T207 Investigating Earth’s Past, Present, and Future with Continental Scientific Drilling

Tuesday, 24 September 2024
1:30 PM - 5:30 PM
212A

IMPROVING THE AGE MODEL FOR LAKE TITICACA, BOLIVIA TO RECONSTRUCT TROPICAL CLIMATE VARIABILITY OVER THE PAST CA. 350 KA

Paper number: T207-13
Program: Technical Sessions
Time: 4:30 PM – 4:45 PM

Authors

Abstract

The 136-meter continuous drill core obtained from Lake Titicaca in Bolivia provides an invaluable repository of climate change data in tropical South America, spanning the past ca. 350 ka. However, the existing Lake Titicaca chronology is largely unconstrained beyond the limits of radiocarbon dating (ca. 45 ka), relying on a series of four U-Th dates on aragonite between 46 and 48 m (~122 kyr), and orbital tuning (Fritz et al., 2007). Unlike marine records, lacustrine sequences cannot be correlated to global ice volume records by analyzing δ18O stratigraphy, resulting in a significant challenge in developing accurate age-depth relationships. Older Ar-Ar dating of ash beds has yielded spurious and unconstrained ages and paleomagnetic dating was not possible as the record is strongly affected by diagenesis (Fritz et al., 2007). Similarly, U-Th dates on carbonate beds have yielded significant uncertainties and produced spurious ages in this lake system. In this study, we address these challenges by using new geochronological techniques: optically stimulated luminescence (pIR-IRSL) dating of sediments and zircon double dating of interbedded ash beds. We find strong agreement between different dating approaches throughout most of the record, demonstrating that well-constrained age-depth models for long sedimentary sequences can be achieved using this combination of techniques. We utilize these new geochronologic constraints in a Bayesian sediment modeling approach to generate a continuous age-depth relationship for 350 ka of sedimentation at Lake Titicaca. Our revised chronology was then employed to assess orbital-scale magnetic susceptibility changes, reflecting Andean glacial retreat, at Lake Titicaca. By implementing more robust age constraints through novel dating methodologies, we aim to strengthen the conclusions of previous work and instill increased confidence in utilizing this record for exploring past climate changes beyond radiocarbon dating.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-404001

© Copyright 2024 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.