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CSPG Special Publications

Abstract


Geology of the North Atlantic Borderlands — Memoir 7, 1981
Pages 333-398
American Borderlands

Labrador Sea, Davis Strait, Baffin Bay: Geology and Geophysics — A Review

S. P. Srivastava, R. K. H. Falconer, B. MacLean

Abstract

The structural developments of the Labrador Sea, Davis Strait and Baffin Bay as obtained from the combined analysis of geological and geophysical measurements are reviewed. Compilation of magnetic and gravity data show that well developed magnetic lineations and a prominent gravity low, coincident with the rift valley of the extinct Labrador Sea Ridge, are present in the southern and central Labrador Sea. In the northern Labrador Sea the magnetic anomalies are subdued in amplitude and the coincidence of the gravity low with the rift valley is obscured by complexities in the basement topography. These have been interpreted as arising from the obliqueness of spreading in this region. In Baffin Bay a similar but smaller amplitude gravity low is also found to be coincident with a rift valley feature and has been interpreted as the northward continuation of the extinct Labrador Sea Ridge. Sufficient reflection seismic data are not available throughout Baffin Bay to delineate such a feature there. The gravity low in Baffin Bay lies at a small angle to magnetic lineations in the central region of the Bay, indicating presence of one or several small fracture zones. Compilation of gravity, magnetic and seismic reflection data in Davis Strait show presence of a prominent basement high oriented northeast-southwest. The high is flanked by thick sediments on landward sides.

These and other geological observations compiled from the deep exploratory wells drilled on the Labrador and Greenland shelves are interpreted as being in accord with the sea-floor spreading hypothesis for the Labrador Sea and Baffin Bay regions. Problems associated with the hypothesis that these regions were formed by the foundering and subsidence of continental crust are discussed and it is shown such a hypothesis is not consistent with the overall development of the North Atlantic as a whole and implies large scale internal deformation of the Greenland and North American plates. The subsidence history of the Labrador shelf obtained from the exploratory wells, correlates well with different episodes of spreading in the Labrador Sea. Micropaleontological studies of the Labrador Shelf wells show that the late Cretaceous-Eocene widespread marine transgression coincided with the opening phase of the Labrador Sea. Deepest conditions existed in the Eocene and a broad shelf marine regression occurred in the Oligocene with the cessation of spreading in the Labrador Sea-Baffin Bay region.

Occurrence of older (Berriasian-Hauterivian) basalt on the Labrador Shelf and younger (Turonian) basalt farther to the north on the Greenland Shelf agrees with a progressive opening from south to north. A later change in the mode of spreading in the Labrador Sea-Baffin Bay regions agrees with the widespread occurrence of Paleocene volcanics inland and offshore in Davis Strait.


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