Records of Late Pleistocene-Holocene climatic change in Mexico - a review

Here we review palaeoclimatic records from Mexico which have a reasonable c hronological framework and are readily accessible. Reconstructions are base d on pollen, diatoms, sediment chemistry and isotopes, packrat middens and glacial records and are discussed within the context of Central Mexico, the Yucatan and Northern Mexico, the three regions for which significant infor mation is available. The available data indicate that over the Late Pleisto cene and Holocene there have been significant climatic changes in Mexico, a lthough smaller in magnitude than in other parts of the northern hemisphere tropics and subtropics. Maps of conditions at 18,000, 9000, 6000, 5000 and 1000 yr BP are presented. These show that northern Mexico and the Yucatan often show opposite climatic signals, whilst the highlands of central Mexic o are more variable. Around the Last Glacial Maximum it seems that the mode rn summer precipitation regime had collapsed. Northern Mexico, however, was much wetter than today due to increased winter rainfall. Modern rainfall p atterns were not fully established until after 9000 yr BP and generally wet conditions prevailed about 6000 yr BP. The mid-Holocene seems to have been a period of great climatic variability with a number of records showing os cillations between 6000 and 5000 yr BP. A period of marked aridity is recor ded in the Yucatan and central Mexico about 1000 yr BP. More well-dated, co ntinuous records are needed, especially covering the last glacial-interglac ial transition. The changing balance between temperate and tropical climate systems and the influence of the Pacific compared with the Gulf of Mexico/ Caribbean warrant further investigation. (C) 2000 Elsevier Science Ltd. All rights reserved.