In addition to having a rich assemblage of mammalian fossils, the Gao Mine locality in the Paskapoo Formation of south-central Alberta has yielded numerous plant specimens of late Paleocene (late Tiffanian or Ti5) age. The plant fossils are preserved in siltstones and fine-grained sandstones interpreted as overbank sediments that were deposited on an aggrading floodplain. The assemblage is dominated by the cupressaceous conifer Metasequoia foxii and the cercidiphyllaceous dicot Joffrea speirsiae, including their well-preserved seedlings. The flora also contains foliage of the ferns Onoclea and Speirseopteris and the woody dicots Palaeocarpinus, Aphananthe/Celtis, Aesculus, Beringiaphyllum, ?Trochodendron, and Wardiaphyllum, as well as seedlings of unknown dicotyledonous angiosperms. Metasequoia foxii and Speirseopteris are unique to the floras of Gao Mine and the nearby Munce’s Hill site (Tiffanian Ti4). The remainder of the taxa are common in late Paleocene floras of North Dakota, Montana, and Wyoming, all USA. The floras of the nearby Joffre Bridge Roadcut and Blindman River sites (both Tiffanian Ti3) are more diverse, but both of those sites encompass a wider range of depositional environments and may include higher percentages of allochthonous material. Most of the Gao Mine material is autochthonous. The seedlings were buried in place, along with the surrounding leaf litter, preserving a record of the local plant community.
Depositional Environments of the Upper Devonian Oneonta Formation of South-Central New York