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The stratigraphy and tectonics of the Skiddaw slates and the relationship of the overlying borrowdale volcanic series in part of the Lake District
Author(s) -
Simpson Alexander
Publication year - 1967
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.3350050211
Subject(s) - slates , unconformity , geology , ordovician , paleontology , volcano , sequence (biology) , dalradian , tectonics , paleozoic , basement , precambrian , volcanic rock , geochemistry , metamorphic rock , archaeology , history , biology , genetics
The Skiddaw Slates consist of eight formations with the substantial thickness of about 30,000 ft. This geosynclinal sequence is of Arenig age though the highest formation may continue into the Lower Llanvirn. The polyphase tectonics of the Skiddaw Slates and the relationship of the overlying Borrowdale Volcanic Series are discussed. It is concluded that the Caledonian tectonic history of this part of Britain contains two paroxysms of orogenic activity. In addition to the orthodox end‐Silurian orogenesis there was also an intra‐Lower Ordovician orogenic episode which took place towards the close of the Llanvirn. During the earlier tectonic climax the Skiddaw Slates were deformed by two phases of folding. Their structure is, therefore, largely of pre‐Borrowdale age and bears little relation to that of the overlying cover. After this dual deformation the slaty basement was truncated by erosion and is separated from the overlying Borrowdale Volcanic Series by an angular unconformity. Only the end‐Silurian folding affects the volcanic superstructure and the younger Lower Palaeozoic sequence.