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Crustal structure and heat-flow history in the UK Rockall Basin, derived from backstripping and gravity-inversion analysis

Alan M. Roberts, Andrew D. Alvey and Nick J. Kusznir
Crustal structure and heat-flow history in the UK Rockall Basin, derived from backstripping and gravity-inversion analysis
Petroleum Geoscience (May 2018) 25 (2): 131-150

Abstract

Seismic data made available by the UK OGA (Oil & Gas Authority) has been used to constrain a model of crustal structure and heat-flow history for the UK Rockall Basin. Top-basement/base-sediment has been interpreted around the full extent of the seismic dataset. This has produced a model for the thickness of the sediment fill within the basin which is thicker than previous published estimates. The new sediment-thickness model has been incorporated into a 3D-backstripping study, producing maps of subsidence and thinning-factor. Analysis of backstripped subsidence shows thinning-factor reaching peak values of approximately 0.8-0.85 (beta -factor >5) in the south-central axial area, reducing in magnitude northwards to approximately 0.7. The new sediment-thickness model has also been incorporated into a 3D-gravity-inversion study, mapping Moho depth, crustal-thickness and thinning/stretching-factor. The results show crustal-basement thickness reduced to approximately 6 km, thinning-factor approximately 0.8, in the south-central area, while it spans the range approximately 6-10 km further north. The results are compatible with previous seismic refraction work in both the UK and Irish sectors of the Rockall Basin. We believe that the extension which created the basin was non-magmatic and that the axial region is underlain by highly-thinned continental crust The results from the gravity inversion have been used to make predictions about top-basement heat-flow history. Heat-flow in the basin centre is predicted to have been initially high, reducing with time, associated with cooling of the transient syn-rift heat-flow anomaly. On the basin flanks heat-flow was less variable over time, its magnitude controlled primarily by constant radiogenic heat input from the basement, rather than by the transient geotherm anomaly. There remain considerable uncertainties associated with our interpretation and analysis. These uncertainties have been addressed with sensitivity analyses. A regional gravity-inversion model, using the new sediment-thickness data spliced into regional public-domain information, shows that structural and stretching continuity can mapped at the crustal scale along the full length of the UK/Irish Rockall Basin, contrary to conclusions from some previous studies.


ISSN: 1354-0793
Serial Title: Petroleum Geoscience
Serial Volume: 25
Serial Issue: 2
Title: Crustal structure and heat-flow history in the UK Rockall Basin, derived from backstripping and gravity-inversion analysis
Affiliation: Badley Geoscience, Spilsby, United Kingdom
Pages: 131-150
Published: 20180515
Text Language: English
Publisher: Geological Society Publishing House for EAGE (European Association of Geoscientists & Engineers), London, United Kingdom
References: 69
Accession Number: 2018-062730
Categories: Solid-earth geophysicsApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., geol. sketch maps
N56°00'00" - N60°00'00", W12°00'00" - W03°00'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201834
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