CLIMATE VARIABILITY ON THE YUCATAN PENINSULA (MEXICO) DURING THE PAST3500 YEARS, AND IMPLICATIONS FOR MAYA CULTURAL-EVOLUTION

Climate variability on the Yucatan Peninsula during the past 3500 yrs is reconstructed from the measurement of delta(18)O in monospecific os tracods and gastropods in a 6.3-m sediment core from Lake Punta Laguna , Mexico. This late Holocene record is divided into three periods base d on changes in mean delta(18)O values. From similar to 3310 to simila r to 1785 C-14 yr B.P. (Period I), low mean delta(18)O values indicate relatively wet conditions (i.e., low evaporation to precipitation rat io, E/P). Mean oxygen isotopic values increased similar to 1785 C-14 y r B.P., and the interval between similar to 1785 and similar to 930 C- 14 Yr B.P. (Period II) was distinctly drier than the periods before or after. The climate during the latter part of Period II was persistent ly dry, with exceptionally arid events centered at similar to 1171, 10 19, and 943 C-14 Yr B.P. (equivalent to 862, 986, and 1051 A.D.). This interval of frequent drought was recorded at several other localities in Mexico and Central America, and coincided with the collapse of Cla ssic Maya civilization. Following the last arid event, delta(18)O valu es decreased abruptly at similar to 930 C-14 Yr B.P. (beginning of Per iod III), signaling a return to wetter conditions that have generally prevailed to the present, with the exception of a dry episode centered at 559 C-14 yr B.P. (1398 A.D.). The paleoclimatic record from Punta Laguna provides evidence that multi-decadal and millennial-scale chang es in E/P occurred on the Yucatan Peninsula during the late Holocene. These wet/dry episodes may have influenced cultural evolution in Mesoa merica. (C) 1995 University of Washington.