Computer Code: |
DO |
Preferred Map Code: |
DO |
Status Code: |
Pending Upgrade |
Age range: |
Ashgill Series (OA)
— Ashgill Series (OA) |
Lithological Description: |
Micaceous siltstones and mudstones with subsidiary sandstone and limestone bands. Variable basal limestone (Dolhir Limestone Member) to fissile mudstone (Tyn-y-Twmpath Member). Formation has rich shelly (brachiopod) fauna. Includes Corwen Grit Member at top of formation. |
Definition of Lower Boundary: |
Unconformable on various Caradoc Formations. |
Definition of Upper Boundary: |
Top of Corwen Grit Member succeeded by pale grey-green siltstones and mudstones of the Fron Frys Formation. |
Thickness: |
490 metres. Lateral variations, 320 - 490 metres. |
Geographical Limits: |
Not defined. |
Parent Unit: |
Not Applicable (-)
|
Previous Name(s): |
Dolhir Beds
(-869)
|
Alternative Name(s): |
none recorded or not applicable
|
Stratotypes: |
Type Area |
Wrexham, Sheet 121. |
Reference(s): |
Hiller, A, 1981. The Ashgill rock of the Glyn Ceiriog district, north Wales. Geological Journal, Vol.16, p.181-200. |
Brenchley, P J, 1978. The Caradocian rocks of the North and West Berwyn Hills. Geological Journal, Vol.13, 137-164. |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
E120
E136
E150
E137
|