GLACIAL GEOLOGY OF JAMES ROSS ISLAND, ANTARCTIC PENINSULA

One of our projects in Antarctica concerns the glacial geology of James Ross Island (JRI), located in the NE part of the Antarctic Peninsula. Late Miocene to Pliocene glacial environments are recognized in the submarine and subglacial pyroclastic/lava sequences of the James Ross Island Volcanic Group. Pleistocene to Holocene glacial and glaciomarine landforms and exposures complete the glacier history of this sector of the Antarctic Peninsula. During the Last Glacial Maximum, JRI bays and channels were occupied by glaciers, with fronts that reached close to the present continental shelf margin. Reworked marine sediments, incorporated in lodgment till at Lachman Crags, Caleta Santa Marta, and Bahía Caña Quemada are related to previous interstadial or interglacial events (MIS 3, MIS 5e?). Cape Lachman provides two lateral moraines that are possibly Lateglacial in age. A deglacial marine transgression was postulated for the Early Holocene on both (east and west) sides of Croft Bay, where a basal deformation till includes marine sediment containing shells, which were radiocarbon dated 8200-7300 cal yrs BP. This glacier transgressive sequence is cut by a 20 m high marine terrace containing shells of 7100 cal yrs BP, bracketing the glacier advance. According to previous stratigraphic works in Bahía Brandy, a second Holocene glacial advance took place shortly before 4850 cal yrs BP. A glacier transgressive sequence was also dated 5900 to 5700 cal yrs BP in Bahía Caña Quemada. In the same bay, a well-shaped frontal moraine rests on top of an up to 4150 cal yrs BP old marine delta. Up valley, two more undated frontal moraines complete the record of Holocene glacier advances.