Silurian biostratigraphy of the Cadia area, South of Orange, New South Wales

New Silurian fossil discoveries in the vicinity of Cadi a Mine indicate ages younger than shown on recent maps. Limestone, intersected in drill core immediately above an unconformable contact with Late Ordovician volcanics of the mine sequence, yielded an early Wenlock conodont fauna including Prerospathodus amorphognathoides. P procerus and P. rhodesi, together with Kockelella ramdiformis. A diverse shelly fauna of late Wenlock to early Ludlow aspect, dominated by brachio pods, is present in a slumped mudstone on the mine access road. South of the mine, in Rodds Creek valley, Silurian rocks are shown to occur as infaulted slices along the Werribee Fault. Limestone pods in this area conta in conodonts (Coryssognatlzus dubius) indicative of a Ludlow age; a graptolite fauna from nearby siltstones inc ludes Monograptus flemingii warreni. M. flexilis, Monoclimacis flwnendosaeflumendosae and Cyrrograptus ex. gr. C. rigidus, and is assigned to the lundgreni· testis Biozone (late We nlock). The youngest graptolite assemblage (Pi'fdolf) occurs in siltstones, tentatively correlated with the Wa llace Shale, exposed in a shallow excavation east of Cadia Mine. Th is fauna, which inc ludes Dictyonema sherrardae mumbilens is, Acanthograpllts aculeaws neureaens is, Pris tiograptus shearsbyi, P cf. P. dubius, Mc nograptus parultimus minutus, M. microdon aksajensis and M. cf. M. yassensis, is younger than all known graptolite faunas from the nearby Four Mile Creek area, and provides the first Australian record of Monograpllls microd on.