The search for "Jenyon's Channel": The missing link between the Permian basins in the North Sea

The Mid North Sea High (MNSH) Seaway, otherwise known as Jenyon's Channel, was the only major marine connection between the Northern and Southern Zechstein Basins during the latest Permian. Current understanding favours a model where marine replenishment began with a northern connection to the Panthalassic Ocean (along a network of basins that were precursors to the North Atlantic Rift System), after which marine water passed into the Northern Zechstein Basin, travelled through the MNSH Seaway before finally reaching the Southern Zechstein Basin. This study delineates evaporite formations in an extensive petrophysical dataset to analyse marine connections and whether they influenced Zechstein facies distribution. The first four Zechstein Cycles (Z1-Z4) are identified on the MNSH platform which shows that this structure was always covered by a thin water column during sea-level highstand; however, during Z2 sea-level lowstand, the MNSH Seaway provided the main connection between the basins. As relative sea-level fell, the MNSH Seaway became increasingly constricted resulting in hypersalinity due to limited volumes of marine water reaching the Southern Zechstein Basin. This system precipitated vast volumes of Z2 (late Wuchiapingian) halite in the Southern Zechstein Basin, whereas this facies remains reduced in the Northern Zechstein Basin. In Z3 and Z4 (Changhsingian) times relative average sea-level was higher resulting in sustained communication between the basins, even in times of sea-level lowstand. This is evidenced through a regionally traceable blanket of Z3 halite, along with occasional examples of Z2 carbonate platforms becoming entombed in Z3 halite. This work provides revised palaeoenvironmental understanding for the latest Permian. The workflow could also aid in the study of other oceanic gateways with further implications for hydrocarbon exploration efforts and emerging energy transition technologies such as subsurface storage on the UK Continental Shelf.