618

Site number:

618

Authors:

IBC, GGC, MRB

Date recorded:

1991/11/22

Reason Sampled:

Permafrost and soil moisture examinations; investigation of differences at a patterned ground crack

Description:

Approximately 4.5km NW of Marble Point peninsula and W of the Marble Point Air Facility; about 100m from the Wilson Piedmont Glacier; on a surface near a small thawing snow patch; 50cm from a shallow patterned ground crack; a gently sloping surface, half way between a knoll crest and a pond at the foot of the slope; the site is between site 616 and 517

Altitude:

70 m

Aspect:

N

Slope:

2 °

Climate

Soil climate zone:

Coastal Antarctic

Estimated mean annual temperature:

-18 °C

Frozen ground depth:

45 cm

Frozen type:

Hard ice-cemented

Frozen comment:

45cm

Geology

Geological setting:

The surface is a gently undulating till plain formed by retreat of the Wilson Piedmont Glacier; the Marble Point region is an old landscape, with deposits of phillipsite, buried soils and oxidised gneiss, which have been covered by advances of the grounded Ross Ice Shelf; later ice retreat and glaciological features have been controlled by changes in the stranded Wilson Piedmont Glacier; the till mantle is patchy and dominated largely by locally occurring rocks; granodiorite, granite, marble, gneiss, and dolerite

Patterned ground:

Weakly developed 20m nets; 5cm troughs with active open cracks

Surface weathering or surface features:

Most boulders angular and unstained; a few with distinct oxide staining; a moderately developed pebble and cobble pavement; calcium carbonate coatings beneath many surface clasts; some surface salt efflorescences adjacent to thawing snow patches

Soil

Soil parent material:

Bouldery sandy gravel till

Previous disturbance:

Extensive mechanical and human activity in the region since the mid-1950's

Soil weathering stage:

6 1 (Campbell & Claridge 1975)

Soil moisture status:

Dry site with no snow thaw k

Biological activity:

Nil at site; moss patches and cyanobacteria are common locally