| Computer Code: |
TNL |
Preferred Map Code: |
TnL |
| Status Code: |
Full |
| Age range: |
Asbian Substage (CR)
— Asbian Substage (CR) |
| Lithological Description: |
[Obsolete: use LEEL]
Regular cyclic alternations of dark grey bioclastic limestone and porcellaneous limestone (birdseye micrite). |
| Definition of Lower Boundary: |
At junction with underlying Basement Beds. |
| Definition of Upper Boundary: |
At junction with overlying Eglwyseg Limestone Formation, which comprises sedimentary cycles of calcareous shale, cross bedded biosparite and massive pale grey biosparite. |
| Thickness: |
c.115m |
| Geographical Limits: |
Llangollen-Minera district, east Wales. |
| Parent Unit: |
none recorded or not applicable
|
| Previous Name(s): |
Lower Brown Limestone [Obsolete Name And Code: See FOF, LEEL, LNML, TNL]
(LBRL)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Due north of Ty-nant Farmhouse. |
| Reference(s): |
| Somerville, I D, 1979. Minor sedimentary cyclicity in Late Asbian (Upper D1) Limestones in the Llangollen district of North Wales. Proceedings of the Yorkshire Geological Society, Vol.42, p.317-341. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E121
|
