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The structure of many interior basins is dominated by lithospheric flexure. A wide range of observations has confirmed that the outer shell of the earth, which has a temperature of less than about 600°C, behaves elastically on geologic time scales. This behavior is consistent with theoretical and laboratory studies of rock rheology. The linear structure of the Appalachian basin and the near circular structure of the Michigan basin can be attributed to lithospheric flexure under loading. In general, the structure of sedimentary basins with horizontal scales of a few hundred kilometers can be attributed to lithospheric flexure. The time evolution of many sedimentary basins appears to be governed by the thermal time constant of the lithosphere (i.e., about 100 m.y.). A imple model for the subsidence of sedimentary basins assumes that the lithosphere is initially hot; as the lithosphere cools its density increases and it subsides. This simple model explains the subsidence record of parts of the Los Angeles basin. This mechanism does not appear to be sufficient, in itself, to explain the subsidence of interior basins such as the Michigan basin. An additional mechanism such as a thermally activated phase change is required.
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