| Computer Code: |
GACO |
Preferred Map Code: |
GCO |
| Status Code: |
Full |
| Age range: |
Early Devonian Epoch (DL)
— Early Devonian Epoch (DL) |
| Lithological Description: |
A poorly sorted, matrix supported, planar bedded, conglomerate with clasts of quartzite, quartz and igneous lithologies. |
| Definition of Lower Boundary: |
A sharp contact with the purple and reddish-grey, sublithic sandstone of the undivided Ruchill Flagstone Formation. |
| Definition of Upper Boundary: |
A sharp contact with the Cromlix Mudstone Formation, which comprises a poorly sorted silty sandstone around Gartartan, commonly with a thin conglomerate bed 30 - 40 m above the junction. North-eastwards, basal Cromlix beds exhibit a transition to a fine-grained, massive, well-sorted sandstone, eg; at Over Shannochil [NS 5428 9930]. |
| Thickness: |
From 20 - 25 m between Gartmore House and Shannochill, increasing to 100 m thickness at Lochan Balloch [NN 592 043]. |
| Geographical Limits: |
Gartmore to Lochan Balloch, north-east of which it virtually coalesces with Ben Dearg Conglomerate to form A'Chrannach Conglomerate (lower leaf) near Callander. |
| Parent Unit: |
Ruchill Flagstone Formation (RLF)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Roadside section on A81 beside Gartartan Cottage. |
| Reference Section |
Outcrop 100m west of Over Shannochill Farm. |
| Reference(s): |
| Browne, M A E, Smith, R A, and Aitken, A M. 2002. Stratigraphical framework for the Devonian (Old Red Sandstone) rocks of Scotland south of a line from Fort William to Aberdeen. British Geological Survey Research Report RR/01/04. 67 pp. |
| Phillips, E R, and Aitken, A M. 1998. The petrology and composition of the Lower Old Red Sandstone exposed in the Aberfoyle Area (Sheet 38E), Central Scotland. British Geological Survey, Technical Report, WG/98/10. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S038
|
