Conodonts, stratigraphy, and relative sea-level changes of the Tribes Hill Formation (Lower Ordovician, east-central New York)

Abstract

Tremadocian onlap is recorded by the Tribes Hill Formation. The formation is a lower Lower Ordovician (upper conodont Fauna B Interval(?)-Rossodus manitouensisZone) depositional sequence that unconformably overlies the Upper Cambrian Little Falls Formation.Depositional environments and stratigraphy indicate that the Tribes Hill was deposited on a wave-, not tide-, dominated shelf and that a uniform, “layer-cake” stratigraphy is present. The deepening-shoaling sequence of the Tribes Hill includes the: 1) Sprakers Member (new; peritidal carbonate and overlying tempestite limestone and shale); 2) Van Wie Member (new; subtidal shale and limestone); 3) Wolf Hollow Member (revised; massive carbonates with thrombolitic cap); and 4) Canyon Road Member (new; glauconitic limestone and overlying evaporitic dolostone). The shoaling half-cycle of the Tribes Hill is older than a shoaling event in western Newfoundland, and suggests epeirogenic factors in earliest Ordovician sea-level change in east Laurentia. Conodont and trilobite biofacies track lithofacies, andRossodus manitouensisZone conodonts andBellefontiaBiofacies trilobites appear in the distal, middle Tribes Hill Formation.Twenty-four conodont species are illustrated.Ansella?protoserratanew species,Iapetognathus sprakersinew species,Leukorhinion ambonodesnew genus and species, andLaurentoscandodusnew genus are described.