84-10 Soil Mantle and Underground Pedosediments in the Karstic Landscapes of Northeastern Yucatan: Legacies of Ancient Maya Landuse.

Session: Geoarchaeology of Sites to Landscapes: Current Research on Long-Term Water and Soil Management and Maladaptation, Part I

Presenting Author:

Authors:

Abstract:

A major part of the Maya Lowlands is characterized by karstic landscapes, in particular the Yucatan Peninsula is a vast area of tropical platform karst. Shallow Rendzic Leptosols (Rendzinas) dominate in the uplands of Yucatan. Usually, these soils are interpreted as poorly developed; however, various profiles have characteristics which disagree with this viewpoint. Despite small thickness and proximity of calcareous bedrock soil matrix of Rendzinas is free of carbonates; high clay (kaolinite and vermiculite) and pedogenic iron content indicate its high weathering status. Few areas occupied by deep red clayey soils are found among Rendzinas, classified as Chromic Cambisols and Luvisols (Terra Rossa). Mineralogical and geochemical composition of Terra Rossa has striking similarities with that of Rendzina. The alternative hypothesis of Rendzina genesis was proposed: they were formed from the materials left after advanced erosion of the pre-existing Terra Rossa. How could large-scale soil erosion develop in the Platform of Yucatan that has even relief with few pronounced slopes and weak surface water flow? Extensive swampy lowlands are occupied by specific hydromorphic Calcisols and have very few pedosediments derived from the upland soils – this confirms that lateral soil erosion along the slope gradient was weak. We state that vertical karstic erosion (“soil piping”) could be responsible for the soil loss. This process consists in the transport of soil material from the surface through the karstic sinkholes to the underground reservoirs: pockets, galleries and caves. We observed red and black pedosediments in the karst pockets and cave floors, which had composition like that of the surface soils. These observations revealed the final destination of soil materials derived from the surface and redeposited by hidden vertical karstic erosion in the underground cavities. Radiocarbon datings of charcoal, humus and mollusk shells from these pedosediments produced ages corresponding to Preclassic and Classic periods (4000 – 1000 yr BP when the spread of agriculture, population growth and the human impact upon tropical landscapes of Maya region reached their maximum. We conclude that these anthropogenic factors accelerated vertical soil erosion and caused major changes in the soil cover, which became thin and discontinuous. We further speculate that this soil cover change could interact with “Maya drought” being responsible for the cultural collapse at the end of the Classic period.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10456

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.