A PLAYA DEPOSIT OF PRE-YELLOW SANDS AGE (UPPER ROTLIEGEND WEISSLIEGEND) IN THE PERMIAN OF NORTHEAST ENGLAND/

A complexly interbedded thin succession of sandstone, siltstone and mu dstone beneath the Permian Yellow Sands Formation (upper Rotliegend/We issliegend) was cored in a borehole 11 km off the coast of northeast E ngland. The cored strata rest unconformably on fissured Westphalian B mudstone and mainly comprise low-dipping fine-to coarse-grained grey s andstone with unevenly spaced thinner dark-red to grey mudstone beds a nd laminae. Most of the sandstone beds are moderately to poorly sorted , fine-to veri fine-grained subarkoses, with some sublitharenites, and are weakly to strongly cemented by dolomite (predominant), kaolinite and illite; sedimentary structures include subhorizontal plane to wavy lamination, ripple lamination, salt ridges and soft-sediment deformat ion. The siltstones and mudstones ate more uniform in lithology and pr imary thickness; they contain sandstone-filled desiccation cracks, mud stone saucers and narrow sandstone dykes. Traces of possible former ev aporite minerals are concentrated in the sandstones. By comparison wit h modern desert depositional environments, these strata to interpreted as the deposits of a playa occupying a depression on a stony, deflati onary desert surface on a rock pediment or peneplain flanking the ance stral Pennines. The floor of the depression, which probably lay in the capillary fringe just above the contemporary water table, was periodi cally flooded so as to form a shallow playa lake. Comparable successio ns beneath the Yellow Sands have nor been recorded from surface exposu res in northeast England but mudstone beds at this stratigraphical lev el have been recorded in four other cored offshore boreholes and are p resumed to be of similar origin to those described in this study. The stratigraphical position of these deposits suggests that they may be o f pre-Yellow Sands age and coeval with or younger than the Basal Permi an Breccia. Palynological analysis of mudstone samples from the core r eveal the presence of plant material and indeterminate, pyrite-investe d, possibly indigenous bisaccate pollen indicative of a vegetated hint erland with deposition occurring within a reducing, possibly sulphide- rich environment.