Conodonts, correlation and stratigraphy of the Plymouth limestones

Orchard, Michael James

Abstract

This work embraces the study of the conodonts and the environments of the Plymouth Limestones (Devonian, South Devon).

Widespread sampling of calcareous strata in the Plymouth area has produced conodonts indicative of high Emsian to mid-Famennian levels.

The European Conodont Standard is reviewed and comparisons are made with North American and Australian successions; the South Devon faunas are examined and discussed in their light. The results indicate that, on the whole, the Upper Devonian faunas are comparable but Middle Devonian successions differ in some respects. Most of the diagnostic conodonts are treated systematically and several new form-species are introduced. Correlation based on the conodont faunas are presented for most of the disjunct sections.

The Plymouth Limestones are discussed in the context of the Variscan geosyncline and Cornubian palaeogeography. A review of the Devonian carbonate buildups, and the facial differentation therein, is followed by an assessment of the local situation in terms of possible European counterparts. It is suggested that the carbonate complex developed in an area of shallowing within the geosyncline and was unrelated to a northern shelf. ' ’Rather, a restricted environment is indicated to the east and southeast in which direction a Plymouth Schwelle may have had its maximum relief. Conodont biofacies are discussed and assessed in relation to the Plymouth distributions and the inferred environmental picture.

An appendix includes biostrati graphical detail, and diagrammatic presentation of sample location and composition and distribution of the conodont faunas in space and time. The conodonts are illustrated on thirty-six plates of stereoscan photographs.

Citation

Orchard, M. J. Conodonts, correlation and stratigraphy of the Plymouth limestones. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4222750

• Thesis Type: Thesis
• Deposit Date: Nov 16, 2020
• Publicly Available Date: Feb 23, 2023
• Keywords: Geology
• Public URL: https://hull-repository.worktribe.com/output/4222750
• Additional Information: Department of Geology, The University of Hull
• Award Date: Jul 1, 1975