A sequence stratigraphic model for deposition of the Lower Kinderscout Delta, an Upper Carboniferous turbidite-fronted delta

SUMMARY Late Kinderscoutian (Upper Carboniferous) strata in the central Pennines, northern England, were deposited in a turbidite-fronted delta, here termed the Lower Kinderscout delta. Existing depositional models of this delta system are based solely on facies analysis and imply that its lithostratigraphic components were coeval and genetically linked. However, detailed sedimentological logging of these strata at outcrop reveals 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) erosion surfaces at the bases of coarse-grained fluvial and deltaic sandstone bodies, (2) thin coals, (3) surfaces across which there are a number of abrupt changes, including changes in depositional process from turbidity-current dominated to traction-current dominated, in sand:shale 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, implying that they have the potential for time correlation within a conceptual sequence stratigraphic framework. A new depositional model is proposed which is based on such a conceptual framework. A crucial feature of this model is the recognition of major erosional unconformities (sequence boundaries) which were produced by fluvial incision during discrete periods of falling relative sea level, when sediment was bypassed into the deep basin, and across which there are no genetic links in facies. Facies architecture is repeated, and therefore predictable, between the sequence boundaries. The sequence stratigraphic model therefore represents an important alternative to existing depositional models, particularly with regard to the timing and distribution of sandstone bodies.