Tephrochronology of Lacustrine Ash Layers in Lake Petén Itzá Sediments drilled in the Frame of the International Continental Scientific Drilling Program (ICDP): Implications for Regional Volcanology and Central American Palaeoclimate

Abstract:

Climate records from lacustrine systems have been established in the last years to improve our understanding of the regional and temporal expression of climate change on the continents, and how it influenced the human evolution. Lake Petén Itzá, located in the center of the climatically sensitive Peninsula Yucatán, is a surficial closed-basin lake located in the lowlands of northern Guatemala drilled by ICDP. The region itself exhibits characteristic climate conditions, making it an ideal region for paleoclimatological and paleoecological studies. A key problem in obtaining a long-lasting climate record is to establish robust chronologies beyond 40 ka since they exceed the range of ¹⁴C dating, but tephra layers within these sediments may provide good age-constraints >40 ka. We here use large-magnitude, widespread, Pleistocene to Holocene silicic eruptions from caldera volcanoes in the Central American volcanic arc (CAVA), contributing to the drilled Petén Itzá lake sediments in the form of numerous lacustrine tephras providing time markers to develop a new, extended age model. We established robust and well-constrained correlations between the tephras in Lake Petén Itzá and the deposits at the CAVA source as well as their marine equivalents in the sediments of the Pacific Ocean based on major and trace element glass compositions. We document here 8 well-constraint time markers for the Petén Itza age models, which so far were only based on younger ¹⁴C dates and some preliminary, only major-element based, tephra correlations. Additionally ongoing Ar/Ar age dating of the Los Chocoyos eruption will provide a new pinning point froma an important regional marker horizon. In summary we have been able to modify the current age models, extend the paleoclimate and paleoecological record in this neotropical region to ~300 ka, and contribute greatly to the determination of the magnitude (eruptive volumes) and more precise eruption dates of CAVA eruptions.