the recurrence of

18 the 'Hamilton Fauna' (Bioevent 2). The variation in δ Oapatite values seems greatest during the

time when the 'Tully Fauna' occupies the NAB, although this interval also has the greatest

18 sampling density. Following the GTB, one sample from the Genesee has a δ Oapatite value of

17.4‰.

6. Discussion

6.1 Carbon Isotopic Record Reconstruction

6.1.1 Comparison to Other Regions

13 To help distinguish whether δ Ccarb changes observed in the type region were global,

13 local, or, possibly, diagenetic, we compared the δ Ccarb record for the type region with data

13 available for coeval sections. Aboussalam (2003) reconstructed δ Ccarb records for a number of

European and Moroccan GTB successions, albeit at a much lower resolution than undertaken in

13 this study. A comparison shows similarities to δ Ccarb record for the type region (Fig. 6).

Although the absolute values, and to some degree timing relative to biostratigraphic boundaries,

13 are different among successions, a positive excursion is observed in all δ Ccarb reconstructions

during the semialternans Zone. In the New York and Syring (Rheinisches Schiefergebirge)

163

13 successions, where the semialternans Zone is most expanded, a similar trend in δ Ccarb values is seen, with the most positive values observed in the lowermost part, and decreasing through, this interval. Other sections that also show a similar positive excursions in this interval include

Blauer Bruch (Rheinisches Schiefergebirge, Germany; Buggisch and Joachimski, 2006, as discussed in Aboussalam and Becker, 2011) and the Iowa Basin (J. Day, pers. comm.).

A positive excursion is observed at the base of the hermanni Zone at Syring, although, the records for Pic de Bissous and Bou Tchrafine as reconstructed by Aboussalam (2003) do not show a correlative excursion at the base of this zone (Fig. 6). However, following a gradual

13 decrease in δ Ccarb at Ouidane Chebbi, an abrupt positive shift has been reconstructed. The

onset of a correlative positive excursion may be recorded in the uppermost portion of the New

York reconstruction. A hermanni Zone positive excursion is also known from the Iowa Basin (J.

Day, pers. comm.).

13 Aspects of the New York to δ Ccarb record reconstruction that cannot be observed in reconstructions from other regions include the negative excursion seen at the Hamilton/Tully contact and the abrupt onset of more positive values within the uppermost ansatus Zone, earlier than at other sections.

6.1.2 Carbon Isotope Record Interpretation

The negative excursion observed in the type region at the onset of the GTB is not

observed in any other succession (although the Pic de Bissous section does show a negative shift

within the lower GTB interval; Fig. 6). The negative excursion is centered on the unconformable

contact between the siliciclastic Hamilton and the carbonate Tully groups (Fig. 4). Diagenesis

cannot be ruled out, as migration of late diagenetic water along this unconformity could create

the isotopic profile observed, with lightest values at the unconformity and progressively, and

164

symmetrical, higher values found above and below the possible diagenetic water conduit

(unconformable surface) and values reaching the 'baseline' of ~1‰ a short distance from the

unconformity both above and below it. Accordingly, reconstruction of the carbon isotopic changes through a more stratigraphically complete section for this interval is needed to rule out diagenesis. Similarly, the lower values within the unconformity bound middle Tully and within the Bellona/West Brook interval are also possibly diagenetically related, as the middle Tully is typically shaly (Baird and Brett, 2003).

13 The δ Ccarb positive excursion coincident with the semialternans Zone observed in the

type region and elsewhere is clearly a signal of global environmental change and therefore can

be used for global chemostratigraphic correlation (Aboussalam, 2003; Abousslam and Becker,

2011). In a biostratigraphic sense, the timing of this excursion is asynchronous. This is likely

attributable to the diachroneity in the first appearance of index taxa in different regions or

possibly the diachroneity in the influence of an oceanic watermass change on regional

watermasses located on different cratons. Afterall, the semialternans Zone is estimated to be

rather short geologically speaking, around 200 Kyr in duration (Ellwood et al., 2011). The

relatively early onset of positive values in New York compared to other regions (Fig. 6) may also

reflect that middle Tully correlatives are missing from other regions, as this sequence is not

readily recognized outside of the type region (Aboussalam and Becker, 2011). Alternatively, the

early onset may be related to the much lower resolution at which Aboussalam (2003) collected

samples.

13 As detailed above, the abrupt onset of positive δ Ccarb values coincident with Bioevent 2

does not appear to be an artifact of the unconformity, as the positive excursion begins below the

13 unconformity, within the uppermost lower Tully, just prior to a global positive δ Ccarb shift. An

165 alternative explanation for the relatively early timing of this positive shift in the type region is that it reflects local watermass changes in the form of a return to estuarine-type circulation (Fig.

3). If the low-diversity, likely oligotrophic, carbonate-dominated lower Tully was indeed deposited under anti-estuarine-type circulation as a result of the onset of aridity, then the positive

13 δ Ccarb shift in the uppermost lower Tully and through the middle Tully may represent a return to estuarine-type circulation and increased primary productivity and organic carbon burial locally. The global positive excursion in the semialternans Zone has likewise been attributed to such a process on a global-scale, although no known widespread organic carbon burial has been recognized at this time. Possibly, organic carbon burial was occurring within ocean settings that are not as likely to be preserved in the rock record, but would create a global signal.

6.2 Oxygen Isotopic Record Reconstruction

6.2.1 Comparison to Other Regions

Recent reconstructions of δ18O from both brachiopod calcite and conodont apatite through the GTB have depicted this interval as a period of global warming as shown by shifts to lighter oxygen isotope profiles (Joachimski et al., 2004, 2009; van Geldern et al., 2006; and

Brand et al., 2008); however, no prior study has produced a high-resolution temperature curve during the GTB interval that can be directly compared to the faunal changes at the resolution at which the bioevents are observed in the type region. Joachimski and others (2009) show the

Taghanic interval (late Givetian) as a time when the general cooling trend that prevailed through the entire prior Devonian ended (with coolest temperatures occurring just prior to the GTB), with the onset of warming through the Frasnian and culminating at the Frasnian-Fammenian boundary. Although we have only one data point for the post-biocrisis interval, in the lowest

18 Frasnian, δ Oapatite values from the Iowa Basin suggest that a brief interval of cooling occurred

166

around the Givetian Frasnian boundary (Joachimski et al, 2004; J. Day, pers. comm.). These

18 comparisons suggest that the δ Oapatite values obtained for the type region represent a global signal.

6.2.2 Oxygen Isotope Record Interpretation

In the type region, the transition from the Hamilton to the Tully Fauna (Bioevent 1)

18 corresponds with lower δ Oapatite values, and therefore an increase in temperature (Fig. 5). This

temperature increase likely resulted in decreased latitudinal (climatic) gradients and with

coincident flooding of the Trans-Continental Arch, led to the incursion of the OWR 'Tully Fauna'

18 into the NAB (Fig. 1). Furthermore, the δ Oapatite values obtained suggest that temperatures did

not return to pre-biocrisis levels during the interval of 'Hamilton Fauna' recurrence. This

suggests that temperature, while a factor in driving faunal transitions in the type region, was not

the only control, as suggested by Zambito and others (in press; see Fig. 3). Additional samples

would be needed to determine if temperatures do indeed become cooler in the type region

around the time of the Givetian/Frasnian (Fig. 5).

