PRELIMINARY ASSESSMENT OF THE FAUNA OF THE UPPER MIOCENE HUMBOLDT FORMATION EXPOSED IN ELKO COUNTY, NEVADA FROM FIELD AND MUSEUM COLLECTIONS

Vertebrate fauna have long been known from the Humboldt Formation of northeastern Nevada, however previous studies have been broad in scale and scope and there has not been a synthesis of the vertebrate remains from this unit geographically and stratigraphically. This study presents the preliminary results based on new materials discovered in 2024 from previously unreported localities on the east side of the Independence Mountains, ~40km northwest of Elko, NV, in combination with ongoing fieldwork and museum collections from Elko County previously investigated by JB.

The Humboldt Formation contains alluvial fan, fluvial, and lacustrine terrestrial deposits with abundant interbedded volcaniclastic intervals. The Humboldt Basin was formed initially by continued gravitational collapse of the Nevadaplano, and subsequently by regional detachment faulting and resulting adjacent accommodation space.

Previous studies have identified horses, camelids, and potential antilocaprids. We confirm and add to these taxa including: Suidae, Camelidae, Equiidae (cf. Neohipparion sp.), Rhinocerotidae (cf. Teleoceras sp.), cf. Mustelidae, Feliformes (cf. Machairodus), Proboscidea (Gomphotheriidae). The presence of the horse taxon Neohipparion is instructive biostratigraphically as this morph is known only from Upper Miocene strata of Clarendonian-Hemphillian North American Land Mammal Ages (13-5 Ma). Continued survey of new sites and museum collections will greatly expand this list and provide for regional stratigraphic refinement of faunal distributions. Further work planned includes chronostratigraphy, and microvertebrate processing of matrix from these sites.