During much of the Triassic, Britain was largely an emergent landmass with little marine deposition. The main phase of marine deposition only occurred at the end of the Triassic, within the Rhaetian Mercia Mudstone Group, Blue Anchor Formation and the succeeding Penarth Group. A brief marine incursion, probably from the north, also occurred in the middle Triassic. Few ostracod assemblages are known from this period. The main Triassic outcrop and key sites in the British Isles are illustrated in Figure 1.
Globally, Triassic ostracod assemblages are generally of low diversity following the end-Permian extinction and the British record is no exception. It is the late Triassic eustatic sea-level rise that opens new biotopes on the transgressed landmasses and mixes marginal marine faunas with new pioneer species.
Figures & Tables
This book charts the stratigraphical distribution of ostracods in the Cambrian to Pleistocene deposits of Britain and outlines their utility for dating and correlating rock sequences, as well as indicating aspects of their palaeoenvironmental and palaeogeographical significance. These small bivalved crustaceans are the most abundant arthropods in the fossil record. Indeed, the stratigraphy of Britain, which embraces many type-sequences, provides a particularly rich and full record of them, from at least the basal Ordovician, and from the British Cambrian there is a biostratigraphy based on their ‘relatives’, the bradoriids and phosphatocopids. Ostracod distributions demonstrate the ecological success story of the group, occupying as they do marine, non-marine and even ‘terrestrial’ habitats. Written by current specialists in the field, this book is an authoritative account and will be welcomed by all micropalaeontologists and applied geologists in the industrial and academic world alike. It is richly illustrated with over 80 plates of electron micrographs and specially drawn maps, diagrams and range-charts.