Palaeoenvironmental reconstruction of Livingston Island, Antarctic Peninsula, in the Early Cretaceous: interpretations from the Walker Bay erratics

Fossiliferous, volcaniclastic sandstone erratics, containing abundant plant fragments, palynomorphs and a possible insect wing, were extracted from the previously unstudied Walker Bay moraine, Livingston Island (ca 62°36ʹS, 60°42ʹW). These samples provide new insights into high southern latitude ecosystems of the South Shetland Islands region during the Early Cretaceous greenhouse interval. The palynofloral assemblage, in particular the co-occurrence of Ischyosporites punctatus, Concavissimisporites penolaensis and Reticulatisporites pudens, suggests that deposition could have occurred between the early Aptian and mid-Albian (ca 125–109 Ma), but was most likely early to mid-Albian (ca 112–109 Ma). The high relative abundance of the pteridophyte taxon, Cyathidites and associated fungal disaster taxa, together with significant quantities of volcaniclastic material, indicates a volcanically perturbed post-eruption riparian environment. Petrologic evidence suggests that the volcanic sediments were deposited rapidly in the above-mentioned fluvial setting. Comparisons to geological studies conducted on Livingston Island reveal an affinity of the Walker Bay erratics to the Byers Group; the unique palynofloral assemblage and petrological features of the erratics suggesting that the volcanogenic lithic sandstone facies may represent a previously undescribed unit of the upper Cerro Negro Formation.