The BGS Lexicon of Named Rock Units — Result Details

Porth Swtan Formation

Computer Code: SWTN Preferred Map Code: notEntered
Status Code: Full
Age range: Floian Age (OFL) — Darriwilian Age (ODW)
Lithological Description: Breccia of mudstone and sandstone with rafts of quartzite and limestone, interbedded with heterolithic sandstone-mudstone units. Locally units of massive unfossiliferous limestone and quartzite.
Definition of Lower Boundary: Stratigraphic contact with Porth Trefadog Volcanic Formation (POTRF) or unconformably overlying Cambro-Ordovican Holy Island Group rocks.
Definition of Upper Boundary: Uncoformably overlain by Porth Wen Group (PORW) or Llyn Alaw Group (ALAW) rocks.
Thickness: none recorded or not applicable
Geographical Limits: Anglesey.
Parent Unit: Cemaes Group (CMES)
Previous Name(s): Porth Yr Ogof Formation (POGF)
Alternative Name(s): none recorded or not applicable
none recorded or not applicable
none recorded or not applicable
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable