The Pennsylvania State University The Graduate School College of Earth and Mineral Sciences STRATIGRAPHY AND PALEOENVIRONMENTS OF THE RED HILL SITE NEAR HYNER, PENNSYLVANIA A Thesis in Geoscience by Daniel Adam Peterson © 2010 Daniel Adam Peterson Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science May 2010 The thesis of Daniel Adam Peterson was reviewed and approved* by the following: Mark E. Patzkowsky Associate Professor of Geosciences Thesis Advisor Rudy L. Slingerland Professor of Geology Russell W. Graham Associate Professor of Geosciences Earth and Mineral Sciences Museum Director Katherine H. Freeman Professor of Geosciences Associate Department Head of Graduate Programs *Signatures are on file in the Graduate School ii ABSTRACT The Red Hill outcrop on Route 120 near Hyner, Pennsylvania, consists of repeating cycles of mostly fining-upward facies ranging from siltstones and lower fine massive sandstones at the base of the cycles to mudstones near the top of each cycle. In the readily accessible portions of the outcrop, a wide variety of vertebrate and plant material can be found. Vertebrates recognized from Red Hill include various fishes (placoderms, chondrychthyans, acanthodians, actinopterygians, and sarcopterygians) as well as two early tetrapods first identified at this site (Hynerpeton bassetti and Designathus rowei). Strata at Red Hill appear cyclical and are interpreted to represent two stages of fluvial deposition. Stage I avulsive deposits include crevasse-splay sandstone bodies and sandy siltstone channel fills, overlain by the fossiliferous siltstones and interbedded erosional-based sandstones. These beds are overlain by simple paleosol packages that indicate Stage II avulsive deposition. High sedimentation rates on the Catskill Delta combined with regularly avulsing fluvial systems likely led not only to an excellent taphonomic setting for preserving early tetrapods, large freshwater fish, and a variety of other fossil material, but also created a highly dynamic environment in which these organisms were interacting and evolving. iii TABLE OF CONTENTS List of Figures...................................................................................................................................... v List of Tables….................................................................................................................................. vi Acknowledgements………………………………………………………………………..………. vii Introduction……………………………………………………………………………………...….. 1 Geologic Setting…………………………………………………………………………………….. 2 Appalachian Basin and Acadian Orogeny…………………………………..…………..….....… 2 Catskill Delta……………………………………………………………………………………. 4 Red Hill…………………………………………………………………………………………. 4 Methods……………………………………………………………………………………...……... 6 Data………………………….…………………………………………………..………...…....…... 9 Lithologic descriptions…..…………..…….………………………………………..………....... 9 Facies proportions…………………………………………………………………....………... 12 Sand body geometry……..…………………………………………………………….……..... 12 Results of fossil material survey……..………………………………………………………... 16 Discussion…………………………………………………………….………………………...…. 16 Evidence for avulsive processes…………………...……………………………...……….…... 16 Further avulsion studies…………………………………………………………...…….……... 22 Circumstantial evidence supporting an avulsion model…………………………….……...….. 23 Significance for alluvial packages in the geologic record, early tetrapod evolution, and fossil prospecting…………………………………………………………………………………….. 24 Possible limitations of the Red Hill and further work………………………..…………..……. 29 Conclusion…………………………………………………………….…………………………… 30 Works Cited……………………………………………………….……………………....…….…. 32 Appendix A – Fossil sampling location data……………….………….………….………...……... 36 Appendix B – Individual fossil data………………….………………….………………….….….. 37 iv LIST OF FIGURES Figure 1. Late Devonian (363 Mya). After Clack, 2002…...……………………………………… 3 Figure 2. Block diagram showing Acadian Mountains, Catskill Delta and Appalachian Basin….... 5 Figure 3. Pennsylvania map showing Red Hill outcrop………………………………………..…... 6 Figure 4. Photomosaic of outcrop with seven measured sections………...….………..………….. 13 Figure 5. Flat-based sandstone (facies F)…………………………………….……………....…… 15 Figure 6. Schematic model of Saskatchewan avulsion belt……………………………………..... 19 Figure 7. Cross section of avulsive sediments…………………………………………….……..... 19 Figure 8. Aerial photo of a trunk channel and crevasse splay in Saskatchewan………..………… 21 Figure 9. Aerial photo of Saskatchewan floodplain during avulsion……………………………... 22 Figure 10. Correlated sections showing lithofacies and avulsive interpretation ………………..... 26 Figure 11. Photomosaic and drawing of Stage I and Stage II at Red Hill………………………… 27 Figure 12. Schematic model of Stage I and Stage II deposits…………………………………….. 