T124 Coastal and Island Geoarchaeology

Monday, 16 October 2023
1:30 PM - 5:30 PM
330

A SYNTHESIS OF SCLEROCHRONOLOGICAL DATASETS TO IMPROVE SEASONAL AND ENVIRONMENTAL INTERPRETATIONS OF ARCHAEOLOGICAL CALIFORNIA MUSSEL SHELLS

Paper number: T124-10
Program: Technical Sessions
Time: 3:45 PM – 4:00 PM

Authors

Abstract

Sclerochronological analysis of archaeological bivalve mollusc shells can improve our understanding of past human-environment interactions and paleoenvironmental variability along coastlines, though species- and site-specific variables can impact interpretations in uncertain or unexpected ways. We aimed to optimize the paleoenvironmental utility of an archaeologically important marine bivalve species from coastal North America, Mytilus californianus (California mussel). Abundant stable isotope (δ18O and δ13C) records exist from 14C-dated archaeological M. californianus shells, originally sampled to study human history at California’s Channel Islands. Here, we compile and analyze over 6000 δ18O and δ13C data points from M. californianus shells from Channel Islands middens spanning 9000 years. Synthesizing and analyzing previously collected sclerochronological data allowed for novel interpretations of spatial, temporal, and biological influences on shell chemistry in a species with cultural, ecological, and archaeological importance. Geographically, we found that M. californianus shells record statistically significant differences in δ18Oshell by site (ANOVA, F5,2658 = 252.7, p < 0.001), with increasingly warmer signals from San Miguel Island to Anacapa Island. Temporal patterns include seasonally driven oscillations in individual δ18Oshell profiles throughout the study period and a negative shift in collective δ13Cshell through time. Lastly, we found shorter δ18Oshell-inferred seasonal cycles with increasing ontogenetic age and high variability in terminal-edge δ18Oshell values in shells from the same harvest date and location, indicating that ontogenetic patterns and sampling methodology can strongly influence seasonal and environmental interpretations. Our analysis contributes new insights into sampling and interpreting widely-studied archaeological M. californianus shells, which grow and record environmental information more irregularly than expected.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-392532

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