Aeolian activity during Late Glacial time, with an example from Mongo, Indiana, USA

摘要

The last aeolian activity of a significant number of inland sand dunes in the southern Great Lakes region (SGLR) was several thousands of years after deglaciation. At Mongo, Indiana, a field of parabolic sand dunes with a variety of morphologies are within the channel bottom of the Pigeon River meltwater channel, with some dunes having climbed up the channel wall onto the adjacent upland surface. The optically stimulated luminescence (OSL) samples from the channel-bottom dunes have a mean age of 14.2 +/- 16 ka (n = 2) and the OSL samples from upland dunes have a mean age of 12.3 +/- 16 ka (n = 4). Dunes and outwash ages and geomorphic setting constrain both the position of the Huron-Erie and Saginaw lobes. The oldest dune age is also a minimum age for cessation of local meltwater flow from the Huron-Erie Lobe of the Laurentide Ice Sheet and formation of the adjacent Sturgis Moraine of the Saginaw Lobe. The final activity of the dunes is coincident with late glacial stadial and interstadial events as recorded in the Greenland ice core records, a similar finding to all other studies of dunes in the SGLR. It is now well recognized that many dunes were last active before, during, and after the Younger Dryas stadial, presumably in response to a climate that was windier and less favorable for vegetation.