Abstrpct: Subsidence analysis of wells in the central North Sea and Labrador-Grand Banks and off the West Greenland, Scotian shelf and United States Atlantic margin shows distinct quantitative stratigraphic correlation patterns of circum North Atlantic sites. A significant departure from the overall decrease in subsidence for the Pliocene occurs in many wells, when the rate is found to have increased one or more orders of magnitude from Oligocence/Miocene rates. Wells were selected along transects from shore to basin to find if relative basin position is influenced by differential basin subsidence. Although stratigraphic resolution is not detailed, more basinward sites experienced up to four times larger subsidence rates in the late Neogene than in the Oligocene/Miocene, with a peak in the Pliocene. Wells at the basin edge experienced much less subsidence or showed uplift. The observations are consistent with a rapid change of intraplate stress at the cause for this observed transition in Neogene subsidence. Major reorganizations of spreading direction and rate occurred during the Pliocene along the entire Atlantic spreading system, possibly in conjunction with more global changes in plate motions. We propose that the associated changes in intraplate stress caused the excess margin subsidence. Relative uplift along basin edges is consistent with this mechanism of relative movement and may explain apparent eustatic changes in sea level.

Seismic profiler surveys have defined the landward limit of presumed Mesozoic–Cenozoic deposits on the continental shelf off Labrador and eastern Newfoundland. Along the Labrador coast the contact of these deposits with Precambrian rocks coincides with a pronounced 'marginal channel'; off eastern Newfoundland their contact with rocks of the Appalachian System is marked by a landward-facing escarpment. The physiographic relief characterizing this contact zone reflects erosional exploitation of the associated contrast in erosional susceptibility. The chief erosional agent is considered to have been the Quaternary glaciers. The marginal channel off northern Labrador is indicated as a zone of major faulting, which probably further enhanced the erosional vulnerability. The transverse depressions cutting the outer shelf off Labrador and Newfoundland are likewise considered to be zones of structural dislocation, which have been physiographically emphasized through processes of erosion.Integration of the seismic profiler results with other geophysical and geological data from the study region consistently supports the concept that the morphology of the continental margin expresses fundamental elements of geologic structure. Available evidence can apparently be reasonably synthesized in terms of a structural model based upon differential vertical movements of segments of continental crust. By this approach the structure of the continental margin north of the Grenville Front off Labrador may be very different from that of the continental margin bordering the western Atlantic Ocean to the south. In addition, the continental fragments represented by Orphan Knoll and Flemish Cap are indicated as having experienced only vertical displacements during postulated episodes of late and post-Cretaceous sea-floor spreading.

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The seismic stratigraphy of the eastern Grand Banks continental margin is examined, and a five-fold division of the sedimentary sequence overlying basement is proposed. Oceanic basement of Cretaceous age underlies the eastern part of the study area; to the west, continental basement ranging in age from Late Precambrian to ?Jurassic underlies the Grand Banks. The sediment units, ranging in age from Early Cretaceous to Recent, have been dated by extrapolation of both commercial and DSDP drilling results from the Grand Banks and from the formerly conjugate Iberian margin. Identification of oceanic magnetic anomalies in the Newfoundland Basin agrees with the proposed age of the two oldest, Early Cretaceous units.

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