Aspects of the geology of the Malin Sea area

Abstract

A complex of sediment-filled graben and half-graben, separated by acoustic basement, occupy much of the northwest shelf of the British Isles. Some were established in the Late Carboniferous, but most were formed during a post-Hercynian tensional phase that adopted Caledonoid-trending structures in the basement. A major graben complex occurs in the Malin Sea area; flanked by the Coll-Tiree-Skerryvore-Stanton Banks basement ridge to the north and by the lslay-Donegal Platform to the south. Rock samples obtained by divers from the two basement ridges confirm their Precambrian character. Limited commercial multichannel reflection seismic data together with BIRPS WIRE lines and structural information supplied by Texaco suggest that the graben complex consists of three major depocentres: the Inner Hebrides Trough, the Malin Basin and the South Donegal Basin. To the west lies the Main Donegal Basin. This basin, in concert with the South Donegal Basin, evolved during the Carboniferous as a result of dextral strike slip movement between the Stanton Banks in the north and the Islay-Donegal Platform to the south. Sea bed core and dredge material and well data recovered from the graben complex indicate that the basin sediments include Upper Carboniferous, Permo-Triassic, Lower Jurassic, Middle Jurassic, with thick Cretaceous and Lower Tertiary in the far west. Periods of uplift and erosion restricted sedimentation during the late Mesozoic, whilst uplift and erosion in the early Tertiary was accompanied by extensive igneous activity, with the development of two plutonic centres and twelve other smaller intrusive igneous bodies. Tertiary sediments arc inferred for the Blackstones Basin by analogy with similar sequences elsewhere in the Hcbridean area. A thick Quaternary section, dominated by glaciomarine sediments, contains three of the five glacial cycles that constitute the Pleistocene in this area.

Constraints on a shallow offshore gas environment determined by a multidisciplinary geophysical approach: The Malin Sea, NW Ireland

“…The Malin Deep Pockmark Field lies on the Irish continental shelf approximately 70 km offshore northwest Ireland (Figure ). The area lies in the Malin Basin, situated in a complex structural setting, delimited to the north by the Stanton Banks fault and to the south by the Malin Terrace [ Dobson and Evans , ; Dobson and Whittington , ]. The Skerryvore fault, a major normal fault, divides the study area into two different basins, the Donegal Basin and the West Malin Basin.…”

“…Geological sketch of the Malin Sea area after Dobson and Whittington []. The red box indicates the study area, the Malin Deep Pockmark field.…”

Dolomitic breccia veins as evidence for extension and fluid flow in the Dalradian of Argyll

“…These trends influenced the location and extension of CarboniferousTriassic basins in the region (Anderson, Parnell & Ruffell, 1995). In particular, basins offshore to the west of Argyll with infills of Carboniferous to Triassic age are partially bounded or segmented by NW-SE faults (Dobson & Whittington, 1992), emphasizing the importance of this orientation in regional extension.…”

Influence of basement on the geometry of Permo-Triassic basins in the northwest British Isles

“…4)). However, some NW-SE faults developed in a dextral strike-slip regime during the late Carboniferous (Dobson & Whittington 1992) and were reactivated during the Mesozoic-Tertiary, in particular controlling Parma-Triassic subsidence (Evans et al 1980). These include those bounding the Colonsay and Loch Indaal Basins.…”