WETLAND AND FLUVIAL AGGRADATION BY ANTHROPOGENIC AND CLIMATIC CHANGE IN THE MAYA LOWLANDS

James C. Knox inspired numerous studies of climate change and human impacts on geomorphology and flooding around the world with his many studies of the Upper Mississippi Valley. The Maya Lowlands, some 3000 km due south of the Upper Mississippi Valley, has become a prime case study of Knox influenced work. Although distant in space and environment, these two low elevation Corn Belts both have fluvial and karst environments, Mollisol and Alfisol soils, and intensive human impacts especially related to pioneer farming. In so many of the upper Midwestern valleys, indigenous American impacts were scant for the millennia of hunting and gathering and farming before European settlement two centuries ago. In contrast, ancient Maya land uses, with or without climate change, led to an erosion cascade in the Maya Lowlands starting about 3,000 years ago when farming intensified and spread up limestone slopes onto Rendoll soils. Conservation curtailed erosion in both places, though it was abandonment in the Maya Lowlands that finally stopped the age of Maya erosion. This paper will combine a synthesis of evidence for landscape aggradation and drivers with new findings from 2012 and 2013 field work on floodplain and wetland formation over the later Holocene. We will examine floodplain aggradation based on multiple proxies from excavations and cores. Like the Upper Mississippi Valley, many Maya sequences have prominent paleosols, ‘Ekluum Soils’, buried 1-2 m in depth and dating to about 2500 BP. These paleosols probably represent stability before the aggradation cascade, though other sequences show complex, long–term interplays between anthropogenic and natural factors such as ancient Maya wetland farming systems, climatic changes, and water table flux.