T112 Oceans and Climates through Earth History: Modeling, Proxy, and Proxy Development Studies (Posters)

Monday, 23 September 2024
8:00 AM - 5:30 PM
Hall D

A LASER ABLATION ICP-MS PROTOCOL FOR HIGH-RESOLUTION I/CA PROFILING IN CORALS

Paper number: T112-24
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

Corals are continuous, time-resolved archives of ambient seawater geochemistry and can extend climate records beyond direct monitoring. The I/Ca ratio may be a proxy for local oxygen depletion, but the current solution-based ICP-MS protocol limits temporal resolution. A protocol was developed for rapid analysis of coral I/Ca using laser ablation ICP-MS. First, iodine analyses were compared between two reference materials: coral JCp-1 and synthetic carbonate MACS-3. The influence of laser parameters (spot size, fluence, repetition rate, and scan speed) on iodine sensitivity from JCp-1 was evaluated to optimize laser settings for accurate and reproducible I/Ca calibration. Then, I/Ca ratios were measured from continuous transects along and across the growth axis of a Porites sp. We find that the repeatability and precision in measuring iodine, as well as other tracers (Sr, Mg, Ba, and U), are improved using the biogenic standard JCp-1 compared to MACS-3. In the coral sample, while there is fine-scale (< 250 μm) I/Ca variability in parallel transects, which may be due to biomineralization processes, large-scale features (> 500 μm) along the growth axis tend to correlate. Laser ablation ICP-MS has great potential for accurate, high-resolution I/Ca profiling in corals using JCp-1 as a suitable calibration standard. Because of compositional variability near centers of calcification, it is important to pay attention to how the laser transect is aligned relatively to the growth axes.

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

doi: 10.1130/abs/2024AM-401515

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