Published online by Cambridge University Press: 01 May 2009
The Glen Park Member of the Sulphur Springs Formation (Devonian) in east-central Missouri contains abundant phosphate nodules. Dissolution of several nodules in hydrochloric acid yielded a diverse, well-preserved Ordovician fauna, containing diagnostic graptolites, ostracodes and conodonts, demonstrating that the Glen Park phosphate nodules are reworked from the Ordovician. Faunal similarities and the in situ occurrence of phosphorite in nearby exposures of the Mequoketa Shale (Ordovician ) strongly suggest hat phosphate nodules in the Glen Park were reworked from the Maquoketa.