Lithospheric density variations and Moho structure of the Irish Atlantic continental margin from constrained 3-D gravity inversion

Welford, J. Kim and Shannon, Patrick M. and O'Reilly, Brian M. and Hall, Jeremy (2010) Lithospheric density variations and Moho structure of the Irish Atlantic continental margin from constrained 3-D gravity inversion. Geophysical Journal International, 183 (1). pp. 79-95. ISSN 0956-540X

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Abstract

A 3-D density anomaly model of the Irish Atlantic continental margin was generated from a regional inversion of the free air gravity data constrained by bathymetric and sediment thickness information. The model results are compared against a recent regional Moho structure compilation from velocity models from crustal-scale wide-angle reflection/refraction surveys. Using the inverted model, a regional map of Moho structure across the margin agrees well with the regional seismic compilation and also provides information in areas lacking deep seismic coverage. The density anomaly structure of the crust across the margin is investigated along model slices and using volume rendering of crustal layers. These views reveal extreme thinning,of the upper crust and a dominance of lower crustal densities in regions where exhumation of,serpentinized mantle has previously been interpreted. Using the regional view afforded by, the,inversion, the areal extent of these zones is tracked into regions lacking seismic constraints. Using the regional density anomaly model, variations in sediment thickness and crustal thickness are investigated to compute stretching factors across the margin and to identify zones,which deviate from local isostatic compensation. These zones generally correlate with faults,and rifting trends providing insights that could be useful for future palaeoreconstructions of North Atlantic rifting.

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