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Garn Prŷs: A mid‐Silurian canyon, feeder to the Denbigh Grits of North Wales
Author(s) -
Cave R.,
Evans J. A.,
Campbell S. D. G.
Publication year - 1992
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.3350270402
Subject(s) - canyon , geology , volcano , siliciclastic , geochemistry , debris , geomorphology , turbidity current , group (periodic table) , volcanic rock , dome (geology) , paleontology , structural basin , sedimentary depositional environment , oceanography , chemistry , organic chemistry
A fining‐upward, siliciclastic sequence of Wenlock strata, coarsely rudaceous at the base, infilled a canyon, about 4.5 km wide and 1700 m deep, in older strata. The rudaceous deposits, at the flat base of the canyon, are composed mainly of rounded cobbles and boulders of acid volcanic rocks. These are interpreted as cohesionless debris‐flow deposits that were succeeded by northward‐directed high concentration turbidity currents. The infill is deduced to have been derived from a terrain of acid volcanic rocks to the south, similar in Nd isotope composition to the Llewelyn Volcanic Group of Snowdonia. It implies mid‐Silurian uplift and erosion of the Harlech Dome.