Continental sedimentation, soil genesis and marine transgression in the basal beds of the Cretaceous in the east of the Paris Basin

Abstract

ABSTRACTIn the eastern Paris Basin, on the boundary of two French ‘départements’, Marne and Meuse, the Cretaceous deposits begin with Wealden facies assigned to the Valanginian. This is overlain by marine Hauterivian and Lower Barremian.Several techniques have been used for studying these deposits: light‐microscope, scanning electron microscope, grain‐size analysis, chemical and mineralogical analysis.Environmental interpretations of the various facies are based on sedimentological, geochemical and pedological criteria (fossil soils are present). Clay minerals are dominantly illite and kaolinite. In the soil horizons kaolinite is dominant. A mixed‐layer illite‐smectite appears at the base of the transgression. Under marine influence a more stable illite dominant suite is formed.The Wealden sediments appear to have been deposited in a very mature flood‐plain. Part of the sequence was subjected to weathering in situ by soil processes under a warm climate with repeated wetting and drying. Paraconformably above, the marine Hauterivian is the product of a shallow sea that tended to form lagoons. A true marine environment was established in the Lower Barremian, when mixing homogenized the sediments.