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Proc Natl Acad Sci U S A. 2015 May 19;112(20):6319-24. doi: 10.1073/pnas.1501904112. Epub 2015 May 4.

Cahokia's emergence and decline coincided with shifts of flood frequency on the Mississippi River.

Author information

1
Departments of Geography and semunoz@wisc.edu.
2
Departments of Geography and.
3
Department of Earth and Planetary Sciences, Washington University, Saint Louis, MO 63130.
4
Anthropology and.
5
Departments of Geography and Center for Climatic Research, University of Wisconsin-Madison, Madison, WI 53706; and.

Abstract

Here we establish the timing of major flood events of the central Mississippi River over the last 1,800 y, using floodwater sediments deposited in two floodplain lakes. Shifts in the frequency of high-magnitude floods are mediated by moisture availability over midcontinental North America and correspond to the emergence and decline of Cahokia--a major late prehistoric settlement in the Mississippi River floodplain. The absence of large floods from A.D. 600 to A.D. 1200 facilitated agricultural intensification, population growth, and settlement expansion across the floodplain that are associated with the emergence of Cahokia as a regional center around A.D. 1050. The return of large floods after A.D. 1200, driven by waning midcontinental aridity, marks the onset of sociopolitical reorganization and depopulation that culminate in the abandonment of Cahokia and the surrounding region by A.D. 1350. Shifts in the frequency and magnitude of flooding may be an underappreciated but critical factor in the formation and dissolution of social complexity in early agricultural societies.

KEYWORDS:

Cahokia; Mississippi River; flooding; geoarchaeology; paleohydrology

PMID:
25941363
PMCID:
PMC4443319
DOI:
10.1073/pnas.1501904112
[Indexed for MEDLINE]
Free PMC Article

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