PALEONTOLOGY ON OIL AND GAS WELL PADS MAY PRODUCE SIGNIFICANT HOLOCENE DATA

Most of the Pleistocene-aged, glacially derived sediments that cover the surface of Michigan’s lower peninsula are topped by a layer of much younger, organic sediment resulting from their exposure to soil formation processes throughout the Holocene Epoch. The relative thinness of this layer compared to that of the glacial material suggests that much of the biologic and geologic history of the region during the latest Pleistocene and Holocene is either obscured by this compressed blanket of organic matter or has been removed by erosional processes prior to the deposition of these organics. Exposures of “mineral soil” sometimes occur as petroleum and natural gas well pads are installed and utilized in the region. Wind and water on these exposures removes virtually all particles with less mass than the sand and gravel of the glacial material. Of A soil’s O-horizon, only larger objects that have been deposited after the deposition of the Pleistocene outwash remain behind, and from a series of these sites (n = 44), bones from the marsupial mammal Didelphis virginiana and a freshwater emydid turtle were located in association with mineral soil exposures from two pads located approximately 100 miles (160 km) north of Saginaw, Michigan. Because of the rapid northward expansion of D. virginiana, and several members of the Emydidae, as well as the population declines of many other freshwater turtles, the paleontology of material exposed in by these erosional processes may provide insight into the late Holocene biogeography of multiple vertebrate groups in the northern Michigan and beyond.