Dynamics of a Coupled Human-Natural System Revealed through Combined Archaeological and Deltaic Landscape Chronologies

Abstract:

Humans are becoming increasingly active and increasingly recognized as geomorphic agents, and a key value of Earth surface processes research is its relevance to society. As 21st century landscapes evolve at unprecedented rates, new insights into human-landscape interactions are of paramount importance to designing effective management strategies that work with society. This is particularly true for deltas, which are among the most densely inhabited, endangered, and dynamic landscapes on Earth. Radiometric dating methods including optically stimulated luminescence (OSL) have created new avenues for using absolute landscape chronologies to study prehistoric peoples, thereby revealing time-tested strategies for living in dynamic landscapes.

Our research embraces this opportunity in the coupled human-natural system of the Mississippi Delta, USA. Here, OSL geochronology provides a high-resolution record of land growth that facilitates the study of ancient settlement patterns in relation to delta evolution. We use this record to show that two Late Holocene earthen mounds were constructed several hundred years after the land emerged from open water. This multi-century pause allowed natural processes of overbank and crevasse splay deposition to elevate the land surface, reduce flood risk, and foster desirable environmental conditions prior to human occupation. These results are applied to obtain new age constraints for a large number of at-risk or lost archaeological sites with little-to-no absolute chronology, and to cross check existent relative archaeological chronologies against the more recent OSL ages. Our approach highlights the novel integration of several geochronologic methods to understand the geomorphic evolution of a coupled human-natural system and gives insights into prehistoric, contemporary, and future human-landscape interactions in the Mississippi Delta and other deltaic environments.