Compound‐specific amino acid δ15N values in archaeological shell: Assessing diagenetic integrity and potential for isotopic baseline reconstruction

摘要: RATIONALE Reconstructing stable isotope (SI) ratios at the base of paleo-food webs is often challenging. For coastal systems, SI organic matter in archeological shell represent a possible solution, providing direct record primary consumer littoral zone. However, porous, with compounds being susceptible to diagenetic alteration or contamination. If molecular isotopic information well preserved, compound-specific amino acid analysis (CSI-AA) has potential provide proxies for baseline ratios, bypass many contamination issues, and allow assessment state. METHODS We collected from both middens nearby zones Alaska, used simple extraction approach based on decalcification sequential weak HCL additions liberate material. We measured CSI-AA patterns, molar AA distributions, degradation parameter (ΣV), context bulk fossil shell, modern soft tissue five common taxa (urchin, limpet, mussel, periwinkle, chiton). RESULTS CSI-AA patterns were consistent consumers, indistinguishable most pairs, showing that δ15N values can be preserved shell. distributions also similar, although was enriched Asx Gly. Comparison between results specimens confirmed source groups (tracking baselines) are transferred without substantial modification into record. In contrast, trophic group had elevated versus all examined, suggesting correction will required any using these AAs. CONCLUSIONS Overall, this new data indicates represents promising determining baselines paleo-ecosystems.