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The stratigraphy and composition of the Latterbarrow and Redmain sandstones, Lake District, England
Author(s) -
Allen P. M.,
Cooper D. C.
Publication year - 1986
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.3350210105
Subject(s) - geology , petrography , group (periodic table) , geochemistry , arenite , sedimentary rock , volcano , volcanic rock , quartz , clastic rock , illite , carboniferous , siliciclastic , sedimentary depositional environment , paleontology , clay minerals , structural basin , chemistry , organic chemistry
The Latterbarrow Formation, 400 m thick, has been mapped and subdivided informally into three members. These consist of quartz wacke sandstone and, in the upper member only, intercalated mudstones. The formation unconformably overlies the fossiliferous Skiddaw Group of late Tremadoc to middle Arenig age and is overlain disconformably by volcanic rocks that have been attributed to the Borrowdale Volcanic Group. Chemically, the sandstones are characterized by very low concentrations of CaO, Na 2 O, and K 2 O and unusually high total iron. MnO and MgO, such that iron, as Fe 2 O 3 , exceeds Al 2 O 3 . Mudstone in the upper member is illite rich, has a high K 2 O content and is compositionally similar to K‐bentonites derived from volcanic ash. Sedimentary structures and petrography suggest that the sediments were deposited in a sandy estuary and were derived from a similar source area to that of the Skiddaw Group. Throughout the succession there is evidence of distal volcanism, probably representing the earliest eruptions of the Borrowdale volcanic episode. The Redmain Formation, 100 m thick, is unconformably overlain by Carboniferous rocks but its relationship to the underlying Skiddaw Group is unknown. Though this lithic arenite shows some petrographic and geochemical similarities with the Latterbarrow sandstone, differences are such that it is possible they are not equivalent in age. The Redmain sandstone may be derived from the erosion of Skiddaw Group rocks.