The group comprises a series of shales and sandstones which in stratigraphic order (youngest/uppermost at top) are:
Lackagh Sandstone Formationedit
The formation is 60-90m thick in the Connaught Coalfield but only about 36m thick on Cuilcagh Mountain where it forms the prominent cliff-edged summit surface as also at Belmore.[2] It is unfossiliferous.
Gowlaun Shale Formationedit
Some 50-60m thickness of shales and mudstones of Arnsbergian age constitute this formation.
Briscloonagh Sandstone Formationedit
About 53m of Pendleian age sandstones with interlayered siltstones and some mudstone make up this formation.
Dergvone Shale Formationedit
Mostly dark coloured iron-rich shales of Pendleian age, it reaches up to 128m thick. From its top downwards, it is divided into the Lacoon Sandstone, Killooman Shale, Tonlegee Shale, Tullyclevaun Shale, Black Mountain Shales and Gubaveeny Shale members.
Carraun Shale Formationedit
From 50m to over 160m thick, this Brigantian age formation is largely shale but contains thin limestones, siltstones and sandstones, some of which are given their own names as members e.g. the Doagh Limestone and Tawnyunshinagh Limestone members.
Bellavally Formationedit
This Asbian to Brigantian age formation varies from 45m to 80m thick and consists largely of sandstones and shales with lesser amounts of siltstone and limestone. From its top downwards, it is divided into the Corry, Sheena Shale, Glenkeel, Doobally Sandstone, Drummangarvagh, Lugasnaghta, Sraduffy, Larkfield and Tullyskeherny members.
Glenade Sandstone Formationedit
Referred to as the Yoredale Sandstone in the late nineteenth century, this Asbian age sequence varies from 4m thick in County Leitrim to as much as 350m in the north of its range. In places it sits directly on the Dartry Limestone where the Meenymore Formation rocks are missing due to the locally high relief of the underlying erosive surface. Animal fossils are almost wholly absent from this formation though fragments of Calamites and leaf remains are more common.
Meenymore Formationedit
The lowermost and hence oldest division of the Group is of Asbian age. It comprises mudstones and limestones and delta sandstones, two of which are mapped as separate ‘members’; the Glen and Quarry Sandstone, the former only being seen west of the Glen Syncline. The thickness of the formation varies from 18m at Doagh to 100m to the east of Cuilcagh Mountain. A depositional hiatus separates this formation from the underlying Dartry Limestone.
^Marble Arch Caves Global Geopark; Exploring the landscape of Fermanagh and Cavan (map), 2015 GSNI ISBN9780751837933
I.C. Legg, T.P Johnston, W.I. Mitchell & R.A. Smith (1998). Geology of the country around Derrygonnelly and Marble Arch, Memoir of the Geological Survey of Northern Ireland, Sheet 44, 56 and 43 (Northern Ireland) (1. ed.). London: The Stationery Office. pp. 26–50. ISBN0118845314.{{cite book}}: CS1 maint: multiple names: authors list (link)
January 01, 1970
leitrim, group, this, article, includes, list, references, related, reading, external, links, sources, remain, unclear, because, lacks, inline, citations, please, help, improve, this, article, introducing, more, precise, citations, january, 2020, learn, when, . This article includes a list of references related reading or external links but its sources remain unclear because it lacks inline citations Please help improve this article by introducing more precise citations January 2020 Learn how and when to remove this message The Leitrim Group is a lithostratigraphical term coined to refer to the succession of rock strata which occur in Northern Ireland within the Visean and Namurian stages of the Carboniferous Period 1 The group disconformably overlies the Dartry Limestone of the Tyrone Group Leitrim GroupStratigraphic range Asbian to Arnsbergian Carboniferous TypeGroupUnit ofCarboniferous Limestone SupergroupSub unitsLackagh Sandstone Gowlaun Shale Briscloonagh Sandstone Dergvone Shale Carraun Shale Bellavally Glenade Sandstone and Meenymore formationsOverliesTyrone GroupLithologyPrimarysandstoneOthermudstone conglomerate shale limestone siltstone brecciaLocationCountryNorthern IrelandExtentCounty Fermanagh County TyroneType sectionNamed forCounty Leitrim Contents 1 Stratigraphy 1 1 Lackagh Sandstone Formation 1 2 Gowlaun Shale Formation 1 3 Briscloonagh Sandstone Formation 1 4 Dergvone Shale Formation 1 5 Carraun Shale Formation 1 6 Bellavally Formation 1 7 Glenade Sandstone Formation 1 8 Meenymore Formation 2 ReferencesStratigraphy editThe group comprises a series of shales and sandstones which in stratigraphic order youngest uppermost at top are Lackagh Sandstone Formation edit The formation is 60 90m thick in the Connaught Coalfield but only about 36m thick on Cuilcagh Mountain where it forms the prominent cliff edged summit surface as also at Belmore 2 It is unfossiliferous Gowlaun Shale Formation edit Some 50 60m thickness of shales and mudstones of Arnsbergian age constitute this formation Briscloonagh Sandstone Formation edit About 53m of Pendleian age sandstones with interlayered siltstones and some mudstone make up this formation Dergvone Shale Formation edit Mostly dark coloured iron rich shales of Pendleian age it reaches up to 128m thick From its top downwards it is divided into the Lacoon Sandstone Killooman Shale Tonlegee Shale Tullyclevaun Shale Black Mountain Shales and Gubaveeny Shale members Carraun Shale Formation edit From 50m to over 160m thick this Brigantian age formation is largely shale but contains thin limestones siltstones and sandstones some of which are given their own names as members e g the Doagh Limestone and Tawnyunshinagh Limestone members Bellavally Formation edit This Asbian to Brigantian age formation varies from 45m to 80m thick and consists largely of sandstones and shales with lesser amounts of siltstone and limestone From its top downwards it is divided into the Corry Sheena Shale Glenkeel Doobally Sandstone Drummangarvagh Lugasnaghta Sraduffy Larkfield and Tullyskeherny members Glenade Sandstone Formation edit Referred to as the Yoredale Sandstone in the late nineteenth century this Asbian age sequence varies from 4m thick in County Leitrim to as much as 350m in the north of its range In places it sits directly on the Dartry Limestone where the Meenymore Formation rocks are missing due to the locally high relief of the underlying erosive surface Animal fossils are almost wholly absent from this formation though fragments of Calamites and leaf remains are more common Meenymore Formation edit The lowermost and hence oldest division of the Group is of Asbian age It comprises mudstones and limestones and delta sandstones two of which are mapped as separate members the Glen and Quarry Sandstone the former only being seen west of the Glen Syncline The thickness of the formation varies from 18m at Doagh to 100m to the east of Cuilcagh Mountain A depositional hiatus separates this formation from the underlying Dartry Limestone References edit https www bgs ac uk lexicon lexicon cfm pub LEG BGS Lexicon of named rock units Marble Arch Caves Global Geopark Exploring the landscape of Fermanagh and Cavan map 2015 GSNI ISBN 9780751837933 I C Legg T P Johnston W I Mitchell amp R A Smith 1998 Geology of the country around Derrygonnelly and Marble Arch Memoir of the Geological Survey of Northern Ireland Sheet 44 56 and 43 Northern Ireland 1 ed London The Stationery Office pp 26 50 ISBN 0118845314 a href Template Cite book html title Template Cite book cite book a CS1 maint multiple names authors list link Retrieved from https en wikipedia org w index php title Leitrim Group amp oldid 1168098723, wikipedia, wiki, book, books, library,
