Sedimentological study of the three geographically separated outcrops of bottom− sets of a single lava−fed delta (Pliocene) in the James Ross Island (Antarctica) allows recognition of six lithofacies. Deposits of traction currents, deposits of volcaniclastic debris flows and products of such flows transformations (both l ow− and high−density turbidity currents) and glacigenic deposits (subaqueous de bris flows and traction/turbidity currents) were all recognised. Existence of submarine proglacial environment formed prior to formation of volcaniclastic deposits partly covering the subaqueous slopes of volcano is supposed. The principal role of mass flow processes was recognised and explained by relative steep slopes of the lava−fed delta. The distribution of lithofacies significantly differs in the individual outcrops. These variations in sedimentary succession an d also in thickness of volcaniclastic deposits of “bottomsets” of the single lava fed delta suggest principal role of local conditions and paleogeography for development and preservation of this part of delta depositional system. Moreover proximal and distal setting can be followed and direct vs . more distant relation to over−riding lava−fed delta supposed. The sedimentary succession terminated by foresets of hyaloclastite breccia.
This study used ground penetrating radar soundings to examine a tongue-shaped rock glacier (64°04’S 58°25’W) on James Ross Island, Antarctic Peninsula, in January 2005. The rock glacier studied has multiple well-developed transverse ridges and approximately 800 m long from the talus of its head to its frontal slopes and is 300 m wide in the middle. The longitudinal ground penetrating radar profile identified debris bands which dip up-glacier, similar to the thrust structures in the compression zone of a valley glacier. Transverse ground penetrating radar profiles indicated a layered structure which is inclined towards the central part of the rock glacier and which resembles the transverse foliation of a valley glacier. Consequently, the internal structure of the rock glacier is revealed as being similar to the “nested spoons” common in the interior of valley glaciers. We concluded that this rock glacier has been created by the deformation of a glacier ice core and a thick and continuous debris mantle.
A glacier lake outburst flood occurred on James Ross Island, Antarctic Peninsula region, during the 2004-2005 austral summer season. The source lake was located on the Lachman II ice-cored rock glacier, and formed prior to 1980. The size of the lake has been increasing gradually since the 1990s. The lake basin extended to approximately 220 m in length and 160 m in width by the end of February 2005. We observed that the lake had drained by February 2005, and found a deep gully on the south side of the lake rim. It appears that the lake level rose and water overflowed the lake rim here. James Ross Island contains a large number of debris-covered glaciers, ice-cored moraines, and rock glaciers with glacier lakes which are dammed by these features or which form upon them. As climatic warming has recently been reported for this region, further glacier lake outburst floods seem likely to occur.
Large-scale stone-banked lobes and terraces are distributed over an area of 1 km2 of gentle slope on Rink Plateau in the northern part of James Ross Island, Antarctic Peninsula region. Topographically, there are two main features: relatively high risers up to 5 m high and distinct frontal ridges. In order to understand the processes responsible for these lobes and terraces, the authors have monitored air and ground temperatures and movement of stones on the surface over the period 1995-2005. In February 2005, the subsurface structures were surveyed by ground penetrating radar and drilling. The ground penetrating radar profiles identified the bedrock surface. The surface morphology of the lobes corresponds closely with that of the bedrock. The relatively high risers of these lobes are presumed to be due to a cessation of frontal advance.