Meltwater features that suggest miocene ice‐sheet overriding of the transantarctic mountains in victoria land, antarctica

Abstract

. We illustrate here spectacular meltwater features associated with outburst floods beneath an ice sheet that overrode the Transantarctic Mountains in southern Victoria Land. Because of long‐term hyperarid polar climate, these features are part of an ancient landscape preserved for about 14 million years. Some channels are associated with areal scouring of basement rocks extending from sea level to as much as 1200–2100 m elevation in coastal regions. Scablands with scallops, potholes and plunge pools are cut in Beacon Super group sandstones and Ferrar Dolerite and cover wide areas of high western plateaus near the mountain crest. Subglacial channel systems commonly originate near divides and converge downhill toward the northeast. We argue that the landforms were created beneath a major Antarctic Ice Sheet that submerged the whole area, with the possible exception of the high peaks of the Royal Society Range, as it flowed northeastward toward the outer Antarctic continental shelf. Areal scouring, associated with warm‐based regimes, is restricted to the lower slopes close to the coast. In the higher terra in, meltwater channels and scabland alongside preserved patches of regolith are best explained by the breaching of cold‐based ice on the mountain rim by subglacial melt water outbursts. Melt from warm‐based ice, along with subglacial lakes trapped upstream of the mountain rim, are possible sources of the meltwater necessary to form the channel systems and scablands.

The evolution of the subglacial landscape of Antarctica

“…Moreover, Denton and Sugden (2005) describe such scoured landscapes extending from sea level to 2100 m in elevation at the front of the Transantarctic Mountains in the Ross Sea sector that are associated with areal scouring under more expansive ice conditions. 25…”

On the reconstruction of palaeo-ice sheets: Recent advances and future challenges

“…et al 2009). Knowledge of the geomorphological and sedimentological impact of such drainage events is still in its infancy but, for example, the 'Labyrinth', an anastomosing network of channels in the Dry Valleys (Antarctica), is thought to have formed by periodic subglacial lake drainage events (Denton and Sugden, 2005).…”

Landscape evolution of Antarctica

“…There is also growing evidence of radial outflow of basal meltwater (Evatt et al, 2006). Hundred-meter-deep rock channels and massive staircases of giant potholes represent large-scale outbursts of subglacial meltwater across the Transantarctic Mountains rim in the McMurdo area (Denton and Sugden, 2005;Lewis et al, 2006).…”

“…Areas formerly covered by an earlier expanded ice sheet display extensive landscapes of areal scouring. This includes oases in East Antarctica, such as the Amery Oasis bordering the Lambert Glacier (Hambrey et al, 2007); the Ross Sea area where the scouring is most prominent near sea level and can be traced to elevations of 1000-2100 m along the Transantarctic Mountains front (Denton and Sugden, 2005); the inner parts of the offshore shelf in many parts of West Antarctica; and the offshore shelves surrounding islands off the Antarctic Peninsula and sub-Antarctic islands (Anderson, 1999). In all these situations meltwater channels testify to the activity of basal meltwater.…”

“…The critical evidence is that warm-based tills in the high mountains bounding the Dry Valleys, and indeed the Sirius Group deposits, have been modified by overriding ice. Typically there are erosional patches excavated into a preexisting till with material dragged out down-ice and ripple corrugations with a spacing of 25-50 m that are a coherent part of the overriding meltwater system (Denton and Sugden, 2005). One important fix on the switch from warm-based to cold-based local glaciation has been reported from the Olympus Range in the McMurdo Sound area of the Transantarctic Mountains (Lewis et al, 2007).…”