This topic has long been a staple of geoarchaeology, given the close relationships between peoples and rivers. A long-standing study of mine, involving the Sny Bottom portion of the Mississippi River in western Illinois, near Hannibal, Missouri, is finally out in review. Based on more than two hundred core holes, geoarchaeological studies at several mitigated sites, and a number of radiocarbon dates obtained by recovering uncarbonized plant macrofossil assemblages, the Sny Bottom record is interpreted to reflect the effects of very large (extra-historical) Upper Mississippi River floods on the Holocene evolution of this floodplain reach.
View from Lovers Leap near Hannibal
of the ca. 6-mile-wide Mississippi
These crevasse splays near Hannibal
formed during a very large flood
event ca. 3,100 years ago.
Using a similar methodological approach, I now am synthesizing several new radiocarbon-dated Holocene fluvial sections from the Mohawk and Upper Hudson River drainages in east-central New York. With these new data, I am re-examining the meaning and extent of similar kinds of sites with multi-story soils (or paleosols) that the late Bob Funk excavated in the Susquehanna basin, to consider some of the internal system controls on how Holocene floodplains like these evolve. By coring, I recover uncarbonized plant macrofossils from basal bar deposits for dating, and then use traditional archaeobotanical methods of column flotation to recover charcoal from topstratum deposits. This allows for much tighter control over the short times involved with sedimentation compared with that wrapped up in soil formation. The floodplain sections containing these stacked soil sequences formed under a limited set of conditions and factors.
Multi-story soils in the Schoharie
Refining chronological control over rates of sedimentation
and soil formation