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Evidence on the deep structure of the Anglo-Brabant Massif from gravity and magnetic data

Published online by Cambridge University Press:  01 May 2009

M. K. Lee ,
T. C. Pharaoh ,
J. P. Williamson ,
C. A. Green  and
W. De Vos
M. K. Lee
Affiliation:
British Geological Survey, Keyworth, Nottingham, U.K.
T. C. Pharaoh
Affiliation:
British Geological Survey, Keyworth, Nottingham, U.K.
J. P. Williamson
Affiliation:
British Geological Survey, Keyworth, Nottingham, U.K.
C. A. Green
Affiliation:
British Geological Survey, Keyworth, Nottingham, U.K.
W. De Vos
Affiliation:
Belgische Geologische Dienst, Brussels, Belgium
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Abstract

Gravity and aeromagnetic data from Britain, Belgium and the southern North Sea have been compiled to provide coverage of the greater part of the Anglo-Brabant Massif. Colour pseudo-relief maps of the gravity and magnetic fields highlight important anomalies and trends which provide new information on the structure of the massif and its margins. Within the massif, prominent SSE-trending geophysical lineaments define the margins of distinctive blocks within the upper crust. These are cross-cut on the northeastern margin of the massif by prominent ESE- and SE-trending magnetic and gravity lineaments. The possible history and origin of the more prominent geophysical anomalies and lineaments are considered. Integrated modelling of the potential field data has been carried out along the BIRPS MOBIL-7 seismic reflection line to provide an interpretation of crustal structure across the northeast margin of the massif constrained by all three datasets. The principal features of the model are a non-reflective, non-magnetic upper crust, interpreted as the Caledonian fold–thrust belt, overlying a heterogeneous middle–lower crust with laterally varying reflectivity, magnetization and density. ESE-trending magnetic anomalies along the northeast edge of the massif are explained in terms of an irregular mid-crustal magnetic layer with a susceptibility comparable to that of the Tubize Group in the Brabant Massif. The top of this body is coincident with prominent dipping mid-crustal reflectors observed on the seismic reflection profile and its overall geometry is compatible with mid-crustal imbrication inferred from the seismic data.

Type
Articles
Information
Geological Magazine , Volume 130 , Issue 5 , September 1993 , pp. 575 - 582
Copyright
Copyright © Cambridge University Press 1993

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