Page 92 - An Atlas of Carboniferous Basin Evolution in Northern England

Chapter 6

Summary

The structures that controlled the Carboniferous tectonic and stratigraphic environments in the south were finally drowned in the early post-rift syn-rift depocentres. Syn-rift siliciclastic reservoirs, associated with the early
development of northern England were inherited from the earlier Caledonian (Pendleian) when the supply of terrigenous clastic sediments outpaced rift phase are located within the isolated, rifted, half graben. Carbonate
orogeny which imparted a strong NW-SE and NE-SW tectonic grain that is subsidence for the first time. Following this, rapid southward progradation reservoirs are controlled by the rift topography and the most prospective rim
evidenced on surface and subsurface data throughout northern England. The of the delta systems occurred as a series of pulses largely controlled by eustatic the margins of the deeper half graben in the south of the province. Delta top
subsequent Variscan plate cycle, which involved the closure of the Rheic and sea-level changes, but with important local controls, namely antecedent rift channel and mouth bar reservoirs are best developed where they axially infill
Rheno-Hercynian oceans, controlled the development of syn-rift, post-rift and physiography. By the early Westphalian, delta top conditions had been remnant rift bathymetry.
inversion megasequences from late Devonian to early Permian times. established over most of northern England. These conditions were progres- Mesozoic burial, ensuring hydrocarbon generation post-dating Variscan
Regionally extensive, seismically resolvable sequences developed within the sively disrupted from late Westphalian C times by inversion related to the trap formation, is considered to be the main control on the present day
Carboniferous were controlled by episodic rifting and fault reactivation, with Variscan orogeny. distribution of hydrocarbons in northern England (Fig. 62). Areas such as the
eustatic sea-level changes providing a high frequency control on depositional Over 70 years of exploration in northern England has resulted in the central Pennines and Northumberland and Stainmore basins which received
sequences that are generally below seismic resolution. discovery of 75 million barrels of recoverable reserves. All hydrocarbon limited Mesozoic burial are considered to have poor hydrocarbon potential.
In the south of the province during the Dinantian, carbonate environments discoveries to date within the Carboniferous have shown some element of The Cleveland, Manx-Furness and Cheshire basins where Mesozoic burial was
were extensively developed in syn-rift basins starved of terrigenous elastics. The Variscan deformation in their trap geometry. Tectonics have also exerted a excessive have gas as the major hydrocarbon phase. The East Midlands, where
north of the region was dominated from early Dinantian times onward by a subtle, but important control on play fairway evolution (Fig. 62). The main Mesozoic burial and post Variscan trap modification have been moderate, has
southward prograding terrigenous clastic delta system. The carbonate source rocks, developed in distal pro-delta environments, are restricted to the therefore emerged as the most successful oil province in northern England.