Dinocyst taphonomy, impact craters, cyst ghosts and the Paleocene–Eocene thermal maximum (PETM)

Abstract

Dinocysts recovered from sediments related to the Chesapeake Bay impact structure in Virginia and the earliest Eocene suboxic environment in Maryland show strange and intriguing details of preservation. Features such as curled processes, opaque debris, breakage, microborings and cyst ghosts, among others, invite speculation about catastrophic depositional processes, rapid burial and biological and chemical decay. Selected specimens from seven cores taken in the coastal plain of Virginia and Maryland show abnormal preservation features in various combinations that merit illustration, description, discussion and further study. Although the depositional environments described are extreme, many of the features discussed are known from, or could be found in, other environments. These environments will show both similarities to and differences from the extreme environments here.

Keywords:

• dinoflagellates
• taphonomy
• preservation
• Paleocene
• Eocene
• Chesapeake Bay impact
• PETM

Acknowledgements

Douglas J. Nichols and the author worked as palynologists for the US Geological Survey in Denver and Reston, respectively, for nearly three decades. Doug was a USGS reviewer for the first papers on the impact-altered dinocysts and provided insightful advice and strong encouragement. David Pocknall is thanked for the invitation to contribute to this memorial volume, and both he and Thomas Demchuk were supportive throughout the publication processes. The drillers at the USGS and at Major Drilling, America provided superb core recovery and Colleen Durand provided excellent sample preparation. Barrie Dale began discussions about cyst formation. Claus Heilmann-Clausen, Rob Weems and an anonymous reviewer provided valuable input on earlier versions.