Upper Cretaceous floras of King George Island, West Antarctica, and their palaeoenvironmental and phytogeographic implications

Abstract

The mega- and palynofloras that occur in the lower part of the volcanic-sedimentary succession of King George Island, northern South Shetland Islands, are of Late Campanian and probably also Early Maastrichtian age. They vary in composition locally, reflecting lateral facies changes, taphonomic processes and climatic differences. Those recovered from sections on the Fildes Peninsula (Half Three Point Formation, Fildes Peninsula Group) are commonly dominated by products of ferns, mainly of the families Cyatheaceae, Dicksoniaceae and Gleicheniaceae, but there are also fungal spores, and pollen grains and foliage of conifers (mostly referable to the Podocarpaceae) and angiosperms. Sometimes the combined remains of conifers and flowering plants may, however, comprise more than 50% of assemblages. By contrast, the megaflora recovered from Admiralty Bay (Zamek Formation, Baranowski Glacier Group) is dominated by angiosperms. These include foliage of Nothofagus and primitive laurophyllous species. The vegetation that is represented mainly clothed the eastern side of high fore-arc uplands, and was affected by the volcanic events implied by the lithologies encountered. The floras contain elements that are found in coeval deposits in other southern continents, the descendants of which today inhabit parts of Australia/Tasmania, New Zealand and South America. One new genus, Sterculiaephyllum, and four new species, S. australis, Ficophyllum skuaensis, Nothofagus zastawniakiae and N. glaucifolia, are described.