STRATIGRAPHY AND STRUCTURE IN THE BLACK COMBE INLIER, ENGLISH LAKE DISTRICT

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Abstract
Summary: The two-fold stratigraphical division of the Skiddaw Group and the simple outcrop pattern proposed by earlier workers are both shown to be oversimplifications. Three formations are recognized each of which has a rather complicated outcrop. The sequence of pelite, silty pelite and minor amounts of greywacke, accumulated in the Caledonian geosyncline during Arenig or Llanvirn times. The Skiddaw Group appears to be unconformably overlain by the Borrowdale Volcanic Group. The basal rocks of the volcanic sequence are essentially sub-aerial. The pre-Carboniferous rocks have been subjected to multiple deformation. Six groups of minor structures have been recognized in the Skiddaw Group, namely, D 1 , D 2 , D 3 , D 4 , D 5 and D 6 ; only the D 1 , D 2 and D 4 minor structures, however, are persistently developed. Larger-scale folds may have been produced during the D 1 and D 2 movements. Evidence presented suggests that following the D 2 deformation, during late-Llanvirn or early-Llandeilo times or both, the rocks of the Skiddaw Group were uplifted and eroded. After the deposition of the Borrowdale Volcanic Group D 4 movements produced the north-easterly trending, end-Silurian anticline in the volcanic sequence and brought the Skiddaw Group to its present structural level.

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