The relatively large variation in values within the lower Tully corresponds with, and is therefore possibly an artifact of, a higher sample density. Alternatively, there may be a meaningful difference in values obtained from polygnathid and icriodid assemblages.

Polygnathid-icrodid ratios obtained from North American epeiric settings, including the Tully

Group, suggest that polygnathids possessed a nekto-benthic life-habit and icriodids that of shallow-pelagic (Sparling, 1984, and references therein; Davis, 1975). Assuming that anti- estuarine conditions did exist during the lower Tully, and icriodids lived in shallower waters than polygnathids, then icriodids would experience relatively higher salinities than polygnathids, as deeper waters would be the result of anti-estuarine mixing with runoff through downwelling (see

167

schematic in Fig. 3). Temperature and salinity affect oxygen isotopic composition inversely, in

that higher temperatures and lower salinities result in depleted δ18O values, and vice versa.

18 Therefore, while all δ Oapatite values would be relatively depleted due to warming, icriodids would be less depleted due to the counteraction of living in a relatively higher salinity compared to polygnathids, whose values would be relatively further depleted by lower salinities.

Interestingly, samples processed from mixed assemblages show, for the most part, intermediate values (Fig. 5). Obviously, this conodont biofacies-isotope model is highly speculative based on

the data available, but, will be investigated further with additional samples.

6.3 Calculating Relative Temperature Changes

18 18 Absolute temperatures calculated from δ Oapatite, assuming a δ O value for Devonian sea

water of -1‰ VSMOW, give unrealistically high values that are too hot for modern marine life

(Kolodny et al., 1983; updated in Pucéat et al., 2010). It is typically assumed that the Devonian was a global greenhouse and ice-free time interval and therefore an oxygen isotopic composition

18 of -1‰ for Devonian seawater is typically used in temperature calculations from δ Oapatite

(Joachimski et al., 2004, 2009). This suggests the possibility that the oxygen isotopic

composition of Devonian seawater was not -1‰. Regardless, not knowing the Devonian sea

water isotopic composition does not prevent calculation of relative temperature change. The

shift from 17.5‰ to 16.5‰ equates to a 4°C increase in temperature (Kolodny et al., 1983;

updated in Pucéat et al., 2010).

6.4 Environmental Changes and Faunal Transitions in the Type Region

In our interpretation of the faunal transitions in the type region, we prefer to follow the

recognition by Aboussalam and Becker (2011) that the GTB is characterized by pulsed rapid

global environmental changes that played out differently in different regions. They observed

168

that the different depositional sequences recognized in the type-region as well as the polyphased nature of this biocrisis can be recognized globally. Furthermore, they observed that some regions other than the type region also show faunal recurrence. This led them to suggest that the rapid and repeated sea-level fluctuations and global overheating (warming and aridity) led to strong biofacies shifts, and, while the habitat tracking of organisms led to 'recurrence' in some cases, in many cases it did not prevent eventual extinction.

This is clearly the case in the type region. OWR incursions into the NAB during the lower Tully are linked with rising sea-level and warming (Fig. 5; Brett et al., 2011, and references therein). However, temperature was not the sole cause of faunal transition since the recurrent "Hamilton Fauna" also occupied the NAB during warm times. Coincident with the onset of the GTB, increased aridity would have influenced the watermass characteristics of the

NAB by reducing freshwater run-off, thereby weakening estuarine circulation, or possibly

inducing anti-estuarine circulation (Fig. 3). Currently, this is the best explanation for the faunal

replacement pattern, i.e., that the "Tully" Fauna is found in deeper and farther offshore settings

relative to the "Hamilton" Fauna when both are present in the basin (Fig. 3).

13 Organic carbon burial, inferred from the positive shift in δ Ccarb values in the middle and

upper Tully, and globally in the semialternans Zone, was also a large part of the environmental

change associated with the GTB. Whether this played a role in driving faunal change is not clear.

Both faunal transition and organic carbon burial may be controlled, in part, by changes in aridity,

with the positive excursion in the semialternans Zone recording the end of a global arid interval

and increased runoff and therefore increased primary productivity on a global-scale. It is

13 interesting to think that the negative excursion in δ Ccarb values seen at the onset of the GTB in

the NAB, if primary, might represent a regional crash in primary productivity in association with

169

the onset of oligotrophic conditions, but, this is purely speculation and a large portion of the

uppermost Hamilton and lowermost Tully is missing in core at this unconformity.

Bonelli and others (2006) report 70% Hamilton taxonomic recurrence within the Bellona

- West Brook interval; presumably, the remaining 30%, less sampling bias, failed to track their preferred habitat through the environmental changes that occurred during the lower and middle

Tully. That being said, temperature and aridity changes obviously impacted the "Hamilton"

Fauna, but did not lead to its demise otherwise we would not recognize its recurrence. The third bioevent, for which we have presented the least geochemical data in this study, resulted in the end of the Hamilton Fauna, through a combination of environmental change driven by regional tectonics and sea-level rise (Chapter 4).

While low-oxygen facies and enhanced burial of organic carbon, as seen in the Geneseo black shale, are observed widely during this time, these are by no means ubiquitous globally, and were most probably accentuated in the type-region by the onset of the third tectophase of the

Acadian Orogeny and subsidence of the basin (Ettensohn, 2008; Aboussalam and Becker, 2011;

Zambito et al., in press). In addition, renewed tectonic activity resulted in the transition from a gently sloping ramp-style foreland basin to the shelf-slope-basin profile, typical of the

Appalachian Basin throughout the Upper Devonian, and increased sediment supply to the basin.

Correspondingly, biofacies variability and composition changed significantly as the preferred habitat of diverse coral and brachiopod taxa no longer existed (Zambito et al., in press; Chapter

4). It therefore appears that the fate of a large portion of the 'Hamilton Fauna' in the NAB was ultimately decided by regional, tectonically-driven environmental changes coincident with the third bioevent, that may have accentuated the effects of eustatic sea level rise and low-oxygen conditions seen at this time

170

7. Conclusions

The type region of the GTB underwent faunal transition in response to global warming, aridity, sea-level fluctuations, and dysoxic conditions. Not only is a combination of these environmental factors necessary to explain the bioevents observed in the NAB, but these changes must be viewed in the context of the regional setting in terms of watermass properties and

13 tectonics. Additionally, it is clear from this study that a globally recognized positive δ Ccarb excursion occurred during the semialternans Zone, the onset of which may be slightly diachronous on a global-scale, yet this excursion should prove to be a useful chemostratigraphic correlation tool, in particular in sections where conodont biostratigraphic data is not available.

Acknowledgements

A. Miller, T. Algeo, D. Meyer, and S. Kolbe provided comments on an earlier draft. Field work was undertaken with the help of N. Bose, I. Von Donkelaar, S. Oser, and J. Sullivan.

Discussions with T. Algeo, J. Day, B. Kirchgasser helped to formulate the ideas presented herein. The New York State Museum provided access to the core.

171

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Appalachian Basin of New York: M.S., University of Cincinnati, Cincinnati, OH, 80 p.

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Middle Devonian conodonts from north-central Ohio. Condont Biofacies and

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YOLKIN, E.A., 2006, Carbon, oxygen and strontium isotope records of Devonian

brachiopod shell calcite: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 240, p.

