Response of Middle Jurassic shallow-marine environments to syn-depositional block tilting: Isles of Skye and Raasay, NW Scotland

Abstract

The Hebridean Province of NW Scotland provides insight into the interaction between tectonics and shallow-marine and tidal strait depositional environments in the Sea of the Hebrides and Inner Hebrides basins. The study tests the influence of syn-depositional block tilting on gross thickness, sand to mud ratio and the distribution of shallow-marine facies in the resulting succession. New Middle Jurassic palaeogeographical maps and stratigraphic correlations are presented that integrate both outcrop and well data and illustrate the evolution of the deltaic sedimentary system in a broad, semi-regional context. Results show that distance from the sediment entry point and the syn-rift tectonic geomorphology were the critical controls on gross thickness, sand to mud ratios and facies types. The impact of relative sea-level change is hard to detect in locations proximal to the Scottish hinterland, where sediment supply was large relative to accommodation (Ss > Ac), but becomes more influential in distal locations where eustasy and tectonic subsidence convolved to increase the influence of accommodation over sediment supply (Ac > Ss). Supplementary material: An outcrop to well log correlation exercise is available at https://doi.org/10.6084/m9.figshare.c.4397858

Catastrophic caldera-forming eruptions and climate perturbations: the result of tectonic and magmatic controls on the Paleocene-Eocene Kilchrist Caldera, Isle of Skye, NW Scotland

“…Skye is situated within two Mesozoic extensional basins which are bounded by NNE/NE-SSW/SW-orientated faults (Figure 1B). North Skye lies within the Sea of the Hebrides Basin which is bounded by the Minch and Camasunary Faults, and South Skye lies within the Inner Hebrides Basin, which is bounded by the Camasunary and Strathconon Faults [Morton 1992;Archer et al 2019]. Both basins are half grabens, developed on ESE orientated downthrown hanging wall blocks [Butler and Hutton 1994] and both the Cuillin Centre, and eastern margin of the Western Red Hills Centre, are juxtaposed with the Camasunary Fault which bounds both basins.…”

“…Both basins are half grabens, developed on ESE orientated downthrown hanging wall blocks [Butler and Hutton 1994] and both the Cuillin Centre, and eastern margin of the Western Red Hills Centre, are juxtaposed with the Camasunary Fault which bounds both basins. Multiphase rifting which generated growth of these basins ceased at the end Jurassic in the North Sea [Archer et al 2019]. The Camasunary Fault partially crops out at Camasunary Bay (Figure 2), but elsewhere on Skye has been largely obscured by Paleocene intrusions.…”

“…The trace probably then extends below the westernmost exposures of pyroclastic rocks on Belig [Peach et al 1910;Bailey 1955;Bell 1966]. To the north and east of the Camasunary Fault are three further Mesozoic extensional faults [Roberts and Holdsworth 1999;Archer et al 2019] (Figure 1B and D): 1) the Scalpay House Fault; 2) the Beinn nan Leac-Applecross Fault; and 3) the Screapadal Fault (aka Raasay Fault). The Camasunary Fault links kinematically with the Screapadal Fault via a series of NW-SE-trending transfer zones, which have been considered influential in localising granite intrusions on Skye [Butler and Hutton 1994].…”

Geology and petroleum prospectivity of the Sea of Hebrides Basin and Minch Basin, offshore NW Scotland

“…Renewed rifting and an establishment of shallow marine conditions during the late Toarcian led to the deposition of the Dun Caan Shale Member of the Bearreraig Sandstone Formation, before an influx of clastic sediment during the Aalenian led to the deposition of the remainder and bulk of the marginal marine, tidally influenced Bearreraig Sandstone Formation (Morton 1983;Morton 1992b;Mellere & Steel 1996;Archer et al 2019). Rifting within both basins continued until the late Bajocian, when thermal subsidence permitted the deposition of the late Bajocian to late Bathonian aged Great Estuarine Group (Morton 1992b).…”

“…Onshore Skye, thick packages of middle Jurassic sandstones in the SOHB are identified within the shallow marine Bearreraig Sandstone Formation (Aalenian-Bajocian), the deltaic Elgol Sandstone Formation (Bathonian) and the deltaic Valtos sandstone Formation (Bathonian) (Harris 1992;Cox & Sumbler 2002;Archer et al 2019). Thinner sandstone beds are also found within the more lagoonal Bathonian middle Jurassic formations (Lealt Shale Formation, Duntulm Formation and Kilmaluag Formation), along with the Bathonian fluvial Skudiburgh Formation (Harris 1992;Cox & Sumbler 2002).…”