A late Eocene wood assemblage from the Crooked River Basin, Oregon, USA

Well-preserved silicified woods are common in the Pacific Northwest, USA. Localities near the town of Post, Oregon, provide insights into the late Eocene vegetation and climate ca. 36 million years ago and data for comparing both older and younger wood floras of the region. New investigations of the late Eocene Dietz Hill locality (UF 278) revealed woods belonging to the families Pinaceae (Keteleeria farjonii sp. nov.), Cupressaceae (Taxodioxylon sp.), Magnoliaceae (Magnolia hansnooteboomii sp. nov.), Lauraceae (Laurinoxylon sp. A and B), Platanaceae (Platanoxylon haydenii (Felix) Süss and Müller-Stoll, 1977), Fabaceae (cf. Styphonolobium sp.), Fagaceae (Fagus dodgei Wheeler and Manchester, 2021, Quercus sp., Red Oak type), Juglandaceae (Carya leroyii sp. nov.), Ulmaceae (Ulmus woodii Wheeler and Manchester, 2007), Sapindaceae (Aesculus constabularisii sp. nov., Klaassenoxylon wilkinsonii gen. et sp. nov.), and Araliaceae (Plerandreoxylon oskolskii sp. nov.). Some woods could be assigned to order, but not to family, Rosales (Urticaleoxylon stevensii gen. et sp. nov., and two unnamed woods with features of  Cannabaceae and Moraceae), Sapindales (cf. Fagaroxylon sp.). There also is a Hamamelidoxylon sp., which has features found in both the Theaceae and Hamamelidaceae. These woods, together with taxa identified from co-occurring silicified fruits and seeds represent a diverse assemblage of warm temperate to subtropical woody plants, some with East Asian affinities. Comparing the wood functional traits of the Dietz Hill assemblage to the older Clarno Nut Beds (mid-Eocene) woods and to the younger woods associated with Oligocene Bridge Creek flora attests to increased seasonality and cooling climate.