STATISTICAL BASIS FOR CYCLOTHEMS: A QUANTITATIVE STUDY OF THE SEDIMENTARY SUCCESSION IN THE EAST PENNINE COALFIELD

Abstract

SUMMARY Study of cyclic sedimentation in the Coal Measures is impeded by confused terminology and ideas. It is suggested that the first steps in the investigation of an area or sequence where cyclic sedimentation is suspected should be: (1) to determine statistically if a modal cycle is present and to define that cycle, (2) to erect a composite sequence representative of the succession. The Coal Measures of the East Pennine (Yorkshire‐Derbyshire‐Nottinghamshire) Coalfield. England, are examined to illustrate the application of this idea. The succession shows a modal cycle of non‐marine shale followed upwards by seat‐earth with secondary modes (also non‐marine sediments) made up of shale—siltstone—shale—seat‐earth and shale—siltstone and sandstone—shale—seat‐earth. The composite sequence for the whole succession is marine shale—non‐marine shale—siltstone and sandstone—non‐marine shale—seat‐earth. Consideration of cycle types, horizontal and vertical variation and thickness, lead to the suggestion that sedimentational controls played the major part in the development of the cyclic succession in the Coal Measures of the East Pennine Coalfield. Only three horizons are exceptional and suggest the possibility of regional diastrophic controls or world‐wide changes of sea level.