The envjronment of deposition of the Caradoc Alternata Limestone and contiguous deposits of Salop

Abstract

AbstractThe middle Caradoc rocks of Salop are a mosaic of sedimentary facies deposited in nearshore environments. The uppermost Horderley Sandstone in the Onny Valley is interpreted as formed by migrating marine bars and proximal and distal stonn deposits. The time equivalent Chatwall Sandstone of the Chatwall district is interpreted as a beach sequence. The overlying Alternata Limestone is a product of both proximal and distal storm deposits, associated with marine bars, in which different faunal assemblages are mized. Correlation of local sections is difficult due to facies and faunal changes and non‐deposition events. Based on a sedimentary model and palaeoecological information it is suggested that the Alternata Limestone in the Chatwall area is older than elsewhere, and that the base of the Cheney Longville Flags youngs southwards. Four faunal events are defined based on transect collecting, discriminant function and cluster analysis. These are the Howellites antiquior, Dalmanella lepta and Bancroftina robuste Associations and the Heterorthis alternata interregnum.