Abstract During the Mesozoic, the present-day Antarctic Peninsula was the site of an active volcanic arc related to the eastwards subduc-tion of proto-Pacific oceanic crust. Alexander Island is the largest of the many islands that lie on the western (forearc) side of the Antarctic Peninsula. The island is comprised of a greenschist facies, accretionary prism complex (LeMay Group), unconformably overlain and faulted against the forearc sedimentary deposits of the Fossil Bluff Group. The Fossil Bluff Group ranges in age from Middle Jurassic to latest Early Cretaceous and has a stratigraphic thickness of 7 km (4.4 mi). Aalonian-Tithonian clastic units are derived from the accretionary complex, recording the transition from trench-slope to forearc basin sedimentation. The upper formations represent a large-scale, shallowing-upwards cycle of Kimmeridgian to Albian age, with a volcanic arc provenance. The Himalia Ridge Formation is a 2.2 km (1.4 mi)-thick sequence of Late Jurassic to Early Cretaceous conglomerates, immature arkosic sandstones, and mudstones, derived from an andesitic volcanic arc, and deposited in a north-south elongate forearc basin. At the type locality (Himalia Ridge on Ganymede Heights), the formation was deposited as a series of migrating, conglomerate-filled, innet-fan channels and associated overbank-crevasse-splay sheet sands, thin-bedded levees, and interchannel mudstones flanking the basin matgin. The basin was inverted within a strike-slip regime in the middle Cretaceous, and the sttata deformed into a broad monocline with associated thrusting. At Himalia Ridge, the formation is exposed as a continuous section dipping southeast at about 30°. The upper part of the formation is repeated

Abstract A compilation of data for Cretaceous and Cenozoic Antarctic fossil wood floras, predominantly from the James Ross Island Basin, provides a different perspective on floristic and vegetation change when compared with previous studies that have focused on leaf macrofossils or palynology. The wood record provides a filtered view of tree-forming elements within the vegetation, something that cannot be achieved from studies focusing on regional palynology or leaf floras. Four phases of vegetation development in the over-storey are recognized in the Cretaceous and Cenozoic of the Antarctic Peninsula based on the distribution and taxonomic composition of wood floras: Aptian–Albian coniferous forests; ?Cenomanian-Santonian mixed angiosperm forests; Campanian–Maastrichtian southern temperate forests; and Palaeocene-Eocene reduced diversity Nothofagus forests. Comparisons between the wood record and information derived from palynological and leaf floras have important implications for our understanding of the spatial composition of the vegetation. There is no doubt that climate change during the Cretaceous and Tertiary influenced the vegetational composition, but evolving palaeoenvironments in the Antarctic Peninsula region were probably of equal, if not greater, importance.