Sequence Stratigraphy and Process Sedimentology of the Cambrian of Wales

A. J. Rees
University of Birmingham, School of Earth Sciences, Birmingham, UK

Outcrops in theWelsh Basin formed the basis upon which the Cambrian System was originally founded. Despite a long history of research, many aspects of Welsh Cambrian stratigraphy remain poorly understood in modern terms.

The study aims to ratify this anomaly by the development of a robust reference stratigraphy based on outcrops in the Pembrokeshire region of SW Wales. Central to this goal is the application of modern sedimentological (regime theory) and sequence stratigraphical methods to obtain a vertical framework of orderly, predictable facies relationships of chronostratigraphic significance. Once established, this will act as a powerful tool in correlation, and allow direct comparison within the basin (North Wales and the Midland Platform) and also test the validity of the unifying “Avalonian” stratigraphy being developed in southeastern Newfoundland.

Recognition and interpretation of sediment transport paths has played a pivotal role in past environment and basin studies and is considered of utmost importance in environmental interpretation of shelf sequences. Unfortunately, outcrops in Pembrokeshire are often devoid of primary sedimentary structures used for such interpretation and therefore it was decided to test the application of magnetic fabric analysis (anisotropy of magnetic susceptibility) to paleocurrent determination. Preliminary results from Middle Cambrian (St. David’s Series) storm beds and Upper Cambrian (Merioneth Series) tidalites are encouraging.

AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid