Scotfot at 19:39, 17 December 2022

2022-12-17T19:39:36Z

← Older revision		Revision as of 20:39, 17 December 2022
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	[[File:P580455.jpg\|thumbnail\|Concretions in the Valtos Sandstone Formation, Bay of Laig, Isle of Eigg. P580455]]		[[File:P580455.jpg\|thumbnail\|Concretions in the Valtos Sandstone Formation, Bay of Laig, Isle of Eigg. P580455]]
	[[File:P580491.jpg\|thumbnail\|Landslips at The Quiraing,Trotternish, Skye. P580491]]		[[File:P580491.jpg\|thumbnail\|Landslips at The Quiraing,Trotternish, Skye. P580491]]
			[[File:P915390.jpg\|thumbnail\|Table 4 Ammonite zonal sequence in the Lower Jurassic and part of the Middle Jurassic of the Inner Hebrides (based on Richey, 1961 and Cope, 1995). P915390.]]
			[[File:P915391.jpg\|thumbnail\|Table 5 Great Estuarine Group and Bearreraig Sandstone Formation in the Inner Hebrides. P915391.]]
			[[File:P915392.jpg\|thumbnail\|Table 6 Ammonite zonal sequence in the upper Middle Jurassic (Callovian) and the Upper Jurassic of the Inner Hebrides (based on Richey, 1961 and Cope, 1995). P915392.]]

	Rocks ranging in age from the Triassic to the Late Cretaceous occur throughout the Inner Hebrides and on Arran ([[Media:P914123.png\|P914123]]). They are part of the extensive basinal deposits found mainly offshore, and in many instances represent the feather edges of these successions. The basins are important structural elements in the Hebridean Igneous Province. In addition to their dominant control on Mesozoic sedimentation, the basins and associated structures appear to have influenced the emplacement of the Paleocene central complexes and possibly also the accumulation of the lava successions.		Rocks ranging in age from the Triassic to the Late Cretaceous occur throughout the Inner Hebrides and on Arran ([[Media:P914123.png\|P914123]]). They are part of the extensive basinal deposits found mainly offshore, and in many instances represent the feather edges of these successions. The basins are important structural elements in the Hebridean Igneous Province. In addition to their dominant control on Mesozoic sedimentation, the basins and associated structures appear to have influenced the emplacement of the Paleocene central complexes and possibly also the accumulation of the lava successions.
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	== Lower Jurassic ==		== Lower Jurassic ==
	In the southern part of the Hebridean area, the lower part of the Lias Group is Hettangian to lower Sinemurian (''bucklandi'' Zone;Table 4), and consists mainly of limestones and fissile calcareous mudstones that are lithologically similar to beds of equivalent age in southern England. They have consequently been termed the Blue Lias Formation (Oates, 1978). In Ardnamurchan, these lithologies interdigitate with more arenaceous rocks (sandstone, sandy limestone, siltstone), which, in turn, become predominant at similar stratigraphical levels to the north on Skye and Raasay, where the beds are now termed the Breakish Formation (formerly the ‘Lower Broadford Beds’). The Breakish Formation is overlain by non-calcareous sandstones, siltstones and mudstones of the Ardnish Formation (formerly the ‘Upper Broadford Beds’; Morton, 1999a, b). The overlying Pabay Shales, Scalpay Sandstone, Portree Shale and Raasay Ironstone formations are recognised throughout the district.		In the southern part of the Hebridean area, the lower part of the Lias Group is Hettangian to lower Sinemurian (''bucklandi'' Zone;([[Media:P915390.jpg\|Table 4]])), and consists mainly of limestones and fissile calcareous mudstones that are lithologically similar to beds of equivalent age in southern England. They have consequently been termed the Blue Lias Formation (Oates, 1978). In Ardnamurchan, these lithologies interdigitate with more arenaceous rocks (sandstone, sandy limestone, siltstone), which, in turn, become predominant at similar stratigraphical levels to the north on Skye and Raasay, where the beds are now termed the Breakish Formation (formerly the ‘Lower Broadford Beds’). The Breakish Formation is overlain by non-calcareous sandstones, siltstones and mudstones of the Ardnish Formation (formerly the ‘Upper Broadford Beds’; Morton, 1999a, b). The overlying Pabay Shales, Scalpay Sandstone, Portree Shale and Raasay Ironstone formations are recognised throughout the district.

	=== Arran ===		=== Arran ===
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	== Middle Jurassic ==		== Middle Jurassic ==
	Onshore deposits of this age are largely confined to the northern part of the district, where the majority of the type sections occur on Skye. The marine, ammonite-bearing Bearreraig Sandstone Formation (Aalenian–Bajocian) includes the thickest sandstones of the onshore British Jurassic. The overlying deposits of the Great Estuarine Group (top Bajocian–Bathonian) (Table 5) were laid down in lagoons, lagoonal deltas and mudflats, which varied from freshwater through brackish to marine (e.g. Harris, 1992). A major hiatus and, locally, an unconformity separate the Raasay Ironstone Formation from the overlying Middle Jurassic strata in the north of the district.		Onshore deposits of this age are largely confined to the northern part of the district, where the majority of the type sections occur on Skye. The marine, ammonite-bearing Bearreraig Sandstone Formation (Aalenian–Bajocian) includes the thickest sandstones of the onshore British Jurassic. The overlying deposits of the Great Estuarine Group (top Bajocian–Bathonian) ([[Media:P915391.jpg\|Table 5]]) were laid down in lagoons, lagoonal deltas and mudflats, which varied from freshwater through brackish to marine (e.g. Harris, 1992). A major hiatus and, locally, an unconformity separate the Raasay Ironstone Formation from the overlying Middle Jurassic strata in the north of the district.

