| Summary: | The Carboniferous Limestone outcrop of Derbyshire forms the southernmost section of the Pennines. It is part of the main waterdivide of Northern England and glaciation has played a crucial role in its Pleistocene development. Throughout the whole epoch, the Derbyshire upland was never of sufficient altitude to generate its own ice sheet and the limestone lay in the shadow of higher Millstone Grit to the north. Derbyshire was therefore subject to external influences. Of the seven cold stages established in the East Anglian sequence, only the last three were cold enough to generate glacial advances. The Anglian and Wolstonian ice sheets certainly crossed Derbyshire, but in the Devensian, the last stage, there is little evidence of glacial debris on the limestone. No interglacial deposits have been found on the plateau surface. In addition to the first detailed mapping and classification of the superficial sediments, geochemical, mineralogical and physical analyses have been made. Using computer analysis of the data for verification, a Pleistocene sequence of events has been established for the area. Problems of dating and distinguishing specific glacial deposits associated with Pleistocene stages have been partly solved by employing a variety of different techniques: emission spectroscopy, X-ray diffraction, scanning electron microscopy, weathering ratio and particle size analysis. Different superficial deposits, till, loess, 'silty drift', insoluble residue, solifluction deposits and erratic content have been compared with each other and limited cave sediments in order to elucidate the former glacial episodes no longer identifiable as distinct deposits on the surface. The analytical results from five important sections point to the existence of two tills on the plateau surface, a northern weathered till in deep limestone joints and over the Tertiary sandpits and a second occurring later within an established drainage system. All are covered indiscriminately by loess, a Devensian product. Surface tills are only ...
|
|---|