Landform and Soil Development in the McMurdo Dry Valleys, Antarctica: A Regional Synthesis
J. G. Bockheim
The McMurdo Valleys Mapping Project (VALMAP) contains soils data collected from 473 sites in the McMurdo Dry Valleys (77°07.5-78°00′S; 160°-164°E), Antarctica. The database includes surface boulder lithology, frequency, and weathering features; observations of patterned ground, permafrost, and ground-ice forms; detailed soil profile descriptions; laboratory characterization; and classification of the soils. Each site was located on 1:50,000 topographic maps from aerial photographs and elevation measurements, digitized, and entered into an ArcInfo Geographic Information System. The sites are arrayed along an ecoclimatic gradient that includes 21 coastal sites (4.4% of total), 109 inland valley floor sites (23%), 196 inland valley side sites (41%), 136 upland valley sites (29%), and 11 plateau fringe sites (2.3% of total). Whereas ice-cemented permafrost was predominant at coastal sites and along the polar plateau, 42% of the sites had dry permafrost in the upper 1 m. Massive ice occurs to a limited extent as ice-wedge polygons, ice-cored drift, and rock glaciers. Sand-wedge casts in upland valleys attest to a recession of the ice-cemented permafrost to greater depths over time. The most strongly developed soils and weathering features are on valley floors and in upland valleys where older deposits and landforms occur. The distribution of anions in soil:water extracts is reflective of air mass movement, with most soils reflecting a coastal source. Seventy percent of the soils examined in the McMurdo Dry Valleys are classified as Anhyorthels reflecting the lack of cryoturbation in the cold desert Antarctic environment.