HWR Chatsworth paper vSept07 unformatted.doc 28/07/2008 REGIONAL EVOLUTION OF A FLUVIODELTAIC CYCLIC SUCCESSION IN THE MARSDENIAN (LATE NAMURIAN STAGE, PENNSYLVANIAN) OF THE CENTRAL PENNINE BASIN, UK. 1 2 3 4 C.N. WATERS , J.I. CHISHOLM , A.C. BENFIELD and A.M. O’BEIRNE 1 British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
[email protected] 2 4 Park Street, Loughborough, Leicestershire LE11 2EG, UK 3 24 Gascoigne Avenue, Barwick-in-Elmet, Leeds LS15 4LW, UK 4 32 Hemberton Road, London SW9 9LJ, UK SUMMARY: Basinwide analysis of sedimentary facies, isopachytes and palaeocurrents for two late Marsdenian (Pennsylvanian) sedimentary cycles within part of the Millstone Grit Group, has led to a new sequence-stratigraphic interpretation for the relationships between its constituent sandstone units (currently named Huddersfield White Rock, Chatsworth Grit, Brooksbottoms Grit, Holcombe Brook Grit, Brown Edge Flags and Redmires Flags). The Bilinguites superbilinguis (R2c1) and Verneulites sigma (R2c2) marine bands related to fourth-order marine highstands show faunal variations possibly reflecting fifth-order sea-level fluctuations. The lower R2c1 cycle consists entirely of deep water mudstone. The overlying R2c2 cycle shows an upward regressive passage through pro-delta and delta-slope deposits to mouthbar and channel sandstones. The latter comprises an ‘eastern inflow’ of northerly provenance, the distribution of which was not influenced by the underlying basement configuration, and a ‘southern inflow’ sourced from the Wales-Brabant High. Falling sea-levels resulted in progressive narrowing of the fluvial pathway within the main sandstone body of the ‘eastern inflow’, with a concomitant increase in flow velocities and grainsize.