A CASE FOR SIRIUS-GROUP ALPINE-GLACIATION AT MOUNT-FLEMING, SOUTH-VICTORIA-LAND, ANTARCTICA - A CASE AGAINST PLIOCENE EAST ANTARCTIC ICE-SHEET REDUCTION

The Sirius Group comprises a suite of consolidated glacial deposits th at are widespread in the Transantarctic Mountains; some of the deposit s contain Pliocene marine diatoms, Because of the interpretation that the Sirius Group tills and the marine diatoms were deposited by the Ea st Antarctic Ice Sheet, it has been inferred that the East Antarctic I ce Sheet was much reduced in area and volume during the Pliocene. Thes e interpretations were evaluated by studying Sirius Group lodgment til ls on Mount Fleming in the Dry Valleys sector of the Transantarctic Mo untains. We infer that the Sirius Group lodgment tills at Mount Flemin g do not support the hypothesis that the East Antarctic Ice Sheet was much reduced during the Pliocene. We demonstrate that Sirius Group lod gment tills on Mount Fleming mere deposited by alpine ice. This conclu sion is founded on ice-now directions inferred from rattails, gravel f abric, and the orientation of bullet boulders, as well as on sediment and gravel characteristics of the tills, Only a very few unidentifiabl e diatom fragments mere recovered, Better preserved, identifiable, Pli ocene marine diatoms occur in moderate abundances in a 5-10-cm-thick u nconsolidated and discontinuous drift that caps the lodgment tills, On the basis of the decline in diatom preservation with depth into the t ill, we dismiss transport of the better preserved diatoms by the ice t hat deposited the underlying Sirius Group lodgment till. Instead, we a ttribute diatom presence to eolian deposition and recycling into lodgm ent tills at a later stage.