Computer Code: |
PSKA |
Preferred Map Code: |
notEntered |
Status Code: |
Full |
Age range: |
Eifelian Age (DI)
— Eifelian Age (DI) |
Lithological Description: |
A pebble and boulder conglomerate, typically containing rounded to subangular clasts of Moine psammite, Reay diorite and some granitic rocks in a matrix of greenish grey fine- to medium-grained sandstone. The unit is locally intercalated with thin beds of grey nodular limestone of the Aryleive Limestone Bed. |
Definition of Lower Boundary: |
The unit rests unconformably, directly on Caledonian igneous or Precambrian Moine (basement) rocks as the basal unit of the Bighouse Formation on the Middle Old Red Sandstone unconformity. |
Definition of Upper Boundary: |
Overlain by an interbedded, sandstone-dominated rhythmic sequence of sandstones, siltstones and laminated carbonate mudstones (fish beds) of the Baligill Limestone Member of the Bighouse Formation. |
Thickness: |
Typically 5 - 10m, and locally more than 40m |
Geographical Limits: |
Onshore and immediate offshore of the Dounreay area, Caithness, northern Scotland. |
Parent Unit: |
Bighouse Formation (BIGH)
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Previous Name(s): |
Basal Conglomerate [Obsolete Name and Code: Use PSKA, TCM]
(-1130)
|
Alternative Name(s): |
none recorded or not applicable
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Stratotypes: |
Type Area |
Portskerra Harbour, about 400 m north of the centre of Portskerra village, Sutherland (Trewin, 1993). |
Reference Section |
Sea cliff exposures at Red Point, 2.5 km northwest of Reay village, Caithness. |
Type Section |
Jetty in Portskerra Harbour. |
Reference(s): |
Trewin, N H. 1993 Old Red Sandstone basin margin deposits at Red Point, Port Skerra and Baligill. 157-166 in Trewin, N H and Hurst, A [editors], Excursion guide to the geology of eastern Sutherland and Caithness. [Edinburgh: Scottish Academic Press.] |
British Geological Survey. (In preparation, to be published in 2005). Bedrock geology. Scotland Special Sheet (Dounreay).1:25 000. |
British Geological Survey. 2003. Bedrock and superficial deposits. Scotland Sheet 115E (Reay).1:50 000. |
Donovan, R N. 1975. Devonian lacustrine limestones at the margin of the Orcadian Basin, Scotland. Journal of the Geological Society of London, Vol.131, 489-510. |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
S115
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