"Bottomsets" of the lava-fed delta of James Ross Island Volcanic Group, Ulu Peninsula, James Ross Island, Antarctica

Abstract

Sedimentological study of the three geographically separated outcrops of bottom- sets of a single lava-fed delta (Pliocene) in the James Ross Island (Antarctica) allows recognition of six lithofacies.Deposits of traction currents, deposits of volcaniclastic debris flows and products of such flows transformations (both low- and high-density turbidity currents) and glacigenic deposits (subaqueous debris flows and traction/turbidity currents) were all recognised. Existence of submarine proglacial environment formed prior to formation of volcani- clastic deposits partly covering the subaqueous slopes of volcano is supposed. The principal role of mass flow processes was recognised and explained by relative steep slopes of the lava-fed delta. The distribution of lithofacies significantly differs in the individual outcrops. These variations in sedimentary succession and also in thickness of volcaniclastic deposits of "bottomsets" of the single lava fed delta suggest principal role of local conditions and paleogeography for development and preservation of this part of delta depositional system. Moreover proximal and distal setting can be followed and direct vs. more distant relation to over-riding lava-fed delta supposed. The sedimentary succession terminated by foresets of hyaloclastite breccia.