The BGS Lexicon of Named Rock Units — Result Details

Misty Law Trachytic Member

Computer Code: MLLA Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: Trachyte and rhyolite lavas with associated volcaniclastic rocks, including pyroclastic breccias and tuffs, minor amounts of trachyandesite and trachybasalt (capping Totterie Law [NS 293 621]) and one major basaltic intercalation.
Definition of Lower Boundary: Along western margin of the centre, the contact of the basal trachytes of the Misty Law Trachytic Member with the underlying Strathgryfe Lava Member is not exposed but appears to be conformable and to dip gently to the south-east.
Definition of Upper Boundary: The more steeply dipping upper boundary of the Misty Law Trachytic Member is believed to be overstepped by the overlying lavas of the Strathgryfe Lava Member but, where exposed, the contacts are generally faulted. Unfaulted junctions are seens only in the River Garnock [NS 293 593] and in the Rough Burn [NS 315 617] outside the faulted south-eastern margin of the main mass.
Thickness: Up to 300m
Geographical Limits: Occurs in the central part of the Renfrew shire Hills. The outcrop is 8km wide in the area around Misty Law [NS 295 620], extending from the headwaters of the River Calder [NS 258 646] in the north-west, to Muirshiel Country Park [NS 315 630] in the south-east, to the Knockside Hills [NS 256 582] in the south.
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): Misty Law Trachytic Centre (-2940)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  An extensive area of high ground between the headwaters of the Gogo Water, North Grane Burn and The River Calder. Within the type area, the six main phases of extrusive activity (in order of formation) are best represented by the following localities: 1:Trachyte lavas exposed in streams south-east of Waterhead Moor [NS 263 621] and around the headwaters of the River Calder [NS 258 646]. 2: Pyroclastic rocks in scarp to east of Waterhead Moor [NS 269 624], also in Gogo Burn, Routdane Burn, Murchan Burn (including lenses of carbonaceous mudstone and plant fragments) and Surge Burn. 3: Trachytic lavas and welded tuffs forming highland to north east of the Gogo Water headwaters [about NS 264 596]. 4: Basaltic and intermediate lavas forming outliers on The Tongue [NS 280 610] and more continuous outcrops around East Girt Hill [NS 279 627], Burnt Hill [NS 270 634] and Queenside Loch [NS 292 642]. 5:Massive flows of trachyte and rhyolite overlying the basic lavas on and west of Queenside Hill [NS 293 638], on Hiil of Stake [NS 274 630] and south-east from East Girt Hill [NS 279 627] to Little Misty Law [NS 299 621] 6:Trachyandesite and trachybasalt capping Totterie Law [NS293 621] and Misty Law [NS 295 620]. Paterson et al. 1990 
Reference(s):
Monro, S K. 1999. Geology of the Irvine District. Memoir of the British Geological Survey, Sheet 22W and part of 21E (Scotland). 
Johnstone, G S. 1965. The volcanic rocks of the Misty Law-Knockside Hills district, Renfrewshire. Bulletin of the Geological Survey of Great Britain. No. 22. pp 53-64. 
Paterson, I B, Hall, I H S & Stephenson, D. 1990. Geology of the Greenock district: Memoir for 1:50000 geological sheet 30W and part of sheet 29E (Scotland). 
Richey, J E. 1928. The north Ayrshire sequence of Calciferous Sandstone volcanic rocks. Transactions of the Geological Society of Glasgow. 18. pp 247-255. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S022 S030