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VER STRAETEN, C.A., and BRETT, C.E., 1997, Lower and Middle Devonian foreland basin fill in

the Catskill Front: stratigraphic synthesis, sequence stratigraphy, and the Acadian

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Stratigraphy in New York State, Fieldtrip Guidebook: University of Rochester,

Rochester, NY, p. 23-54.

WALLISER, O.H., 1990, How to define "global bio-events": Lecture Notes in Earth Sciences, v.

30, p. 1-4.

WALLISER, O.H., 1996. Global Events in the Devonian and Carboniferous. In: O.H. Walliser

(Editor), Global events and event stratigraphy in the Phanerozoic. Springer, Heidelberg,

pp. 225-250.

ZAMBITO, J.J., I.V., BAIRD, G.C., BRETT, C.E., and BARTHOLOMEW, A.J., 2009, Depositional

Sequences and Paleontology of the Middle – Upper Devonian Transition (Genesee

Group) at Ithaca, New York: A Revised Lithostratigraphy for the Northern Appalachian

Basin; Chapter 3, in Studies in Devonian Stratigraphy: Proceedings of the 2007

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edited by D. Jeffrey Over: Paleontographica Americana, v. 63, p. 49-69.

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ZAMBITO, J.J.I.V., BRETT, C.E. AND BAIRD, G.C., in press. The Late Middle Devonian (Givetian)

Global Taghanic Biocrisis in its Type Area (New York State Appalachian Basin):

Geologically Rapid Faunal Incursion, Replacement, Recurrence, and Extinction as a

Result of Global and Local Environmental Changes. UNESCO/International Year of

Planet Earth volume entitled ‘Global Biodiversity, Extinction Intervals and

Biogeographic Perturbations through Time’ Edited by John Talent.

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Figure 1: Paleogeographic reconstruction of the world (A) and study area before (B) and after

Taughannock Falls, Trumansburg, NY, represented by ‘star’) that record this biocrisis were deposited approximately 30° S of the paleo-equator. OWR and EAR denote the positions of

‘Old World Realm’ and ‘Eastern Americas Realm’ faunas, respectively; note the position of the

Trans-Continental Arch (‘Continental Backbone’ of Johnson (1970)) relative to these faunas.

Red dashed line represents approximate biogeographic boundaries. Abbreviations NA, SA, and

AF denote North America, South America, and Africa, respectively. Paleogeographic maps adapted from Blakey (2008).

Figure 2: Outcrop belt for the Hamilton, Tully, and Genesee groups in the Appalachian Basin of New York State. Abbreviations for geographic reference include: BUF, Buffalo; GEN,

Geneseo; CAN, Canandaigua; ITH, Ithaca; SHB, Sherburne; ONT, Oneonta; GIL, Gilboa. ‘Star’ denotes type locality (see Figure 1 caption).

Figure 3: Schematic summary of the faunal and environmental changes during the Taghanic

Biocrisis in the northern Appalachian Basin, adapted from Zambito et al. (in press). Biofacies and watermass circulation reconstructions from Zambito et al. (in press) and Chapter 4, temperature changes after Joachimski et al. (2009), and aridity after Marshall et al. (2011).

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13 Figure 4: δ Ccarbonate values through the Global Taghanic Biocrisis from the Cargill Salt Co.

Test Core 17 (Lansing, NY; Table 1). Abbreviations as follows: CON = Conodont Zonation;

GRP = Group; MBR = Member, although for the Hamilton Group, submembers of the Windom

Member are identified; GG = Gage Gully submember; B/W = Bellona/West Brook interval;

herm. = hermanni zone; GEN = Genesee Group. Dashes lines represent position of unconfirmities, gray line highlights the generalized isotopic pattern.

18 Figure 5: δ Oapatite values from samples before, during, and after the Global Taghanic Biocrisis

(see Table 1). Error bars are one standard deviation calculated from triplicate measurements of

each sample. Samples without visible error bars means that the one standard deviation is smaller

than the size of the symbol used. Stratigraphic succession is a composite between Geneseo and

Moravia, NY, with vertical lines representing intra-Devonian erosion. ko.-en. = kockelianus- ensensis zone; h. = hemiansatus zone; timor. = timorensis zone; r./v. = rhenanus/varcus zone; semi. = semialternans zone; her. = hermanni zone; disp. = disparalis zone; n. = norrisi zone; 1,2, and 3 = Montagne Noire Zones 1-3, respectively. Bed denoted DeRuyter is a condensed burrow prod at the base of the Tully at the Long Hill section. Litho- and bio-stratigraphic succession and placement of faunas after Brett et al. (1996); Over et al., (2003); Bartholomew et al. (2006);

Baird and Brett (2008); DeSantis and Brett (2011); and Zambito et al. (in press).

Figure 6: Biostratigraphic correlation of Taghanic Biocrisis sections with corresponding carbonate d13C reconstructions. New York reconstruction is from this study, all others from

Aboussalam (2003).Wavy lines represent unconformities. Dashed boxes represent the biocrisis interval as recognized at each section.

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Figure 1:

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Figure 2

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Figure 3

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Figure 4

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Figure 5

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Figure 6

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Table 1 - Location of type-section and sample localities for materials analyzed in this study.

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Table 1

Approximate Distance from Sample type-section Locality Name Material Sample Interval Latitude Longitude (km) Taughannock Falls n/a n/a 42.53° -76.6° 0 Cargill Drill Core carbonate all 42.52° -76.5° 8 West River Fall Brook apatite Shale 42.77° -77.83° 100 Long Hill Roadcut apatite Tully Group 42.71° -76.44° 24 Bear Swamp Fall Brook apatite Beds 42.77° -77.83° 100 Moonshine Falls apatite Centerfield Lst. 42.73° -76.69° 22 Honeoye Falls Quarry apatite Cherry Valley 42.94° -77.63° 95

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Chapter 5

Quantitative Paleoecological Analysis of the Post-Taghanic Genesee Fauna and its Relationship

to the Pre-Biocrisis Hamilton Fauna

Abstract:

Devonian northern Appalachian Basin deposits and fossils have served as test cases for numerous sedimentological, stratigraphic, paleoecological, and evolutionary investigations. In this study, we examine faunal and environmental changes during the latest Middle Devonian, within the deposits of the uppermost Hamilton and lowermost Genesee groups. The faunal transition recognized in these strata has been used previously as the reference example for the paleoecological hypothesis of Coordinated Stasis, and, furthermore, these strata and the corresponding faunal changes represent the type region and biotic transition for the Global

Taghanic Biocrisis. In the lowermost Genesee Group, 11 communities are recognized, corresponding with an onshore-offshore gradient. Sedimentation rate and oxygenation levels seem to be the dominant controls on community composition. Compared to the nearshore

Hamilton Fauna, the Genesee Fauna shows high taxonomic similarity, but, the biofacies discussed in this study differ in community structure. This is caused by a combination of extinction of Hamilton taxa, incursion of extra-basinal taxa, and speciation within Hamilton genera, all coincident with the faunal turnover associated with the Taghanic Biocrisis.

