Geomorphic, geophysical and quaternary studies of ice and soil wedge features in the Foucault River valley, Northern Quebec.

摘要

In the Foucault River valley on the south coast of the Hudson Strait, geomorphic, stratigraphic and periglacial evidence was collected to determine the post-glacial evolution of the valley, including the determination of periods of the Holocene favorable for the establishment and growth of ice wedge polygonal networks.; Evidence of glaciation was collected in the form of indicators of direction of ice flow (north to northwestward flow) and the location of glacigenic deposits. With the disintegration of the inlandsis, a marine transgression followed, with a maximum recorded sea level of 147 m at the valley mouth. Radiocarbon dates from fossilized marine shells attest to the occupation by the sea from 7600 to 4800 BP.; Coincident with a slowly dropping sea level was the formation of various terrace levels along the river. These terraces have sedimentary sequences which evolve down towards the mouth of the river, exhibiting characteristics ranging from parts of a delta, through shallow water cross-bedding features.; As the terraces emerged from the river, climatic conditions allowed the establishment of permafrost. Vegetation was slow to colonize these terraces, and aeolian conditions dominated for long periods of time. In keeping with the periglacial climate, ice wedge networks began to grow starting from frost fissures on the newly emergent surfaces. These networks have persisted through at least 5 subsequent climatic periods (two warm and 3 cold phases). These periods are recorded in the sedimentary deposits surrounding the various ice wedges. The current climatic phase is a cold phase of growth, seen by the multiple stages topping many of the ice wedges studied herein.; A recording station tracked various climatic parameters over three years, and these data allowed calculation of the average annual air temperature ({dollar}rm-9.5spcirc C),{dollar} as well as the establishment of the thermal conditions that lead to frost cracking and ice wedge growth.; Use of a Ground Probing Radar helped to locate and determine the size of various ice wedges within the substrate under different hydrological and sedimentological conditions. Analysis of the resultant data proved the usefulness of this geophysical tool for locating buried ground ice bodies.