01893nas a2200193 4500008004100000245011200041210006900153300001400222490000700236520123900243653002901482653002101511653002601532653001501558100002001573700001701593700001601610856007301626 1993 eng d00aLower Ordovician (Ibexian) Trilobites from the Tribes Hill Formation, Central Mohawk Valley, New York State0 aLower Ordovician Ibexian Trilobites from the Tribes Hill Formati a1618-16330 v303 a

The Early Ordovician Tribes Hill Formation of east-central New York State is a sequence of peritidal to subtidal carbonates and minor shales that rests disconformably on Late Cambrian carbonates and is, in turn, succeeded disconformably by Middle Ordovician strata. More than 800 trilobites from 24 collections are assigned to six species: Bellefontia gyracantha (Raymond), Clelandia parabola (Cleland), Hystricurus ellipticus (Cleland), Hystricurus cf. Hystricurus oculilunatus Ross, Symphysurina convexa (Cleland), and Symphysurina cf. Symphysurina woosteri Ulrich. Two distinct biofacies are present: the Bellefontia Biofacies in subtidal shales with thin, storm-generated bioclastic interbeds, and the Gastropod–rostroconch Biofacies in shallow, carbonate bank lithofacies. The trilobites of the Tribes Hill Formation are assigned to a single, informal biostratigraphic unit, the Clelandia parabola Fauna, which is correlative with trilobite Zone B of the Garden City Formation of Utah and with the Bellefontia franklinense Subzone of the McKenzie Hill Formation of Oklahoma.

10aClelandia parabola Fauna10aEarly Ordovician10aTribes Hill Formation10atrilobites1 aWestrop, S., R.1 aKnox, L., A.1 aLanding, E. uhttp://www.nrcresearchpress.com/doi/abs/10.1139/e93-140#.Vl4BO7-1W70