From Bureau of Economic Geology, The
University of Texas at Austin (www.beg.utexas.edu).
Bureau Seminar, February 24, 2006
Modeling of allochthonous salt extrusion, roof dispersion, and intrusive import and export of salt in squeezed stocks
The physical modeling laboratories at the BEG have been extensively renovated, expanded, and re-equipped in the past 2 years. We illustrate these innovative technologies before showing spectacular animated results from one particular topic of salt tectonics we have modeled.
Regional shortening readily squeezes salt stocks and expels their salt as extrusive allochthonous sheets. Our modeling of squeezed stocks explores how they absorb compression by major expulsion of salt both upwards and—more surprisingly—downwards. Marker layers within the stock and the source layer track the flow of salt at all stages. Source-layer salt enters the stock as an inward plume that resists diapir pinch-off and feeds allochthonous salt outpouring at the surface. Sedimentary roofs break up into rafts that disperse radially owing to traction from underlying salt flow. As roof rafts approach the front of the flow, they ground, which impedes glacial spreading and creates a scalloped extrusion front. Outward plumes from the stock intrude downward into the source layer on the seaward side of the diapir. These plumes intrude in response to compressional loading of the stock and uplift of the overburden.