Taxonomic similarity is the result of persistence of siliciclastic-dominated nearshore settings

found in eastern Hamilton Group deposits through the Taghanic Biocrisis, and the subsequent

expansion of these settings during deposition of the Genesee Group in association with delta

progradation that resulted from renewed tectonic activity. Although global environmental

changes led to widespread restructuring and the onset of faunal cosmopolitanism during the

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Taghanic Biocrisis, the regional overprint of tectonic activity allowed for the persistence of

lithofacies, and correspondingly, the persistence of organisms that preferred siliciclastic- dominated settings.

Introduction:

The Middle Devonian (Givetian) Hamilton Fauna of the Appalachian Basin has been studied extensively by geologists for over 150 years since the initial works of James Hall (1843).

More recently, the Hamilton Fauna has been described as the 'type' fauna for the evolutionary- ecological pattern termed 'Coordinated Stasis'. Coordinated Stasis proposes that a majority of taxa show little or no morphologic change and that biofacies are relatively constant during stable intervals up to a few million years in duration and that these stable blocks are punctuated by geologically rapid and major biotic tunronover events (Brett and Baird, 1995; Brett et al. 1996;

Brett, in press). One hypothesis to explain this pattern is that communities of organisms that prefer similar environments will track their preferred habitats during times of environmental change rather than adapt to new environmental conditions (a process termed 'habitat tracking'); the net effect being that suites of communities (faunas) persist for geologically long periods, on the order of millions of years, until an environmental change of magnitude great enough to disrupt habitat tracking occurs (Brett et al., 1996, 2007a). The Hamilton Fauna is documented as persisting for 4-5 million years, during which low levels of extinction and origination, and high levels of community-level stability, are reported (Brett and Baird, 1995; Brett et al., 2007b;

Ivany et al., 2009).

Following a geologically rapid series of global and regional environmental changes, the

Hamilton Fauna ultimately met its demise. Coincident with the end of the Hamilton Fauna was the Global Taghanic Biocrisis, a period of abrupt climate change, eustatic sea level fluctuations,

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and global carbon-cycle changes (Baird and Brett, 2008; Aboussalam and Becker, 2011;

Marshall et al., 2011; Zambito et al., in press). The type-region of the Taghanic Biocrisis is the

northern Appalachian Basin (Fig. 1), into which warmer-water faunas incurred briefly to the near exclusion of the Hamilton Fauna (Johnson, 1970; review in Zambito et al., in press). Following the regional return of environmental conditions more typical of pre-biocrisis times, the Hamilton

Fauna exhibits a widespread, albeit short-lived, recurrence towards the end of the biocrisis

(Bonelli et al., 2006; Baird and Brett, 2008; Brett et al., 2009; Zambito et al., in press). This recurrence terminated in a subsequent eustatic sea level rise and the development of widespread dysoxic conditions, accentuated by the onset of the third tectophase of the Acadian Orogeny and corresponding rapid basin subsidence. During this interval a majority of the Hamilton Fauna, in particular the diverse coral and brachiopod assemblages, went extinct, at least locally. These observations led Zambito et al. (in press) to hypothesize that regional tectonic activity, which altered a gently sloping ramp to a shelf/slope-profile foreland basin and induced a significant increase in sediment supply, was the proximate cause of transition from the Hamilton ecological- evolutionary subunit, to the Genesee.

The term 'Genesee Fauna' was initially applied to low-diversity, offshore dysaerobic assemblages observed in western and central New York State. Dysaerobic communities and their taphonomy were described by Baird and Brett (1986) and Brett et al. (1991). The dysaerobic communities have since been described in more detail by Boyer and Droser (2007, 2009). Thayer

(1974) was the first to describe the nearshore portions of the Genesee Fauna from eastern New

York State in detail in his classic paleoecological works. In this study, we expand upon these investigations, focusing in particular on the nearshore assemblages of the Genesee Fauna, using a more quantitative analytical protocol and a higher-resolution stratigraphic framework to better

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understand the post-extinction fauna. Additionally, we compare the Genesee Fauna with

nearshore communities of the Hamilton Fauna to better understand the extent of the end of the

Hamilton ecological-evolutionary subunit and the transition to the overlying Genesee.

In this context, the goal of this study is two-fold:

1) To quantitatively describe the Genesee Fauna from assemblages collected from the lowest

portion of Genesee Group, representing the post-biocrisis, post-Hamilton fauna.

2) To determine the origin of the Genesee Fauna. Specifically, we hypothesize that the Genesee

Fauna was composed of eurytopic (generalized) taxa from the nearshore, siliciclastic dominated portion of the Hamilton Group, with the addition of cosmopolitan taxa that became widespread during this time as biogeographic barriers were removed by eustatic sea level rise and a reduction in climatic (latitudinal) gradients. At the same time, we investigate whether some portion of the Genesee Fauna was composed of species originating from Hamilton genera in response to changing environmental conditions (new niche space) as well as an increase in habitable space as Genesee Group deposits prograded into the foreland basin and low-oxygen black shale facies were thereby replaced by more hospitable environments through the lower

Genesee Group.

Materials and Methods:

Abundance data for post-extinction Genesee Group communities were derived primarily

from bulk samples originally collected by Charles Thayer and reposited at the Yale Peabody

Museum (Thayer, 1974). Thayer took great care to sample stratigraphic intervals representing

distinct lithofacies, and the stratigraphic contexts of all samples was recorded at high resolution.

As part of the present study, extensive fieldwork and mapping was undertaken to update the

stratigraphic context of Thayer's collections, since the stratigraphic framework for the Taghanic

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Biocrisis interval has been updated substantially since Thayer's original study (Baird and Brett,

2008, and references therein; Baird, Zambito, and Brett unpublished data). At the same time,

additional samples were collected from Thayer's localities and other outcrops, to supplement the

faunal dataset. While Thayer's work focused on the entire Genesee Group, the present study

covers only the lowest part of the interval, given that the primary goal of this study is to describe

the post-Taghanic Biocrisis recovery fauna for the type region (Fig. 2). This interval

encompasses the lowermost Geneseo and Unadilla formations (latest Givetian, hermanni and

disparilis Zones).

We identified taxa in these samples to the species-level when possible using the taxonomy outlined in Linsley (1994). For crinoid materials and bryozoan morphotypes, only presence/absence data were recorded, since individual abundances of these groups are difficult to quantify, but their presence is still meaningful. Since moldic preservation was common in the siliciclastic facies, a modified version of Minimum Number of Individuals (MNI) was used in order to prevent over estimation of taxonomic abundances, in which counts for both moldic and skeletal material were made and the MNI methodology applied (Gilinsky and Bennington, 1994).

Ultimately, a dataset of 142 samples containing a total of 124 taxa was developed. Prior to quantitative analysis, taxa occurring in only one sample (singletons) and samples comprised of a single taxon were removed, resulting in a final dataset of 133 samples containing 89 taxa.

Multivariate analyses were undertaken using PC-ORD version 6.0 (McCune and Mefford, 2011).

