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- Structural trends in the concealed basement of eastern England from images of regional potential field data
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Structural trends in the concealed basement of eastern England from images of regional potential field data
Abstract
New colour and grey-tone shaded-relief images of the gravity and aeromagnetic fields in eastern England are presented. These define the lineaments and correlations between anomalies in somewhat more detail than previous broad-scale images and have been used to update the analysis of structural trends and basement geology. The dominant trends in eastern England, on both the gravity and magnetic images, are SE and ESE. Structures which appeared to have an arcuate form on previous images have been resolved into separate SE- and ESE-trending segments. Likewise, the broad magnetic ridge extending from northern England to East Anglia has been resolved into separate SE- and ESE-trending components which are observed to intersect in the region of the postulated concealed granites at Market Weighton and around The Wash. The pattern of SE-trending lineaments associated with the northeastern margin of the Midlands Microcraton suggests that this boundary may be more irregular than previously supposed. The presence of the SE and ESE trends where the Upper Palaeozoic cover is relatively thin suggests that the lineaments correspond to structures within the concealed Precambrian to Lower Palaeozoic basement. The occurrence of the same trends in the northeast Midlands where the Upper Palaeozoic cover is thicker, strongly supports the widely held view that Lower Carboniferous sedimentation was controlled by reactivation of SE- and ESE-trending structural discontinuities in the underlying basement as a result of crustal extension during the Dinantian. The origin of the basement trends remains unclear. Both SE- and ESE-trending structures are seen in the Precambrian but it is also possible that major discontinuities in either, or both, of these directions originated during closure of the Tornquist Sea during the Ordovician or during end-Caledonian (Acadian) transpression.
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About: M.K. Lee
British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
About: T.C. Pharaoh
British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
About: C.A. Green
British Geological Survey, Keyworth, Nottingham NG12 5GG, UK