The BGS Lexicon of Named Rock Units — Result Details

Rowley Regis Microgabbro Lopolith

Computer Code: RRLO Preferred Map Code: RRL
Status Code: Full
Age range: Bolsovian Substage (CC) — Bolsovian Substage (CC)
Lithological Description: Olivine basalt to microgabbro (dolerite) with phenocrysts of altered olivine and subordinate augite and/or plagioclase that commonly form glomerophyric masses. The groundmass displays ophitic or subophitic texture. Listric cooling joints are pervasively developed.
Definition of Lower Boundary: Sharp boundary seen in Hailstone Quarry [SO 9665 8835]. Basal 0.5 m of dolerite comprises joints sub-parallel with an igneous lamination and the basal boundary. Above this near vertical cooling joints are developed. Below the sharp boundary the Etruria Formation country-rock comprises 1.5 m of sandstone, underlain by black, hardened mudstone.
Definition of Upper Boundary: Sharp boundary formerly seen in Darby's Hill Quarry [SO 9683 8962]. About 1.6 m of finely crystalline microgabbro (dolerite) overlain by 1.8 m of unbaked red, mottled silty mudstone of the Etruria Formation.
Thickness: Up to 100 m.
Geographical Limits: Rowley Regis, southwest of Oldbury. Extends for about 3 km from Darby's Hill [SO 966 899] in the north to Hawes Hill [SO968 868] in the south. Also, isolated area around Tansley Hill [SO 956 894].
Parent Unit: Brierley Hill Cluster (BRIER)
Previous Name(s): Rowley Regis Laccolith (-5009)
Alternative Name(s): none recorded or not applicable
Type Section  Hailstone [SO 966 882] and Edwin Richards [SO 968 884] quarries, Rowley Regis. Sharp boundary seen in Hailstone Quarry [SO 9665 8835]. Prominent listric joints evident within both quarries. Described by Powell et al. (2000). 
Powell, J H, Glover, B W and Waters, C N. 2000. Geology of the Birmingham area. Memoir of British Geological Survey Sheet 168 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E168 E169