Palynomorph assemblages dominated by dinoflagellate cysts are described from seventeen samples from the Rabot Member of the Santa Marta Formation at Ekelöf Point, eastern James Ross Island, Antarctic Peninsula. Although the assemblages are of relatively low diversity, the dinoflagellate cyst taxa recorded indicate a mid to late Campanian (Late Cretaceous) age. Changes in species diversity, dominance and gonyaulacacean ratio suggest a gradually reducing distance from shore during deposition, with a return to more offshore conditions towards the section top. A new species of dinoflagellate cyst, Isabelidinium papillum, is described.

Palynomorph assemblages from the Lachman Crags Member of the Santa Marta Formation, north-west James Ross Island, Antarctic Peninsula are described. By basis of comparison with other Southern Hemisphere localities, particularly southern Australia, an early Santonian–early Campanian age is indicated. The results broadly corroborate previous stratigraphical interpretations based on macrofaunal evidence, although the presence of a significant thickness of Santonian strata, not previously recognized, is suggested. The dinoflagellate cyst floras allow the recognition of the local equivalents of the Australian Odontochitina porifera, Isabelidinium cretaceum, Nelsoniella aceras and Xenikoon australis Interval Zones. Some recycling of mid Cretaceous (and possibly Late Jurassic) taxa is also indicated. The miospore flora is composed of relatively long-ranging species, although the local appearance of certain taxa may be of stratigraphical significance. Ranges recorded support previous interpretations of heterochroneity in Southern Hemisphere floras. The palynoflora comprises 76 dinoflagellate cyst, 40 miospore and 7 acritarch, prasinophyte and chlorophyte taxa. Six undescribed species of dinoflagellate cyst are recorded and placed in open nomenclature.