Foraminiferal response to mid-Cenomanian (Upper Cretaceous) palaeoceanographic events in the Anglo-Paris Basin (Northwest Europe)

We have analysed the sedimentology, macrofossil event horizons (including pulse faunas) and foraminiferal succession (80 samples) from an 8 m succession in the upper Lower and lower Middle Cenomanian (Upper Cretaceous) at Folkestone, Southeast England. Comparative sedimentological analysis of successions in southern and northeastern England indicates the presence of three hierarchies of cycle: 20 kyr productivity (chalk-marl couplets) cycles attributed to the Milankovitch precession cycle; 100 kyr sea-level cycles attributed to the Milankovitch eccentricity cycle; and 1 Myr cycles attributed to longer-term sea-level cycles. Previously recognised macrofossil pulse faunas occur preferentially at the bases of the 100 kyr eccentricity cycles. We analysed the foraminiferal fauna across the Lower-Middle Cenomanian boundary at Abbottʹs Cliff, Folkestone, in great detail (80 samples in 8 m). The foraminiferal succession is also intricately related to the 1 Myr sea-level, and 100 kyr eccentricity cycles. Changes related to the long-term cycles include variations in the abundance of the benthic foraminifera Tritaxia, Gyroidinoides, Lingulogavelinella and Dorothia, and an increase in benthic diversity in the transgressive deposits. Changes related to the 100 kyr eccentricity cycles include: the presence of Rotalipora ex gr. reicheli in the lower part (and rarely upper part) of cycles; the abundance of planktics (both absolute and relative) in the middle to upper part of cycles; an increase in the proportion of Gavelinella berthelini and G. reussi in the upper part of cycles. We present a stratified water column model to explain the changes related to the 100 kyr scale cycle.