Short Paper: The subaerial setting of the Ordovician Borrowdale Volcanic Group, English Lake District

Abstract

Most Ordovician volcanic rocks of southern Britain were produced in volcanic island settings and the Borrowdale Volcanic Group (BVG) of the Lake District has traditionally been interpreted in this way. However, a review of lithofacies associations in the BVG indicates a subaerial environment. Pyroclastic surge deposits, thin welded tuff beds, lava flow morphologies, abundant erosional unconformities, and fluviatile and laharic facies indicate widespread subaerial emplacement. Volcano-tectonic subsidence aided preservation of subaerial facies, although a preservation bias favoured lacustrine deposits. Erosional unconformities above subaerial aggradational volcanic sequences are to be expected, so the sub-Windermere Group unconformity does not necessarily imply tectonic uplift.