Geology of the Lower Rennick Glacier, Northern Victoria Land, Antarctica

Abstract

Abstract Along the east side of the Lower Rennick Glacier in the far north of northern Victoria Land, Antarctica, metamorphic basement is preserved as a large block of high grade quartzo‐feldspathic schist and minor amphibolite (Wilson Group) in fault contact with Ross Supergroup sediments to the east. The Wilson Group has been intruded by post‐tectonic biotite adamellite plutons which are considered to be correlatives of the Granite Harbour Intrusives (Cambrian‐Ordovician). The Ross Supergroup has been divided into two suites of geosynclinal sediments: the Robertson Bay Group which consists mostly of quartzo‐feldspathic grey‐wacke and argillite, and the Bowers Group for which three major lithostratigraphic subdivisions are proposed. The oldest formation (Carryer Conglomerate) consists of at least 5000 m of polymict conglomerate, greywacke, and argillite. The overlying Sledgers Formation comprises 13 000 m of sandstone, siltstone, conglomerate, spilitic lavas, basic flow breccias, volcanic‐derived sediments, and rare limestone. The youngest unit is the Camp Ridge Quartzite which contains up to 7000 m of quartz arenite, quartz conglomerate, and minor red argillite. Ross Supergroup sediments were uplifted and folded in mid‐Paleozoic times, and have been intruded by post‐tectonic biotite granodiorite of the Admiralty Intrusives (Devonian‐Carboniferous). At Gallipoli Heights, a sequence of Devonian rhyolitic lavas and ignimbrites (Gallipoli Rhyolites) are possibly extrusive equivalents of the Admiralty Intrusives. An extensive surface of erosion, here called the Sub‐Beacon Surface , was cut across Granite Harbour Intrusives in the Freyberg Mountains and across rocks which are probable correlatives of the Robertson Bay Group in the central and southern Morozumi Range. Thin but widespread outcrops of Beacon Supergroup sandstones and shales (Takrouna Formation) rest unconformably on this surface, and a well‐preserved Permian Glossopteris flora is described from Takrouna Bluff. Takrouna Formation sediments have been intruded, and frequently rafted, by sills of Ferrar Dolerite.