No abstract

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.