25 Paleo-climate and -ecosystems of the Southwest and High Plains: From the Paleozoic to the Quaternary (Posters)

Many Phanerozoic climates and ecosystems serve as potential analogues for the future; others highlight the Earth system response to tectonic and climatic forcings. We invite abstracts that probe the paleoclimate/ecosystems of the US Southwest

Tuesday, 19 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Constraining seasonal and paleoclimate conditions of Central America using Triple Oxygen Isotopes of Pomacea Shell record from Belize

Paper number: 25-0
Program: Technical Sessions
Time: 8:00 AM – 8:15 AM

Authors

Abstract

Freshwater mollusk shells provide high-resolution archives of hydroclimate variability in tropical environments. We investigate triple oxygen isotope (δ18O, Δ′17O) variability preserved in Pomacea shells from Belize spanning from modern to ~10,000 years to evaluate their potential for reconstructing seasonal changes in meteoric water isotopic composition and hydrologic balance. Previous regional studies (e.g., Kennett et al., 2012; Winter et al., 2020) demonstrate that speleothem archives from Belize and Guatemala record precipitation shifts linked to tropical climate dynamics. However, sub-annual hydroclimate records of freshwater mollusk shells from the tropics in Central America remain underexplored.

We microsampled carbonate along shell growth increments from multiple Pomacea shells across the record to generate intra-shell δ18O and Δ′17O profiles. The resulting isotopic oscillations exhibit systematic variability consistent with seasonal wet–dry cycles. Our preliminary analysis show that the measured carbonate Δ′17O values range from –20 to –130 per meg (VSMOW), while δ′18O values range from ~ –7.5 to –4.5‰ (VPDB). The δ18O and Δ′17O values of precipitation calculated from the isotopic shell carbonate values in the region vary from –6 to –3.5‰ (VSMOW) and –25 to 55 per meg (VSMOW) respectively.

Repeated cyclic patterns across specimens indicate that Pomacea shells reliably record seasonal hydroclimate variability. These findings demonstrate that freshwater shells from Belize provide sub-annual resolution records of tropical hydroclimate and offer a valuable complement to speleothem archives for reconstructing Holocene hydroclimate in Central America.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410729

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