Two-way cluster analysis was first used to identify groups of samples within the dataset that were similar in taxonomic composition and relative abundance (i.e., fossil communities, or biofacies). Two-way cluster analysis was undertaken using the Bray-Curtis distance measure

(joint absences of taxa do not improve similarity with this method), a Flexible Beta (of -0.25)

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method of group linkage (similar to Ward's method), and, for R-mode clustering of taxa,

abundances of each taxon were scaled to the maximum value for that taxon ("percent maximum

transformed"). We tested the significance of cluster grouping and performed pairwise

comparisons using MRPP (Multi-Response Permutation Procedures), a non-parametric

procedure for testing the hypothesis of no difference between two or more groups that is similar

to ANOSIM and perMANOVA (Mielke and Berry, 2001), using the Bray-Curtis distance

measure. The relationship of the biofacies identified was then further evaluated using Detrended

Correspondence Analysis (DCA) and Non-metric Multidimensional Scaling (NMS) using the

Bray-Curtis distance measure and, for NMS, Kruskal's Secondary Approach (to account for tie

handling of ordination distances, i.e., samples with the same taxonomic composition and

abundance values) (McCune and Mefford, 2011).

After determining the community structure of the post-Taghanic Biocrisis Genesee

Fauna, we wanted to assess its relationship to the pre-Taghanic Biocrisis Hamilton Fauna, in

particular, the portions of the Hamilton Fauna occupying comparable paleoenvironments (Figs. 2

and 3). To do this, we compiled the abundance-category data collected by Prosser (1897, 1899) for the eastern Hamilton (Moscow and Cooperstown formations) and Genesee groups (Geneseo and Unadilla formations), and we updated this dataset taxonomically using Linsley (1994). In the field, we assessed the stratigraphic context of Prosser's faunal lists as had been done with

Thayer's collections. In addition, we collected a small number of samples from the Hamilton

Group during fieldwork to further test the compatibility of our samples with Prosser's.

To numerically compare our samples with Prosser's, we transformed our dataset to abundance categories comparable to those of Prosser. Although not explicitly stated, information provided by Prosser in his texts (1897 and 1899), indicated that these ranks can be approximated

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by the following abundance ranges: very abundant (>= 40 specimens), abundant (14-39),

common (6-13), rare (3-5), and very rare (<=2). Direct comparison was not entirely

straightforward because Prosser did not use a MNI method, such that our abundance counts were

generally less than his in samples that could be compared directly because they occurred in

similar geographic areas and stratigraphic intervals. This was expected because the MNI

methodology, in effect, minimizes taxonomic counts. That said, preliminary analyses of the

combined dataset showed that virtually identical ordinations were produced regardless of

whether our data set was transformed to abundance categories using Prosser's inferred abundance

distributions, two-thirds of his abundance distributions, or one-half of his abundance distributions. Furthermore, this was the case even when data were analyzed based only on presence/absence. In the analyses presented herein, we reduced the abundance distributions that

Prosser assigned to each category by approximately two-thirds and assigned our abundance data to the corresponding categories (see Gilinsky and Bennington, 1994). Since Prosser did not collect data on bryozoans, these were removed prior to analysis as were singletons, resulting in a dataset of 257 samples comprised of 140 taxa (Fig. 3). Ordination methods were used to describe the relationships between the pre- (Hamilton) and post-extinction (Genesee) faunas. All data have been uploaded into the Paleobiology Database (PBDB; References 30118, 30119,

28312, 29162, and 30564).

Results:

Genesee Group (post-Taghanic) Communities

Initial analysis of the Genesee Group dataset using absolute abundances, relative

abundance (crinoids and bryozoans removed), and presence/absence resulted in similar

ordinations in both DCA and NMS. Because this dataset contains a mix of counts (e.g.,

199 brachiopods, bivalves, etc.), as well as presence/absence (crinoids and bryozoans), and, furthermore, because preliminary analyses suggested that crinoids and bryozoans were meaningful components of communities, we chose to use absolute abundances whenever possible rather than relativizing the dataset and unfairly weighting, or excluding, crinoids and bryozoans.

Two-way cluster analysis resulted in the recognition of 14 groups at 29% information remaining, of which 11 appear to represent distinct communities based on taxonomic composition (Figures 4 and 5). Use of MRPP found significant differences among these 12 groups (T= -40.287, p < 0.00000001) and for all pairwise comparisons (least significant pairwise comparison was T< -3.517, p < 0.01). The three groups that escape definition (taxonomic structure is not readily apparent) are composed of an assortment of taxa, lack visible similarity in taxonomic composition based on two-way cluster analysis, and consist of somewhat 'chained' clusters on their own branch at the base of the Q-mode dendogram (Figure 4).

As noted earlier, ordination techniques were utilized to further visualize the relationships among communities. DCA and NMS produced similar results, so only DCA is presented herein

(Figure 6). In ordination space, the communities identified using two-way cluster analysis can generally be identified based on position along Axis 1, and to some degree, Axis 2, albeit with a fair degree of overlap. A clear outlier is the Nuculoidea community. Along Axis 1, the

Orthospirifier-Cupularostrum and the Tylothyris-Orthospirifer communities plot with the highest values, the Orthospirifer-Actinopteria, Tropidoleptus-Tylothyris, Diverse Brachiopod and Bivalve, and Nuculoidea communities with high to 'intermediate' values, and the

Devonochonetes, Chonetid-Leiorhynchid, Crinoid-Camarotoechia, Cyrtina, and Echinocoelia communities with the lowest values. On Axis 2, there is a clear separation between the

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Echinocoelia and the Cyrtina communities, and a gradational separation between the

Devonochonetes, Chonetid-Leiorhynchid, Crinoid-Camarotoechia communities.

Relationship between Genesee and Hamilton Faunas

Samples from the Genesee and Hamilton Groups were compared using NMS (Fig. 7).

While DCA showed very similar ordination results, NMS is more appropriate for this dataset

because the data are categorical and NMS uses a rank-based approach, whereas DCA is more appropriate for interval data. In Fig. 7A, Hamilton and Genesee samples, regardless of whether collected by Prosser or for the present study as described above, show strong within-group similarity; Hamilton samples cluster toward the upper right portion of the plot, while Genesee samples cluster toward the lower left. Also clear is that this study's relatively few Hamilton samples fall within the variation exhibited by Prosser's plentiful Hamilton samples, and Prosser's less plentiful Genesee samples fall within the variation of this study's abundant Genesee samples.

Genesee samples collected for this study that do not overlap with those collected by Prosser come from localities and/or geographic areas unique to one study or the other, while the same holds true for the Hamilton. Furthermore, ordination of samples at the genus-level (not shown) plotted similarly, further suggesting a robust difference between a large portion of the Hamilton and Genesee faunas.

The same NMS plot is shown in Figure 7B, except that samples are coded simply as

Hamilton and Genesee and the principal zone of overlap between these two groups is shaded.

Genesee Fauna samples that were grouped into communities previously and found within the overlapping area, and therefore show similarity to Hamilton Fauna samples, were those identified earlier as belonging to a variety of communities (Fig. 7C), including: Orthospirifer-

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Cupularostrum (n=1), Tylothyris-Orthospirifer (n=2), Tropidoleptus-Tylothyris (n=6), Diverse

Brachiopod and Bivalve (n=3), Devonochonetes (n=3), Crinoid-Camarotoechia (n=2), Cyrtina

(n=1), and Nuculoidea (n=1); additionally, a large number of samples collected by Prosser

(n=16) from the Genesee as well as samples that were not designated as recognizable biofacies

(n=4) are positioned within this area of overlap (Fig. 7C).

