The BGS Lexicon of Named Rock Units — Result Details

Laundry Mudstone Formation

Computer Code: LYMD Preferred Map Code: LdM
Status Code: Full
Age range: Hirnantian Age (OH) — Aeronian Age (SA)
Lithological Description: Mudstone, silty, grey, weathers buff, bioturbated, thinly interbedded with sandstones (< 15cm). The basal few metres comprise beds of fine-grained sandstone about 0.5m thick.
Definition of Lower Boundary: The lower boundary is marked by the change in lithology from the underlying Powys Castle Conglomerate.
Definition of Upper Boundary: Upper boundary gradational with pale grey-green mudstones of the Dolgau Formation.
Thickness: 160 to 170m
Geographical Limits: Widespread on the Welshpool sheet (151) west of the river Severn. Also occurs in the south of Oswestry (137), in the Meifod area and in the north of Montgomery (165).
Parent Unit: Not Available (!)
Previous Name(s): Llwyn-Y-Brain Formation [Obsolete Name And Code: Use LYMD] (LYM)
V2 Beds (-3546)
Alternative Name(s): Fron Frys Formation
Lluyn-Y-Brain Formation
Stratotypes:
Type Area  Laundry Lane, Guilsfield; several smaller quarries on the north side of the lane. 
Reference(s):
King, W B R. 1928. The geology of the country around Meifod, Montgomeryshire. Quarterly Journal of the Geological Society of London, Vol. 84, 671 - 704. 
Cave, R and Dixon, R J, 1993. The Ordovician and Silurian of the Welshpool area. In Woodcock, NH, Bassett, MG. (eds.) Geological Excursions in Powys, Central Wales. University of Wales Press, National Museum of Wales, Cardiff. 
Cave, R. 1965. The Nod Glas sediments of Caradoc Age in North Wales. Geological Journal, Vol. 4, 279 - 298 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E137