We will shortly be considering the role of thermal subsidence in the creation of rifted margin (miogeoclinal) sedimentary packages. In thermal subsidence models, (1) the sedimentary piles and underlying crust are considered to be in isostatic equilibrium and (2) compaction of sediments is considered to be (relatively) instantaneous. Thermal subsidence models predict accumulation of sediment on the order of 100m/My (0.1 mm/yr). Are these two assumptions warranted, or should models more properly include the interaction of compaction and isostatic adjustment along with the thermal subsidence? Justify with an observational argument (i.e., do not seek out theoretical or even empirical relationships, but find observations that are relevant and interpret those).
Hint 1: Are other processes instantaneous when their rates are significantly faster or significantly slower than the rates for thermal subsidence?
Hint 2: Observational constraints will come from places where rates of compaction can be directly observed and where rates of isostatic adjustment can be directly observed.
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C. H. Jones | CIRES | Dept. of Geological Sciences | Univ. of Colorado at Boulder
Last modified at Tuesday, September 14, 1999 2:18 PM