36. Earliest Eocene Mammalian Fauna from the Paleocene-Eocene Thermal Maximum at Sand Creek Divide, Southern Bighorn Basin, Wyoming

Author(s): Kenneth D. Rose, Amy E. Chew, Rachel H. Dunn, Mary J. Kraus, Henry C. Fricke, Shawn P. Zack

Publication 36


An extensive earliest Eocene mammalian fauna is described from the PETM interval of Sand Creek Divide, about 17 km northeast of Worland, Wyoming. The assemblage, consisting of more than 1000 specimens representing 56 species, was collected over the last decade by surface prospecting, screen-washing, and limited excavation. Samples come from more than 40 localities spread throughout a 45-m section representing the entire PETM (~200 ka). Carbon isotope records from bulk sediment and from mammalian tooth enamel were compiled and used to delimit the PETM and to correlate the Sand Creek Divide section with the Polecat Bench section. The lowest 1-2 m of the PETM section at Sand Creek Divide appears to correspond to the Wa-M biozone at Polecat Bench, although the only taxon in common is the condylarth
Haplomylus zalmouti. This narrow interval at Sand Creek Divide has also produced the lowest occurrence of Diacodexis, but has not yielded Meniscotherium, the index taxon for which the biozone was named. The remainder of the PETM section at Sand Creek Divide represents the Wa-0 biozone. About 15-20m below the PETM faunas is a small sample of late Clarkforkian mammals. The upper boundary of the Wa-0 biozone is demarcated by the lowest occurrences of several Wa-1 taxa (Hyracotherium grangeri,Cardiolophus radinskyi, Cantius ralstoni, Haplomylus speirianus), which are found between 45 and 50 m. This is ~15-20 m higher than the lowest Wa-1 samples from the No Water Creek section of Bown (1979), indicating a thicker PETM section at Sand Creek Divide. An unexpected first occurrence at 50m is the perissodactyl Homogalax protapirinus, otherwise unknown until Wa-3. (Go to the link and see more of this paper.)

Publication Information:

Publisher: University of Michigan

Month of Publication: February

Year of Publication: 2012

Location: Ann Arbor, MI

Volume Number: 36

# of Pages: 136