CLAS: Colby Liberal Arts Symposium

Fluctuations in global ice volume during the Pennsylvanian shown through direct and indirect glacial records

Parker-Reed, SSWAC

During the late Paleozoic era (359 252 million years ago; Ma), the Earth underwent extensive glaciation. Glacial ice began to form in the southern hemisphere during the Mississippian (359 323 Ma), waxed and waned during the Pennsylvanian (323 299 Ma), and came to its acme in the earliest Permian (~299 Ma) before reaching its demise later in the Permian. The fluctuations in the volume of glacial ice during the Pennsylvanian were a result of dynamic climatic conditions controlled by Milanković cycles. The resultant glacial/interglacial sequences are recorded both in the direct as well as the indirect glacial record. Glacial deposits and glacial topography provide direct evidence for glaciation in the southern hemisphere. The direct record is less complete than the indirect record, which records transgressive-regressive depositional sequences (sediments deposited during alternating high and low sea level) in stratigraphic sequences called cyclothems. Cyclothems reflect glacio-eustatic changes (change in sea level caused by the formation and melting of glacial ice), and can be used to infer ice volume fluctuations. By investigating the direct and indirect glacial records, it is possible to model the extent, positioning, and movement of continental ice sheets as well as the volume and area of ice. The goal of this project is to determine how ice sheets fluctuated during the Pennsylvanian in response to a number of dynamic factors including: pCO2, tectonic activity, and Milanković cyclicity. Of these three factors, Milancović cycles contribute the most to glacial fluctuations. Ultimately it will become clear that Milanković cycles (1) were the primary force driving ice sheet fluctuations and (2) controlled three distinct episodes of glaciation during the Pennsylvanian.

https://digitalcommons.colby.edu/clas/2015/program/161