28 v LIST OF TABLES Table 1. Facies of lower portion of Red Hill outcrop……………………………………………... 14 Descriptions of color, texture, geometry, internal structure, contacts, and fossil material found in the accessible lower portion of the Red Hill outcrop Table 2. Interpretation of paleoenvironments………………………………………………….…. 25 Descriptions of facies placed in interpretive paleoenvironmental context vi ACKNOWLEDGMENTS I would like to thank Mark Patzkowsky for helping me through the rough periods and guiding me toward completion. I would like to thank my other committee members, Rudy Slingerland and Russell Graham for their continued support and advice throughout the data-gathering and writing process. I am extremely appreciative for the help of Doug Rowe, the Red Hill site curator, who was on site nearly every day that I was, and who was an invaluable source of information on fossil locations and identifications at the outcrop. I would like to thank Ted Daeschler and Walt Cressler for talking over their thoughts on the site and my research with me. Thanks also to everyone at Penn State who helped with my learning process including, but certainly not limited to, Doug Edmonds, Zachary Krug, Jocelyn Sessa, James Bonelli, Matthew O’Donnell, Ellen Currano, Peter Flemings, and Peter Wilf. I would like to thank Ray Rogers, my advisor and friend at Macalester College who often had a useful bit of advice to help get me through. And most of all, I would like to thank my parents Mark and Julie Peterson and my sister Leah Peterson for loving, supporting and advising me through all my trials and endeavors. vii Introduction The nature of the Late Devonian world into which the earliest tetrapods crawled is of great interest in evolutionary studies. Even so, there is still no consensus as to the environments in which tetrapods first evolved or the evolutionary impetus for leaving their aquatic habitats and venturing onto land. In the early part of last century, Alfred Romer hypothesized that the basins of the Old Red Sandstone continent were characterized by regularly occurring semi-arid seasons that pressured the first tetrapods to migrate from drying pools to wetter, more permanent ones (1933). The theory was widely accepted and was consistent with the general idea that redbeds are a strong indictaor of dry spells that would account for such behavior. Inger (1957) cited several studies showing that contemporary red soil beds form almost exclusively in warm, humid, rainforest-like conditions, often lacking any dry season or semi-arid conditions. He suggested that terrestrial conditions in the Late Devonian were likely far more hospitable to aquatic animals than Romer had envisioned. Orton (1954) suggested that tetrapod limbs were not, at least initially, adapted as a means of locomotion on land at all. Rather, these robust limbs were used to dig into the mud to stay cool and moist during estivation. However, certain living lungfishes (close relatives of the early tetrapods) commonly burrow into the mud with limbs distinctly dissimilar to those of early tetrapods (Clack 2002). Moreover, this leaves unanswered the question of why early tetrapods eventually became terrestrial, and what those paleoenvironments looked like. The oldest tetrapods currently known are Obruchevichthys and Elginerpeton from the Frasnian of Latvia and Russia (Ahlberg 1995). Both were described over a century ago, but have only recently been classified as tetrapods (Ahlberg 1995). There is still some debate as to whether Obruchevichthys falls within or just outside of the tetrapod clade (Ahlberg 1995; Clack 2002). 1 These earliest tetrapods are followed in the Famennian by Acanthostega, Ichthyostega, Designathus and Hynerpeton, the last of which was discovered at the Red Hill locality near Hyner, PA (Clack 2002.) More recently, Tiktaalik, a transitional organism between the Sarcopterygians (lobe-finned fish) and tetrapods, was described in meandering stream facies from the early and middle Frasnian of Ellesmere Island, Nunavut, Canada (Daeschler et al. 2006). Initial paleoenvironmental descriptions of Red Hill were made as vertebrate material was being discovered. These interpretations combined the general overview of the environments present on the Late Devonian Catskill Delta with specific observations of the fossil-bearing beds (e.g. Daeschler, et al. 1994; Woodrow, et al. 1995; Daeschler 2000a, b). The prevailing interpretation of paleoenvironments at Red Hill describes the lateral migration of a large broad river channel with seasonal drying of the proximal floodplain (Woodrow et al. 1995). This interpretation of Red Hill supports the general notion that early tetrapod environments were seasonally dry in this and other previously