TESTING NARRATIVES OF ECOCIDE WITH THE STRATIGRAPHIC RECORD AT CAHOKIA MOUNDS STATE HISTORIC SITE, ILLINOIS

Narratives of ecocide, when a society fails due to self-inflicted ecologic disaster, have been broadly applied to many major archaeological sites based on the expected ecological consequences of known land-use practices of past peoples. These theories of ecocide often become accepted in academic and public discourse despite a lack of direct evidence that the hypothesized ecological consequences of land-use practices occurred. Cahokia Mounds, located in American Bottom floodplain of the central Mississippi River Valley, is one such major archaeological site where untested narratives of ecocide have persisted in discourse. The wood-overuse hypothesis suggests tree-clearance in the uplands surrounding Cahokia led to erosion, causing increasingly frequent and unpredictable floods of the local creek drainages in the floodplain where Cahokia Mounds was constructed. Archaeological excavations conducted on the toe slope of a Mississippian occupation (AD 1050-1400) oval mound in the Cahokia Creek floodplain shows that the same A-horizon on which the oval mound was constructed remained stable until industrial development in the 1800s. The presence of a stable ground surface from Mississippian occupation to the Industrial Era does not support the expectations of the wood-overuse hypothesis; however, the expected stratigraphic evidence of the wood-overuse hypothesis is present after AD 1800. After industrial development in the uplands, as indicated by the presence of coal clinker, there is a ubiquitous signal of fluvial deposition from Cahokia Creek in both archaeological excavations and terrestrial sediment cores. These fluvial deposits are approximately 1.5 meters thick and represent an average sedimentation rate of 2.2 cm/yr. The high rate of sedimentation since the 1800s has dramatically altered the human-constructed landscape from Cahokia’s occupation, demonstrating the need for site formation analysis and paleo-environment reconstructions along tributary floodplains.