Blackwell Publishing Journal Backfiles 1879-2005
Intracratonic sag sedimentary basins occur in the middle of stable continental or cratonic blocks. They are rarely fault bounded, although strike-slip faulting can occur within them. A simple model for the development and evolution of these basins is proposed. The mechanism is driven by mildly-coupled convective down-welling of the asthensophere beneath the lithosphere. Initially, a rapid alteration of the mantle convective system causes a descending plume to develop. A depression, which can be of the order of 600 m, can be formed at the earth's surface; this depression, when loaded with sediment, will form a sedimentary basin of the order of 2.5 km thick. If the convective downwelling remains, a period of thermal cooling of the lithosphere occurs, which is similar to the thermal cooling subsidence phase of passive continental margins. This thermal cooling occurs because of the thermal anomaly (temperature decrease) beneath the lithosphere caused by the convective downwelling. If a change of convective pattern occurs and the descending plume is removed, the basin will undergo uplift and erosion, whereby a significant thickness of the sedimentary basin can be removed. The Ordovician and Silurian tectonic development of the Canning Basin, Western Australia, appears to be well explained by this model.
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