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Mastodon-Bearing Springs and Late Quaternary Geochronology of the Lower Pomme de Terre Valley, Missouri

By
C. Vance Haynes, Jr.
C. Vance Haynes, Jr.
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Published:
January 01, 1985

Fourteen consecutive field seasons of scientific excavations of alluvial deposits of the lower Pomme de Terre Valley, southeastern Missouri, have provided a radiocarbondated (154 analyses) chronostratigraphic sequence in four terraces reflecting five major episodes of aggradation and degradation. Probably all of Wisconsinan time and the Holocene is represented. A sixth alluvial deposit is probably Illinoian and possibly older Pleistocene alluvium. Spring deposits within the terraces contain bone beds associated with peat lenses containing pollen, plant, and beetle remains, all of which have provided paleoecological data.

The springs appear to have erupted initially, in response to either tectonic disturbance or hydrostatic pressure near the peak of a glacial maximum. Subsequent episodes may correlate with later maxima. Peat deposits correlate with interstadials on the bases of fauna, flora, and radiocarbon dating. Gravel deposits of spring conduits contain bones and plant remains that are considerably older than overlying peat deposits. Some of these older elements have been redeposited in younger spring deposits via spring action. Other evidence suggests that some animals may have fallen into springs and intruded older deposits. A developmental sequence for the origin of concentric spring deposits in alluvium is proposed.

None of the six spring deposits excavated contained any associated archaeological remains older than 10,500 B.P., which marks the first appearance of artifacts in the stratigraphic record at Rodgers Shelter. Extinction of the Pleistocene big-game animals occurred sometime between then and 16,000 B.P.

A major episode of degradation occurring between 10,500 and 13,000 B.P. probably coincides with similar episodes occurring approximately 12,000 B.P. on many if not most streams in the United States. With some exceptions, subsequent epicycles of cutting and filling appear to correlate generally over the same area.

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GSA Special Papers

Mastodon-Bearing Springs and Late Quaternary Geochronology of the Lower Pomme de Terre Valley, Missouri

C. Vance Haynes, Jr.
C. Vance Haynes, Jr.
Search for other works by this author on:
Geological Society of America
Volume
204
ISBN print:
9780813722047
Publication date:
January 01, 1985

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