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Petrography of the Mesozoic Succession of South Wales

Published online by Cambridge University Press:  01 May 2009

C. B. Crampton
Affiliation:
Rothamsted Experimental Station, Harpenden, Herts.

Abstract

The heavy mineral suites of the Trias, Rhaetic and lowermost zones of the Lower Lias in the Vale of Glamorgan of South Wales are described. The northerly coastline of the Mesozoic sea, roughly coincident with the present-day periphery of the Coalfield, consisted mainly of Carboniferous Limestone and in places, the Old Red Sandstone and Millstone Grit. The mineral assemblage at any particular point in the littoral zone was determined largely by the nature of the outcropping rocks of the coastal mainland, the derivation of detritus being very localized. Within this zone some degree of gravity sorting of the detritals occurred, this implying a relatively steeply inclined coastal sea-bed. An off-shore current carried detritus from the Armorican land-mass of Britanny and granite of South-West England to this area where the detritals were dispersed thinly throughout the locally derived sediment.

Type
Articles
Copyright
Copyright © Cambridge University Press 1960

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