Stratigraphy of the Worston Shale Group (Dinantian), Craven Basin, north-west England

Abstract

SUMMARY The Worston Shale Group of Earp et al. (1961) is made up of four formations: the Clitheroe Limestone, Hodder Mudstone, Hodderense Limestone and Pendleside Limestone. Within these formations fifteen members are defined: the Thornton Limestone, Coplow Limestone, Peach Quarry Limestone, Bellman Limestone, Limekiln Wood Limestone. Phynis Mudstone, Whitemore Limestone, Hetton Beck Limestone, Leagram Mudstone, Buckbanks Sandstone, Embsay Limestone, Rain Gill Limestone, Chaigley Limestone, Twiston Sandstone and Rad Brook Mudstone. A particular bed within the Hodder Mudstone Formation, the Dunbarella Bed, is also recognised. Four unconformities are recognised. The most widespread is at the base of the Hodder Mudstone Formation; the others, which are more restricted, occur at the base of the Embsay Limestone Member (and equivalents), at the base of the Twiston Sandstone Member and at the base of the Pendleside Limestone Formation. Diagnostic Viséan foraminifera and conodonts first enter within the basal part of the Hodder Mudstone Formation, suggesting that the Tournaisian-Viséan boundary lies much higher than previously supposed. All the Dinantian stage boundaries in the Arundian to Asbian interval have been re-correlated. The Craven Basin is thought to have been underlain by an asymmetric graben within the pre-Carboniferous basement and the depositional history of the basin to have resulted from a combination of both syndepositional tectonics and eustatic processes. Consequently, the basinal sediments portray a transition from carbonate shelf to slope (Gawthorpe 1987), involving a change during deposition of the Clitheroe Limestone and Hodder Mudstone formations from shallow-water carbonates, generated within the basin, to deep-water hemi-pelagic sediments with limestone turbidites fed from the surrounding carbonate shelves and platforms. Intermittent supply into the basin of terrigenous sand and reworked faunas is related to the emergence and erosion of the surrounding areas.

Sedimentology and microfacies of a mud-rich slope succession: in the Carboniferous Bowland Basin, NW England (UK)

“…All organic matter values either measured (using TOC or RockEval methods) or calculated reported in this study are present-day values. (after Gawthorpe 1986;Riley 1990;Aitkenhead et al 1992) and seismic stratigraphy (after Fraser & Gawthorpe 2003).…”

“…1). The margins of the Bowland Basin are defined by the Bowland Line to the north, the Craven Fault System to the NE (forming the boundary with the Askrigg Block 'high'), and the Pendle Fault to the south (forming the boundary with the Central Lancashire High; Gawthorpe 1987;Arthurton et al 1988;Riley 1990;Fraser & Gawthorpe 2003). Initiation of the Bowland Basin occurred in the latest Devonian to Tournaisian, with two further distinct episodes of rifting occurring during the ChadianArundian and Asbian-Brigantian (Gawthorpe 1987).…”

Shale prospectivity onshore Britain

“…In the Lower unit of the Bowland-Hodder sequence thicker, syn-rift, shale-dominated facies passed laterally to age-equivalent limestones on adjacent highs and platforms. The presence of slumps, debris flows and gravity slides (Gawthorpe & Clemmey 1985, Riley 1990) is evidence for relatively steep slopes, and a combination of syn-depositional tectonics, fluctuating sea levels, climate change, and evolution of the carbonate ramps/platforms surrounding the basin resulted in a variety of sediments being fed into the basin at different times. However, there is so little well control for the Lower unit in the deep basins, that it is unclear how regionally correlative these intervals are.…”

High resolution biostratigraphy of the Tournaisian-Viséan boundary interval in the North Staffordshire Basin and correlation with the South Wales-Mendip Shelf

“…Later, Fewtrell et al (1981b) documented foraminiferal generic ranges in relation to the British Dinantian stages but failed to repeat the Eoparastaffella record of George et al (1976) in the Chadian stratotype at Chatburn. The absence of this guide fossil in the Chatburn section and the Chadian biostratigraphy of the Craven Basin were discussed in detail by Riley (1990Riley ( , 1993Riley ( , 1995 who stressed that the correlation of the base of the Chadian is impossible and that it is only the late Chadian that has a distinct biostratigraphic signature. A review of the validity of the Chadian and of the suitability of the Chatburn section as its stratotype is provided in Adams et al (2004).…”

“…However, subsequent workers have failed to repeat this foraminiferal record at the Chatburn stratotype in the Craven Basin (Fewtrell et al 1981a, b;Riley 1990Riley , 1993. Subsequently however refinements in our understanding of foraminiferal lineages across the Tournaisian-Viséan (T-V) boundary have led to the redefinition of the base of the Viséan and its stratotype changed.…”