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Gulf of Mexico crustal structure and plate kinematics from gravity inversion

Author(s): Andy Alvey Badley Geoscience Ltd., North Beck House, North Beck Lane, Hundleby, Spilsby, Lincolnshire, PE23 5NB, UK, UK
N.J. Kusznir Badley Geoscience Ltd., North Beck House, North Beck Lane, Hundleby, Spilsby, Lincolnshire, PE23 5NB, UK/Earth & Ocean Sciences, University of Liverpool, Liverpool, L69 3BX, UK
A.M. Roberts Badley Geoscience Ltd., North Beck House, North Beck Lane, Hundleby, Spilsby, Lincolnshire, PE23 5NB, UK

An understanding of crustal thickness, ocean-continent-transition structure, the distribution of oceanic lithosphere and kinematic evolution 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.

Superposition of shaded-relief satellite free-air gravity anomaly onto maps of crustal-basement thickness and lithosphere thinning from gravity inversion show clearly the pattern and location of the extinct ocean-ridge and transform segments within the western and central GoM. These in turn reveal sea-floor spreading trajectory and provide important indications of pre-breakup rifted-margin conjugacy. By aligning small-circles with the transform faults visible in the free-air gravity data, the poles of rotation for the opening of the GoM can be refined. As a result of doing this we find that the opening of the GoM occurred in two stages. Initial rifting and breakup occurred along a N-S trajectory with the Yucatan block still linked to South America and to which the West Florida margin acted as a transform boundary. In the second stage, subsequent propagation of sea-floor-spreading between Yucatan and South America caused the Yucatan block to rotate anti-clockwise, resulting in sea-floor spreading within the GoM occurring about a pole locally-situated off the SW coast of Florida. In this second stage of GoM formation, the West Florida margin becomes an extensional feature. By refining the plate-reconstruction models in this way, we also gain a better insight into the linked development of the GoM in the context of the formation of the early Central Atlantic.

Crustal cross-sections using Moho depths from the 3D gravity inversion show the form of the ocean-continent transition, the distribution of crustal type (continental crust, oceanic crust, exhumed mantle) and help constrain models for petroleum-system development in the overlying stratigraphy. Building on this new understanding of kinematics in the GoM, 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 eastern GoM.


Title:
Gulf of Mexico crustal structure and plate kinematics from gravity inversion
Type:
Oral
Origin:
Mixed
Day:
2
Session:
2
Daily sequence no.:
13
Lead author last name:
Alvey
Lead author first name:
Andy
Affiliation(s):
Badley Geoscience Ltd., North Beck House, North Beck Lane, Hundleby, Spilsby, Lincolnshire, PE23 5NB, UK
Country:
UK
Abstract status:
ok
UID:
58