Evidence for an earliest Oligocene ice sheet on the Antarctic Peninsula

Abstract

There is growing consensus that development of a semipermanent ice sheet on Antarctica began at or near the Eocene-Oligocene (E-O) boundary. Beyond ice-rafted debris in oceanic settings, however, direct evidence for a substantial ice sheet at this time has been limited and thus far restricted to East Antarctica. It is unclear where glacier ice first accumulated and how extensive it was on the Antarctic continent in the earliest Oligocene. Sediments at the top of the Eocene marine shelf section on Seymour Island, Antarctic Peninsula, include glacial marine deposits and a lodgment till with clasts derived from a variety of rock units on the peninsula. Dinoflagellate biostratigraphy and strontium isotope stratigraphy indicate an age at or very close to the E-O boundary. Glacier ice extending to sea level in the northern peninsula at this time suggests the presence of a regionally extensive West Antarctica ice sheet, and thus an even more dramatic response to the forcing factors that facilitated high-latitude ice expansion in the earliest Oligocene.

Major shifts in calcareous phytoplankton assemblages through the Eocene‐Oligocene transition of Tanzania and their implications for low‐latitude primary production

“…EoceneOligocene marine sedimentary records are characterized by large, $1.0 to 1.5%, positive excursions in benthic foraminiferal oxygen and carbon stable isotopes and a rapid deepening of the calcite compensation depth (CCD) [Coxall et al, 2005;Zachos et al, 1996]. Coincident with these changes in the deep sea, significant glaciomarine sedimentation commences around the margins of both East and West Antarctica indicating the first Cenozoic advance of continental-scale ice sheets in southern high latitudes Ivany et al, 2006;Wise et al, 1991Wise et al, , 1992Zachos et al, 1992]. Estimates of the increase in global ice volume through this transition, based on records of benthic foraminiferal d 18 O, Mg/Ca ratios and sequence stratigraphy, are similar to or greater than the volume of the present-day Antarctic ice sheet [Billups and Schrag, 2003;Coxall et al, 2005;Katz et al, 2008;Lear et al, 2004Lear et al, , 2008Pekar et al, 2002].…”

Eocene relatives of cod icefishes (Perciformes: Notothenioidei) from Seymour Island, Antarctica

“…The geo chem i cal anal y ses made on the fos sil bi valve shells from the La Meseta For ma tion sug gest a cli ma tic cool ing event dur ing the time of de po si tion of the up per most part of the for mation (GaŸdzicki et al, 1992;Din gle et al, 1998;Ivany et al, 2006Ivany et al, , 2008Cione et al, 2007;Fran cis et al, 2009;B³a¿ejowski et al, 2010). This is cor re lated with the first Ce no zoic gla ci ation of Antarctica and with the open ing of the Drake Pas sage at the Eocene-Oligocene bound ary (Zachos et al, 2001;Birkenmajer et al, 2005).…”

“…(Telm7) are rec og nized in the La Meseta For ma tion. In the for ma tion a grad ual de te ri o ra tion of cli mate is re corded, with the ev i dence of de creas ing tem per atures through the later Eocene cul mi nat ing with the first Antarc tic glaciations at the Eocene-Oligocene bound ary (GaŸdzi -cki et al, 1992;Din gle et al, 1998;Birkenmajer et al, 2005;Ivany et al, 2006Ivany et al, , 2008Tatur et al, 2006;Fran cis et al, 2009; see also Cantrill and Poole, 2012). Most pos si bly, the or i gin of the notothenioids is linked to this cli ma tic event, as was hypoth e sized al ready by Regan (1914) and men tioned by Grande and East man (1986: p. 134).…”

The Late Devonian (Frasnian/Famenian) mass extinction: a proposed test of the glaciation hypothesis

“…The prob lem is that Oi-1 gla cial sed i ments on land in Antarctica have been re moved by the ero sive ac tion of the larger mid dle Mio cene gla ciers, with two pos si ble ex cep tions (Strand et al, 2003;Ivany et al, 2006). The size of the first step Oi-1 gla ciers has been es ti mated to have been in the range of 7.0-11.9 ´ 10 6 km 2 (Zachos et al, 2001;Pusz et al, 2011).…”