Howell, L, Egan, SS, Leslie, G and Clarke, S (2019) Structural and geodynamic modelling of the influence of granite bodies during lithospheric extension: application to the Carboniferous basins of northern England. Tectonophysics, 755. pp. 47-63.

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Abstract

Intra-basinal highs within classic ‘block and basin’ style tectonic frameworks are underpinned by large granite bodies. This is widely believed to relate to the relative ‘rigidity’ and ‘buoyancy’ of granite in relation to accommodating basement. It has been suggested that during periods of tectonic extension, normal faulting around the peripheral regions of granite batholiths permits granite-cored blocks to isostatically resist subsidence, thus forming stable areas during periods of widespread faulting-induced subsidence. However, one-dimensional modelling indicates that relatively less dense crust is incapable of resisting subsidence in this way. Instead, when local isostasy is assumed, the occurrence of granite-cored, intra-basinal highs relates to initial isostatic compensation following granite emplacement. Differential sediment loading during extensional tectonism exaggerates this profile. An integrated two-dimensional lithospheric numerical modelling approach highlights the role of flexural rigidity in limiting the amplitude whilst increasing the wavelength of isostatic deflection. In light of these models, it is suggested that such a response leaves residual second-order stresses associated with the under-compensated buoyancy of the granite body and flexural tension. The observed basin geometries of the Carboniferous North Pennine Basin can be replicated by incorporating a density deficiency within the crust, flexural rigidity, simple shear deformation within the shallower subsurface and pure shear deformation within the deeper subsurface. In adopting this technique, the regional flexural profile in response to underlying granite bodies and large extensional faults can be reproduced and thus, to an extent, validated. It is proposed that the interaction of three factors dictate the tectonic framework within a partially granitic, brittle-ductile lithosphere and the occurrence of inter-basinal highs: 1) non-tectonic, ‘second-order’ stresses such as the flexural response of the lithosphere and residual, under-compensated buoyancy forces in relation to granite bodies; 2) extensional tectonic stress and importantly; 3) inherited basement fabric.

Item Type: Article
Additional Information: This is the accepted author manuscript (AAM). The final published version (version of record) is available online via Elsevier at https://doi.org/10.1016/j.tecto.2019.02.008 - please refer to any applicable terms of use of the publisher.
Uncontrolled Keywords: Extensional basin, Flexural isostasy, Lithosphere, Granite, Block
Subjects: G Geography. Anthropology. Recreation > G Geography (General)
Divisions: Faculty of Natural Sciences > School of Geography, Geology and the Environment
Depositing User: Symplectic
Date Deposited: 18 Feb 2019 09:07
Last Modified: 06 Mar 2019 15:10
URI: http://eprints.keele.ac.uk/id/eprint/5854

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