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.

Palaeomagnetism and chronology of Caledonian igneous episodes in the Cross Fell Inlier and northern Lake District

“…The research of recent years has, however, shown that these igneous episodes occurred at several different periods between and after Caledonian tectonic events. For example, eruption of the Eycott Group of the north Lake District comprising basalts and basaltic andesites (Eastwood et al 1965) commenced during the Didymograptus bifidus time zone of the Llanvirn (Downie and Soper 1972), and was tilted prior to eruption of the Borrowdale Volcanic Group (palaeomagnetic sites 1 to 4 of this study), comprising predominantly andesites and rhyolites (Firman 1957;Mitchell 1956;Moseley 1960Moseley , 1964. This latter group lies unconformably on Llanvirnian slates east of Keswick but may be essentially conformable in the southwest of the Lake District outcrop; it was in turn folded and partly eroded prior to deposition of the (Caradocian) Coniston Limestone Group including minor volcanic components (Eastwood 1953 for palaeomagnetic study.…”

The geochemistry and significance of sills within the Ordovician Borrowdale Volcanic Group around Black Combe, SW English Lake District

“…1), BVG rocks are discontinuously present and basal units of the Windermere Supergroup locally rest directly on Skiddaw Group. The geology of the SWLD has been described previously by Green (1913), Mitchell (1956), Firman (1957 and Mathieson (1986). Data from this last mentioned study form the core of this paper.…”

The borrowdale volcanic rocks of the Seathwaite Fells, Lancashire

“…1). This group, though thinning northwards, presumably includes both representatives of the Dunnerdale Tuffs and the Duddon Bridge or Duddon Hall Tuffs (Mitchell 1956;Firman 1957). …”

“…Copper veins were formerly worked near Seathwaite Tam (Eastwood in Dewey and Eastwood 1925, p. 69) and there are other disused mineral adits at Cockley Beck. The adjoining area to the north was described by Hartley (1932); that to the west by Firman (1957) and the ground to the east and south by Mitchell (1940Mitchell ( , 1956). The Seathwaite Fells are shown on the Geological Survey's one-inch Sheet 38 (1882) and the accompanying six-inch maps, but no account of the rocks themselves has been published.…”