The sedimentology of the Middle and Upper Border groups (Viséan) in the Stonehaugh Borehole, Northumberland

Abstract

SUMMARY A sedimentological study has been made of the core from the Stonehaugh Borehole, which proved strata from the Viséan Middle and Upper Border groups of central Northumberland. Much of the Middle Border Group was deposited in a fluvially dominated delta, in interdistributary bays, minor mouth bars, crevasse splays and backswamps. However, a significant part of the group was deposited under more arid conditions in temporary lakes and on muddy floodplains. Sediments of the Upper Border Group were more tidally influenced, being deposited on tidal flats and as bay in-fills. All of these associations are locally cut by major fluvial and delta distributary channels. The transition from fluvial to tidally influenced sedimentation close to the Middle/Upper Border Group boundary is broadly coincident with a period of volcanism, footwall uplift and changing palaeogeography associated with the transition from extensional to thermal relaxation subsidence in the Northumberland Trough.