CLAS: Colby Liberal Arts Symposium

Shifting Continents, Growing Ice: a Look at How Tectonic Activity Effected Glacial Onset in the Late Mississippian

Parker-Reed, SSWAC

During the Mississippian, 359-323 Million years ago (Ma), the continents were clustered around the South Pole, and shifting continental plates were closing in around the Tethys Ocean in the Eastern Hemisphere. This landmass (Gondwana), centered at high latitudes in the southern hemisphere, included South America, Africa, India, and Australia, and served as a base where ice sheets formed and grew towards the equator in the Late Mississippian (late Visean to Serpukhovian). Evidence for glaciation is widespread in South America and scattered through other regions around the globe. Diamictites, unsorted sedimentary rocks deposited during glacial retreat, and paleovalleys, carved by glaciers as they moved through a region, are direct evidence of one of the most expansive and long-term glaciations in Earths history, the late Paleozoic ice age (LPIA). The LPIA began with an initial ice age in the Late Devonian and continued into Early Mississippian; this glaciation cooled the Earth considerably, causing a major mass extinction ~375 Ma. A roughly 15 m.y. warm period followed deglaciation, before the Late Mississippian, when ice once again extended from the poles, this time lasting almost 100 m.y.. Few ice ages in Earths history have lasted as long as the LPIA, and perhaps the most important factor in making the LPIA so extensive was the closing of the Tethys Ocean, which pushed warm wind and water poleward, resulting in increased precipitation at the poles and ice build up. This paper argues that tectonic activity associated with the closing of the Tethys Ocean during the Late Mississippian is, in large part, responsible for the onset and extent of the LPIA.

https://digitalcommons.colby.edu/clas/2015/program/159