SUBSIDENCE AND UPLIFT IN EAST YORKSHIRE AND LINCOLNSHIRE: A DOUBLE INVERSION

Abstract

Summary The land ward part of the Mesozoic southern North Sea Basin in eastern England includes two major structural units, the Cleveland Basin of north-east Yorkshire * and the East Midlands Shelf. The Market Weighton Block north of the Humber is the northernmost sector of the Shelf. Each of these units continues offshore, the Cleveland Basin linking with the Sole Pit Trough, a Jurassic and Lower Cretaceous basin which was inverted in the late Cretaceous, and the East Midlands Shelf continuing as far east as the Dowsing Fault belt. The Market Weighton Block terminates eastwards beyond the coast some 80 km east of the Jurassic outcrop. Differential subsidence of the Cleveland Basin relative to the East Midlands Shelf took place in the Lower and Middle Jurassic. During this time the Market Weighton Block was relatively more buoyant (frequently marked by shoal areas and deposition of thinner sediments) than the more southerly parts of the East Midlands Shelf, and true uplift with erosion of accumulated sediments took place at intervals, specifically in the late Pliensbachian, Aalenian/Lower Bajocian and Callovian. During the earlier Upper Jurassic the regional relationship changed and the Cleveland area functioned as a stable shelf, with attenuated and shallow water deposits, while the East Midlands Shelf (with the Market Weighton Block) continued to subside normally, with Oxford and Ampthill Clays deposited in deeper water than the equivalents in Cleveland. Major uplift and erosion preceded Albian (Red Chalk) deposition over the northern part of the East Midlands Shelf, with a culmination in the Market Weighton sector. In this and the earlier phases, southward tilting extended some 120 km southwards across the Market Weighton Block into Lincolnshire. Subsequently the East Midlands Shelf retained in part its Upper Cretaceous cover, while the Cleveland Basin was uplifted, gently folded and extensively eroded, a phase of inversion relative to the Shelf, similar on a smaller scale to that of the Sole Pit Trough. On land, deep boreholes show a comparable earlier history. The Cleveland area coincides with a Lower Carboniferous basin which was extensively eroded before the Permian, whereas the East Midlands Shelf shows block-type Lower Carboniferous with thin Upper Carboniferous but still retains its Coal Measures cover, an inversion analogous to that of the Mesozoic.