| Computer Code: |
CHAI |
Preferred Map Code: |
CHAI |
| Status Code: |
Full |
| Age range: |
Cryogenian Period (AC)
— Cryogenian Period (AC) |
| Lithological Description: |
20 to 40cm-scale tabular to lenticular bedded grey to pinkish brown quartzite and quartzose psammite. Banded ribbed quartzite and semipelite unit comprising 5 to 10cm-scale interbeds of semipelite. The uppermost part of formation is more thinly bedded (3 to 5cm), and flaggy, comprising white-grey quartzite with minor biotitic quartzite and dark semipelite, and is probably about 5 to 10m thick. |
| Definition of Lower Boundary: |
Abrupt change to white-weathering pinkish-brown quartzose psammite and quartzite from the preceding psammite to quartzose psammite of the Auch Gleann Psammite Formation. |
| Definition of Upper Boundary: |
Abrupt change to the calcareous garnet-mica semipelite and muscovite-quartz semipelite marking the base of the Coire Daingean Semipelite Formation or to the massive garnet-mica semipelite and muscovite-quartz semipelite where the calcareous facies is not developed. |
| Thickness: |
Ranges from 10 - 20m up to c.250m thick, thicker typically in the southern part of the outcrops mapped to date. Approximately 90m thick at Beinn a'Chaisteil. |
| Geographical Limits: |
Can be traced as a prominent marker at base of Lochabar Subgroup from western edge of Crianlarich, east then northeastwards into southern parts of Blackwater, then eastwards across southern parts of Loch Rannoch to boundary with Schiehallion. |
| Parent Unit: |
Lochaber Subgroup (DALO)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Reference Section |
Western slopes of Beinn a'Chaisteil, Auch Gleann. Details will be included in Sheet Description for Sheet 46W (Crainlarich). Presently in draft BGS internal report: Leslie et al., Progress Report on the Geology of the Tyndrum area, 2003. 1:50k Sheet 46W (Crianlarich). |
| Reference(s): |
| Will be included in Sheet Description for Sheet 46W (Crianlarich) and 46E (Killin). |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S046
|
