Early Cretaceous palynology of the Upper Member of the Missisauga Formation in Panuke B-90, Scotian Margin, Canada.

Biostratigraphic studies of Mesozoic-Cenozoic strata along the Scotian Margin began in the early 1970s, focussing on zonation schemes for separate disciplines. Subsequent works, however, have evolved into an event stratigraphic approach, combining palynologic with micropaleontologic and nannofossil events, as well as seismic horizons. Extensive taxonomic treatment of Late Cretaceous and Cenozoic palynomorphs from the Scotian Margin were also undertaken but did not encompass the Triassic to Early Cretaceous interval. Thus, we aim to develop a detailed taxonomic review and a comprehensive event-stratigraphic scheme for this earlier interval based on palynology, integrated with paleoenvironmental and sequence stratigraphic interpretations. Our initial focus is on conventional cores in Panuke B-90 and Cohasset A-52 to develop a composite Lower Cretaceous succession, supported by analyses of cuttings from deeper wells that penetrate pre-Cretaceous strata (e.g., Argo F-38) to provide a broader context. The sedimentary facies, trace fossils and initial palynologic data of the Panuke B-90 cores indicate, at the base, a transition from a shoaling marine to a mainly estuarine setting, followed by a transgressive cycle through the Upper Member of the Missisauga Formation that culminates in normal marine environments again near the base of the overlying Naskapi Member of the Logan Canyon Formation. It is apparent that this transgression is not continuous but intercalated with smaller cycles, well documented by the fluctuations of terrestrial (pollen and spores) versus marine (mainly dinoflagellate cysts) palynomorph dominance across this interval. The assemblages from the Upper Member of the Mississauga Formation are typical of the Early Cretaceous, probably Barremian. An Aptian age is expected for the overlying Naskapi Member based on previous studies that reported the presence of the age-diagnostic ammonite Deshayesites sp. Ongoing work on the Panuke B-90 conventional cores and coeval successions will contribute to a comprehensive event-stratigraphic framework for the Scotian Margin. [ABSTRACT FROM AUTHOR]