	=== Skye and Raasay ===		=== Skye and Raasay ===
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	== Upper Jurassic (and upper part of the Callovian) ==		== Upper Jurassic (and upper part of the Callovian) ==
	The principal developments of the Oxfordian and Kimmeridgian occur in Skye but no strata younger than the Kimmeridgian have been reported from the district. The beds were deposited in offshore marine conditions. The transgression began in the Callovian with the deposition of the fully marine Carn Mor Sandstone Member of the Staffin Bay Formation, followed by the Upper Ostrea Member, which has a marine to brackish water fauna and has yielded Callovian palynomorphs (Riding, 1992). The overlying, fully marine Staffin Shale Formation contains an abundant fauna, including ammonites that permit zonal correlation with the Upper Jurassic strata of England (Table 6) and the Boreal Realm of Greenland and the Arctic.		The principal developments of the Oxfordian and Kimmeridgian occur in Skye but no strata younger than the Kimmeridgian have been reported from the district. The beds were deposited in offshore marine conditions. The transgression began in the Callovian with the deposition of the fully marine Carn Mor Sandstone Member of the Staffin Bay Formation, followed by the Upper Ostrea Member, which has a marine to brackish water fauna and has yielded Callovian palynomorphs (Riding, 1992). The overlying, fully marine Staffin Shale Formation contains an abundant fauna, including ammonites that permit zonal correlation with the Upper Jurassic strata of England ([[Media:P915392.jpg\|Table 6]]) and the Boreal Realm of Greenland and the Arctic.

	=== Skye ===		=== Skye ===

Dbk at 11:23, 1 February 2018

2018-02-01T11:23:27Z

← Older revision		Revision as of 12:23, 1 February 2018
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	'''From: Emeleus, C H, and Bell, B R. 2005. [[British regional geology: The Palaeogene volcanic districts of Scotland\|British regional geology: The Palaeogene volcanic districts of Scotland]]. Fourth edition. Keyworth, Nottingham: British Geological Survey.'''		{{PVDS}}
	__FORCETOC__		__FORCETOC__
	== Introduction ==		== Introduction ==

Scotfot at 21:34, 22 July 2015

2015-07-22T21:34:43Z

← Older revision		Revision as of 22:34, 22 July 2015
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	__FORCETOC__		__FORCETOC__
	== Introduction ==		== Introduction ==

			[[File:P914123.png\|thumbnail\|Mesozoic basins of the Inner Hebrides and onshore outcrops. P914123]]
			[[File:P914124.png\|thumbnail\|Upper Triassic to Jurassic lithofacies of the Inner Hebrides. P914124]]
			[[File:P580459.jpg\|thumbnail\|Honeycomb weathering in the Elgol Sandstone, Elgol, Skye. P580459]]
			[[File:P580455.jpg\|thumbnail\|Concretions in the Valtos Sandstone Formation, Bay of Laig, Isle of Eigg. P580455]]
			[[File:P580491.jpg\|thumbnail\|Landslips at The Quiraing,Trotternish, Skye. P580491]]

	Rocks ranging in age from the Triassic to the Late Cretaceous occur throughout the Inner Hebrides and on Arran ([[Media:P914123.png\|P914123]]). They are part of the extensive basinal deposits found mainly offshore, and in many instances represent the feather edges of these successions. The basins are important structural elements in the Hebridean Igneous Province. In addition to their dominant control on Mesozoic sedimentation, the basins and associated structures appear to have influenced the emplacement of the Paleocene central complexes and possibly also the accumulation of the lava successions.		Rocks ranging in age from the Triassic to the Late Cretaceous occur throughout the Inner Hebrides and on Arran ([[Media:P914123.png\|P914123]]). They are part of the extensive basinal deposits found mainly offshore, and in many instances represent the feather edges of these successions. The basins are important structural elements in the Hebridean Igneous Province. In addition to their dominant control on Mesozoic sedimentation, the basins and associated structures appear to have influenced the emplacement of the Paleocene central complexes and possibly also the accumulation of the lava successions.

Scotfot at 21:11, 21 July 2015

2015-07-21T21:11:05Z

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Lmo at 13:01, 27 May 2015

2015-05-27T13:01:58Z

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Jurassic, Palaeogene volcanic districts of Scotland - Revision history

Scotfot at 19:39, 17 December 2022

Dbk at 11:23, 1 February 2018

Scotfot at 21:34, 22 July 2015

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Dbk: 1 revision imported

Lmo at 13:01, 27 May 2015