ANTARCTIC PENINSULAR CRYOSPHERE - EARLY OLIGOCENE (C. 30 MA) INITIATION AND A REVISED GLACIAL CHRONOLOGY

Strontium isotope stratigraphy provides a chronology for Cenozoic cryo genic strata in the northern Antarctic Peninsula and allows an assessm ent of diachronism in onset of glacial conditions between East and Wes t Antarctica. The earliest observed event on the Antarctic Peninsula w as late Early Oligocene (29.8 +/- 0.6 Ma) (at least c. 4 Ma later than in East Antarctica), with a second in the early Early Miocene (22.6 /- 0.4 Ma). Both glacials and intervening interglacial were continent- wide phenomena. Two late Neogene glaciations are distinguished: early Late Miocene (9.9 +/- 0.97 Ma) (Hobbs Glacier/Jones Mountains) and lat est Miocene (Alexander Island). A further late Neogene glacial deposit (Weddell Formation) can be constrained only as < c. 10 Ma.