Geologic and Geophysical Observations in the Northern Labrador Sea

Abstract

Reports and discusses the results of a 3500 mi magnetic, bathymetric and seismic reflection reconnaissance survey concentrated in the area 61 - 64 N in Aug-Sept 1967 by the USCGC Mariposa in cooperation with the US Naval Oceanographic Office and the Univ of Wisconsin. The continental shelf off West Greenland is ~100 fathoms shallower than that off the east coast; the continental slope is precipitous and the continental rise poorly developed and irregular. The origin of the marginal trench at the base of the slope seaward of Godthaab is either tectonism, bottom current erosion or a combination. Depths of the Labrador continental shelf break range 250-300 f; its slope gradients are 1:20-1:40 and there is a well developed continental rise. A number of canyons are noted in the sea floor of the area, and Northwest Atlantic Mid-Ocean Canyon is the dominent feature as far as 60 N. Seismic data suggest a continuous buried ridge near the geographic axis of the basin, the Mid-Labrador Sea Ridge, traced to the Davis Strait sill. It is suggested that this ridge is a relic of Mid-Oceanic Ridge which, as it developed, separated the continental blocks of Greenland and Canada. The bottom conditions of the sea indicate major sculpting by bottom currents.