Seismic and borehole-based mapping of the late Carboniferous succession in the Canonbie Coalfield, SW Scotland: evidence for a ‘broken’ Variscan foreland?

Howell, Louis; Besly, Bernard; Sooriyathasan, Surika; Egan, Stuart; Leslie, Graham. 2021 Seismic and borehole-based mapping of the late Carboniferous succession in the Canonbie Coalfield, SW Scotland: evidence for a ‘broken’ Variscan foreland? Scottish Journal of Geology, 57 (1), sjg2020. 10.1144/sjg2020-007

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Official URL: http://dx.doi.org/10.1144/sjg2020-007

Abstract/Summary

Local seismic and borehole-based mapping of the Carboniferous Pennine Coal Measures and Warwickshire Group successions in the Canonbie Coalfield (SW Scotland) provides evidence of repeated episodes of positive inversion, syn-depositional folding and unconformities. A Duckmantian (Westphalian B) episode of NE–SW transpression is recognized, based on onlapping seismic reflector geometries against NE-trending positive inversion structures and contemporaneous NNE-trending syn-depositional growth folding. The basin history thus revealed at Canonbie is at variance with generally accepted models in neighbouring northern England that imply subsidence was due to post-rift thermal subsidence during late Carboniferous times. A late Westphalian–Stephanian unconformity recognized within the Warwickshire Group succession signifies NW–SE, c. 10% local basin shortening during a time of major shortening in the late Carboniferous Variscan foreland, contradicting suggestions that maximum Variscan shortening had negligible impact on Carboniferous basins in northern Britain. Local inversion structures appear to have strongly influenced local late Westphalian–Stephanian depocentres. In this respect, the Variscan foreland at Canonbie may have resembled a ‘broken’ foreland system. Variations in crustal rheology, fault strength and orientation, and mid-crustal detachments are suggested to have played important roles in determining strain localization and the nature of Westphalian–Stephanian depocentres in the Canonbie Coalfield.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1144/sjg2020-007
ISSN:	0036-9276
Date made live:	22 Dec 2020 13:46 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/529253

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1144/sjg2020-007

ISSN:

0036-9276

Date made live:

22 Dec 2020 13:46 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/529253