Paleosol-sedimentary sequences of the Glacis de Buenavista, Central Mexico: interaction of Late Quaternary pedogenesis and volcanic sedimentation

Two sections (Buenavista and Ahuatenco) of Late Quaternary paleosol-sedimentary sequences of the Glacis de Buenavista, Morelos, Central Mexico, were studied and interpreted as a regional record of climatic change and interaction of pedogenesis and volcanic sedimentation. Buenavista is the deepest section and includes seven pedostratigraphic units, with Andosol (surface unit) and Luvisol (all underlying units) types of pedogenesis. Both types indicate a humid forest environment, the divergency being related to differences in pedogenesis duration. Albeluvisol with a bleached E horizon in unit 5 indicates cooler but still moist conditions in the final Late Pleistocene, whereas strong vertic properties in unit 4 indicate a climate with contrasting seasonal variation of precipitation during the first part of the Holocene. In the upper part of the Ahuatenco section, Bt horizons of different pedogenetic events form a welded Luvisol profile instead of a set of separate paleosols due to less intensive sedimentation. Material of indurated Cm horizons (tepetates) in the lower part of the Ahuatenco section is a mixture of fresh coarse volcanoclastic components and re-deposited Luvisol clayey material, formed by mass movement associated with volcanic events. The resulting granulometric composition of these layers is favourable for structural collapse and hydroconsolidation, which caused hardening together with subsequent pedogenic illuviation and redoximorphic processes.