Low field nuclear magnetic resonance as a potential tool for differentiating bedded and nodular cherts outcrops

Abstract Siliceous rocks, mainly nodular cherts, served as raw materials in the production of stone tools from the Middle Paleolithic onwards. Due to migration, the provenance of archaeological artefacts can differ from their outcrop location. The aim of this work was the application of 1D and 2D low-field nuclear magnetic resonance (LF-NMR) relaxometry to distinguish cherts by sampling location. Herein, bedded cherts and accompanying nodular cherts coming from three different outcrops were investigated. 1D and 2D (T1-T2) experiments of saturated rock samples delivered T1, T2 times and T1/T2 ratios of distinct hydrogen populations – parameters sensitive to pore size, surface properties, and hydrogen bonding length. An in-depth analysis of porosity showed substantial differences in the pore structure properties which made it sufficient for grouping chert samples by outcrop location, using principal component analysis (PCA). All proposed NMR parameters obtained nondestructively allowed to distinguish not only different chert types but also different outcrops of bedded and nodular cherts.