Dinocyst distributions and stratigraphy of two Cenomanian–Turonian boundary (Upper Cretaceous) sections from the western Anglo-Paris Basin

Abstract

Abstract. The dinoflagellate cyst distributions and stratigraphies of two representative Cenomanian/Turonian (C/T) boundary sections from the Maine and Normandy regions of northern France are described. Siliciclastic-rich sediments which characterize the Upper Cenomanian in Maine, contrast with the coeval nodular chalk and hardground lithofacies of Normandy. Both areas display a transition to marly chalks in the Lower Turonian. Dinocyst assemblages are characterized by low diversities (38 taxa) and low overall abundances, and relatively few stratigraphically significant species. The continued occurrence of Epelidosphaeridia spinosa (Cookson & Hughes) Davey in the Upper Cenomanian of Maine is noted. Results are compared and contrasted with those from coeval sections elsewhere in the Anglo-Paris Basin. A major decline in cyst abundance and diversity is typical of the C/T boundary interval, which is characterized by a dominance of tolerant cosmopolitan forms such as Circulodinium distinctum (Deflandre & Cookson) Jansonius, Hystrichosphaeridium bowerbankii Davey & Williams, Oligosphaeridium complex (White) Davey & Williams, Odontochitina costata Alberti; emend. Clarke & Verdier and O. operculata (O. Wetzel) Deflandre & Cookson.

Biotic and Isotopic Vestiges of Oligotrophy on Continental Shelves During Oceanic Anoxic Event 2

“…In oceanic conditions, it is widely accepted that the dominance of heterotrophic dinoflagellate cyst assemblages can be indicative of active upwelling (Pospelova et al., 2006; Reichart & Brinkhuis, 2003), which is rather ambiguous in shelf environments (Aytan et al., 2018). The absence of heterotrophic dinoflagellate cysts in the lower part of the section and their insignificant contribution in the upper part is in clear contrast with previous studies from England, France, and Spain (Clarke & Verdier, 1967; Foucher, 1979; Dodsworth, 2000; Peyrot et al., 2011; Robaszynski et al., 1980; Tocher & Jarvis, 1995) where dinoflagellate assemblages in the Cenomanian‐Turonian boundary interval were conspicuously dominated by these forms. This may be related to differences in the characteristics of these basins, such as the depth and palaeogeographic location, and in particular the distance to the continental slope where upwelling could have been a substantial driver of nutrient availability.…”

Trans-Atlantic dinoflagellate cyst stratigraphy across the Cenomanian–Turonian (Cretaceous) Stage boundary

“…A marked decrease in the diversity and abundance of dinoflagellate cysts has been reported from the uppermost Cenomanian -lowermost Turonian at some localities (e.g., Jarvis et al, 1988;Nuiiez-Betelu & Hills, 1995;Tocher & Jarvis, 1995;FitzPatrick, 1996;. It has been suggested that a major reduction in primary productivity, chiefly of coccolithophores but including that of dinoflagellates, could have led to starvation higher up the food chain and the marked turnovers of foraminifera and molluscs documented from the interval (Lamolda et al, 1994;Paul & Mitchell, 1994).…”

<i>Senoniasphaera turonica</i> (Prössl, 1990 ex Prössl, 1992) comb. nov., senior synonym of <i>Senoniasphaera rotundata alveolata</i> Pearce <i>et al</i>., 2003: an important dinocyst marker for the Lower Turonian chalk of NW Europe

“…The rationale for describing this form at sub-specific level was to retain the species name S. rotundata as a regional marker for the Lower Turonian since the name was in popular usage (e.g. Robaszynski et al, 1982;Jarvis et al, 1988a,b;FitzPatrick, 1995;Tocher & Jarvis, 1995;Lamolda & Mao, 1999) and it is synonymous with a well-established Lower Turonian zone (e.g. Foucher, 1980Foucher, , 1981.…”