Abstract

DIAZ-ORTEGA, Jaime; SOLLEIRO-REBOLLEDO, Elizabeth; SEDOV, Serge  and  CABADAS, Héctor. Paleosols and tepetates of the Buenavista glacis, Morelos (Mexico): witnesses of climatic events during the transition Pleistocene-Holocene. Bol. Soc. Geol. Mex [online]. 2010, vol.62, n.3, pp.469-486. ISSN 1405-3322.

The knowledge of paleoclimatic records from the late Pleistocene, and in particular from the transition to the Holocene, is essential for understanding modern climate. From this period, the Younger Dryas stadial is noteworthy because it represents one of the most dramatic climate transitions in recent geological history. Paleoclimatic records of this period from the inland area of the continent are of great importance for understanding the response of geosystems to abrupt changes: deterioration of the climate and rapid recovery. In this paper, we present the paleopedological evidence found in the Glacis de Buenavista, Morelos, in order to show the trend of environmental change that occurred during that period. The current climate in the area shows marked contrasts, as the north (altitudes between 2000 and 2200 m) is warm and humid, while the south (altitudes between 1800 and 1600 m) is warmer and sub-humid. As a result, the current soil cover forms a climo-toposequence, which varies from Andosols-Luvisols to Vertisols. The studied paleosols correspond to an Albeluvisol (Buenavista), located on the north side, and a Gleysol (Ahuatenco) in the central part of the landform. Their ages, obtained by AMS, are 12160 years B.P. and 12930 years B.P. (uncalibrated), respectively. The properties shown by these soils (presence of an eluvial horizon with surficial stagnic processes in the Albeluvisols, strong gleying in the Gleysol, moderate weathering in both cases) indicate a wet and warm environment of formation. Consequently, they do not reflect the climatic gradient observed today. The Gleysol is interbedded in a sequence of tepetates (hardened layers of volcanic materials), which form a stratum between the Pleistocene paleosols and Holocene soils. Its presence is associated with unstable climatic and geomorphic conditions due to intense volcanic activity and torrential rain events that transported volcanic materials and soil remnants to the middle part of the landform. This environmental instability is related to the Younger Dryas.

Keywords : Albeluvisols; Gleysols; tepetates; paleoenvironmental change; Younger Dryas.

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