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Structure and stratigraphy of the Borrowdale Volcanic rocks of the Kentmere area, English Lake District
Author(s) -
Soper N. J.,
Numan N. M. S.
Publication year - 1974
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3350090204
Subject(s) - geology , anticline , monocline , andesites , andesite , pyroclastic rock , volcanic rock , volcano , paleontology , stratigraphy , fold (higher order function) , geochemistry , lithostratigraphy , geomorphology , tectonics , structural basin , mechanical engineering , engineering
The Borrowdale Volcanic rocks of Kentmere have been reinvestigated. A previous structural interpretation (Mitchell 1929) involving Caledonian isoclines superimposed upon pre‐Caradocian NNE trending folds is shown to be incorrect; neither set of structures exist. The geometry of the major structural elements in the area, the Nan Bield Anticline and the Caledonoid cleavage, is described. Evidence is adduced which suggests that the anticline was formed in pre‐Caradocian time as a large open fold trending approximately E‐W. Its present geometry and that of the Wren Gill Monocline result from the superimposition of the regional end‐Silurian cleavage obliquely and inhomogeneously across this pre‐existing fold. The volcanic succession is divided into four compositionally and petrographically defined formations. In upward sequence these are the Nan Bield and Wren Gill formations (andesitic lavas and tuffs), Kentmere Formation (mainly dacitic pryoclastic rocks) and the Garbourn Formation (andesites and dacites), totalling over 2800 m. It is thought that much of this succession was deposited subaqueously.