ABSTRACT: Late Paleozoic-Early Mesozoic History of the Pacific Margin Along Antarctica

James W. Collinson, John L. Isbell, Molly F. Miller

The late Paleozoic-early Mesozoic Pacific margin of Gondwanaland from eastern Australia to Patagonia was characterized by a series of back-arc and foreland basins associated with subduction and volcanism. The Transantarctic basin, including the present Transantarctic Mountains and Tasmania, evolved from a middle Paleozoic passive continental margin to an Early Permian back-arc basin and a Late Permian-Triassic foreland basin. The earliest evidence of a volcanic arc and subduction is the appearance of abundant volcanic detritus at the base of the Early Permian postglacial marine shale-and-sandstone sequence in the Ellsworth Mountains. Volcaniclastic forearc sediments of Permian(?) to Triassic age are known from the Antarctic Peninsula. The introduction of abundant volcanic detritus to the East Antarctic craton and a 180° paleocurrent reversal in the Late Permian in the Beardmore Glacier area is the earliest evidence of folding along the Antarctic-Pacific margin. By the Early Triassic, folding involved Late Permian sequences in the Ellsworth and Transantarctic (Pensacola) mountains. Thick Upper Permian and Triassic braided-stream deposits of mixed volcanic and cratonic provenance accumulated in this foreland basin. Subsidence ended in the Early Jurassic with uplift and diabase intrusion associated with the breakup of Gondwanaland.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990