Reconstruction of Channel and Barform Architecture in a Pennsylvanian Fluvio-Deltaic Succession: Brimham Grit, Northern England
Soltan, Roman; Mountney, Nigel; McCaffrey, William D.; Paton, Douglas A.
Pebbly fluvio-deltaic sandstones of the Brimham Grit (Kinderscoutian, northern England) form a complex array of Millstone Grit tor outcrops, which enable 3-D lithofacies architecture to be determined in detail whereby relationships between adjacent sand-bodies representing a range of channel, barform, dune and sheet-like elements can be used to reconstruct the flow behavior of a braided channel network.
Although the depositional paleoenvironment was supplied with sediment delivered from a range of provenances, the dominant supply was from eroded remnants of Scottish and Norwegian Caledonian Mountains located ~450 and ~950 km towards the north and northeast, respectively. Previous studies suggest that the system evolved from a shelf-edge- to slope-ramp delta, which ultimately delivered sediment to a series of submarine fans developing in the deep-water depocenter of the Craven Basin.
A detailed depositional model depicting the fluvial processes responsible for generating the preserved stratigraphic architecture has been developed through high-resolution architectural analysis utilizing 1D sedimentary logs, 2-D architectural panels, pseudo-3-D fence diagrams and paleocurrent rose diagrams. Sedimentary lithofacies include trough- and planar cross-bedded sets, compound co-sets of cross-strata, planar-bedded sandstones and gravel beds, collectively organized to define a variety of architectural elements including single-story, multilateral- and multi-story channel elements, downstream- and laterally-accreting macroforms. Architectural elements are typified internally by distinctive lithofacies arrangements with highly variable paleocurrent distributions that are indicative of barforms that systematically changed from lateral to downstream accretion, with accumulation occurring in a poorly-confined network of fluvial channels allied with major sandy barforms, indicative of a frequently avulsing braided fluvial system in an upper-delta plain setting. The presence of plant fossils (e.g. calamites stem remnants) implies local swamp-like conditions adjacent to active channel belts and a degree of channel-bank stability.
Data from this study are contributing to a broader research program investigating the linkage of fluvio-deltaic successions from shelf-edge deltas to slope and submarine-fan successions, with a focus on the influence of basin morphology on sediment delivery mechanisms in the Craven, South Pennine and North Staffordshire Basins of the UK.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013