## Abstract Pendent didymograptid graptolites are described from mudstones immediately overlying the Henβdyβcapel ironstone (St. Tudwal's Peninsula, LlyΜn, North Wales). The graptolites indicate a Llanvirn age for these beds, implying a Llanvirn or Arenig age for the ironstone, in contrast with the
Age and controls of ironstone deposition (Ordovician) North Wales
β Scribed by R. J. B. Trythall; C. Eccles; S. G. Molyneux; W. E. G. Taylor
- Book ID
- 102845344
- Publisher
- John Wiley and Sons
- Year
- 1987
- Tongue
- English
- Weight
- 836 KB
- Volume
- 22
- Category
- Article
- ISSN
- 0072-1050
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β¦ Synopsis
Post-Arenig ironstones and associated sediments of North Wales have yielded Upper Llanvirn, Llandeilo and Lower Caradoc acritarch assemblages. The occurrence of most ironstones coincides with a eustatic regression and subsequent transgression, and the emergence to the northwest of the Irish Sea Landmass, the probable source of the iron. The majority of ironstone deposition within the basin was restricted to short-lived local submarine rises most likely produced by synsedimentary faulting.
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Hen-dy-cape1 (St Tudwal's) ooidal ironstone is of Lower Llanvirn age, based on the discovery of pendent didymograptid graptolites from a locality adjacent to the ironstone at Pen-y-gaer. These findings differ from previous published ages of Lower to Middle Llandeilo age for the Hen-dy-cape1 Ironston
Graptolite assemblages of multidens Biozone age have been recovered from mudstones immediately above and below the Llyn Conwy Formation, the local representative of the regionally extensive acid tuffs that mark the end of vulcanicity in the south and east of the Harlech Dome. They include several ta
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