The Kukri Erosion Surface; a reassessment of its relationship to rocks of the Beacon Supergroup in the central Transantarctic Mountains, Antarctica

Abstract

Much of Antarctica's Devonian to Jurassic geological history is interpreted from the study of the Beacon Supergroup in the central Transantarctic Mountains. The upper part of the succession has been extensively investigated, although, few studies focus on the basal rocks. Deposition occurred within a Transantarctic basin believed to have extended along the edge of the East Antarctic Craton in early Beacon time, either as a marginal, passive margin, or a cratonic basin. Early basinal deposits include the Devonian Taylor Group and Upper Carboniferous–Lower Permian glacial sediments. Previous studies concluded that the Taylor Group in CTM was deposited as a continuous sheet across the low-relief Kukri Erosion Surface that developed on the planed Ross orogenic belt. These interpretations also concluded that late Palaeozoic glaciation truncated the Devonian sheet. New data suggest that this view, and current models for the early Beacon basin, maybe incorrect. Lithofacies, palaeocurrent orientations, sandstone composition, and stratigraphical relationships of central Transantarctic Mountains rocks suggest that deposition occurred within two intermontane or successor basins following post-orogenic uplift of the Ross terrain. Segregation of lithofacies and onlap of Taylor Group rocks onto an undulating Kukri Erosion Surface show that a basement high separated non-marine deposits between the Byrd and Ramsey glaciers from marine sediment in the Ohio Range. Onlap of glacial rocks and palaeocurrent data suggest intermontane conditions continued until the Early Permian.