| Computer Code: |
LYFS |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Arundian Substage (CJ)
— Arundian Substage (CJ) |
| Lithological Description: |
Calcareous sandstones and sandy limestones (grainstones), locally cross-bedded and dolomitised. Records high energy, near shore bar deposition during the early stages of the Arundian transgression of North Wales, at a time when siliciclastic detritus was still actively being supplied to the developing carbonate ramp margin. |
| Definition of Lower Boundary: |
Taken as corresponding to the entry of calcareous sandstone 13m above the base of the Llanarmon Limestone Formation in the Alyn Valley Borehole.. |
| Definition of Upper Boundary: |
Entry of dark brown-grey, less sandy, crinoidal limestones (packstones) of the overlying part of the Llanarmon Limestone Formation. |
| Thickness: |
20 to 30m |
| Geographical Limits: |
Llanarmon-yn-Ial area [SJ1958], east of the Clwydian Range, northeast Wales. |
| Parent Unit: |
Llanarmon Limestone Formation (LNML)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Alyn Valley Borehole [SJ15NE/8] and Pistyll Gwyn Quarry. Base of member proved at 16.72m depth in the borehole;top of member located c.14m above the base of the quarry section. Grid reference given is for Alyn Valley Borehole. Davies, et al., 1989. |
| Reference(s): |
| Davies, J R, Riley, N J and Wilson, D, 1989. Distribution of Chadian and earliest Arundian strata in North Wales. Geological Journal, Vol 24/1, 31-47. |
| Somerville, I D and Strank, A R E, 1984. Discovery of Arundian and Holkerian faunas from a Dinantian platform succession in North Wales. Geological Journal, Vol.19, 85-104. |
| Davies, J R, Wilson, D and Williamson, I T. 2004. Geology of the country around Flint. Memoir for 1:50 000 Geological Sheet 108. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E108
|
