Lithostratigraphical subdivision of the Sherwood Sandstone Group (Triassic) of the north-eastern part of the Carlisle Basin, Cumbria, and adjacent parts of Dumfries and Galloway, UK.

This report presents a review of the history of the lithostratigraphical subdivision of the Triassic Sherwood Sandstone Group of the north-eastern part of the Carlisle Basin, Cumbria, and adjacent parts of Dumfries and Galloway, UK. Two formations, the St Bees Sandstone and Kirklinton Sandstone, have been mapped in the past. However, previous workers have found considerable difficulty in consistently identifying, defining and mapping the Kirklinton Sandstone Formation. Moreover, previous accounts of the sandstones in the Carlisle area appear to suggest that the succession there differs in several key aspects from its correlatives in other parts of Cumbria and, in particular, the adjacent offshore area. As a result of a short period of field work in the area, it is concluded that the principal lithological change is between mainly fine-grained sandstones, that are generally or commonly micaceous and contain common or numerous mudstone interbeds, in the lower and middle parts of the group, and fine- to coarsegrained sandstones with rare or no mica and mudstone partings at the top of the group. This change occurs within the Kirklinton Sandstone Formation as previously mapped, and it is suggested that this unit is now invalid. Several options are considered as to how the group should be subdivided and the nomenclature to be adopted. All options presently have some associated problems, but the adoption of the same terminology as in the continuous offshore is suggested, i.e. St Bees Sandstone Formation below (subdivided where possible into Rottington Sandstone and Calder Sandstone Members) and Ormskirk Sandstone Formation above.