A palynological investigation of Upper Jurassic basal Cretaceous sediments from England, France and Iberia

A broad palynological study has been made of field samples of Kimmeridgian to Berriasian age from a number of localities in Western Europe:- 1) Southern England - Dorset; Kimmeridgian - Berriasian. 2) Eastern England - Norfolk; Portlandian - Berriasian. 3) Northern England - Yorkshire; Kimmeridgian. 4) Northwest France - the Boulonnais; Kimmeridgian - Portlandian. 5) North Spain - Ribadesella; Kimmeridgian 6) Portugal - Cabo Espichel; Kimmeridgian. An account of the origins, distribution and occurrence of various sedimentary organic materials (kerogens) is presented and the results obtained are discussed in the light of earlier accounts of the sedimentology, mineralogy, biostratigraphy and palaeogeography. Two applications of this data are demonstrated:- 1) Palynofacies types can be recognized which can be related to to environmental parameters such as distance from shore-line, water depth and turbulence. 2) The kerogen types present and their degree of maturation allow some comment to be made on the potential of the sediments for sourcing hydrocarbons. In particular it is demostrated that the highly bituminous Kimmeridgian sediments from Dorset and Yorkshire ha ve considerable potential for sourcing oil. Microplankton assemblages (dinoflagellate cysts and acritarchs are recorded and described from the English and French sections which are well dated upon independent palaeontological evidence. The various taxa constituting the microplankton assemblages are - described and in part illustrated in a systematic section. 195 taxa and taxonomiC groupings are recorded; 10 new genera, 19 new species and 1 new subspecies are proposed; in addition the diagnosis of 4 genera and 5 species are emended, 5 genera and 8 species are treated as junior synonyms and rejected, and 20 new taxonomic combinations are proposed. The recorded taxa have been tabulated qualitatively for each of the sections and a series of informal microplankton zones and associations of local stratigraphic value have been established. The data from these charts has been used to compile a range chart which incorporates 52 selected "key-species" for the Upper Oxfordian - Berriasian interval. Earlier studies concerning Upper Jurassic and Lower Cretaceous microplankton are reviewed in light of the present study. Although the above biostratigraphic units are mainly of local stratigraphic value only, the observations and results presented here have been substantiated and enlarged upon by work currently being undertaken by the writer. It is concluded that the use of palynological assemblages will provide a useful tool for correlation purposes and the elucidation of the depositional histories of marine basins. Furthermore it is considered that the use of micro plankton will provide a reliable time - strati graphical control in marine sediments of Late Jurassic - Early Cretaceous age