As seen in Fig. 7D, the recognized Genesee Group communities still ordinate along Axis

1 in a similar fashion to that of Fig. 6, even after the dataset transformation from absolute

abundances to abundance categories, removal of bryozoans, and ordination by a different method

(NMS) that was performed with both the Genesee and Hamilton samples; all of this argues for an

exceptionally robust Genesee Fauna community pattern. In further comparing Figures 6 and 7D,

it is clear that Axis 2 community relationships in Fig. 6 are not seen in Fig. 7D. This is an

artifact of ordinating the Genesee and Hamilton samples together, as NMS of only the Genesee

samples collected for this study (not shown) is similar to Fig. 6. Thus, in Fig. 7, Axis 2 can be

interpreted to represent the compositional differences between the Hamilton and Genesee faunas.

These taxa fall into two groups: 1) taxa present in the Hamilton Fauna, but not in the Genesee

Fauna such as Allanella tullius (r = 0.335), Athryis spiriferoides (r = 0.221), and Longispina

mucronata (r = 0.193); and, 2) taxa common in both the Hamilton and Genesee faunas, such as

Mucrospirifer mucronatus (r = 0.364), Spinocyrtia granulosus (r = 0.294), and Tropidoleptus

carinatus (r = 0.393).

Discussion

Genesee Fauna

The Genesee communities described herein represent biofacies more nearshore than those

described previously, including the low-oxygen Leiorhynchid communities of Thompson and

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Newton (1987) and Boyer and Droser (2007, 2009). The Chonetid-Leiorhynchid and Crinoid-

Camarotoechia (a leiorhynchid) communities defined in this study are the most similar to these

communities. As seen in Figure 6, the Devonochonetes community plots near these communities

on Axis 1; this is not surprising as chonetids are common in dysoxic settings and Camarotoechia

mesacostales is also abundant in this community (Fig. 5; Brett and Baird, 1995; Brett et al.,

2007; Zambito et al., 2008). This suggests that lower values on Axis 1 are, in part, related to

lower oxygen levels, which, in turn, has commonly been related to depth in the northern

Appalachian Basin.

If Axis 1 is depth related, then we would expect a correlation between longitude and

DCA Axis 1 scores because depositional strike is roughly perpendicular to the outcrop belt.

Baird and Brett (1988) and Zambito et al. (2009) showed that the source of sediment during the

onset of the third tectophase of the Acadian Orogeny entered the northern Appalachian Basin

from the present-day southeast direction. In Fig. 8 we plotted longitude vs. DCA score and

found an r-squared value of 0.405. Given the temporal duration (hermanni - disparilis Zones)

within samples, the spatial distribution of the samples in this study (Fig. 3B), and the observation

that the outcrop belt does not perfectly parallel depositional strike, this nevertheless suggests that

DCA Axis 1 indeed likely represents the onshore-offshore gradient.

The only communities found at lower Axis 1 values are the Cyrtina and Echinocoelia communities. Within the samples representing the Cyrtina community, C. mesacostales is common and, to a lesser degree, so is the chonetid Devonochonetes scitulus (Fig. 5). However,

Cyrtina is not commonly found in dysoxic settings, at least not in the Hamilton Group, except in some pyritic associations (Brett et al., 2007b), and in fact is observed in a number of different communities in this data set including those that have higher Axis 1 scores, such as the Diverse

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Brachiopod and Bivalve community (Figs. 4 and 5). As for Echinocoelia, it too can be found in

communities in samples associated with higher Axis 1 scores than that of the Echinocoelia

community, such as the Devonochonetes community and the Crinoid-Camarotoechia

community.

The three samples representing the Echinocoelia community come from two localities in

which the sedimentation rate was extremely high, represented by ~100 m of fossil-poor fine-

grained sandstones. The environment of deposition for these samples has been interpreted as a

pro-delta setting that received sediment which 'bypassed' up-ramp shelf settings; the delta prograded to the present day Homer and Cortland, NY areas, just east of Ithaca, by disparilis

Zone time (Figs. 1 and 2; see also Zambito et al., 2009, for a related study). Positioning of

samples representing the Cyrtina community may also relate to sedimentation rate. The majority

of these samples are located in the area of Earlville and Sherburne, NY within the lowermost

Genesee Group strata (hermanni Zone age). Further east, and therefore closer to the source of

sediment than the Homer/Cortland area, the majority of Cyrtina-rich samples come from older

(hermanni-age) rocks, deposited when the delta had yet to prograde to these areas and the depositional environment was a dysoxic basin (Figure 2). In the field, the stratigraphic succession typical of Cyrtina community samples consisted of dysoxic shaly siltstones and thin- bedded siltstones, interbedded on a 3-5 m, possibly cyclical, scale (unpublished field observations). These successions are interpreted to represent the encroachment of the prograding delta during times of low background sedimentation rate, yet periodically high during pulses of sediment influx. If sediment supply is indeed a factor in the ordination position of these communities, then perhaps sedimentation rate is the controlling environmental factor for Axis 2: higher values representing higher rates and lower Axis 2 values representing lower rates.

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Communities with intermediate Axis 1 and 2 values include the Diverse Brachiopod and

Bivalve, Tropidoleptus-Tylothyris, and Orthospirifer-Actinopteria communities. Based on

geographic position and field investigation of lithofacies, these communities are interpreted as

proto-shelf and shelf depositional settings, for the hermanni and disparilis zones respectively

(Fig. 2). The Tropidoleptus-Tylothyris community likely subsisted in the lowest oxygen levels

of any of these communities as evidenced by the common occurrence of C. mesacostales, and

was typical of proto-shelf settings at or just below storm wave base during the hermanni Zone.

Dark colored, thin-bedded siltstones are common lithologic features of these samples. The

Diverse Brachiopod and Bivalve community is interpreted as representing the most hospitable

conditions in the basin during this time, a well-oxygenated shelf setting at or above storm

wavebase; these samples were typically obtained from condensed, transgressive deposits that

contained reworked clasts. This community has a high diversity, and possesses most taxa that

are also diagnostic of the other communities, and also exhibits the most uniform distribution of

taxa in terms of abundance and presence within samples (Fig. 5). These characteristics likely represent the generalistic nature of the Genesee Fauna. This fauna does not contain a highly specialized community adapted to such conditions, rather when conditions are optimal a community assembles from the pool of species that compose the other communities that themselves are specialized for sub-optimal conditions. The Orthospirifer-Actinopteria

community also occurred at or above storm wavebase, but this biofacies represents a much

higher sedimentation rate than the Diverse Brachiopod and Bivalve community; thick to

medium-bedded sandstones are common. The Nuculoidea community also plots at intermediate

values for Axis 1, but at some of the highest values for Axis 2. Again, if Axis 2 is related to

sedimentation rate, then this would make sense as nuculids are mobile, infaunal bivalves that

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would do well in shifting substrates. The Nuculoidea community samples, as outliers, may

represent extreme sediment input events.

The shallowest communities include the Orthospirifer-Cupularostrum and Tylothyris-

Orthospirifer communities. Several samples for these communities come from swaley cross-

bedded (shoreface) coarse-grained sandstones and contain reworked red mudstone clasts,

suggesting extremely shallow depositional settings. Compositionally, the Orthospirifer-

Cupularostrum community is most similar to the Orthospirifer-Actinopteria community, and,

therefore, probably reflects relatively higher sedimentation rates (Figs. 4 and 5). The Tylothyris-

Orthospirifer community may represent slightly lower oxygenation levels, based on the presence

of chonetid brachiopods (Fig. 5).

