Sedimentary dynamics of the Anglo-Paris Basin during the Aptian-Albian period

The Aptian-Albian deposits of the Anglo-Paris Basin consist of terrigenous sediments formed in shallow continental and coastal environments within an extensional intracratonic basin. The Aptian-Albian interval is rarely exposed, except in the Wessex Basin, where subsiding sub-basins developed during the Early Cretaceous and were later exposed due to tectonic inversion (Chadwick, 1993). Outcrops in southern England, Cap de la Hève (Normandy), and Burgundy quarries complement subsurface data from Paris Basin drill cores. Stratigraphic correlations from wireline logs and outcrops at the basin's margins have highlighted nine transgressive/regressive cycles constrained by biostratigraphy, showing subsidence variations between the Paris and Wessex Basins.

The Lower Aptian deposits are affected by the sub-Aptian discordance. In the Paris Basin, many ammonite-bearing zones are absent due to significant erosion, and the Lower Aptian deposits consist of marine shales. This interpretation is supported by signs of reworking, attributed to localized tidal influences, ruling out offshore deposition. In contrast, the Lower Aptian in the Wessex Basin is unaffected by the sub-Aptian unconformity and records thick sand layers resulting from deltaic progradation eastward, with significant subsidence located in the Isle of Wight (Channel Basin).

During the Upper Aptian, southern England and the English Channel are marked by lower subsidence and are characterized by estuarine deposits of the Sandrock Formation. In the Paris Basin, Late Aptian subsidence was also significant and accompanied by major hiatuses in ammonite’s zones, with the Sables Verts deposited in estuarine and tidal-dominated environments overlying an unconformity. The Wessex and Paris basins were separated by the "Hampshire-Dieppe” structural High (Jollivet-Castelot 2018), forming the northern boundary of the Paris Basin.

The onset of the Albian marks a shift in dynamics between the Paris and Wessex Basins. In the Wessex, reduced subsidence led to continental sedimentation (Monk’s Bay Sandstone Formation) over an erosion surface. Meanwhile, increased subsidence in the Paris Basin resulted in the deposition of the Sables des Drillons, indicating a shift from transgressive tidal-dominatedsands to regressive shoreface deposits. Structural highs in the northern basin continued to limit communication between the basins.

The Middle Albian is characterized by diachronous subsidence between the Paris and Wessex Basins. In Wessex, the Gault Clay Formation was deposited due to significant subsidence, while in the Paris Basin, this period corresponds to the deposition of the Sables de Frécambault, indicating littoral sands progradation followed by offshore clay deposits with Gault facies at the top of the Middle Albian. This marks the first communication between sub-basins, forming the Anglo-Paris Basin. The  top of the Middle Albian is marked by a significant regression, with incised valleys filled with fluvio-estuarine deposits, preceding the major Late Albian transgression marked by shale sedimentation with Gault facies, heralding the major Cenomanian transgression.

The Upper Albian is marked by homogeneous subsidence in both basins, strengthening communication with marine domains such as the North Atlantic and North Sea (Amédro and Matrion, 2014). In the Wessex, tidal-dominated shallow marine deposits (Upper Greensand Formation) transition eastward into outer platform deposits (Rawson, 2006), while in the Paris Basin, the Late Albian corresponds to outer platform deposits (Gault Formation).