26 Old Collections, New Tricks

This session highlights how re-examination and contemporary analysis of geoscience collections (i.e., rock, fossil, and archival collections, or geologic maps) can advance science, rewrite historical narratives, and contribute to discussions on social justice.

Monday, 23 March 2026
1:30 PM - 5:30 PM
CCC, Room 25

The Paleoecological Significance of Seasonal Intra-tooth Triple Oxygen Isotope (Δ′17O) Variations in Zambian Fossil Herbivores

Paper number: 26-1
Program: Technical Sessions
Time: 1:35 PM – 1:55 PM

Authors

Abstract

The triple oxygen isotope system (Δ′17O, or paired δ17O- δ18O measurements) is useful to study terrestrial hydroclimate because Δ′17O in the hydrologic cycle is strongly influenced by evapotranspiration but negligibly influenced by rainout during cloud transport. Δ′17O values recorded in the tooth enamel of terrestrial animals can therefore be used as an aridity proxy in the fossil record. However, most analyses use bulk samples of enamel that are assumed to reflect mean annual conditions, and the significance of Δ′17O variation across the tooth crown remains understudied. Seasonal conditions are important for understanding the ecology of organisms in the past because they represent the real context within which microevolutionary processes took place.

We present new Δ′17O measurements on Late Quaternary (23-6 ka BP) herbivore fossil teeth (N = 15) from the Leopard’s Hill locality near Lusaka, Republic of Zambia, which today is in a semiarid environment. These specimens are part of a collection recovered in 1958 by L. Hodges and J.D. Clark. Reconstructing environmental conditions at the site is of interest to understand human use of the area in the Pleistocene and explain the presence of extralimital herbivores in the fossil record. Overall, we found evidence for a wetter environment during the sampled time interval, compared to today. Eleven of the teeth were sequentially sampled to obtain intra-tooth series showing seasonal variation in Δ′17O values. We detected large variations in some of the teeth (up to 0.058‰), with lower values during the dry season (inferred from high δ18O values) and higher values during the wet season. In the combined data, Evaporation Sensitive (ES) taxa (taxa that obtain a large portion of their body water through food) have lower Δ′17O values than Evaporation Insensitive (EI) taxa (obligate drinkers), as expected. However, when the data is divided by season, this difference persists only during the wet season, when EI taxa yield higher Δ′17O values than in the dry season. Conversely, Δ′17O values in ES taxa do not change seasonally. Finally, we discuss how intra-tooth variation in Δ′17O values biases aridity reconstructions based on bulk values when the timing of tooth formation is not accounted for in sampling strategies. This study shows that legacy collections re-investigated with new methods represent an invaluable resource for paleoecological studies.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411148

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