A SEQUENCE STRATIGRAPHIC MODEL FOR DEPOSITION OF THE LOWER KINDERSCOUT DELTA, AN UPPER CARBONIFEROUS TURBIDITE-FRONTED DELTA

Late Kinderscoutian (Upper Carboniferous) strata in the central Pennin es, northern England, were deposited in a turbidite-fronted delta, her e termed the Lower Kinderscout delta. Existing depositional models of this delta system are based solely on facies analysis and imply that i ts lithostratigraphic components were coeval and genetically linked. H owever, detailed sedimentological logging of these strata at outcrop r eveals a range of key elements, some of which can be traced regionally and which record distinct breaks in deposition, thereby contradicting these models. Key elements include: (1) high-relief (up to 40 m) eros ion surfaces at the bases of coarse-grained fluvial and deltaic sandst one bodies, (2) thin coals, (3) surfaces across which there are a numb er of abrupt changes: including changes in depositional process from t urbidity-current dominated to traction-current dominated, in sand:shal e ratio and in ichnofauna, (4) intensely-bioturbated siltstones and (5 ) condensed shales, including marine bands. Each of these key elements records a change in sediment supply and/or accommodation space, imply ing that they have the potential for time correlation within a concept ual sequence stratigraphic framework. A new depositional model is prop osed which is based on such a conceptual framework. A crucial feature of this model is the recognition of major erosional unconformities (se quence boundaries) which were produced by fluvial incision during disc rete periods of falling relative sea level, when sediment was bypassed into the deep basin, and across which there are no genetic links in f acies. Facies architecture is repeated, and therefore predictable, bet ween the sequence boundaries. The sequence stratigraphic model therefo re represents an important alternative to existing depositional models , particularly with regard to the timing and distribution of sandstone bodies.