T160 New Frontiers in Cave and Karst Research: In Honor of the International Year of Caves and Karst

Tuesday, 11 October 2022
8:00 AM - 12:00 PM
Mile High Ballroom 3C

RESOLVING HIGH-RESOLUTION PALEOCLIMATE VARIABILITY FROM SUBARCTIC CANADA SPELEOTHEMS ACROSS THREE PLEISTOCENE INTERGLACIALS PERIODS

Paper number: T160-7
Program: Technical Sessions
Time: 9:40 AM – 10:00 AM

Authors

Abstract

Recent increased effort has been focused on reconstructing past climate variability, as increased variability and resulting extreme weather conditions may be more difficult for society to adapt to than disparate mean climatic states. The Pleistocene Epoch (2.5-0.117 Ma) is an ideal target for generating paleoclimate records to investigate past climate variability due to several well-constrained climate forcings and feedbacks present. Despite this, very few Pleistocene climate records exist, primarily because of geochronological dating limitations. Speleothems, however, are one type of terrestrial archive that can be dated back 600 ka (U-Th dating) or beyond (U-Pb dating). The oxygen isotopes (δ18O) of speleothem calcite is relict of former precipitation δ18O from which the calcite precipitated, and can be used to reconstruct changes in past hydroclimate. Speleothem calcite layers can also contain annual growth bands that can be analyzed to reconstruct sub-annual climate records.

In this study, we combine micro-imaging (confocal laser fluorescent microscopy; CLFM) and micro-analysis of oxygen isotopes (δ18O) on six speleothems from the subarctic region of the Northwest Territories, Canada that grew during three Pleistocene interglacial periods: Marine Isotope Stage (MIS) 11, 9, and 5. We measured 10-μm sized δ18O analyses using the Secondary Ion Mass Spectrometer (SIMS) across several fluorescent and non-fluorescent growth bands, that are perhaps annual, in each speleothem to resolve ultra-high-resolution (decadal to interannual) snapshots of climate variability during these three interglacials. Preliminary results of large-scale isotopic changes reveals that speleothem δ18O increases (by ~1.0‰ VPDB) from older to younger interglacials. This isotopic increase could be due to the temperature effect on water-calcite fractionation, as more negative δ18O values indicate warmer temperatures. The decadal to sub-annual variability of this δ18O change has yet to be analyzed but will be done by characterizing intra-band δ18O analyses within fluorescent laminations. Nonetheless, this study will be the first to produce ultra-high-resolution δ18O records from subarctic Canada to better our understanding of Northern Hemisphere Pleistocene climate variability during former Interglacial Periods.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-380082

© Copyright 2022 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.