| Computer Code: |
TYG |
Preferred Map Code: |
TYG |
| Status Code: |
Index Level |
| Age range: |
Caradoc Series (O4)
— Caradoc Series (O4) |
| Lithological Description: |
[Obsolete: use NOG] Black pyritous graptolitic mudstone. |
| Definition of Lower Boundary: |
Base succeeds green calcareous volcaniclastic sandstones of the Gelli Grin Calcareous Ash Formation and laterally the Upper Crafnant Volcanic Formation acid tuffs. |
| Definition of Upper Boundary: |
Unconformably overlain by bioclastic limestone - Rhiwlas Limestone. |
| Thickness: |
2.5m thick in type section; lateral variations - 0-25m. |
| Geographical Limits: |
Not defined. |
| Parent Unit: |
none recorded or not applicable
|
| Previous Name(s): |
Tyn-Y-Glyn Mudstone Member [Obsolete Name and Code: Use TYG]
(-3739)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
Corwen, Sheet 120. |
| Reference(s): |
| Campbell, S D G. 1983. The geology of an area between Bala and Betws-y-Coed, North Wales. Unpublished PhD Thesis, University of Cambridge. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E120
|
