Abstract

SOLIS-CASTILLO, Berenice; SOLLEIRO-REBOLLEDO, Elizabeth; SEDOV, Sergey  and  SALCIDO-BERKOVICH, Cesar. Paleosoils in Pleistocene-Holocene colluvial-alluvial sequences in Tlaxcala: paleoenviromental record of early population in central Mexico. Bol. Soc. Geol. Mex [online]. 2012, vol.64, n.1, pp.91-108. ISSN 1405-3322.

The study of paleosols becomes important when considering the position that they occupy in the landscape because they are a continuum changing in relation to the landform, constituting a toposequence. Here we present the results from three paleopedological sections located in the Tlaxcala Block, the effects of pedogenesis depending on their relief position and the kind of parent material (colluvio-alluvial). The studied sections are located at the higher positions (Tlalpan C), in the talus (Concepción C), and in the valley bottom (Huexoyucan), and cover from the Oxygen Isotope Stage 3 (OIS3), the Last Glacial Maximum (LGM), the Late Glacial (LT), to the early Holocene (EH), the last being important because of the early peopling of Mexico. The soil-forming processes were deduced through analysis of the morphological characteristics, grain size distribution, magnetic susceptibility, paleomicrobotanical content, the δ¹³C data, and the dating analysis. Results show that paleosols developed during the OIS3 are Luvisols with vertic features, present in the higher altitudes, changing to histic Fluvisols at the base of the toposequence, evidencing a seasonal climate (oscillating between cold-humid and dry conditions). During the LGM, Luvisols are present at the top and base of the landscape, and are interpreted as the result of a humid and cool environment. The LG soils are less developed, containing reworked and redeposited material, that form Gleysols at different relief positions, indicating unstable environments. Paleosols of the LH are Luvisol with stagnic properties, formed in a humid and cool climate, but well drained in the higher elevations. Paleosols of LH offer a good perspective for archaeological prospection of the early peopling sites.

Keywords : coluvio-alluvial paleosols; toposequence; Pleistocene-Holocene; Tlaxcala; early peopling.

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