Pearse Valley

In contrast to Beacon and Arena valleys, the elevation Pearse Valley is much lower and ranges between 400 and 500 m MSL. Our camp was on an alluvial terrace located at the eastern edge of Lake House (325m; S77°42.101′ E161°26.924′) and was selected for its proximity to a source of water. Wind direction and strength seems highly variable throughout the valley and diurnal variations were common. During the field visit, winds did not exceed 20 knts and seemed strongest from 2 – 5 am. In general wind strength and duration were in-between those of Beacon and Arena valleys.

Pearse Valley contains mostly glacial deposits representing the retreat of the main Taylor Glacier and subsequent retreat of the lateral valley glaciers. As a result, the chemical development of the soils should reflect this Holocene deposition and contrast to the older soils in Beacon and Arena valleys. Polygonal ground covers 40 – 50% of the valley floor and slopes, however, this was difficult to estimate due to the lack of snow in polygon troughs.

About 10% of the valley floor is covered by sand from eolian deposition and this does not include numerous pockets of sand lodged in troughs of polygons and in other sheltered areas. Much of this sand is protected by a lag of 5 – 8 mm grannules and therefore is not mobile under winds of about 50 knts. Much of the sand probably came from stream page 6 systems draining meltwater from the retreating glaciers. The main sand dune, climbing the northeast slope of the valley apparently has brine flowing on top of ice cemented sand which accumulates in salt pond (dry on the surface) at the base of the dunes. Ice cemented samples from the dune and brine from approximately 50 cm deep in the salt pond were taken for chemical analysis.

Depth to ice cement and clear ice under moraines varies in the valley from 0.25 m to >1m and was encountered in every pit except PV-LAK1, the sediments of which may represent and old lake deposit. It is not clear what factors control the depth to ice cement but aspect and moisture regime do not seem to have a direct relationship. In addition, the degree of polygonal ground development does not appear to be related to the depth of the ice cement. For example, two pits were dug in the vicinity of PV-7, one in well developed polygonal ground and the other in poorly developed polygonal ground and ice cement was found at 25 cm in both pits.

Perhaps our most interesting find in Pearse Valley is the presence of clear ice in pits PV-1, 2, 3 & 6. This ice possibly represents and ice cored moraine which may have derived from the Schlatter Glacier. The surface of this ice is smooth and it is not clear how the contact between it and loose sand above can be so sharp. Why there is not ice cemented sand above, suggests the clear ice is ablating under the sand. Although the clear ice seems to have a limited extent, it may have a greater extent if it lies below ice cemented soil in other parts of the valley.