Early stages in the physiographic evolution of a portion of the East Midlands

Abstract

Summary The paper deals with an area of over 600 square miles falling largely within the drainage basins of the rivers Nene and Welland. Formations present comprise a succession from the Lower Lias to the Oxford Clay and Pleistocene-Recent drifts. Six-inch mapping, supplemented by numerous borehole records, discloses differences between the present and the sub-boulder-clay topography. The significance of these differences is discussed. Relics of the surface on which the present cycle of erosion was initiated are preserved as bevels on the solid formation. This surface, which falls from 750 feet O.D. in the west to below 250 feet in the east, is believed to have been tilted toward the North Sea basin. Study of the stages of river diversion and capture provides strong evidence of an original W.-E. consequent drainage. The controlling effect of structure on river development is clearly shown. Certain lines of drainage are believed to have existed as subsequent streams before the start of the present cycle of erosion. The origin of the large-scale superficial structures of the region is reconsidered. It is claimed that they were produced under periglacial conditions. The authors suggest that an important part was played by perennially frozen ground in the physiographic evolution of the region.