Gill Beck

Also within

Cumbria County LAKE DISTRICT National Park

Condition (Natural England)

Habitats

Fast flowing river and stream

Geology & landscape

Geological Feature: Fissure · Geological Period: Carboniferous, Ordovician · Rock Type: Limestone

Landscape processes: Volcanic / Igneous

Description

Description Gill Beck is situated in a small valley just south of the village of Blindcrake, six kilometres northeast of Cockermouth. It forms a short tributary of the River Derwent to the south. The Cockermouth Lavas, of Dinantian age, record a volcanic episode linked with the initiation of the southern margin of the Northumberland Trough during early Carboniferous times. The volcanism was preferentially located along the hinge zone between areas of subsidence, to the north and uplift, to the south. The absence of pyroclastic rocks suggests that extrusion was relatively quiet, probably along a series of fissure vents. The suite is geochemically distinguished by the presence of lavas of intermediate composition and the Northumberland Basin is, in this sense, transitional between the Scottish Midland Valley where such compositions are relatively common and Derbyshire where they are unknown. Gill Beck provides good stream exposures through a circa 60 metres thick sequence of the Cockermouth Lavas. The suite is in general not well exposed and this fact makes the Gill Beck sequence especially valuable. At least four lava flows are present including both basalts and tholeiitic andesites. The site is also important as the Ordovician Skiddaw Slates lie unconformably beneath the lavas. Sediments overlying the lavas have yielded a Courceyan stage age and a sequence of rocks ranging from Courceyan Basement Beds to the Holkerian 7th Limestone is seen. Taken in conjunction with age evidence found below the lavas elsewhere in the area, this enables the age of the volcanism to be tightly established.

Plant communities