58 D12. Paleoclimatology/Paleoceanography (Posters)

Tuesday, 20 March 2018
8:00 AM - 12:00 PM
Lake Champlain Exhibition Hall

REPLICATION OF A SPELEOTHEM STABLE ISOTOPE RECORD OF SOUTH AMERICAN SUMMER MONSOON VARIABILITY OVER THE LAST ~6 KA FROM THE CENTRAL PERUVIAN ANDES

Paper number: 58-6
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Oxygen and carbon isotopes contained in speleothems are excellent high-resolution proxy archives for reconstructing terrestrial paleoclimates. However, it is becoming increasingly clear that replication in these studies is necessary to develop robust climate records. A previous study by Kanner et al. (2013; QSR 75:1-10) investigated two speleothems from the central Peruvian Andes to study variability of the South American Summer Monsoon (SASM) over the last seven millennia. The authors made a continuous record of δ18O values from 50 to 7150 years BP (the two speleothems overlapped by about 1000 years), and found that precipitation amount is the greatest control on δ18O values during the last ~7 ka. However, δ18O and/or δ13C values in speleothems may not directly represent their primary environmental signals because kinetic processes (non-equilibrium carbonate precipitation) and vadose processes, such as water being evaporated at or near the Earth’s surface may interfere. Thus, a replication test should be performed in order to determine if the cave was in isotopic equilibrium during deposition. A recent 2017 expedition obtained another speleothem from the same cave in order to perform a replication test on the δ18O values obtained from the speleothems used in the previous study, and to develop a record of δ13C values for the central Peruvian Andes. U/Th dating was used to derive an age model for the speleothem, which was found to range in age from 583 ±4 to 6036 ±21 years before present. High-resolution stable isotope samples (δ18O and δ13C) were collected along the growth axis of the speleothem. Results will be compared to the previous speleological studies by Kanner et al., as well as other local terrestrial climate proxy records, such as glacial ice cores and lake sediments.

Geological Society of America Abstracts with Programs. Vol. 50, No. 2

doi: 10.1130/abs/2018NE-310795

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