THE STRATIGRAPHY, CORRELATION, PROVENANCE AND PALEOGEOGRAPHY OF THE SKIDDAW GROUP (ORDOVICIAN) IN THE ENGLISH LAKE DISTRICT

A new lithostratigraphy is presented for the Skiddaw Group (lower Ordo vician) of the English Lake District. Two stratigraphical belts are de scribed. Five formations are defined in the Northern Fells Belt, rangi ng in age from Tremadoc to early Llanvirn. They are all mudstone or sa ndstone dominated, of turbidite origin; in ascending order they are na med the Bitter Beck, Watch Hill, Hope Beck, Loweswater and Kirk Stile formations. Two formations are defined in the Central Fells Belt, rang ing in age from late Arenig to Llanvirn. These are the Buttermere Form ation - a major olistostrome deposit - overlain by the Tarn Moor Forma tion, consisting of turbidite mudstones with volcaniclastic turbidite sandstone beds. A revised graptolite and new acritarch biostratigraphy for the Skiddaw Group is presented with eight graptolite biozones and thirteen acritarch assemblages and sub-assemblages. The provenance of the group is assessed from detailed petrographical and geochemical wo rk. This suggests derivation, in the early Ordovician, largely from an old inactive continental are terrane lying to the southeast, with the appearance of juvenile volcanic material in the Llanvirn. Comparisons and correlations of the Skiddaw Group are made with the Isle of Man a nd eastern Ireland.