15 Terrestrial records of hydroclimate variability from the Pleistocene through the Common Era

Landscapes respond to climatic variability, extreme hydrologic events, and long-term environmental change, informing water resource management. We invite terrestrial proxies of hydroclimate from perspectives in paleoclimatology, geomorphology, or hydrology. Submissions from early-career scientists are encouraged.

Monday, 9 March 2026
1:30 PM - 3:30 PM
RCC, 105

Stable carbon isotope composition of Quercus virginiana, Louisiana, USA

Paper number: 15-4
Program: Technical Sessions
Time: 2:20 PM – 2:35 PM

Authors

Abstract

The remains of fossil plants are preserved throughout the geologic record. This includes fossil leaves, pollen, fruit, flowers, wood, and bulk terrestrial organic matter. Carbon isotopes of these substrates are widely used to reconstruct past environmental conditions, including precipitation, temperature, salinity, atmospheric carbon dioxide, air pollutants, elevation, shading, reproduction strategy, and photosynthetic pathway (i.e., C3 versus C4), among others. The genus Quercus (oaks) is globally expansive and species rich, particularly in the northern hemisphere, spanning from the equator to the boreal forest. Oaks leaves are known from the fossil record fromthe Eocene through to the present; however, their stable carbon isotope composition in modern settings is limited relative the more widely sampled temperate conifers (e.g., Pinus, Picea, Larix, and Juniperus). Here we present a large dataset of stable carbon isotope measurements (n=150) on the iconic Quercus virginiana (southern live oak) growing in southwestern Louisiana. We report variability among leaves and trees growing in a single landscape across 2 months of sampling, and among different plant tissues (e.g., leaves versus bark). We find up to ~2.5‰ differences in carbon isotope value among leaves on a single tree, ~1.5‰ between tissues, and ~2.0‰ differences among trees. We also find a ~0.3‰ smaller difference from month to month, that we interpret as being caused by changes in rainfall. Comparison of these data with the limited published data on Quercus reveals our values to be significantly lower than previous measurements. We interpret these differences as resulting from anthropogenic CO2 rise, resulting in a lower carbon isotope composition of the atmosphere and higher CO2 concentrations, both of which cause lower carbon isotope values in plants. We discuss how these data may be used to infer environmental change across the Cenozoic using remains of fossil Quercus.  

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411860

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