The Geologic History of the Passive Margin Off New England and the Canadian Maritime Provinces

Abstract

Uchupi, E. and Austin, J.A., Jr. 1979. The geologic history of the passive margin off New England and the Canadian maritime provinces. In: C.E. Keen (Editor), Crustal Properties across Passive Margins. Tectonophysics, 59: 53–69. The geologic history of the passive continental margin off the east coast of North America from New England to Newfoundland is described using all available geological and geophysical information. “Rift” and “drift” phases of the margin's evolution are recognized, with rifting initiated in Late Triassic and completed by Early Jurassic. The plate decoupling process created a complex block-faulted terrain as a result of uplift and tensional fracturing. The approximate plane of continental separation is marked by a “hinge zone” characterized by a pronounced steepening of basement gradients. Since the Early Jurassic, the margin has undergone continual subsidence in response to cooling and sediment loading. This “drift” sequence attains its maximum thickness in the vicinity of the continental slope, and thins both landward and seaward. On the shelf, this unit consists of Mesozoic evaporites, carbonates, and deltaic deposits. Overlying these sediments is a prograding wedge of Cenozoic clastics. On the rise, the Mesozoic sediments are evaporites, hemipelagic limestones and shales, and carbonaceous clays. The Cenozoic is dominantly terrigenous material. Separating these two sedimentary provinces is the continental slope, a site of major facies changes and a Mesozoic reef complex.