PETROGRAPHY AND PROVENANCE OF THE MARAMBIO GROUP, VEGA-ISLAND, ANTARCTICA

Late Cretaceous sedimentary rocks assigned to the Santa Marta (Herbert Sound Member) and Lopez de Bertodano (Cape Lamb and Sandwich Bluff me mbers) formations of the Marambio Group, crop out on Cape Lamb, Vega I sland. Although previous studies have recognized that these sedimentar y rocks were derived from the northern Antarctic Peninsula region, the work presented here allows the provenance and palaeogeographical evol ution of the region to be described in detail. On the basis of both sa ndstone petrography and clay mineralogy, the Herbert Sound and Cape La mb members reflect sediment input from a low relief source area, with sand grade sediment sourced from low grade metasediments, and clay gra de sediment ultimately derived from the weathering of an andesitic sou rce area. In contrast, the Sandwich Bluff Member reflects a switch to a predominantly andesitic volcaniclastic source. However, this sedimen t was largely derived from older volcanic suites due to renewed source area uplift, with only a minor component from coeval volcanism. Regio nal uplift of both the are terrane and the western margin of the James Ross Basin was likely during the Maastrichtian.