PALEOSOLS DEVELOPED IN A COASTAL DUNE SYSTEM IN THE GULF OF MEXICO: CAN THEY BE USED AS PALEOENVIROMENTAL INDICATORS OF THE LAST 100,000 YEARS?

Coastal dunefields are dynamic systems where several factors are interrelated in their evolution. In this work, we present a paleosol sequence developed in a coastal dunefield in the Gulf of Mexico (Veracruz state, Mexico), which is a large transgressive system, migrating alongshore and obliquely onshore. Three sections along the dunefield are analyzed: La Mancha, Palma Sola, Punta Delgada (from south to north). The Palma Sola section comprises the oldest ant the youngest part of the sequence, however it shows a hiatus of several thousand years. Paleosols are separated by sandy dune sediments. The base of the section has two paleosols, resting on basaltic lavas. From the sandy dune sediment, a paleosol with 5Bw/5C horizons is developed. The next level is constituted by a well-developed paleosol with a 4Bt/4Btg/4BC/4C profile. The youngest paleosols observe a different morphology. The profiles are formed by 3Ai/3Bk/3C, and 2A horizons. The OSL dating of the lowermost level (5C horizon) gives an age of 91.7 ± 7.1 ka, while radiocarbon age of the organic horizons at the top, 3Ai and 2A, are 8500 cal yr BP and 5700 cal yr BP, respectively. The “lost” part of the sequence is found in the La Mancha and Punta Delgada sections, where, radiocarbon datings of 34,000 to 18,000 Cal yr BP are obtained from pedogenic carbonates. Paleosols found in both localities are similar, with a less degree of development, but containing abundant pedogenic carbonates with different morphologies. Although the problems for the interpretation of this sequence, we consider that our observations give the first insights of environmental change in the dune system, that can be related to the climatic oscillations in the last glacial –interglacial cycle.