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Subseasonal variations in marine reservoir age from pre-bomb Donax obesulus and Protothaca asperrima shell carbonate

Miguel F. Etayo-Cadavid·C. Fred T. Andrus·Kevin B. Jones·Gregory W. L. Hodgins
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Abstract

Two Donax obesulus and two Protothaca asperrima shells collected prior to the nuclear testing of the 1950's were micromilled at sub-seasonal resolution to yield new reservoir effect (ΔR) estimates for the coast of Peru. Shells from northern (4°40′S to 8°14′S) and central (13°52′S) Peru produced ΔR values of 123 ± 50 and 110 ± 49 years respectively. We found such values statistically indistinguishable from each other while reporting intra-annual ΔR variability along shells ontogeny in agreement with previously published regional ΔR values. This similarity suggests radiocarbon dating of short-lived (<1.5 years) mollusks shells is a useful tool for comparing marine radiocarbon signals. Additionally, our analysis of ΔR and δ 18 O changes along shells' ontogeny found a tenuous relationship between them. We are not the first one to report these phenomena in Peruvian upwelling , but we are the first to suggest that fast Lagrangian water mixing as a mechanism behind it.

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Miguel F. Etayo-Cadavid, C. Fred T. Andrus, Kevin B. Jones, Gregory W. L. Hodgins. 2018. Subseasonal variations in marine reservoir age from pre-bomb Donax obesulus and Protothaca asperrima shell carbonate. https://doi.org/10.1016/j.chemgeo.2018.07.001

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