Cenozoic glacigene sedimentation and erosion at the Menzies Range, southern Prince Charles Mountains, Antarctica

Abstract

The Menzies Range in the southern Prince Charles Mountains, Antarctica, records at least four intervals of Cenozoic terrestrial glacigene sedimentation, and two periods of glacial erosion. The oldest Cenozoic strata, here named the Pardoe Formation, are >240 m thick, and consist of variable diamicts with subordinate sandstones and minor laminated lacustrine siltstones. The Pardoe Formation overlies a rugged erosion surface cut into Precambrian basement. Two subsequent Cenozoic sequences are here named informally the Trail diamicts and the younger Amphitheatre diamicts. The latter infilled the lower regions of an extremely rugged erosion surface, many components of which still dominate the present topography. The palaeodrainage of this erosion surface is markedly discordant with that of the older erosion surface underlying the Pardoe Formation. These three depositional events and the two associated erosion surfaces record warmer climates and increased snow accumulation under conditions of temperate wet-based glaciation. During the excavation of the sub-Amphitheatre diamict erosion surface, the East Antarctic ice sheet was either absent, further inland or the height of its surface relative to the Menzies Range was considerably lower than at present. The fourth and youngest depositional episode, recorded by a veneer of boulder gravel distributed along the northern flank of the Menzies Range, is from dry-based glacier ice, and assumed to be <2.6 Myr.