Landscape development and vegetation of the Vestfold Hills, East Antarctica
thesisposted on 2022-03-28, 01:33 authored by John Pickard
The Vestfold Hills (68°35'S 78°00'E) are a 400 km² ice-free oasis on the coast of East Antarctica. Low hills of Archaean gneisses are draped with Holocene till. The area is bounded in the east by the ice sheet and in the south by the Sørsdal Glacier. Present geomorphic processes are variable across the Hills from the coast to the ice sheet. Active melt processes have been measured on the ice margins and on an ice-cored moraine. Rivers flowing through the Hills carry meltwater from the ice sheet and glacier via a series of lakes to the sea. The Druzhby River system is one of the largest externally-draining systems in Antarctica. Pingos occur on the ice-cored moraine, the only-known site in the Southern Hemisphere. Freeze/thaw activity is high across the Hills, but periglacial landforms are not uniformly distributed. -- Vegetation is sparse overall but most abundant in a zone a few kilometres from the ice sheet, due to the interaction of windblown salt, water, and nutrient availability. The HIlls belong to the Coastal Zone of the Continental Antarctic Region. Within a single moss bed, chance is important in determining distribution. Mosses are among the oldest Holocene fossils in the Hills. Problems with moss taxonomy severely retard ecological and physiological research. -- Tertiary marine sediments mark the location of a Late Miocene coast remarkably close to the present coastline, during an interglacial period with climate similar to the present. The terminal Pleistocene expansion of the ice sheet (Vestfold Glaciation) swamped the Hills under > 1000 m of ice. Holocene ice retreat has exposed the Hills. Retreat is documented and radiocarbon-dated by abundant marine fossils above hypersaline lakes. -- Marine inlets isolated by isostatic uplift became chains of lakes with complex Holocene histories, All Holocene marine fossils are extant species with wide ecological tolerances. Holocene climates in the Hills were little different from present. Fossil mosses and stromatolites indicate unusual lakes which have changed from marine to fresh and vice versa. -- Low altitude makes the Hills an excellent site for the preservation of evidence hearing on the Holocene collapse of the antarctic ice sheet.