Antarctic Peninsular cryosphere: Early Oligocene (c. 30 Ma) initiation and a revised glacial chronology

Strontium isotope stratigraphy provides a chronology for Cenozoic cryogenic strata in the northern Antarctic Peninsula and allows an assessment of diachronism in onset of glacial conditions between East and West Antarctica. The earliest observed event on the Antarctic Peninsula was 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 latest Miocene (Alexander Island). A further late Neogene glacial deposit (Weddell Formation) can be constrained only as <c. 10 Ma.