Post-Glacial Fluvial Response and Landform Development in the Upper
Muskegon River Valley in North-Central Lower Michigan, U.S.A.
Alan F. Arbogast, J.R. Bookout,
Brad R. Schrotenboer, A. Lansdale, G.L. Rust, and
V.A. Bato
This study focuses on the upper part of the Muskegon
River system in north-central Lower Michigan and is the first to reconstruct
the post-glacial history of fluvial landform development in the core of North
Americas Great Lakes region. Results indicate that the upper Muskegon River
valley contains four alluvial terraces and numerous paleomeanders. Radiocarbon dating of peats within these old
channels provides a good chronology for stream behavior and landform
development. The T-4 terrace is a paired
Pleistocene outwash/lacustrine surface that probably formed about 12,500 years
ago. The T-3 terrace is a fill-strath surface that was cut between about 12,000 and
perhaps 9,500 years ago. The geometry of
macromeanders on this surface suggests that stream discharge
was ~ 8 times greater than during the Holocene.
The
Pleistocene/Holocene transition is marked by a major period of downcutting that likely began as the climate warmed/dried
and sediment yield diminished. This
period of downcutting potentially lasted through the
drier middle Holocene, creating a 6-m-high escarpment in the valley. The Muskegon River then began to aggrade when the climate became wetter. Subsequently the river again incised,
creating the paired T-2 terrace, about 3400 years ago when the climate became
still wetter. T-2 paleomeanders
indicate that stream discharge at this time was consistent with the modern
river. In the past 2500 years, the
stream has constructed a poorly defined complex of T-1 terraces. These surfaces likely formed due to complex
response associated with more variable climate.
This study demonstrates that the upper Muskegon River has a similar
post-glacial history as streams on deglacial and
periglacial landscapes elsewhere in the world.
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