Carboniferous biostratigraphy of the Rookhope Borehole, Co. Durham

Abstract

AbstractA deep borehole drilled at Rookhope in Weardale, Co. Durham in 1960–61 proved the Weardale Granite below Carboniferous sediments at a depth of 390 m; an account of the Carboniferous rocks is presented. The boring commenced in the basal Namurian Great Limestone and entered the Dinantian at the bottom of the limestone at 25 m. Most of the ten Brigantian cyclothems sectioned in the borehole are compound and average 30 m thick. They consist of an initial cycle often more than 20 m thick and overlying minor cycles that are usuallyless than 6 m thick. Each of the cycles, both initial and minor, are coarsening upwards sequences from marine limestone or mudstohe to deltaic and fluvial mudstone, sandstone, seatearth and occasionally a thin coal seam. The underlying Asbian consists of seven cyclothems averaging 8 m thick. By contrast they are simple coarsening upwards sequences similar to the Brigantian initial cycles, but no minor cycles are developed.Marine fossils are abundant in the majority of cyclothems and are listed against their stratigraphical horizon in the borehole. Special studies of miospores, conodonts and foraminiferans from the borehole are presented. A consensus of biostratigraphical evidence shows that the base of the Carboniferous succession in the borehole is of early Asbian age.