Modifying the McKenzie Stretching Theory for Sedimentary Basins to Account for the Depth Dependence of Sediment Density

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The Ohio State University

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The McKenzie stretching theory is a simple model for the evolution of sedimentary basins such as basins underlying most continental shelves. McKenzie’s model explains basin subsidence as the isostatic response to and subsequent cooling of the lithosphere. In addition to the stretching factor, and the initial thickness of the continental crust, the history of subsidence also depends on the average density of the basin fill (e.g., water or sediment). McKenzie’s model requires prior specification of fill density, but it really depends only on the vertical average density of fill. In reality, sediment density varies with depth as it compacts in response to burial. To simulate a varying density, a simple mathematical model for density based on changes in porosity is proposed to be inserted into the McKenzie model. Only after the testing to be sure that the new model matches McKenzie’s original findings can the preliminary investigation into the case study commence so as to compare the newly created model with trusted observations. The model we adopt to characterize the density of sedimentary fill is simplistic: we assume fill density is purely a function of depth. But it is a more general formula than McKenzie’s, and provides an approximate basis for accommodating spatial (and temporal) variation in sediment density.



McKenzie, Stretching, Density, Sedimentary, Basins