SECTIONS THROUGH THE SKIDDAW–BORROWDALE UNCONFORMITY IN EASTERN LAKELAND

Abstract

Summary Four sections are described through the controversial junction between the Skiddaw Group and the Borrowdale Volcanic Group within the Lower Ordovician sequence of eastern Lakeland. An angular unconformity between the groups is exposed in Matterdale Beck and at Causeway Foot. At Matter-dale, the underlying Skiddaw beds, yielding Lower Llanvirn graptolites, are interbedded with volcanics older than the Borrowdale volcanic sequence. Coarse Borrowdale conglomerates overlie the unconformity and are succeeded by andesites. At Low Rigg, the field relations suggest that the Threlkeld Micro-granite is pre-Borrowdale in age. The distribution of graptolite faunas within the Skiddaw outcrop supports the view of a regional unconformity, and suggests that a pre-Borrowdale anticline was developed similar in position and trend to the later Skiddaw Anticline.