Paleobotanical and Environmental Implications of a Buried Forest Bed in Northern Lower Michigan, USA
Randall J. Schaetzl, Catherine H. Yansa and Michael D. Luehmann
Sediments and stratigraphy at the Tower Buried Forest site provide a glimpse into the immediate post-glacial environment of northern Lower Michigan, USA. At this site, sandy glacial outwash is overlain by (1) ≈37 cm of peat associated with a wetland, above which are (2) flat lying spruce and larch logs and branches that date between ≈10,910 and 10,340 cal yr BP. Above the woody materials are ≈55-75 cm of sand, interbedded with organic muck laminae, which we interpret as local alluvium. This stratigraphic sequence is overlain by muck soil materials associated with the modern wetland. Pollen and plant macrofossil analysis of the lower peat indicate that a tundra-boreal parkland had been established here, shortly after final deglaciation. Later, Picea glauca (white spruce), Picea mariana (black spruce), Larix laricina (larch) and Abies balsamea (balsam fir) became abundant in an open boreal forest-Spaghnum peatland. Subsequent increases in Pinus (pine) and Typha (cattail) indicate drying and possibly warming conditions. At ca. 10,340 cal yr BP (or a few centuries prior), nearly two millennia after final deglaciation, water flowed across the site, possibly knocking over the trees.. Interbedded sand and muck deposits above the flat-lying logs are interpreted as alluvial deposits from this event, after which the wetland became quiescent again.