| Computer Code: |
MU |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Llanvirn Series (OE)
— Llanvirn Series (OE) |
| Lithological Description: |
Mafic agglomeratic tuff, tuffite and thin mafic pillowed lava flows with interbedded silty mudstones. |
| Definition of Lower Boundary: |
Conformably overlies the volcaniclastic sandstones of the Allt Lwyd Formation and passes laterally into the undivided siltstones and mudstones of the Aran Volcanic Group; locally, conformably overlies the felsic tuffs of the Offrwm Volcanic Formation. |
| Definition of Upper Boundary: |
Conformably overlain by silty mudstones of the Aran Volcanic Group over much of the Harlech district, but locally overstepped by the Benglog Formation with apparent unconformity/disconformity. |
| Thickness: |
To 220m |
| Geographical Limits: |
Harlech and Bala districts, North Wales. |
| Parent Unit: |
Aran Volcanic Group (AVG)
|
| Previous Name(s): |
Melau Tuff Formation [Obsolete Name and Code: Use MU]
(-4208)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Partial Type Section |
River section and adjacent crags in the Afon Melau. Allen, P M and Jackson, A A. 1985. |
| Reference(s): |
| Allen, P M, and Jackson, A A. 1985. Geology of the country around Harlech. Memoir of the British Geological Survey, Sheet 135 with part of Sheet 149 (England and Wales). (London: HMSO.) 112 pp. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E136
E135
|
