Preliminary Jurassic and Cretaceous dinoflagellate cyst stratigraphy of the James Ross Island area, Antarctic Peninsula

Palynological analyses of Jurassic and Cretaceous rock samples from the James Ross Island area have allowed the application of southern hemisphere, principally Australasian, dinoflagellate cyst zonations to this back-arc basin sequence. The results corroborate, and in some cases refine, existing macrofaunal age assessments. The Nordenskjold Formation yielded dinoflagellate cysts indicative of the Tithonian (probably mid Tithonian) Stage. Dinoflagellate cysts including Endoceratium turneri indicate that the Kotick Point Formation (Gustav Group) is early Albian in age, refining the macrofaunal dating. The overlying Whisky Bay Formation was adduced to be late Albian to early-mid Turonian on dinoflagellate cyst evidence. The presence of the Australian zonal index Conosphaeridium striatoconus, together with Disphaeria macropyla and macrofaunal data, indicate that the Hidden Lake Formation is Coniacian to earliest Santonian. Reworking of Jurassic and Cretaceous palynomorphs into the youngest three formations of the Gustav Group was recognised; this is attributed to basin margin tectonic activity. The Santa Marta Formation (Marambio Group) sampled here is early Santonian to early Campanian in age based on the recognition of the Australian Odontochitina porifera, Isabelidinium cretaceum and Nelsoniella aceras zones. The overlying Lopez de Bertodano Formation on Vega and Humps islands was found to be late Campanian to early Maastrichtian; late Maastrichtian strata were identified at Cape Lamb, Vega Island.