Geological investigations in southern Victoria Land, Antarctica

The basement complex exposed in the Wright Valley consists of more than 15,000 ft of lolded Precambrian — Lower Cambrian marbles, hornfelses, and schists (Asgard Formation), invaded by acid plutonic rocks. The plutonic rocks comprise three intrusive phases. The oldest intrusives are a strongly foliated granite‐gneiss (Olympus) and a porphyritic granite (Dais), cut by pegmatite dykes and veins. The second intrusive phase consists of microdiorite (Loke) and granodiorite (Theseus) dykes intruding the metasediments, granite‐gneiss, and granite. The third intrusive phase includes an undeformed homogeneous granite (Vida) containing in a few localities large bodies of amphibolite, and dense swarms of younger lamprophyre and porphyry dykes (Vanda) invading all earlier rocks. The peneplained basement surface is overlain unconformably by more than 4,000 ft of mid‐Paleozoic to mid‐Mesozoic sediments of the Beacon Sandstone (Group). Ferrar Dolerite sills and dykes intrude the basement complex and the Beacon Sandstone. Late Quaternary deglacierisation has left the Wright Valley ice‐free for approximately 30 miles.