LATE PALEOCENE ALMONT AND BEICEGEL CREEK: FLORISTIC COMPARISONS ARE RELATED TO DEPOSITIONAL ENVIRONMENT

The Late Paleocene floras of the Northern Hemisphere are often characterized as being  low diversity assemblages. However, the Almont and Beicegel Creek silicified floras of North Dakota are considerably diverse, with over 50 genera identified from 22 families.  The classic Almont Lagerstätten which has been studied for over two decades is located in the center of the North Dakota in an area lacking the topographic relief needed for clearly understanding its paleoenvironmental context. Beicegel Creek, a recently discovered series of outcrops in the western part of the state, is a second floral assemblage very similar in composition to Almont.  This locality, in the North Dakota Badlands, has considerably more exposed strata.  We have found the silicified floras in situ and ascertain the diogenesis of the area.  While floras from the two sites are very similar, there are interesting differences in the occurrence of particular taxa, that appear to be correlated with preservation and, ultimately, depositional environment. For example, the Almont site hosts a hamamelid infructesence, Nordenskioldia, and the recently described nymphaeaceous seed Susiea that are lacking at Beicegel Creek.  In contrast, Beicegel Creek contains several types of ferns, as well as the lycopod Isoetes, none of which are known from Almont. Vegetative remains of a distinct monocot plant and seeds and embryos of Spirematospermum are more common at Beicegel Creek, and Ginkgo at Almont. Fish scales are found sporadically both at Almont and several individual outcrops in the west. Together these remains demonstrate that the megafossil assemblages at the two sites are indicative of different depositional environments and taphonomic settings.