The Northeast Arran Trough, the Corrie conundrum and the Highland Boundary Fault in the Firth of Clyde, SW Scotland

Young, Grant M.; Caldwell, W. G. E.

doi:10.1017/s0016756811000823

Cited by 12 publications

(16 citation statements)

References 31 publications

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“…The last two comprise similar facies. They consist of fluvial, cross‐bedded sandstone in upward‐fining cycles, interbedded with red and purple mudstone, multiple intervals with carbonate nodules and thin beds of concretionary limestone (‘cornstones’; Read & Johnson, ; Eyles et al ., ; Francis et al ., ; Leeder, ; Leeder & Bridges, ; Young & Caldwell, , ). The ‘cornstones’ are palaeosols containing extensive pedogenic carbonate and indicate a semi‐arid or arid environment (Burgess, ; Leeder, ; Andrews et al ., ; Wright et al ., ).…”

Section: Geological Settingmentioning

confidence: 99%

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Early Mississippian evaporites of coastal tropical wetlands

et al. 2018

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Extensive evaporites in Lower Mississippian successions from palaeoequatorial regions are commonly used as evidence for an arid to semi‐arid palaeoclimate. However, in this article, detailed studies of evaporites and their context refute this interpretation. Detailed sedimentological and petrographical analysis of the Lower Mississippian of northern Britain, is combined with archived log data from more than 40 boreholes across southern Scotland, northern England and Northern Ireland, and published literature from Canada. Two key cores from the Tweed Basin and the northern margin of the Northumberland – Solway Basin contain 178 evaporite intervals and reveal twelve distinct forms of gypsum and anhydrite across seven facies that are associated with planar laminated siltstone and intercalated thin beds of ferroan dolostone. Nodular gypsum and anhydrite, typically in intervals <1 to 2 m thick, are integral components of the succession. Nodular evaporite occurs within about 1 m of a palaeosurface, but most evaporite deposits represent ephemeral brine pans to semi‐permanent hypersaline lakes or salinas on a floodplain that was subjected periodically to storm surges introducing marine waters. Formation of evaporites under a strongly seasonal climate in a coastal wetland is supported by palaeosol types and geochemical proxies, and from palaeobotanical evidence published previously. Although 65% of modern equatorial areas experience a strongly seasonal climatic regime, salinas and sabkhas are a minor component today in comparison with the evidence from these Lower Mississippian successions. This implies that the earliest terrestrial environments were complex and dynamic, providing a diverse range of habitats in which the early tetrapods became terrestrialized and represent a setting that is rarely preserved in the geological record.

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Section: Geological Settingmentioning

confidence: 99%

“…Evaporite rock is absent from the succession in boreholes along northern and north‐eastern flanks of the Southern Uplands. Also, it is absent where the formation thins towards the northern margin of the Midland Valley, for example on the isles of Bute and Arran (Young & Caldwell, , ).…”

Section: Evaporite Occurrence and Distributionmentioning

confidence: 99%

Early Mississippian evaporites of coastal tropical wetlands

et al. 2018

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“…The Highland Boundary Fault, the major crustal lineament that separates the Dalradian rocks of the Grampian Terrane to the north from the Midland Valley Terrane to the south (Fig. 1), is known to cross Arran, but its exact trace is uncertain (Young and Caldwell, 2012).…”

Section: Geological Settingmentioning

confidence: 99%

The stratigraphy and eruptive history of the Palaeogene Arran Volcanic Formation, western Scotland: a proximal record of caldera-forming eruptions