Genesee Group Faunal Affinities

While collectively, the Genesee and Hamilton faunas occur in fairly distinct parts of

ordination space, there is a clear area of overlap (Fig. 7C). In fact, this can be expected given

that eastern Hamilton and Genesee faunas have been noted in the past as being rather similar

(Prosser 1893; Clarke 1894; and Williams, 1886). Out of the 11 recognizable communities for

the Genesee Group, a surprisingly high number (eight) show similarity to the Hamilton Fauna by

occupying similar portions of ordination space the: Orthospirifer-Cupularostrum, Tylothyris-

Orthospirifer, Tropidoleptus-Tylothyris, Diverse Brachiopod and Bivalve, Devonochonetes,

Crinoid-Camarotoechia, Cyrtina, and Nuculoidea, in addition to numerous samples not

classified into communities. Those that do not overlap include the: Orthospirifer-Actinopteria,

Orthospirifer-Cupularostrum, and Echinocoelia communities.

The two Hamilton outliers in Fig. 7 collected by Prosser are two of the farthest eastern

(onshore Hamilton) samples in our dataset. The Genesee samples most similar to these represent

206 to the Orthospirifer-Actinopteria, Orthospirifer-Cupularostrum, and the Tylothyris-Orthospirifer communities. Additional sampling of the Hamilton, in particular at localities east of the samples presented here (essentially where Prosser's studies left off), might bolster this suggestion of strong similarity between Hamilton and Genesee (Orthospirifer) nearshore communities.

Therefore, samples from all but one of the 11 nearshore Genesee Fauna communities described herein shows at least some similarity based on positioning in ordination space to

Hamilton Fauna communities from eastern New York State. Furthermore, what is clear for a large majority of Genesee communities described is that they are composed of at least some

Hamilton taxa that survived the Taghanic Biocrisis. Some of the Hamilton taxa, such as

Tropidoleptus carinatus, Strophodonta demissa, Cyrtina hamiltonensis, Rhipidomella vanuxemi,

Eldredgeops rana, Cypricardella bellistriata, Paracyclas rugosa, and Ambocoelia umbonata have long been noted as survivors of the biocrisis, and have been observed anachronistically in younger (Frasnian) strata near Ithaca, NY (Fig. 1 and 2; Kindle, 1896; Williams, 1913). It is now understood that these Hamilton forms probably survived in nearshore refuges while anoxic conditions reflected by black shale prevailed in offshore Genesee environments. Subsequently, these survivors migrated westward as conditions progressively improved in an offshore direction through delta progradation and basin fill (Fig. 2; Zambito et al., 2009; this study).

Mixing with these Hamilton taxa, resulting in a new biofacies spectrum for the northern

Appalachian Basin, were incursion taxa associated with the eustatic sea level rise that occurred during the Taghanic Biocrisis (Fig. 4; Zambito et al., in press). These include Tylothyris mesacostalis, Echinocoelia ambocoelioides, Camarotoechia mesacostales, Schizophoria impressa, "Nervostrophia" tulliensis, and "Pugnoides" pugnus. Incursion taxa are found in all of the communities described, and particularly dominate in the Echinocoelia community, which is

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the only community not to show some similarity to Hamilton samples as it plots to the far bottom

left in Fig. 7. However, the Echinocoelia community nonetheless contains Hamilton survivor

taxa, such as Paracyclas rugosa (Fig. 5).

Additionally, several Genesee communities include species that likely originated within

the northern Appalachian Basin from pre-existing (Hamilton) genera. In our dataset, these include Cupularostrum eximia, Leiorhynchus sinuatus, Cornellites chemungensis, Sphenotus contractus, Pterinopecten suborbicularis, and Gyronema multilirata, which all have congeneric representation in the Hamilton (Linsley, 1994). Finally, some genera first appeared in the

Appalachian Basin this time, such as Whidbornella and Algaeoglypta. It is not surprising that a majority of these taxa were mobile bivalves and gastropods, and that the genus Whidbornella was a productid brachiopod; these organisms would all be well-suited to live in environments characterized by the higher sedimentation rates and shifting substrates of the Genesee Group, relative to the Hamilton Group.

Positioning of faunas along Axis 2 (Fig. 7) seems to be in part related to differences in the taxa comprising the faunas (for example, the Hamilton-exclusive brachiopods Athyris,

Longispina, and Allanella), as well as changes in the distributions of taxa that are shared. Shared taxa, such as Mucrospirifer mucronatus and Spinocyrtia granulosus likely experienced changes in their distribution in response to the incursion and /or expansion of similar forms that characterize the Genesee Fauna, such as Tylothyris mesacostalis and Orthospirifer mesastrialis, respectively. Tropidoleptus carinatus apparently became much more widespread in the Genesee

Group, and is present within a number of Genesee communities (Figs. 4 and 7).

Implications for Coordinated Stasis

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In the context of ongoing discussions in the literature about the hypothesis of

Coordinated Stasis (CS) (Brett and Baird, 1995; Brett et al., 1996; Ivany et al., 2009), two

metrics often used to quantify faunal turnover between blocks of ecological-evolutionary stability are the carryover and holdover indices. From the data set used in this study, it is possible to calculate: 1) the Hamilton Fauna carryover, which is the proportion of Hamilton taxa that become incorporated into the Genesee Fauna; and 2) the Genesee Group holdover, which is the ratio of the number of taxa derived from the Hamilton Fauna to the number of taxa in the

Genesee Fauna (see Brett and Baird, 1995, for further carryover and holdover details).

Because this study only compares the nearshore Hamilton taxa observed in the northern

Appalachian Basin immediately prior to the Taghanic Biocrisis, not all taxa observed in the entire Hamilton Fauna over a ~5 million year period are included in our dataset. Since carbonate mud-dominated settings typical of western New York in the Hamilton no longer existed post-

Taghanic (Fig. 2), the most meaningful comparison for the Genesee Fauna is the nearshore, siliciclastic dominated portion of the uppermost Hamilton Moscow and Cooperstown formations.

Prior to this study, which incorporates Prosser's samples from these lithofacies and with our samples greatly expands the Genesee Group taxonomic list, the extent of biotic turnover between the Hamilton and Genesee groups in this portion of the faunal spectrum had not been adequately characterized.

Since Prosser did not collect data on bryozoans, they were not included in turnover assessment, and four alternate sets of calculations were designed based on different assumptions

(Table 1). The first was made under the assumption that singletons (i.e., taxa observed only once) represent a sampling bias, in that they may have been present at multiple times but were too rare to be sampled more than once, and therefore should be removed. The second was made

209 under the assumption that singletons were meaningful, and thus included. The third was made after augmenting the dataset under the assumption that some taxa present in western NY

Moscow Fm. settings subsequently migrated to eastern NY through the interval of the Taghanic

Biocrisis, and, therefore, the presence of these taxa in western NY should be counted along with the nearshore Hamilton data; data for western New York were obtained from Grabau (1898),

Brett and Baird (1994), Linsley (1994), Boyer and Droser (2007), Zambito et al. (2008), and any appropriate references in the PBDB (checked July 11, 2011). The fourth was made using the maximum diversity value for the Hamilton Group of 335 taxa (Brett et al., 2009).

