Computer Code: |
CYH |
Preferred Map Code: |
CYH |
Status Code: |
Full |
Age range: |
Ludlow Epoch (SU)
— Ludlow Epoch (SU) |
Lithological Description: |
Interlaminated and very thinly interbedded grey silty mudstone, siltstone/fine-grained sandstone and carbonaceous (anoxic) hemipelagite; disruptive bioturbation negligible. |
Definition of Lower Boundary: |
Disappearance of thick mudstone turbidite units of underlying undifferentiated Bailey Hill Formation. |
Definition of Upper Boundary: |
First appearance of significant disruptive bioturbation, indicating onset of oxic bottom conditions. |
Thickness: |
Up to 220m thick. |
Geographical Limits: |
Dies out southwards; southern limit at c. (SO 158 795); northwards extends at least as far as (SO 120 850). |
Parent Unit: |
Bailey Hill Formation (BAI)
|
Previous Name(s): |
none recorded or not applicable
|
Alternative Name(s): |
Approximately Equivalent To The Monograptus Leintwardinensis Shales.
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Stratotypes: |
Type Section |
Track section north-east of the old (now abandoned) Cwm-yr-hob farmhouse, Felindre, Powys. |
Reference Section |
Lyrychyn Quarry, Cilfaesty Hill. |
Reference(s): |
Earp, J R, 1938. The higher Silurian rocks of the Kerry district, Montgomeryshire. Quarterly Journal of the Geological Society of London. Vol.94/1, p.125-160. |
Cave, R and Hains, B A. 2001. Geology of the country around Montgomery. Memoir of the British Geological Survey, Sheet 165 with part of 151 (Welshpool) (England and Wales). |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
E165
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