Thermal Effects of the Formation of Atlantic Continental Margins by Continental Break up

Abstract

Summary The thermal history of Atlantic continental margins resembles that of the oceanic crust as it spreads away from a mid‐oceanic ridge, since the margin was formed when a ridge began spreading beneath a pre‐existing continent. During break‐up the thickness of the continental crust along the new margin was reduced by subareal erosion and subcrustal processes. Afterwards the continental shelf subsided, probably due to thermal contraction of the lithosphere. The observed subsidence rate on the Atlantic and Gulf coasts of the United States declined exponentially with a time constant of about 50 My, as it does for ridges. Except for the Florida peninsula, deviations of the observed sedimentation from a smooth curve with respect to time could be associated with eustatic changes and variations in the supply of sediments. The subsidence rate of basins in the mid‐continent of North America also decreases with a 50 My time constant. In Kansas a subcrustal process must have thinned the crust and initiated subsidence as a sequence of thinly bedded sediments beneath the basin is uneroded.

Evolution of Passive Rifted Margins—Perspective and Retrospective of DSDP Leg 48

“…The most widely accepted mechanism of post-rift subsidence is thermal contraction of the lithosphere initiated as the heat source migrates away from the margin at the onset of spreading (Sleep, 1971). The exponential decrease in subsidence with time has been considered to be similar to that deduced for the ocean crust.…”

Speculations on the formation of cratons and cratonic basins

“…At present there is no agreement on how such cratonic basins form. Basins formed by extension, either on continental margins, or, like the North Sea, in continental interiors, subside with the same thermal time constant as oceanic lithosphere (Sleep 1971). The thermal anomaly required is now generally accepted to be produced by extension (M c Kenzie 1978).…”

Impacts of Neogene-Recent compressional deformation and uplift on hydrocarbon prospectivity of the passive southern Australian margin

“…Wilson, 1966), these rifte d continental margins remain tectonically quiescent subsequent to their formation. They are predicted to experience no significant deformation, only exponentially decreasing subsidence as the crust and mantle cool down during the 'post-rift' stage of the their tectonic evolution (Sleep, 1971;McKenzie, 1978). However, it is being increasingly recognised that many passive margins do not show a simpl e pattern of uninterrupted post-rift subsidence following continental separation (Johnson et al, 2008).…”