DC: Dutch Creek Fissure,    E: Empty Fissure 

Paleoecological Interpretation of the Late Quaternary Wapsipinicon Local Fauna (Empty Fissure and Dutch Creek Fissure local faunules), Jones County, Iowa Principle investigator: Steven Wallace This project was funded by the Paleobiological Fund

    Fossiliferous deposits from Dutch Creek Fissure of the Wapsipinicon local fauna, located within the Dutch Creek valley of Wapsipinicon State Park, Jones County, Iowa, have produced abundant late Wisconsinan microvertebrate remains. Taxa recovered include boreal indicators [Phenacomys intermedius (heather vole), Synaptomys borealis (northern bog lemming), and Clethrionomys gapperi (southern red-backed vole)]; a taiga indicator [Microtus xanthognathus (yellow-cheeked vole)]; and tundra indicators [Dicrostonyx torquatus (collared lemming), Microtus miurus (singing vole), and Lemmus sibiricus (brown lemming)]. None of these taxa is found in the area today. Although this assemblage does contain some Holocene material, the bulk of the specimens are late Wisconsinan in age.

    AMS ¹⁴C dates of 13,460 + 120 (NZA 10446), 17,280 + 170 (NZA 10444), 17,810 + 160 (NZA 10443), and 25,470 + 350 yr B.P. (NZA 10445) obtained from four mandibles of Microtus xanthognathus span most of the late Wisconsinan and include the oldest Midwestern date for the species. Three eastern Iowa fossil localities (Figure 1) suggest the presence of M. xanthognathus during the glacial maximum. Although dated by associated plant macrofossils, M. xanthognathus remains from Elkader (20,530 + 130 yr B.P.; Woodman 1996) and Duhme Cave (21,780 + 240 yr B.P; Jans 1993) represent the earliest part of the last glacial maximum, whereas specimens from Conklin Quarry represent the end of the last glacial maximum (18,090 + 190 to 16,710 + 210 yr B.P.; Baker et al. 1986). These associations, along with the new dates from Dutch Creek, indicate that M. xanthognathus was present in eastern Iowa from 25,500 yr B.P. to 13,500 yr B.P., including the entire glacial maximum (c. 20,000-18,000 yr B.P.).

    The occurrence of Microtus xanthognathus, a species indicative of taiga (Figure 1), during the full glacial and glacial maximum suggests that there was a forest component to the flora of eastern Iowa during this period. This interpretation supports the Baker et al. (1986) conclusion that a widespread tundra-parkland was prevalent in eastern Iowa during the full glacial, and suggests that this parkland was present during the glacial maximum as well.

    I would like to thank the Paleobiological Fund for their financial support of this project; Nancy Beavan at Rafter Radiocarbon Laboratory for her valiant efforts to date such small specimens; and Holmes A. Semken, Jr. for reviewing this note.

References Cited:

Baker, R.G.; Rhodes, R.S., II; Schwert, D.P.; Ashworth, A.C.; Frest, T.J.; Hallberg, G.R.; and Janssens, J.A.  1986  A full-glacial biota from southeastern Iowa, USA. Journal of Quaternary Science 1(2):91–107.

Jans, C.M.  1993  Anomalous dentitions in Holocene woodland voles (Microtus pinetorum) from Duhme Cave, eastern Iowa. Current Research in the Pleistocene 10:103-105.

Woodman, N.  1996  Paleoecology of subarctic faunal assemblages from the Woodfordian age (Pleistocene: Wisconsinan) Elkader site, northeastern Iowa. University of Kansas Natural History Museum Occasional Papers 178:1-33.

Wallace, S.C., 2000, Four New AMS ¹⁴C Dates on Microtus xanthognathus with comments on Midwestern paleoecology: Current Research in the Pleistocene, v. 17, p. 138-139.

• Department of Geosciences
• Wapsipinicon Page
• Home Page of Steven Wallace