Evolving depositional geometries in the North Sea Jurassic rift

Abstract

The tectonic history of the North Sea during the Middle and Upper Jurassic consists of initial basin-scale uplift, followed by subsidence. The subsidence is at least partly associated with a major rifting episode culminating in the Early–Mid-Kimmeridgian. Shallow marine depositional cycles of progradation and retrogradation are recognized throughout this time interval, with a periodicity of 1–5 million years.Twelve of these units, selected from data-constrained study areas, are described, and quantified data are presented on their geometry, duration, and the implied variations in accommodation volume.Sediment input rates into the basin decreased through the Middle and Upper Jurassic as hinterlands were drowned, and source/basin relief decreased. A corresponding evolution in the geometry of the units is seen, from wide tabular units in the Bajocian/Bathonian to narrow ribbon-geometry units in the Kimmeridgian.The continued decrease in sediment input resulted in an interval of basin-wide marine condensation. On seismic data this forms a prominent surface of marine onlap known as the Base Cretaceous (or Late Cimmerian) ‘Unconformity’.This pattern of decreasing depositional dimensions of shelf/shoreline systems is to be expected in marine rifts without access to continental drainage systems, where sediment supply decreases with syn-rift and post-rift subsidence of drainage basins. This decrease may happen throughout the late pre-rift to early post-rift, and the change from structure-independent to structure-dependent facies trends may not occur suddenly at the onset of rifting.

Changes in physical properties of a reservoir sandstone as a function of burial depth – The Etive Formation, northern North Sea

“…The basin have been subjected to two main rift episodes since Devonian time, on in Permian to earliest Triassic and a second in Late Jurassic to earliest Cretaceous, which both were followed by post-rift thermal subsidence (Ziegler and von Hoorn, 1989;Gabrielsen et al, 1990;Roberts et al, 1990;Ziegler, 1990;Yielding et al, 1992;Ziegler, 1992;Milton, 1993;Rattey and Hayward, 1993;Nøttvedt et al, 1995;Faerseth, 1996;Faerseth et al, 1997;Christiansson et al, 2000;Odinsen et al, 2000a,b). The Brent Group was deposited in the northern Viking Graben area prior to onset of Late Jurassic rifting, and the deposition of these sediments were mainly controlled by the thermal subsidence following the Permian-Triassic rift event (Yielding et al, 1992).…”

Controls on Upper Jurassic sediment distribution in the Durward–Dauntless area, UK Blocks 21/11, 21/16

“…The position of the most proximal facies within the progradational genetic unit is referred to here as the surface of maximum regression (mrs), equivalent to the maxim u m extent of progradation (e.g. Milton 1993). The correlation between the sequence framework employed here and other stratigraphic schemes is shown on Fig.…”

“…In this part of the WCS, progressive coastal onlap culminates in the widely documented eudoxus mfs sea-level maximum, which occurs throughout the Central North Sea (e.g. Donovan et al 1993;Milton 1993;Partington et al 19936;Underhill & Partington 1993;Carruthers et al 1996;Davies et al 1996;Harker & Rieuf 1996).…”

Fulmar: a mature field revisited

“…However, ongoing crustal thinning and subsequent post-rift thermal cooling created a dominantly transgressive depositional regime during the Oxfordian to Kimmeridgian, which resulted in the development of an overall back-stepping trend within the basin (Partington et al 1993). This transgressive trend was further enhanced by a reduction in sediment supply, as hinterlands were drowned (Milton 1993). Basin formation in the Greater Fulmar area started in the northeast, during the Oxfordian, and progressed in a southwesterly direction affecting the Fulmar Field during the latest Oxfordian to early Kimmeridgian.…”