Category:Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Difference between revisions
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[[Category:Scotland_Chalk_nomenclature_(Scottish_Chalk_Province)]] | Name | ||
The Inner Hebrides Group was formally proposed by Braley (1990). See also Lowden, Braley, Hurst, and Lewis, (1992) and Mortimore, Wood, and Gallois, (2001) in which volume a number of the correlations in the earlier work are adjusted and the dating of the sequence refined. | |||
''Type section'' | |||
At various localities for the constituent formations in the Inner Hebrides and Morvern. Principal exposures are at Beinn Iadain and Loch Aline Mine in Morvern, at Gribun, Carsaig and Auchnacraig on Mull, at Clach Alasdair and Laig Gorge on Eigg and Strathaird on Skye. | |||
''Primary Reference Section'' | |||
At the type-sites of the constituent formations and members. | |||
Formal subdivisions | |||
Divided into seven formations and a number of constituent members. These are from the oldest the Morvern Greensand Formation, Lochaline White Sandstone Formation, Coire Riabhach Phosphatic Formation, Gribun Chalk Formation, Feorlin Sandstone Formation, Strathaird Limestone Formation (including the Clach Alasdair Conglomerate Member and Laig Gorge Sandstone Member) and the Beinn Iadain Mudstone Formation. This latter probably principally of basal Palaeogene in age a description is included herein for completeness. | |||
''' ''' | |||
''Lithology '' | |||
Glauconitic sandstones, pure silica sands, silicified chalks, flints and conglomerates. | |||
''Definition of upper boundary'' | |||
Unconformable beneath the Paleocene lavas or conformable (?) beneath the Beinn Iadain Mudstone Formation of presumed Paleocene age. | |||
''Definition of lower boundary '' | |||
Unconformable at the erosion surface below the Morvern Greensand Formation. | |||
''Thickness'' | |||
The group comprises a highly condensed sequence and is variable in thickness depending on the relative development of its constituent parts. The group may be as little as a few metres thick but is between 10 to 15 m on Mull and between 11 to 22 m in Morvern. | |||
Distribution | |||
Known from the Inner Hebrides islands of Mull, Eigg, Skye, Scalpay, Soay and Raasay and also from the Morvern district of the Scottish mainland. | |||
''Previous names'' | |||
Generally the Cretaceous rocks of the Inner Hebrides have been described using that title or, because of their limited outcrop, as individual constituent units attached to a locality i.e. Morvern Greensand. Some of these gained greater acceptance and were applied more widely. | |||
Parent | |||
None | |||
Age and biostratigraphy | |||
Upper Cretaceous, Cenomanian to early Campanian. | |||
''References'' | |||
Braley (1990); Lowden, Braley, Hurst and Lewis (1992); Mortimore, Wood and Gallois (2001). | |||
[[Category:Scotland_Chalk_nomenclature_(Scottish_Chalk_Province) | ]] |
Revision as of 10:59, 28 January 2014
Name
The Inner Hebrides Group was formally proposed by Braley (1990). See also Lowden, Braley, Hurst, and Lewis, (1992) and Mortimore, Wood, and Gallois, (2001) in which volume a number of the correlations in the earlier work are adjusted and the dating of the sequence refined.
Type section
At various localities for the constituent formations in the Inner Hebrides and Morvern. Principal exposures are at Beinn Iadain and Loch Aline Mine in Morvern, at Gribun, Carsaig and Auchnacraig on Mull, at Clach Alasdair and Laig Gorge on Eigg and Strathaird on Skye.
Primary Reference Section
At the type-sites of the constituent formations and members.
Formal subdivisions
Divided into seven formations and a number of constituent members. These are from the oldest the Morvern Greensand Formation, Lochaline White Sandstone Formation, Coire Riabhach Phosphatic Formation, Gribun Chalk Formation, Feorlin Sandstone Formation, Strathaird Limestone Formation (including the Clach Alasdair Conglomerate Member and Laig Gorge Sandstone Member) and the Beinn Iadain Mudstone Formation. This latter probably principally of basal Palaeogene in age a description is included herein for completeness.
Lithology
Glauconitic sandstones, pure silica sands, silicified chalks, flints and conglomerates.
Definition of upper boundary
Unconformable beneath the Paleocene lavas or conformable (?) beneath the Beinn Iadain Mudstone Formation of presumed Paleocene age.
Definition of lower boundary
Unconformable at the erosion surface below the Morvern Greensand Formation.
Thickness
The group comprises a highly condensed sequence and is variable in thickness depending on the relative development of its constituent parts. The group may be as little as a few metres thick but is between 10 to 15 m on Mull and between 11 to 22 m in Morvern.
Distribution
Known from the Inner Hebrides islands of Mull, Eigg, Skye, Scalpay, Soay and Raasay and also from the Morvern district of the Scottish mainland.
Previous names
Generally the Cretaceous rocks of the Inner Hebrides have been described using that title or, because of their limited outcrop, as individual constituent units attached to a locality i.e. Morvern Greensand. Some of these gained greater acceptance and were applied more widely.
Parent
None
Age and biostratigraphy
Upper Cretaceous, Cenomanian to early Campanian.
References
Braley (1990); Lowden, Braley, Hurst and Lewis (1992); Mortimore, Wood and Gallois (2001).
Pages in category "Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group"
The following 7 pages are in this category, out of 7 total.
- Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Morven Greensand Formation
- Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Lochaline White Sandstone Formation
- Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Coire Riabhach Phosphatic Formation
- Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Gribun Chalk Formation
- Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Strathaird Limestone Formation
- Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Feorlin Sandstone Formation
- Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Beinn Iadain Mudstone Formation