The Raised Features of Billefjord and Sassenfjord West Spitsbergen

Abstract

platforms, raised cliffs and shingle beaches, in places up to 300 feet above sealevel, being present except where scree cones have on steeper slopes occasionally obliterated the features. The absence of any detailed work on the area and the ease with which past shorelines may in places be traced, suggested that an intensive study with mapping and levelling might throw light both on the formation of shingle ridges in a region slowly emerging from a glacial period and also upon the recovery of the district. Plane-table mapping was carried out on a scale of 4 inches to 1 mile and numerous lines of tacheometric levels were run. In the following pages it is hoped to give a general account of the existing features, suggestions as to their mode of origin, and finally a brief discussion of the relative changes of level which have taken place as indicated by the levelling. The region is largely dominated by a series of rectangular mountain masses with steep escarpments, the remains of a dissected plateau some 3000 feet in height. The escarpments, although modified by corrie erosion, have in many cases a buttressed appearance which bears striking resemblance to forms associated with the cycle of arid erosion. In the north the topography is largely obscured by the New Friesland ice-cap, but over most of Dickson Land and Bunsow Land permanent snow is not extensive and apart from the glaciers which come from the ice-cap the main glaciation consists of snow patches and corrie glaciers. The glaciers all show evidence of retreat and wide U-shaped valleys are common. The rocks of the region are mainly of Permo-Carboniferous age, and over most of the area the limestone and gypsum beds dip gently to the south at 2-5 degrees. Underlying them is a pre-Devonian metamorphic complex. Between the mountain masses lie wide valleys, in many cases arms of the sea, with a general rectangular pattern. A. M. Peach suggested * that these valleys were the product of pre-glacial river erosion and that they were drowned by a pre-glacial inundation. On the coastal lowlands however occasional outcrops afford clear evidence of considerable downthrow and show that the physiography has to some extent been determined by block faulting. This suggests that in any study involving isostatic recovery the approach should in the first instance be local rather than regional, and offers a more logical explanation of the wide and rectangular patterned valleys with their steep flanking escarp? ments. The Campbell range is thus interpreted as a miniature block mountain with fault scarps. On the east side of Billefjord, Carboniferous limestone and gypsum beds