The BGS Lexicon of Named Rock Units — Result Details

Allt Dhub Member

Computer Code: ALTDU Preferred Map Code: Mods
Status Code: Pending Upgrade
Age range: Triassic Period (T) — Triassic Period (T)
Lithological Description: Fossiliferous, grey, well-bedded sandstones. Fragments of plant, wood, fish, shells and ostracods are common. The lithology changes to siltstone and the fossils found signify an enviromnent change from alluvial to estaurine and shallow-marine conditions that prevailed at the Jurassic, but the unit cannot be accurately dated as such. Not shown on 50k maps.
Definition of Lower Boundary: Fossiliferous sandstones overlying conglomerates (usually red) of the Sgaorishal Member.
Definition of Upper Boundary: No overlying unit on Rum.
Thickness: 18m
Geographical Limits: Isle of Rum/Sea of the Hebrides Basin.
Parent Unit: Monadh Dubh Sandstone Formation (MODS)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Type Section  A'Mharagach, northwest Rum. Emeleus, 1997. 
Steel, R J. 1974. New Red Sandstone piedmont and floodplain sedimentation in the Hebridean province, Scotland. Journal of Sedimentary Petrology, Vol.44, 336-357. 
Emeleus, C H. 1997. Geology of Rum and the adjacent islands. Memoir (sheet) of the Geological Survey of Great Britain (Scotland) (60). (The Stationery Office for the British Geological Survey.) 171pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: