Sedimentary Evolution of Rifted Continental Margins

Abstract

Geologic studies of present ocean basins and continental rift systems suggest a four-stage sedimentary model for evolution of rifted continental margins. Each stage produces a diagnostic sedimentary record, and examples of each can be seen today.( 1 ) Uplift, volcanism, rifting, and nonmarine sedimentation patterns characterize the rift valley stage. (2) In the Red Sea stage and later, restricted size and circulation of the proto-ocean create a reducing environment; chemical precipitates (halides, gypsum, and metallic sulfides) and saprophitic muds are deposited.(3) Gravity-induced processes dominate the sedimentary regime during the turbidite-fill stage, and flat-lying beds of coarse-grained, highly reflective sediments are formed. (4) Strong thermohaline contrasts in the mature ocean basin indicate geostrophic deep-water circulation. This deep-ocean current stage results in current-controlled sediment deposition and redistribution. 109 on July 29, 2015 memoirs.gsapubs.org Downloaded from 110

Thermal Contraction and Flexure of Mid-Continent and Atlantic Marginal Basins

“…It is useful to compare our results with the subsidence history of the Atlantic coast of the United States, as the geology there has been extensively studied. Although the general pattern of subsidence in Cretaceous and Tertiary times is compatible with the thermal contraction mechanism (Vogt & Ostenso 1967;Schneider 1969;Sleep 1971 ;Keen & Keen 1973), the sharp seaward termination of the marginal basin permits complications not relevant to closed basins, including seaward creep and thinning of the continental crust (Bott 1971) or the sedimentary prism (Cloos 1968) due to gravitational instability. Flexure due to sedimentary loads on the continental rise (Dietz 1963;Walcott 1972a) can be eliminated as the principal cause of subsidence on the east coast of the United States since the free air anomaly over the continental rise is too negative for an edge effect (Emery et a1 1970).…”

“…In the paper we mathematically model the hypothesis that gradual thermal contraction of the lithosphere causes the subsidence (Vogt & Ostenso 1967;Schneider 1969Schneider , 1972Sleep 1971Sleep , 1973; Keen & Keen 1973), explicitly including regional isostatic effects. * The qualitative reason for including this coupling of adjacent points can be seen as follows (McGinnis 1970;Walcott 1972a;Sleep 1971Sleep , 1973.…”

Triassic rift sedimentation and palaeogeography of central East Greenland

“…When viewed in the light of plate tectonics and rifting of a divergent continental margin the discussed Triassic basin ean be related to early Atlantic rifting and break-up of the 'Laurasian' megacontinent. Similar early rifting phases have variously been termed the rift valley stage (Schneider, 1972), the arching stage (Lowell et a1., 1975), the continental rift valley stage (Kinsman, 1975) and the intracontinental ':ift basin stage (Selley, 1976).…”

“…According to Schneider (1972) the diagnostic sedimentary record of this stage should be a mixture of normal terrigenous material, basic and alkaline volcanic rocks, granitic conglomerates, river and lake deposits, and non-marine evaporites. Apart from the faet that volcanic rocks are totally absent in the Triassic infill of the Central East Greenland Basin the rocks in question possess the above-mentioned characteristics.…”

Continental strike-slip rifts and their stratigraphic signature: application to the Bangong/Nujiang zone (Tibet) and the South Penninic zone (Alps)

“…Shoulder uplift provides a major clastic source for the rift basins whose stratigraphic record provides a sensitive tool for dating rift shoulder uplift (Favre and Stampfli 1992). The sedimentary record of regions undergoing such rifting is characteristically dominated by nonmarine deposits (Schneider 1972).…”