Chert Sourcing

Project Outline

The abundance of lithic material thus far recovered from the Gault site makes it important to understand the site in its wider context,specifically raw material procurement and Clovis mobility. In this regard, it is reasonable to suggest that broad patterns in raw material use and mobility can be determined by analytical provenance studies. To test this assumption, and place the Gault site in the context of the wider Texas Paleoindian landscape, two analytical techniques, Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry (LA-ICP-MS) and portable X-Ray Fluorescence(pXRF) have been used to source artifacts to their geologic outcrops.Geochemical variability in chert stems from a complex diagenetic processes,which, when combined with the post-depositional chemical enrichment / depletion in artifacts, provides unique challenges to sourcing. This poster outlines anew methodological approach for the use of LA-ICP-MS and pXRF in sourcing chert artifacts from the Gault Site, specifically the diagnostic Clovis points, to some of the primary outcrops of the Edwards Plateau. By combining two non-destructive analytical techniques, archeologists have the potential to study mobility and procurement patterns during the Clovis occupational horizon.

Laser Ablation – Inductively Coupled Plasma – Mass spectrometry

Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry (LA-ICP-MS) is a non-destructive technique that rapidly and efficiently characterizes many different archaeological materials. LA-ICP-MS samples do not require any pretreatment before being analyzed. The sample just needs to have a clean surface free of debris. ICP-MS can detect elements with atomic masses in the range of 7-250. This means elements from lithium through uranium. This is a tremendous advantage because during sample introduction there is no possibility of contamination from reagents present from sample preparation.

Portable X-ray Fluorescence Spectrometry

X-ray Fluorescence Spectrometry (XRF) has been widely used by archaeologists studying the provenance of archaeological obsidian.Increasingly, portable XRF units (pXRF) are being used in data generation and sourcing studies. pXRF provides researchers with a non-destructive technique that can detect elements with atomic masses in the range of 11 – 92.Increasingly, units can detect concentrations ≥ 1 ppm. The rapid and cost-effective nature of pXRF analysis enables researchers to assess the macro-regional scale. As such, preliminary source determination is possible using pXRF before LA–ICP–MS is used for regional and local analysis.