The tectono-stratigraphy of the Solan Basin, west of Shetland

Abstract

The Solan Basin lies in a part of the West Shetland continental margin that has had a complex tectonic history, dominated by extension but punctuated by several episodes of inversion, transpression and extensive erosion. The oldest sedimentary sequence, identified on seismic but not yet penetrated by drilling, may comprise Devono–Carboniferous clastics. In the Permo-Triassic a large system of half-grabens was filled with a thick succession of coarse, continental clastics. These appear to have entered the basin system in two discrete pulses and it is speculated that a third pulse, representing a transition to marginal and fully marine environments, occurred in the Early Jurassic. The area was effectively peneplaned in the late Middle to early Late Jurassic, with the removal of up to 1.5 km of section. Overlying this unconformity is a thin sequence of marginal marine sandstones and organic-rich marine shales, deposited in the latest Jurassic to earliest Cretaceous. Although parts of the region received a major influx of sand derived from the West Shetland Platform in the Early Cretaceous, the equivalent strata throughout most of the Solan Basin are a thin succession of pelagic shales and carbonates. In the early Turonian the basin was inverted. During the Late Cretaceous, extension, related to rifting along the line of the Faeroe–Shetland Trough, resulted in the development of large normal fault systems, providing the space in which a thick sequence of deep marine shales was deposited. In the earliest Paleocene, transpressional reactivation of some faults produced intense, but localized, inversion structures. Generally, however, sedimentation continued uninterrupted through the Paleocene, with the accumulation of deep marine sandstones in the east of the basin. The culmination of Thulean volcanism in the earliest Eocene was marked by the deposition of tuffaceous mudstones, which are overlain by thin coal-bearing, paralic to continental sediments. Regional thermal subsidence began in the early Eocene and continued into the Oligocene with the deposition of a thick sequence of marine clastics. In the Miocene, erosion removed up to 1.2 km of sediment from parts of the Rona Ridge and produced a basin-wide unconformity. This is overlain by Pliocene to Recent glacio-marine sands and gravels.

An overview of the Upper Palaeozoic–Mesozoic stratigraphy of the NE Atlantic region

“…14b). In general, a tripartite subdivision has been established for this area: (1) an upper clastic succession assigned to the Triassic Papa Group, which predominates across the region (Booth et al 1993;Ritchie et al 1996;Quinn & Ziska 2011); (2) a middle evaporite succession that has been assigned to the West Orkney Evaporite Formation of the Late Permian Zechstein Group (Ritchie et al 1996); and (3) a lower sequence of sandstone and conglomerate of the Solan Bank Formation, originally assigned by Ritchie et al (1996) to the Zechstein Group, although reassigned by Glennie (2002) to the Upper Rotliegend 2 unit, comparable with the Late Permian sequences in the North Sea Basin (Glennie et al 2003) (Fig. 9).…”

“…The Upper Cretaceous sequence is more widely developed and by the end of the Cretaceous period most of the major basement highs, including the Rona High, had been isolated or drowned (Dean et al 1999;Stoker & Ziska 2011). In the Faroe -Shetland region, an angular unconformity separates folded and eroded Turonian and older strata from Coniacian -Maastrichtian rocks in the West Shetland, North Rona, East Solan and West Solan basins, as well as the Foula Sub-basin (Booth et al 1993;Dean et al 1999;Goodchild et al 1999;Grant et al 1999;Stoker 2016). In other West Shetland Shelf basins, much of the Cenomanian -Turonian section is absent, and the unconformity essentially separates Upper and Lower Cretaceous (Fig.…”

The origin and genesis of major Jurassic unconformities within the triple junction area of the North Sea, UK

“…10) show that the intra-Callovian unconformity is related to active fault block rotation. It may be no coincidence that in the Solan Basin, west of Shetland, Booth et al (1993) suspect that a major intra-Callovian unconformity marks the development of large half-graben structures. The actual stratigraphic gap noted in the wells within this study area appears to increase onto present intra-rift highs (for example the Puffin High) and onto rift flanks (for example the Kittiwake Platform).…”

Cretaceous revisited: exploring the syn-rift play of the Faroe–Shetland Basin

“…The main episode of Cretaceous rifting began in the Valanginian as dated by coarse, clastic sediments in wells from the West Shetland and Solan Basins (Booth et al 1993). Although the presence of older faults is acknowledged in the study area, the recognition of NE-SW oriented faults of Aptian -Albian age is interpreted as a significant and dominating overprint.…”