As shown in Table 1, regardless of the calculation used, Hamilton Fauna carryover and

Genesee Fauna holdover indices show a high value for those indices (>63%) between the nearshore Hamilton and Genesee faunas, relative to what is generally expected in the transitions between ecological-evolutionary subunits (Brett and Baird, 1995). If western New York Moscow

Fm. faunal lists were included in these calculations, the Hamilton carryover index would obviously decrease, especially when coral beds are included; this is currently beyond the scope of this dissertation, but will be assessed later. However, a calculation of Hamilton carryover can be made using the maximum diversity value (n=335) for the Hamilton Group, which results in an index of ~30%. This would just barely meet the threshold for an E-E subunit boundary.

Regardless, this does not change the fact that the most conservative calculated Genesee holdover value is still 66.4% (Table 1).

While the sampling scheme (narrow stratigraphic and geographic range) of this study cannot test CS, and blocks of stability, directly as currently defined (see Brett and Baird, 1995;

Brett et al., 1996), we can say something about biotic turnovers. The turnover patterns described herein document that as long as comparable environments (in this case generalized lithofacies)

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persist, so do the biota that occupy them. Environmental changes that cause turnovers are

defined by Brett et al. (1996) as "perturbations that were too pervasive and/or abrupt to permit

local tracking of environment to continue". While the western portion of the study area

underwent a transition from a shallow carbonate-mud setting to a deeper, low-oxygen black shale facies, it is clear from the data presented in this study that nearshore siliciclastic-dominated environments in the eastern portion of the northern Appalachian Basin were more stable, thereby permitting local tracking of preferred habitat for a large portion (roughly two-thirds, Table 1,

Fig. 2) of the eastern Hamilton Fauna into the overlying Genesee.

Conclusions

Environmental changes in the type region of the Global Taghanic Biocrisis have been described previously as a combination of local and global transitions (Zambito et al., in press;

Chapter 3). Globally recognized sea level, temperature, and carbon-cycle changes are observed within the northern Appalachian Basin, but overprinted by local tectonic effects. Based on this study and patterns documented in chapter 3, the main controls on faunal transition from the

Hamilton to Genesee faunas appear to have been a combination of eustatic sea-level and renewed tectonic activity. Western portions of the type-region underwent the most dramatic environmental changes: rapid deepening resulting from subsidence due to tectonic loading and sea level rise caused a transition from carbonate-mud dominated settings to black shale facies, and a dramatic faunal transition is observed (Brett et al., 2009). Conversely, sea level rise shifted the position of the shoreline slightly in an eastward direction and renewed tectonic activity increased the overall rate of sediment input to the basin, but the overall depositional environment in nearshore settings remains relatively static, and correspondingly, a large portion of the taxa survive. However, the incursion of taxa into the basin, and the overall change to basin

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morphology, led to significant biofacies re-organization. Eventually, with the full development of a shelf-slope-basin profile (Fig. 2), communities may have been further altered, or possibly even reduced in number, but detailed sampling in the lowest Frasnian portion of the Genesee

Group would be necessary to fully test this.

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Figure 1: Outcrop map for the Hamilton, Tully, and Genesee groups. Dashed box indicates

sampling area for this study. Star is type section at Taughannock Falls, Trumansburg, NY.

Abbreviations are for geographic reference and are as follows: BUF=Buffalo, GEN=Geneseo,

CAN=Canandaigua, ITH=Ithaca, SHB=Sherburne, ONT=Oneonta, and GIL=Gilboa.

Figure 2: Time-Rock-Environment diagram for the Middle and lowermost Upper Devonian of

the Northern Appalachian basin. See Figure 1 for geographic reference.

Figure 3: Longitudinal sample distribution for the samples analyzed in this study (see Figure 1

for reference). A) Genesee Group samples collected by Prosser (n=33), B) Genesee Group

samples collected for this study (n=142), C) Hamilton Group samples collected by Prosser

(n=65), and D) Hamilton Group samples collected for this study (n=17).

Figure 4: Two-way cluster analysis of lowermost Genesee Group bulk samples. Community

names derived from Figure 5. Red dots are some of the typical 'Hamilton' taxa, identified by

Williams (1913) as recurring in the Upper Devonian (surviving the Taghanic Biocrisis). Blue

dots are 'incursion' taxa that first appear in the Northern Appalachian Basin during or

immediately following the Taghanic Biocrisis (Zambito et al., in press). Sample numbers are

PBDB collection numbers.

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Figure 5: Taxon distributions for lower Genesee Group communities (see Fig. 4). Black bars represent the percent of within-community individuals that belong to a given taxon as shown on the left-side y-axis; i = total number of individuals for all samples in a given community. White bars represent the percent of within community samples in which a given taxon is present as shown on the right-side y-axis; s = total number of samples recognized as a given community.

White and Black bars are not stacked.

Figure 6: DCA of lowermost Genesee Group samples (groupings after Figs. 4 and 5).

Figure 7: NMS of samples from Prosser (1897, 1899) and this study. A) Polygons are drawn around the extent of ordination space occupied by the different groups show in the key. B) Same

NMS plot as shown in part A, but all Hamilton and Genesee samples are keyed as red and blue, respectively. Shaded areas represent the principal parts of ordination space in which Hamilton and Genesee samples overlap. Stress = 31.846. C) Same NMS plot shown in B, except that

Genesee samples are coded by community designation. D) Same NMS plot, but only samples that were designated to community groups are shown.

Figure 8: Longitude vs. DCA score for lowermost Genesee Group samples collected in this study.

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Figure 1

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Figure 2

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Figure 3

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Figure 4

224

Figure 5

225

Figure 6

226

Figure 7

227

Figure 8

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Table 1: Carryover and holdover indices for Hamilton and Genesee group samples from this and

Prosser's studies. See text for explanation of data augmentation and maximum Hamilton diversity.

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Table 1

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Chapter 6

Conclusions

The northern Appalachian Basin, underwent dramatic environmental and corresponding

faunal changes during the Global Taghanic Biocrisis. The following conclusions are made based

on the research undertaken for this dissertation:

1) Global environmental changes in temperature, aridity, eustatic sea-level, and the

carbon-cycle can be recognized in the type region.

2) Global warming and eustatic sea-level rise broke down biogeographic barriers and facilitated the incursion of tropical 'Tully' taxa in to higher latitudes. In the type region, the distribution of invasive taxa was controlled by changes in watermass circulation resulting from

increased aridity and the influx of higher salinity waters. Watermass circulation and salinity

played a greater role than temperature on the presence of the 'Hamilton Fauna' in the type region.

3) The fate of the 'Hamilton Fauna' was ultimately decided not by global environmental

change, but by regional environmental changes caused by renewed Acadian tectonism. The

'Genesee Fauna' was taxonomically similar to nearshore portions of the 'Hamilton Fauna', but

significantly different in community structure. Taxonomic similarity resulted from the

persistence of siliciclastic-dominated, shallow settings, while differences were likely driven by

changes in sedimentation rate, basin-wide decreases in oxygen levels, and the basin transition

from a gently sloping ramp to the development of a shelf-slope profile.

4) Anachronistic 'Hamilton' taxa in the Upper Devonian Ithaca Formation were taxa that

survived the Taghanic Biocrisis in nearshore settings, only to later migrate offshore as the delta

prograded and sediment input into the basin overwhelmed dysoxic black shale facies.

I can't believe you read the whole thing.... Thanks!

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