The BGS Lexicon of Named Rock Units — Result Details
Sealyham Volcanic Formation
Computer Code: | SVO | Preferred Map Code: | notEntered |
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Status Code: | Pending Upgrade | ||
Age range: | Fennian Stage (OF) — Fennian Stage (OF) | ||
Lithological Description: | The lower part of the formation comprises green-grey, pillowed, andesitic or dacitic hyaloclastites (Bevins et al, 1992; cf. Thomas and Cox, 1924) The upper part of the Formation comprises rhyolitic tuffs.Geochemical investigations undertaken by Bevins et al (1992) confirm the calc-alkaline chemistry of these rocks, indicating that they are the continental-side products of island arc magmatism. | ||
Definition of Lower Boundary: | Gradational passage from shales of underlying Rosebush Formation. Boundary is drawn where volcanic rocks become dominant over shales. | ||
Definition of Upper Boundary: | Unconformable contact with the base of the Aber Mawr Shale Formation. | ||
Thickness: | 90 - 200m | ||
Geographical Limits: | none recorded or not applicable | ||
Parent Unit: | Not Entered (?) | ||
Previous Name(s): | Sealyham Volcanic Group [Obsolete Name and Code: Use SVO]
(-1211)
Sealyham Volcanic Series [Obsolete Name and Code: Use SVO] (-2464) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
none recorded or not applicable | |||
Reference(s): | |||
none recorded or not applicable | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
E210 |