Tectonic signature on the ice cap surface pattern in Dome C area, East Antarctica

The bedrock morphology in Dome C area in East Antarctica is characterised by the presence of a series of elongated depressions separating ridges, with the Aurora and Concordia trenches representing the major depressions with a length of over 100km. In this area the ice cap reaches a thickness of up to 4000 m, leaving the possibility to have water formation and accumulation at its bottom. Vostok Lake is the largest, most famous among these subglacial depression. The geodynamic scenario responsible for the tectonic origin of these structural depression is not still clear: some Authors hypothesise the existence of an Early Paleozoic regional rifting, others propose a Paleozoic compressional tectonic setting. TheAurora and Concordia trenches can be associated to the Vostok Lake to the West, and together form a set of elongated, roughly N-S to NNW-SSE structural depressions, not perfectly parallel. Therefore, it is reasonable to frame their evolution within a NE-SW trending trans-extensional corridor characterised by left lateral, strike-slip shear, with the depressions associated to faults in horse tail geometry (Cianfarra et al., 2003). The relative young age of the Antarctic Ice Cap, about 38 Ma, compared with the old, Mesozoic age of the former, peneplanised landscape constrains the age of these sharp and fresh structures in Late Cenozoic time. The majority of the observed lakes and depressions are situated in relatively close proximity to ice divides where both the surface slope and ice velocity is small. The presence of this morphology induces variations in the surface texture of the ice cap either due to the movements of the ice sheet on the roughness of the bedrock morphology, and/or to the interaction with active tectonic processes. A series of preferential orientations may relate also to exogenous processes as regional winds. The resulting textural anisotropy of the ice surface can be easily detected from regional scale remotely sensed images. Radarsat mosaic of Antarctica proved a useful tool to investigate the active tectonic processes of the bedrock. Automatic lineament domain analysis performed on a pre-processed subset of the radarsat mosaic allowed to identify the morphological alignment of the surface ice cap whose origin is connected with Cenozoic tectonic processes acting in the bedrock. Images were processed by a series of dedicated algorithms (among which threshold slicing and edge continuity enhancement) to enhance linear textural variations. An original algorithm developed in SID software allowed to detect the main lineament domains of the surface ice cap in the investigated area. The statistical (gaussian) analysis eventually made possible to understand the nature of the linear texture changes as observed in the regional scale images by discriminating features directly produced by wind activity and the tectonic induced linear features. SID analysis showed that the main lineament domain detected on the ice sheet surface is compatible with the principal N-S to NNW-SSE morpho-tectonic bedrock directions in Dome C area (Aurora, Concordia and Vostok structural depression) and that morpho-tectonic directions control the ice-sheet dynamics in the investigated area.