Academic journal article Michigan Academician

Fossil Dunes and Soils near Saginaw Bay, A Unique Herpetological Habitat

Academic journal article Michigan Academician

Fossil Dunes and Soils near Saginaw Bay, A Unique Herpetological Habitat

Article excerpt

ABSTRACT

A study of archaeological records and documented modern records of the herpetofauna of the fossil low dune and dune soil counties of Saginaw, Midland, Bay, and Tuscola, Michigan, indicates that 34 species have existed in the area in Holocene times. The number of modern herpetological species indicated for this area by the five field guides of the 1990s is 41, 7 more than could be verified. Of the 34 species documented by the 2000-2001 study, 22 occupy wetland and/or aquatic habitats and only 11 are terrestrial. Among the terrestrial species, none of the three species of mole salamanders (Ambystoma) that occur in other Michigan counties at this general latitude are recorded. It is suggested that the absence of these species may be due to the acidic, saline, sandy soil of the area. The extralimital slider turtle (Trachemys scripta, archaeological record) , and six-lined racerunner lizard (Cnemidophorus sexlineatus which occurs in Michigan only in Tuscola County) may be relicts from the Middle Holocene warm, dr y period (hypsithermal). The inland archaeological and modern occurrences of the eastern fox snake (Elaphe gloydi) in the area indicate the species occupied and occupies habitats other than the marshy areas adjacent to Lake Erie and Lake Huron that are suggested as the habitat for Michigan Lower Peninsula fox snakes in the literature. The author plans a future paleontological sieving project in undisturbed Holocene soils in the area in an attempt to document additional herpetological records. It is suggested that relict herpetological habitats in Michigan be identified and protected.

INTRODUCTION

A recent survey by the author (Holman 2001) shows, not unexpectedly, that the distribution of many amphibians and reptiles in Michigan is much more fragmented and spotty than modern range maps indicate. This situation is undoubtedly due, in part, to human modifications of the environment. But one must remember that herpetological habitats were quite recently obliterated by Pleistocene ice masses and then re-occupied in a relatively random fashion rather than by an orderly march of plant and animal communities northward. Moreover, some Michigan herpetological species are undoubtedly in the process of re-occupying new habitats (Holman 1992) while others have probably been left in relict habitats since the Middle Holocene warm, dry period (hypsithermal event). This paper deals with a preliminary study of what appears to be a relict herpetological habitat in the low fossil dune and dune soils area near Saginaw Bay, Michigan, and some observations that have grown out of this study.

THE FOSSIL INLAND DUNE FIELDS NEAR SAGINAW BAY

The inland dunes of Michigan are the oldest dunes in the state (Dorr and Eschman 1970). These dunes formed around the borders of the ancient Great Lakes and glacial outwash plains when the ancient Great Lakes levels were higher and the lands lower due to previous Wisconsinan ice depression. Unlike the active coastal dunes, the inland dunes are presently in growth stasis as they were stabilized by the growth of vegetation long ago. On the other hand, in many areas, poor or overzealous farming practices have destroyed vegetation and reduced soil moisture to such an extent that many inland dune areas are again subject to wind erosion.

Inland dunes are actually widely distributed in the state (Figure 1). Major areas of such dunes are in western Michigan from Berrien to Manistee Counties; the eastern one-half of the Upper Peninsula; the tip of the Lower Peninsula in Emmet, Cheboygan, Presque Isle, and Alpena Counties; and in the Saginaw Bay area. Lesser inland dune areas occur southeast of Traverse Bay in Kalkaska and Roscommon Counties and in southeastern Michigan in St. Clair and Macomb Counties.

The general Saginaw Bay fossil dune field and dune soil area is outlined in

Figure 2. Dr. Alan Arbogast of the Department of Geography at Michigan State University is studying a specific dune field in Midland County and has kindly supplied me with the following information. …

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