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An Analysis of Multiple Trackways of Protichnites Owen, 1852, from the Potsdam Sandstone (Late Cambrian), St

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An Analysis of Multiple Trackways of Protichnites Owen, 1852, from the Potsdam Sandstone (Late Cambrian), St AN ANALYSIS OF MULTIPLE TRACKWAYS OF PROTICHNITES OWEN, 1852, FROM THE POTSDAM SANDSTONE (LATE CAMBRIAN), ST. LAWRENCE VALLEY, NY by Matthew E. Burton-Kelly A Bachelors Thesis Submitted to the Faculty of the Department of Geology of St. Lawrence University in partial fulfillment of the requirements for the degree of Bachelor of Science with Honors in Geology Canton, New York 2005 1 2 3 This thesis submitted by in partial fulfillment of the requirements for the degree of Bachelor of Science with Honors in Geology from St. Lawrence University is hereby approved by the Faculty Advisor under whom the work was done. Faculty Advisor Date Department Chairman Date ii 4 ACKNOWLEDGMENTS The author would like to thank Dr. J. Mark Erickson for his assistance and guidance throughout the course of this project, as well as the St. Lawrence University Geology Department, which provided research materials and covered transportation costs. Attendance at the annual meeting of the Northeastern Section of the Geological Society of America to present preliminary results was funded by the Jim Street Fund, St. Lawrence University Geology. Jim Dawson provided vital insight into the nature of these trackways. Any number of additional people provided support for the author, most notably Camille Partin, Trisha Smrecak, and Joanne Cavallerano, but thanks go out to all the members of the St. Lawrence University Geology Department and the St. Lawrence University Track and Field teams. iii 5 TABLE OF CONTENTS THESIS APPROVAL..........................................................................................................ii ACKNOWLEDGMENTS..................................................................................................iii TABLE OF CONTENTS....................................................................................................iv LIST OF FIGURES............................................................................................................vi LIST OF PLATES..............................................................................................................vii LIST OF TABLES............................................................................................................viii ABSTRACT........................................................................................................................ix INTRODUCTION...............................................................................................................1 SYSTEMATIC PALEONTOLOGY...................................................................................12 Ichnogenus Protichnites.........................................................................................12 Emended diagnosis................................................................................................13 Discussion..............................................................................................................14 Similar ichnofauna.................................................................................................18 ARTHROPOD TERRESTRIALIZATION........................................................................20 TERMINOLOGY...............................................................................................................23 Notation..................................................................................................................23 Identifying tracks...................................................................................................23 DESCRIPTION.................................................................................................................27 Trackway 1.............................................................................................................27 Trackway 2.............................................................................................................30 Trackway 3.............................................................................................................32 iv v6 DISCUSSION....................................................................................................................34 Ichnotaxonomy.......................................................................................................34 Organisms responsible...........................................................................................36 Functional morphology..........................................................................................40 Paleoecology..........................................................................................................42 Preservation............................................................................................................46 CONCLUSIONS...............................................................................................................50 WORKS CITED................................................................................................................52 ADDITIONAL WORKS REVIEWED..............................................................................57 7 LIST OF FIGURES Figure 1. Regional bedrock map of southern Canada... .....................................................2 Figure 2. Bedding-plane exposure showing at least 11... ..................................................3 Figure 3. Plaster cast of Protichnites septem-notatus... .....................................................5 Figure 4. Plaster cast of Protichnites octo-notatus... .........................................................6 Figure 5. Plaster cast of Protichnites latus... .....................................................................7 Figure 6. Plaster cast of Protichnites multinotatus... .........................................................8 Figure 7. Plaster cast of Protichnites lineatus... .................................................................9 Figure 8. Plaster cast of Protichnites alternans... ............................................................10 Figure 9. Two ways of grouping individual tracks... .......................................................25 Figure 10. Schematic diagram of trackway 1... ...............................................................28 Figure 11. Schematic diagram of trackway 2... ...............................................................31 Figure 12. Schematic diagram of trackway 3... ...............................................................33 Figure 13. Plaster cast of Protichnites septem-notatus with... .........................................35 Figure 14. Cambrian arthropods... ...................................................................................37 Figure 15. Later forms possessing morphologies... .........................................................39 Figure 16. Bedding-plane surface including arthropod... ................................................41 Figure 17. Limulus polyphemus male mounting a female... ............................................45 Figure 18. Exposed bedding-plane surfaces at trackway... ..............................................47 vi 8 LIST OF PLATES Plate 1. Bedding plane exposure showing at least 11... .............................................folded Plate 2. Schematic diagram of trackway 1 (actual size)... ...............................................63 Plate 3. Schematic diagram of trackway 2 (actual size)... ...............................................65 Plate 4. Schematic diagram of trackway 3 (actual size)... ...............................................67 vii 9 LIST OF TABLES Table 1. Stride length and external width of trackway 1... ..............................................29 Table 2. Mean stride and standard deviation of paired tracks... .......................................29 Table 3. Stride length and external width of trackway 2... ..............................................30 Table 4. Stride length and external width of trackway 3... ..............................................32 viii 10 ABSTRACT ! Late Cambrian arthropod trackways from the Potsdam Sandstone have been known since the 1850’s. A site in northern New York is an outcrop of fine-grained, quartz-rich, rippled, micro-laminated Potsdam Sandstone. A similar site near Kingston, Ontario, has been described as the first evidence of land animals. Our study area includes evidence of microbial mat growth on the original surface on which the trackways were produced. Ripple marks presumably underlay and therefore were generated prior to the microbial mat. Preservation of these trackways is variable over the outcrop and is indicative of a high intertidal or low supratidal environment with microbial growth. At least eleven distinctive trackways of multi-legged telson-bearing individuals are present with a roughly bimodal size distribution (widths of 11.6 cm, 6.5 cm, 10 cm and 7.2 cm). A disturbance at the intersection of trackways 1 and 2 has been interpreted to show the earliest evidence of invertebrate mating activity (Erickson, 2004). Trackway 1 (11.6 cm wide) consists of repeated series of seven pairs of imprints arranged in a chevron pattern. The organism was traveling in the direction of the convergence of the chevron pattern. The trackways are consistent in number of imprints per series (leg number?) and stride lengths with members of the original descriptions of Protichnites Owen, 1852, although a tridactyl condition cannot be recognized on any digit. Variable preservation probably resulted from varying thickness of the microbial mat and/or
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