PALEOLIMNOLOGICAL RECORDS OF CLIMATE-CHANGE IN MEXICO - FRUSTRATING PAST, PROMISING FUTURE

Central and northern Mexico contain numerous closed-basin lakes that m ay preserve valuable palaeoclimatic records in their sediments. Resear ch has, however, focused on the basins of the Trans Mexican Volcanic B elt (TMVB), in particular, the Basin of Mexico. Results from the Zacap u Basin, Michoacan, are used to illustrate both the potential benefits and problems of palaeoclimatic studies in such basins. Three diatom s equences provide a discontinuous record spanning 30,000 years. The pre sence of a deep lake, before 28,000 BP, is indicated. There are no sed iments covering the Pleistocene/Holocene transition. During the Holoce ne, only minor changes in lake level are indicated, with drying about 5000 BP and, most importantly, about 1100 years BP. Difficulties in re constructing past climates in this basin, and in many others in Centra l Mexico, include: discontinuous sedimentation; obtaining a reliable c hronology; the possible impacts of tectonism and the effects of long-t erm human disturbance. In spite of these problems, the records from Za capu and other basins in the region provide a basis for preliminary pa laeoclimatic interpretation. There is a clear need for long records, f or high resolution studies to investigate the detailed nature of clima te and for more work outside the TMVB. (C) 1997 INQUA/Elsevier Science Ltd.