Aberlady Formation
Aberlady Formation (ABY), Carboniferous, Midland Valley of Scotland
The Aberlady Formation is part of the Strathclyde Group in the Lothians.
Lithology
The Aberlady Formation consists of a cyclical sequence predominantly of pale coloured sandstone interbedded with grey siltstone and grey mudstone. Subordinate but common lithologies are coal, seatrock, ostracod-rich limestone/dolomite and sideritic ironstone, and marine bands or bioclastic limestones with relatively rich and diverse faunas. The last-named feature distinguishes the unit from the Gullane Formation. The depositional environment was fluviodeltaic, into lakes and marine embayments.
Type section
The type section of the Aberlady Formation (Figure 2, column 11) is from 21.64 to 155.44 m in the Spilmersford Borehole (NT 4570 6902) (BGS Reg. No. NT 46 NE/73). Other characteristic sections occur from 28.88 to 168.10 m in the Skateraw Borehole (NT 7373 7546) (BGS Reg. No. NT 77 NW/47) and (partially) on the coast at Cove (NT 78 71) in the Oldhamstocks Basin (Figure 2, column 12) and at Kilspindie (NT 46 80) by Aberlady Bay.
Upper and lower boundaries
The base lies in a transitional sequence and is taken at the base of the lowest of the Macgregor Marine Bands. The formation is laterally equivalent to and has a laterally transitional boundary with the West Lothian Oil Shale Formation to the west, being distinguished from it chiefly by the rarity of oil shales. The top is drawn at the base of the Hurlet Limestone.
Thickness
The maximum thickness of the formation is about 140 m (Chisholm et al., 1989, section 4.4)[1].
References
- ↑ Chisholm, J I, McAdam, A D, and Brand, P J. 1989. Litho-stratigraphical classification of Upper Devonian and Lower Carboniferous rocks in the Lothians. British Geological Survey Technical Report, WA/89/26.