Cahokia's emergence and decline coincided with shifts of flood frequency on the Mississippi River.
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.
Departments of Geography and semunoz@wisc.edu.
Samuel E
SE
Munoz
Departments of Geography and.
Kristine E
KE
Gruley
Departments of Geography and.
Ashtin
A
Massie
Department of Earth and Planetary Sciences, Washington University, Saint Louis, MO 63130.
David A
DA
Fike
Anthropology and.
Sissel
S
Schroeder
Departments of Geography and Center for Climatic Research, University of Wisconsin-Madison, Madison, WI 53706; and.
John W
JW
Williams
D000367:Age Factors; D001106:Archaeology; D002250:Carbon Radioisotopes / Q000032:analysis; D055868:Floods; D019015:Geologic Sediments / Q000737:chemistry; D049691:History, Medieval; D006801:Humans; D007087:Illinois; D007198:Indians, North American / Q000266:history*; D013058:Mass Spectrometry; D010316:Particle Size; D045483:Rivers
D002250:Carbon Radioisotopes
Cahokia; Mississippi River; flooding; geoarchaeology; paleohydrology