Aalenian and Bajocian transgression sequences in the southeastern Paris Basin, France

Sedimentologic, biostratigraphic and diagenetic studies made on Middle Aalenian to Lowermost Bathonian deposits in 25 outcrops of the Burgundy High (southeastern Paris basin) lead to a sequence stratigraphy subdivision of the early Dogger record into 7 third order depositional sequences. These sequences make up a second-order transgressive phase whose lower limit is a tectonically enhanced unconformity (the Mid-Cimmerian unconformity), associated with a large scale uplift during the Upper Toarcian and the Lower Aalenian. In the largest outcrops, where the geometry of sedimentary bodies is observable at the hectometre to kilometre scale, the combination of diagenetic, biostratigraphical, spatial and sedimentologic studies is useful to understand the evolution of sediment distribution in the sequences. This approach also allows the measurement of sea level falls at the origin of the sequence boundaries. For example, we show that Lower Bajocian sequences end with decreases of accommodation space <10 m in amplitude, leading to temporary emergences of some reef complexes. Without interrupting the sedimentation on submarine peri-reef pediments during lowstands, these decreases of a few metres of accomodation space can be related to either tectono-eustatic events or thermo-eustatic events.