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Regional Crustal Structure of the Gulf of Mexico From Gravity Inversion

Abstract

An understanding of crustal thickness, ocean-continent-transition structure, continent-ocean-boundary location and crustal type (continental, oceanic or exhumed mantle) is a critical component of petroleum systems evaluation in the Gulf of Mexico (GoM) and elsewhere. Using public-domain data and OCTek 3D gravity inversion, we have produced regional grids and maps of Moho depth, crustal-basement thickness, continental-lithosphere thinning-factor and residual continental-crustal-thickness for the GoM. Crustal-basement thickness and lithosphere thinning from the 3D gravity inversion show the distribution of oceanic crust within the GoM and constrain continent-ocean-boundary location. Crustal cross-sections using Moho depths from the 3D gravity inversion show the form of the ocean-continent transition. Superposition of shaded-relief satellite free-air gravity onto maps of crustal-basement thickness and lithosphere thinning from gravity inversion show clearly the pattern and location of ocean-ridge and transform segments within the western and central GoM. These in turn reveal sea-floor spreading trajectory along with pre-breakup rifted-margin conjugacy. Maps of crustal thickness with superimposed shaded-relief free-air gravity may be used to test and refine plate-reconstruction models for the development of the GoM and its relationship to the formation of the early Central Atlantic. 2D and 3D flexural-backstripping and subsidence modelling, driven by lithosphere thinning/beta-factors from gravity inversion, have been used to predict the evolution of palaeobathymetry through the post-breakup history of the GoM. We also use lithosphere thinning determined from gravity inversion, together with crustal type, to predict the residual continental radiogenic heat-flow contribution and the post-rift transient heat-flow component, which together permit predictions of heat-flow history. Outputs from 3D gravity inversion for the GoM include grids of lithosphere thinning, β-factor and heat-flow history for input to petroleum systems modelling.