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Using Deep-Seismic Data to Model Crustal Structure, Geodynamic Evolution and Thermal History in the Eastern Gulf of Mexico


We have used the SuperCache seismic survey, acquired by Dynamic Data Services, to investigate the crustal structure and geodynamic evolution of the Gulf of Mexico (GoM). Here we focus on a comprehensive analysis of one line from the eastern (Florida) area of the GoM (Line 3200), which illustrates very clearly the transition from inboard rift-basin to outboard continental margin. The analysis is based on a workflow previously deployed at rifted margins worldwide (Roberts et al 2013, Petroleum Geoscience). In this study the workflow comprises: 3D gravity inversion (with Line 3200 embedded), predicting depth to Moho, crustal thickness, thinning/beta-factor, OCT structure and COB location. The results are used to build crustal-scale cross-sections constrained by the gravity inversion. 2D flexural backstripping, modelling subsidence history and palaeobathymetric evolution, together with prediction of thinning/beta-factor and OCT location. 2D/3D heat-flow prediction, top-basement heat-flow history, breakup to present, has been derived from maps and profiles of thinning-factor produced by gravity inversion and backstripping. A critical component is the prediction of residual continental radiogenic heat-productivity. Analysis of fault kinematics, we have assessed whether the amount of interpreted extension on Line 3200 can explain the subsidence history and predictions of crustal thinning and have then assessed the implications for stretching mechanisms during breakup. Whole-lithosphere thermal modelling, heat-flow and horizon-temperature history have been investigated close to an inboard and an outboard well location. The critical tectonic input to the thermal models has been constrained by the prior geodynamic analysis The results of this combined analysis suggest that the inboard area of the eastern GoM, the shallow-water Florida Platform, has extended in the Jurassic and then evolved to the present with the characteristics of a “simple” rift basin, showing only moderate extension and crustal thinning. By contrast, the outboard deep-water area shows that the margin-breakup process, following the initial rift, was associated with high extension and possible depth-dependent-thinning. The rapid subsidence of the deep-water area during breakup created the space required for the development of the Jurassic salt basin but was also responsible for its rapid drowning.