Depositional trends in the Upper Jurassic-Lower Cretaceous of the northern margin of the Wessex Basin

In the exposed Upper Jurassic and Lower Cretaceous sediments along the northern margin of the Wessex Basin (Buckinghamshire to Wiltshire), structural and minor depositional basin orientations are often aligned NW to SE. Local depocentres in the late Jurassic and earliest Cretaceous rarely coincide with those of the mid-Cretaceous Lower Greensand. The “inversion” of these sub-basins is commonly across major NW-SE orientated faults; this change in the position of basins subsidiary to the Wessex Basin occurred in the time gap now represented by the base Lower Greensand unconformity (?Berriasian-mid-Aptian). It was during this time that subtle (or long term) shifts in basement structure became amplified. In this case sub-basin inversion is adequately explained by a long sedimentary hiatus rather than short lived active tectonism.