Sediments from Lake Chalco in central Mexico spanning from ca. 150 to 35 ka ago provide evidence of paleoclimatic variability in the North American tropics associated with the end of Marine Isotopic Stage (MIS) 6, the transition to the last interglacial (MIS 5.5, ca. 130-115 ka ago), and part of the last glacial (MIS 5.4 to early MIS 3, 115 to 35 ka ago). We applied a multiproxy approach based on the analysis of mineral magnetism, diatom assemblages and major elements geochemistry. The reconstructed paleoenvironmental history identify the end of the globally cool MIS 6 as wetter than present, with high lake level, and a subsequent change to drier climates at the onset of the last interglacial (ca. 130 ka). Large amplitude changes in most of the analyzed parameters from ca. 130 to 74 ka are approximately coincident with MIS 5 (130-71 ka). The amplitude of these changes decreases in MIS 4 (71-57 ka) and the early part of MIS 3 (57-35 ka). We proposed that the inferred climatic oscillations follow insolation variations during MIS 6 and part of MIS 5 (150-88 ka). Low summer and spring insolation and lower seasonality inhibited evaporation and favored high lake levels. Conversely, maxima in spring and summer insolation promoted dry conditions and low lake levels. The major wet-cold glacial and dry-warm interglacial relationship found in Lake Titicaca (Bolivia) and Lake Chalco records shows the sensitivity of high altitude tropical sites to climatic variability.
Bibliographical noteFunding Information:
This project was possible by the financial funding of projects UNAM-PAPIIT (Universidad Nacional Autónoma de México) IV100215 , IN105918 , IN103819 and CONACyT 130963 ; and the support of the Ejido Tulyehualco authorities that facilitated the access to the drilling site. We thank the staff of National Lacustrine Facility (LacCore, University of Minnesota), D. Schnurrenberger, A. Myrbo, A. Noren and K. Brady for assistance with initial core description. XRF core scanning were performed at the Large Lakes Observatory, University of Minnesota-Duluth. Hysteresis parameters were measured at the Institute for Rock Magnetism, University of Minnesota. The IRM is made possible through the Instrumentation and Facilities program of the National Science Foundation , Earth Science Division and by funding from the University of Minnesota . We thank M. Jackson and all the IRM staff for their invaluable assistance. We also thank Dr. Susana Sosa for technical support during field and laboratory work. C.L. Romero and S. García collaborated in the elaboration of the figures. The authors thank to two anonymous reviewers whose comments and suggestions improved the manuscript.
- Magnetic properties
- North America