Abstract Detail

Paleobotany

Paleocene lacustrine floras of the Tongue River Member, Fort Union Formation, in and near Birney, Montana, USA.

Lacustrine deposits interbedded with coal seams in the Tongue River Member of the Fort Union Formation in southeastern Montana provide insights into the composition of vegetation growing adjacent to coal-forming swamps about 60 to 62 million years ago. Typical megafossil sites include impressions of fruits and seeds as well as leaf impressions. The sites are relatively low in diversity, each with about 15 to 20 genera. The main components of deposits near Birney include Equisetum and a fern resembling Dennstaedtiopsis, plus Taxodium (based on cone scales as well as foliage branches and associated pollen cones) and a low-diversity angiosperm assemblage dominated by Platanaceae (Platanus, Macginitiea), Cornales (Cornus swingii, Davidia antiqua, Amerisinia obtrulata, Browniea serrata), Sapindaceae (Aesculus hickeyi) and Nordenskioeldia borealis, augmented by Betulaceae (Palaeocarpinus), Juglandaceae (Polyptera), Saxifragales (Jenkinsella/Trochodendroides), Ulmaceae (Ulmites), Cannabaceae (Celtis aspera) and probable Rutaceae (Porosia verrucosa). Many of these taxa were widespread in the Northern Hemisphere by the late Paleocene. Most of these plants are inferred to have been woody and deciduous. Only a few angiosperm morphotypes continue to elude systematic placement, including Averhhoites affinis, Pistilipollianthus and an unidentified but locally common serrate leaf. Field and museum work continues in an effort to link isolated fruits and seeds with the leaves of their likely host plants through co-occurrence analyses to provide more characters for taxonomic placement

1 - Florida Museum Of Natural History, Dickinson Hall, Museum Rd & Newell Dr., Gainesville, FL, 32611, United States

Keywords:
Tertiary
Cenozoic
fossil leaves
fossil fruits.

Presentation Type: Oral Paper
Number: PB5001
Abstract ID:1051
Candidate for Awards:None