Gooday¹,

Brown²,

Goodenough³

et al. 2018

Preprint

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Caldera-forming volcanic eruptions are among the most dangerous, and can generate extensive pyroclastic deposits and deliver ash into global atmospheric circulation systems. As calderas collapse, the eruptions can deposit thick proximal ignimbrite sequences and thinner ignimbrites more distally. However, the proximal record of caldera collapse is often obscured by later intrusions, volcanism, faults, alteration, water and sediments, which significantly limits our understanding of these eruptions.A Palaeogene caldera system in central Arran, western Scotland, preserves a rare proximal caldera-fill succession, the Arran Volcanic Formation. This caldera largely comprises highly heterogeneous ignimbrites and minor intra-caldera sedimentary rocks. The current level of erosion, and the general absence of faults, intrusions and sediments, allows a complex stratigraphy and collapse history to be determined, which can be linked to changing eruptive styles at a constantly-evolving volcano.The first recorded phase was eruption of a homogeneous rhyolitic lava-like tuff, deposited from high temperature, high mass-flux pyroclastic density currents generated from low fountaining columns that retained heat. A succeeding phase of highly explosive Plinian eruptions, marked by a thick blanket of massive lapilli tuffs, was then followed by piston-like caldera collapse and erosion of steep caldera walls. Volcanism then became generally less explosive, with predominantly lava-like and eutaxitic tuffs and cognate-spatter-rich agglomerates interbedded with non- homogenous lapilli tuffs. High topographic relief between distinct units indicate long periods of volcanic quiescence, during which erosive processes dominated. These periods are, in several places, marked by sedimentary rocks and evidence for surface water, which includes a localised basaltic-andesitic phreatomagmatic tuff.The caldera-forming eruptions recorded by the Arran Volcanic Formation provide an important insight into caldera collapse processes and proximal ignimbrite successions. The lack of thick autobreccias and lithic-rich lapilli- and block-layers indicates that subsidence was relatively gradual and incremental in this caldera, and not accompanied by catastrophic wall collapse during eruption. The relatively horizontal nature of the caldera-fill units and paucity of intra-caldera faulting, indicate piston subsidence was the dominant method of collapse, with a relatively coherent caldera floor bounded by a steeply-dipping ring fault. Possible resurgence may have caused later doming of the floor and radial distribution of subsequent ignimbrites and sedimentary rocks. Our work emphasises the continued need for field studies of caldera volcanoes.Proximal records of caldera-forming eruptions are relatively rare and the Arran Volcanic Formation provides evidence of these processes. The ignimbrites typically lack the thick autobreccias and lithic-rich lapilli- and block-layers expected of proximal eruptions, indicating that subsidence was relatively gradual and incremental in this caldera, and not accompanied by catastrophic wall collapse during eruption.

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“…North of the upper Firth, the southwesterly trending Highland Boundary Fault (HBF), separating the Grampian and Midland Valley terranes, is a composite fracture (Qureshi, 1970; McLean, Deegan & Wren, 1978; Paterson, Hall & Stephenson, 1990; British Geological Survey, 1985, 1996 a , 2008), with the key components uniting and bending to a more southerly course through Bute. Thereafter, fragmented by a group of northwesterly trending faults with strong strike-slip displacements, the HBF is believed to follow a disjointed course through Arran to the Mull of Kintyre (Young & Caldwell, 2012), resulting in an anomalous narrowing of the Midland Valley (British Geological Survey, 1996 a ). As with the physiographical setting, this points to important differences in tectonic history and calls for further investigations of the Firth of Clyde area on both local and regional scales.…”

Section: Introductionmentioning

confidence: 99%

“…11). The fault parallel to the E coast of mid-Bute that, together with the Great Cumbrae Fault, defines the Cumbraes Trough (Young & Caldwell, 2012) is included in this last group (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Structural controls in the western offshore Midland Valley of Scotland: implications for Late Palaeozoic regional tectonics

Caldwell¹,

Young²

2013

Geol. Mag.

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New detailed mapping and related field studies, together with re-assessment of prior investigations, have revealed that three groups of faults, orientated broadly NE, N and NW, have been the primary controls on stratigraphical, structural and geomorphological evolution in the upper Firth of Clyde since their initiation by proto-Variscan stresses in Late Devonian time. Extended control has been achieved through repeated episodic reactivation, during which existing lines of fracture were rejuvenated and others of similar orientation initiated. Movements on two (if not all three) groups of faults persisted until middle Palaeogene time at least. The faults have been augmented by two sets of irregularly distributed, open, plunging folds, broadly N-S and E-W in their axial orientations. Some N-S folds may be attributed to oblique or strike-slip movement on reactivated caledonoid faults, others to intermittent transpression, probably in Namurian-Westphalian times, affecting mainly the northeastern Midland Valley but stretching beyond the massif of the Clyde Lava Plateau to register a weakened presence as far W as the upper Firth. The N-S folds and dextral strike-slip movements on some faults may be far-field expressions of the Uralian Orogeny, whereas earlier, sinistral displacements on NE faults and the development of small, later and less-significant E-W folds may be related to different phases of long-lived Variscan compression from the S.

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The Northeast Arran Trough, the Corrie conundrum and the Highland Boundary Fault in the Firth of Clyde, SW Scotland

Cited by 12 publications

References 31 publications

Early Mississippian evaporites of coastal tropical wetlands

Early Mississippian evaporites of coastal tropical wetlands

The stratigraphy and eruptive history of the Palaeogene Arran Volcanic Formation, western Scotland: a proximal record of caldera-forming eruptions

Structural controls in the western offshore Midland Valley of Scotland: implications for Late Palaeozoic regional tectonics

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