87SR/86SR Analysis as a Method to Explore Human Ecology and Forest Resilience in Ancient Meroe, Sudan

Abstract

Archaeologists frequently apply 87Sr/86Sr geoprovenance to human and animal bone to answer questions surrounding foodways and migration. Utilizing this method to source archaeological timber has recently expanded, enriching the archaeological record and enhancing studies in wood geochemistry. Due to the effects of time and post-depositional alteration, a considerable portion of archaeological wood is found in the form of charcoal. However, the impacts of carbonization and chemical contamination on wood strontium resilience—and therefore, the applicability of 87Sr/86Sr geoprovenance for anthropogenic charcoal—have not yet been examined. Experimental analysis comparing 87Sr/86Sr ratios and δ13C values in wood and experimental charcoal (heated at ~400°C and 900°C) from two Vachellia nilotica trees sourced in modern Sudan illustrated a consistency between untreated wood and both forms of charcoal sufficient to suggest that pyrolysis alone does not significantly alter 87Sr/86Sr ratios or δ13C values in V. nilotica. 87Sr/86Sr values ranged from 0.71715 – 0.71740 (GZL 1) and 0.71678 – 0.71692 (GZL 2). Carbon isotope values ranged from -26.4±0.06؉ (VPDB) to -28.4±0.06؉ (VPDB). Tests on V. nilotica charcoal remnants from late Holocene iron smelting contexts in Meroe, Sudan show that it is possible to produce 87Sr/86Sr ratios from anthropogenic charcoal. Further, these preliminary indications suggest that 87Sr/86Sr data from charcoal supported by carbon isotope data from the same material can be used as a reliable indicator for wood provenance. 87Sr/86Sr data from the Meroe material ranged from 0.70724 - 0.70737, with δ13C values ranging from -26.9±0.06؉ to -24.6±0.06؉ (VPDB). Using this knowledge, I posit that iron smelting fuel charcoal at Meroe may have come from one region between the Atbara confluence and the confluence of the Blue Nile and the White Nile from 400 BCE – 400 CE. Carbon isotope analysis supports this hypothesis. These results suggest that the preference of local V. nilotica charcoal for iron smelting, combined with intensive production ca. 400 – 200 BCE, may have been a catalyst for a break in iron smelting activity at Meroe due to resource exhaustion or climatic variability evidenced throughout the region. Additional improvement in 87Sr/86Sr and δ13C methods for charcoal analysis will enhance this and similar studies in the future.