MIOCENE GLACIOMARINE SEDIMENTATION IN THE NORTHERN ANTARCTIC PENINSULA REGION - THE STRATIGRAPHY AND SEDIMENTOLOGY OF THE HOBBS GLACIER FORMATION, JAMES-ROSS-ISLAND

The onshore record of Cenozoic glaciation in the Antarctic Peninsula r egion is Limited to a number of isolated localities on Alexander Islan d, the South Shetland Islands and in the James Ross Island area. In th e James Ross Island area, Late Cretaceous sedimentary rocks are unconf ormably overlain by a unit of diamictites and tuffs, which occur at th e base of the James Ross Island Volcanic Group. These rocks are here d efined as the Hobbs Glacier Formation, and on the basis of palynologic al studies are assigned to a Miocene (?late Miocene) age. The diamicti tes are interpreted as representing glaciomarine sedimentation close t o the grounding Line of either a floating ice shelf or a grounded tide water glacier in a marine basin. Provenance studies indicate that the glacier was flowing from the Antarctic Peninsula towards the southeast . Volcanic tuffs conformably overlie the diamictites and are interpret ed as representing deposition in a periglacial delta front setting in either a marine or non-marine basin, away from direct glacial influenc e. The Hobbs Glacier Formation and overlying James Ross Island Volcani c Group help to enhance our understanding of the Neogene glacial chron ology of West Antarctica.