THE BORROWDALE VOLCANIC SERIES BETWEEN WASTWATER AND DUDDON VALLEY, CUMBERLAND

Abstract
Summary: The Borrowdale Volcanic Series of this area have been sub-divided into six groups. The lowest group overlies the Skiddaw Slates and consists of up to 5500 feet of predominantly massive andesites. These Lower Andesites thin south-westward. Together with a small patch of tuffs near Wastwater, they are considered to have originated from a volcanic centre north-east of the area. All other groups probably originated from vents in the south-west. They range from sub-aerial andesitic and rhyolitic agglomerates to fine, delicately bedded tuffs which are thought to have been deposited in tranquil water. Rhyolites and andesites occur at several horizons in both types of tuff and a group of massive andesites comes in at the top of the succession. The pre-Bala movements tilted the area eastward and caused some gentle folding. During the Caledonian orogeny open folds trending north-east developed. Folding was most intense in the south-west and here the northern limb of the major syncline is vertical. Possibly the Eskdale Granite was involved in this folding. The rocks were later faulted and cleaved. Tear faults and normal faults affect both the granite and the volcanic rocks.