VARISCAN STRUCTURES IN THE KENT COALFIELD, SOUTHEAST ENGLAND, AND THEIR REGIONAL SIGNIFICANCE

The Upper Carboniferous Kent Coalfield lies concealed beneath various Mesozoic formations, its southern areas lying about 20 km north of the commonly accepted position of the main Variscan Deformation Front. Ho wever, despite intense intra-coal deformation, the existing literature is ambivalent about compressional Variscan features in Kent, the gene ral view being that coal deformation is largely the product of the dep ositional environment. The main deformation is interpreted here as the result of Variscan compression, the structural style being imposed by the sandstone-dominated Lithology. This conclusion is necessitated by the regularity of deformational structures revealed by mine workings, and supported by coal sequence irregularities suggestive of thrusting , especially in the lower Westphalian strata, all of which is parallel ed in parts of the South Wales Coalfield. The Kent data indicate that, as in South Wales, a zone of thrusting many tens of kilometres wide l ies in advance of the main deformation front. Structural trends are co nsistent with an overall swing in the front from east-west across much of central-southern England, to more northwest-southeast across north eastern France. This swing may represent a transpressional transfer zo ne, within which stress deflection and block rotation produced thrust vergence oblique to the overall direction of maximum compression.