PHYTOLITH RECOVERY FROM A DUNG BALL AS A PALEOBOTANICAL ARCHIVE OF EARLY OLIGOCENE VEGETATION FROM THE BADLANDS OF SOUTH DAKOTA

The Eocene-Oligocene transition (EOT) was a rapid climate change that marked the global shift from “greenhouse” to “icehouse” conditions. The nonmarine White River Group (WRG) of the northern Great Plains straddles this climatic transition; however the lack of macrobotanical fossils preserved in the WRG has inhibited detailed analysis of vegetative response across the EOT. Most plant remains in the WRG are limited to clay filled root traces, carbonate rhizoliths, and uncommon silicified seeds and wood. Phytoliths (plant opal) have taxonomically diagnostic morphologies and high preservation potential due to their siliceous composition, and thus can provide insight into the missing macrobotanical record. Analysis of phytoliths from the Badlands of SD has yet to be carried out in great detail. A dung ball (Coprinisphaera sp.) from the early Oligocene Poleslide Member of the Brule Formation was chosen for analysis because of the high preservation potential and likely high concentration of phytoliths. Phytoliths were separated from the dung ball through standard dissolution and disaggregation practices followed by heavy liquid separation. From one dung ball 258 total phytoliths were counted by mounting extracted sample in glycerin and scanning the slide systematically. Initial analysis yields 84.1% identifiable morphologies consisting of several grass subfamilies, palms, sedges, and woody dicots. Future work will address taphonomic biases by examining a dung ball and encasing sediment that was associated with an in situ fossil herbivore mandible, which marks an ancient soil surface. Phytolith comparison between the sediment and dung ball will elucidate any dietary or mechanistic biases versus the background floral community during the early Oligocene.