Desert varnish in southern Victoria Land, Antarctica

Abstract

Desert varnish occurs principally as a thin reddish brown (lOR 4/6) coating on the surface of dolerite in elevated regions of southern Victoria Land, Antarctica. It is best developed on northfacing sides of dolerite in areas which have a prevailing southerly wind. Much thinner and less well developed examples of desert varnish were also observed on Beacon Supergroup sandstones and basement granites. The varnish occurs predominantly at high altitude and its distribution appears to be controlled primarily by lithology and secondarily by altitude, prevailing wind direction, and orientation with respect to the sun. The varnish is formed by chemical weathering of the rock as a result of wind-induced, forced advection of moisture from the upper surfaces of the rocks in this arid, windswept, desert environment. Present evidence suggests that the varnish is formed by leaching of elements from the inner regions of the substrate rock, rather than from an external source.

Keywords:

• desert varnish
• Antarctica