Micropalaeontological dating of the prémontré mammal fauna (MP10, Prémontré Sands, EECO, early late Ypresian, Paris basin)

Abstract

At their type locality the Prémontré Sands contain fairly well-diversified organic-walled microfossil assemblages attributable to the lower part of dinoflagellate cyst Zone D9 and indicating a transition from an estuarine to a lagoonal depositional regime, up-section as well as laterally. Identical assemblages have been recorded in the inner to mid-neritic Merelbeke Clay Member in Belgium, allowing the Prémontré Sands to be positioned within lower NP13 and early Chron C22r. The deposition of the MP10 Prémontré mammal fauna is estimated to postdate the onset of both NP13 and Chron C22r, which are nearly coincident, by about 200 to 300 kyr. The biostratigraphic dating refers this deposit to the early late Ypresian and to the final phase of the Early Eocene Climatic Optimum (EECO) at about 50.4 to 50.3 million years ago. The Prémontré Sands, as well as their distal equivalent the Merelbeke Clay Member, were deposited following a major sea-level rise, the highest of the late Ypresian in the southern North Sea Basin s.l. (including the Paris Basin). They are separated from the overlying “Glauconie grossière” (zone NP14; middle part of zone D9) by a hiatus of approximately 2.5 myr.