Metcalfe 1976 PhD Thesis

Abstract

The conodont faunas of the Lower Carboniferous succession of the Craven Lowlands of Yorkshire and Lancashire are described. Sections in the Skipton, Clitheroe, Broughton, Swinden and Eshton-Hetton Anticlines have been sampled. The sampled sections were measured and the logs of these are presented.

A total of 16,082 conodonts have been extracted from 402 digestible samples and 74 species including four subspecies identified, belonging to 28 genera. These are systematically described and possible phylogenetic relationships discussed. Observations are made using a scanning electron microscope on the micro-ornamentation of selected specimens. One new named genus and species, Embsaygnathus asymmetricus, four other new genera and species and five new species referrable to existing genera are proposed.

Tables giving the numerical distribution of species and abundance figures for the sampled sections are presented. Six concurrent range zones and one subzone are proposed based on the first appearances of selected species. The zones are in ascending order:-Pseudopolygnathus multistriatus zone, Mestognathus beckmanni - Polygnathus bischoffi zone, Gnathodus homopunctatus zone, Gnathodus commutatus zone with a Gnathodus girtyi subzone at the top, Gnathodus bilineatus zone and Gnathodus nodosus zone. The proposed zones are correlated with conodont zones and sequences elsewhere in Britain, Belgium, Germany, Spain and Portugal, North America and Australia.

Correlations within the Craven Basin are made using the conodont zones and the stratigraphical implications of these correlations are discussed. The succession and structure of the Broughton Anticline is modified following work on the cores of 21 boreholes sunk in the area. The relationship of the sedimentary cycles of Ramsbottom (1973) to the Craven Lowlands sequences is discussed and the positions of the Cycle 2/Cycle 3 and Cycle 4/Cycle 5 boundaries modified. The Cycle 1/Cycle 2 boundary is recognised in the St. Helen's Well Borehole sunk into the Eshton­Hetton Anticline. A brief description of the probable facies variation from Clitheroe-Swinden-Broughton-Skipton and tentative interpretations on sedimentation in the Craven Basin are made.