The BGS Lexicon of Named Rock Units — Result Details

Auchenhew Mudstone Formation

Computer Code: AHM Preferred Map Code: notEntered
Status Code: Full
Age range: Early Triassic Epoch (TE) — Ladinian Age (TD)
Lithological Description: Intertidal and tidal-flat facies with halite pseudomorphs within sandstones, siltstones and mudstones comprise the majority of the succession. Bimodal palaeocurrents, symmetrical ripples, flaser and wavy bedforms are common. Trace fossils are also commonly found.
Definition of Lower Boundary: Iron stained-sandstones at the top of the Lag a Bheith Formation, are overlain abruptly by the Auchenhew Mudstone Formation.
Definition of Upper Boundary: Overlain by dark grey to black marine muds of the Levencorroch Mudstone Formation.
Thickness: 300m, although 45m is the maximum thickness recorded in a single exposure.
Geographical Limits: Arran.
Parent Unit: Mercia Mudstone Group (MMG)
Previous Name(s): Auchenhew Beds [Obsolete Name And Code: Use AHM] (AHB)
Alternative Name(s): none recorded or not applicable
Type Section  Auchenhew, Arran, Strathclyde, Scotland Pollard, 1978. 
Emeleus, C H and Bell, B R. 2005. British Regional Geology: the Palaeogene volcanic districts of Scotland (Fourth Edition). (Nottingham: British Geological Survey.) x + 214pp. 
Craig, G Y. 1965. Geology of Scotland, 1st Edition. [Geological Society of London.] 
Lovell, J P B. 1991. Permian and Triassic. 421-438 in Craig, G Y, Geology of Scotland 3rd Edition. [Geological Society of London.] 
Pollard, J E and Steel, R J. 1978. Intertidal sediments in the Auchenhew Beds (Triassic) of Arran. Scottish Journal of Geology, Vol.14, 4, 317-328. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S013 S021 S338