Sequence palynology of the lower Jurassic (Sinemurian - Toarcian) strata of N.W. Europe

Quantitative palynological and palynofacies analyses of sediments have been interpreted and described within a genetic sequence stratigraphic framework for the Lower Jurassic succession of the Dorset Coast (England), the Pliensbachian stratotype section at Pliensbach, Baden-Württemberg, Germany and the Pliensbachian - Toarcian boundary section at Zell-unter-Aichelberg, also in Baden-Württemberg.Insoluble organic matter, when acid-macerated from a sediment, has been utilised to interpret the environment prevailing when the sediments were deposited. It has proved possible to determine variations in the proximal-distal location of the depocentre with respect to sedimentary source and the regressive-transgressive trends in a stratigraphic sequence through the study of consecutive palynofacies assemblages. The multifaceted approach employed assessed various palynological criteria adopted from published sources (e.g. both relative and absolute particle abundance data, ratio's of allochthonous versus autochthonous palynomorphs, phytoclast type, etc.), as well as parameters developed herein (e.g. ratios of acritarch spine length).Interpretation of palynofacies trends within the Dorset succession (Sinemurian - Lower Toarcian) identified eight distinct genetic sequences, informally designated Genetic Sequences I to VIII. Maximum flooding surfaces are placed at the following horizons: Mongrel, Grey Ledge, Pavior, the Coinstone, Hummocky, the Belemnite Stone, Day's Shell Bed and the margaritatus Stone. Maximum flooding surfaces in the Dorset succession were observed to coincide with significant first and last appearance datums for a number of microplankton taxa.Between study areas it has been possible, often irrespective of lithology to recognise and correlate discrete genetic sequences by studying the characteristic palynofacies signature of each signature and its constituent microplankton assemblage. Interpreted results, for all three sections, are compared with published sequence strategraphic frameworks (developed by alternative means), for the Lower Jurassic interval both in Dorset and elsewhere in NW Europe.