Buried palaeosols of the Nevado de Toluca:: an alternative record of Late Quaternary environmental change in central Mexico

Buried palaeosols of central Mexico, not previously analysed from a palaeopedological standpoint, have helped to develop a reliable regional model of Gate Quaternary climatic change. This paper focuses upon morphological and micromorphological properties, particle-size distribution, and extractable Fe, Al and Si of seven palaeosols (named PT1-PT7) in the vicinity of the Nevado de Toluca volcano. The characteristics of Andic Cambisol PT1, similar to those of modern soils in semi-arid environments, indicate a drier climate in the first half of the Holocene. Humic Andosols PT2-PT3 are analogous to modern volcanic soils of humid forest environments. They show evidence that a moist palaeoclimate prevailed during marine oxygen isotope stages (OIS) 2 and 3. Luvisols PT5 and PT6, which are assumed to have formed at the end of marine OIS S to marine OIS 3. also indicate humid conditions. We attribute the differences between Andosols PT2-PT4 and Luvisols PT5-PT7 to variations in the duration in the pedogenesis rather than to changes in palaeoclimate. Micromorphological features of Andosol to Luvisol transition confirm that these soils form an evolutionary sequence. Being for the most part consistent with lacustrine records, the palaeosol properties do not reflect the episodes of 'drier climate' during the Last Glacial Maximum, however, as shown by diatom and palynological data from lake sediments. Mesoclimate variations and/or incompleteness of 'soil memory', reflecting mostly periods of humid pedogenesis, probably provide the reason for this disagree ment. Copyright (C) 2001 John Wiley & Sons, Ltd.