THE GENESIS AND GEOCHEMISTRY OF ANCIENT AGRICULTURAL SOILS WITHIN A FORESTED WETLAND IN NORTHWESTERN BELIZE

Abstract

Through many field seasons of study, we have begun to develop a chronosequence for soils within forested wetland environments in the Maya Lowlands of Belize. We present our ongoing geochemical and isotopic analysis within the Birds of Paradise wetland in Northwestern Belize, which has undergone extensive modification of field building and channelization during the Maya Classic (1650-1050 BP) with use possibly extending into the early Maya Postclassic (1050-700 BP). This wetland is located within the seasonally inundated Rio Bravo fluviokarst system, which drains eastward into the coastal plain of Belize, and is aggrading at a rate of approximately 0.1 cm annually over the Late Holocene, a rate which doubled in the Maya Classic. The paleosols on this floodplain lie below the last throes of wetland field burning, field raising, and canal digging at the end of the Classic period. Many exposures of these paleosols have light layers that we hypothesized were burned layers to remove forest before field construction. One of our goals is to test this hypothesis by exploring the lines of evidence for and against an anthropogenic burn layer that could represent wide scale clearing during the Terminal Classic. Through our ongoing geochemical work, we compare the formation, timing, and spatial extent of paleosols from throughout our excavations within the Birds of Paradise system. Here we characterize soil profiles, present new geochemical (ICP-MS) and isotopic (δ13C) analysis of these buried soils, and refine our understanding of soil development and sedimentation within the system based on new AMS ages. Through this research, we can better understand how tropical wetlands, especially anthropogenically influenced systems, respond to large scale drought cycles. Further, this study helps us to refine our understanding of how Maya agriculture and resource extraction within wetland environments either persisted or changed through such events.