Environmental magnetic, Geochemical and Sulfur isotopic imprints of an Indus archaeological site 4MSR from western India (Rajasthan): Implications to the Indus industrial (metallurgical) activities

Abstract

A high number industrial hearths, furnaces, and kilns were excavated from an Indus archaeological site 4MSR (western Rajasthan, India) on the dry bed of Ghaggar-Hakra (erstwhile Saraswati) river channel near India-Pakistan international border, providing numerous artifacts of Indus metallurgical activity (jewellery items made of Copper (Cu), Gold (Au) and Silver (Ag), anvil, fishhook, arrowhead, spearhead, moulds, slag etc.). Array of inter-connected hearths, vats, range of stone weights and beads made of semi-precious stones (steatite, terracotta, paste) further suggest the site was being used as a metal-craft factory. Nine 14C ages (seven AMS and two conventional) from cultural layers provided site occupational history spanning from the early Harappan phase to the termination of the mature phase. Maximum number of industrial hearths and furnaces were found during the mature phase (2341 ± 30 to 1691 ± 100 BCE). Highly enriched magnetic susceptibilities (χlf: 114 ± 61.2 × 10−8m3kg−1) in the industrial hearths indicate intense burning activities at these metallurgical factory. Similar enrichments were seen in hearth-sediments for Sulfur (S), Calcium (Ca), Strontium (Sr) and Phosphorous (P) contents. Transition elements viz. Copper (Cu), Zinc (Zn) and Lead (Pb) were significantly enriched in these hearths possibly as major leftovers of the Harappan metallurgical activities. High S contents found in industrial hearths could be due to usage of Sulfur rich material used for metal-works and usage of gypsum for polishing metal ware and floors. Excesses of Calcium (Ca) and Strontium (Sr) could be due to enhanced usage of river-shells used in ornaments and bead making, while elevated Phosphorous (P) contents might be due to presence of charred bones of cattle, tortoise and fish.