Geological and geotechnical conditions of the Beaufort Sea coastal zone, Arctic Canada

Abstract

The coastal zone of the southern Beaufort Sea and Mackenzie Delta forms an extensive area of coastal lowlands in northern Canada. This region is underlain by unstable, perennially frozen soils subjected to high rates of marine erosion and deposition. The nearshore sediments off northern Richards Island are comprised of a wedge of Holocene marine sand, silt and clay underlain by early Wisconsinan sand and clay. The geothermal regime is complex, reflecting deep permafrost conditions established during a period of terrestrial exposure and more recent marine submergence, which results in moderating ground temperatures and creation of a thick thawed layer at the sea bottom. Geotechnical problems encountered in the nearshore area include frost heave of Holocene sediments, thaw settlement related to degradation of ground ice in the early Wisconsinan sediments, and ice push and scour effects Onshore sediments consist of early Wisconsinan and older glacial, fluvial and marine sediments overlain by late Wisconsinan and Holocene, eolian and lacustrine sediments. Ground ice, which forms a significant volumetric component of the near-surface soils, occurs as pore ice, wedge ice, pingo ice and as massive bodies of segregated ice of various ages. Geotechnical problems in onshore areas include thaw settlement due to degradation of ground ice, creep of ice-rich soils and frost heave.