Palaeolimnological records of climate change in Mexico - Frustrating past, promising future?

Central and northern Mexico contain numerous closed-basin lakes that may preserve valuable palaeoclimatic records in their sediments. Research has, however, focused on the basins of the Trans Mexican Volcanic Belt (TMVB), in particular, the Basin of Mexico. Results from the Zacapu Basin, Michoacan, are used to illustrate both the potential benefits and problems of palaeoclimatic studies in such basins. Three diatom sequences provide a discontinuous record spanning 30,000 years. The presence of a deep lake, before 28,000 BP, is indicated. There are no sediments covering the Pleistocene/Holocene transition. During the Holocene, only minor changes in lake level are indicated, with drying about 5000 BP and, most importantly, about 1100 years BP. Difficulties in reconstructing past climates in this basin, and in many others in Central Mexico, include: discontinuous sedimentation; obtaining a reliable chronology; the possible impacts of tectonism and the effects of long-term human disturbance. In spite of these problems, the records from Zacapu and other basins in the region provide a basis for preliminary palaeoclimatic interpretation. There is a clear need for long records, for high resolution studies to investigate the detailed nature of climate and for more work outside the TMVB. (C) 1997 INQUA/Elsevier Science Ltd.