The Geology from the Upper Rennick Glacier to the Coast, Northern Victoria Land, Antarctica

Abstract

The Polar Plateau in this area is a rock surface thinly veneered with ice and lies at a height 8,000 to 11,000 ft above sea level. Three major groups of rocks are present: (1) Volcanics of late Tertiary and Quaternary age including kenyte and related rock types; (2) Volcanics (mostly basalt) of Triassic-Jurassic age with minor sediments; and (3) A basement complex consisting mostly of granite and gneissic granite digesting regional biotite schist of probable Precambrian age. The Tertiary volcanics are sufficiently young to form conspicuous features on the landscape (mostly volcanoes), and they all occur altmg two north-trending belts on the eastern margin of the area. The basalts of Jurassic age are at least 4,500 ft thick, and resemble very closely both in field occurrence and lithology the Drakensburg and Batoka Basalts of southern Africa. Within the basalts and at their base are beds of arkosic sandstone up to 60 ft thick that are carbonaceous in parts and contain silicified tree trunks in place of growth. The lavas dip regionally at 2°–3° to the north-west and are probably in fault contact with Precambrian gneissic granite and schist on the west side of the Rennick Glacier. The Precambrian schists and the gneissic granites intruding them strike regionally north and dip 60°–80° west and were probably peneplained (the Kukri Peneplain) before the extrusion of the Jurassic lavas. Apart from one small area of schist several miles in extent and including a thick bed of marble, the schists have been mostly digested by the granites to such an extent that only xenoliths, ranging from a few yards to several hundred yards in width, now remain.