A new fossil locality yielding rare conodonts of probable late Arenig to early Llanvirn age in the previously unfossiliferous Melbourne Formation of the Appalachian Humber Zone has been discovered in the Eastern Townships of Quebec. The presence of a continental-margin fauna at the northeast end of the Sutton Mountains Anticlinorium suggests a continuity of sedimentation, and this contradicts previous suggestions of a major disconformity between the Lower and Middle Ordovician rocks in this part of the Quebec Reentrant. Moreover, recent geological mapping shows that the contact between the conodont-bearing Melbourne Formation and the underlying Sweetsburg Formation of the Oak Hill Group is conformable and gradational. Consequently, it is proposed that the graphitic limestone of the Melbourne Formation represents the youngest unit of the Cambro-Ordovician Oak Hill Group.

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