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In recent years, considerable progress has been achieved in modeling the subsidence and temperature histories of sedimentary basins. A knowledge of the mechanisms of basin formation may make it possible to compute the variation of heat flow with time, and consequently the temperature distribution in the sediments with time, if the basin geometry and sediment material properties are known. Further studies are necessary to understand how thermal conductivity, radiogenic heat production, and ground-water flow influence the subsurface temperature distribution in different types of basins.
Model-derived temperatures can be used to make theoretical predictions of organic maturity using chemical reaction kinetic theory. In addition to vitrinite reflectance, a promising technique involves looking at aromatization-isomerization (A-I) reactions associated with biologic marker compounds that commonly occur in most organic-rich sediments. These are unimolecular, first-order reactions that precede the main phase of oil generation and therefore can be used to locate the top of the "oil window." The Labrador continental margin off northeastern Canada is a typical rifted margin, believed to have formed by stretching of the crust and subcrustal lithosphere during rifting, followed by thermal contraction subsidence. A 1-dimensional, finite element model that considers nonuniform ext nsion and allows for variations in sediment thermal properties was used to compute the thermal history of sediments in this region. It is assumed that thermal conduction is the primary mode of heat transfer in this style of basin and that advection of heat by fluid motion is negligible. Model results can be compared with direct maturity measurements (A-I products, vitrinite reflectance), crustal thickness estimates from seismic refraction experiments, and corrected bottom-hole temperatures or heat-flow measurements.
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