Notes on magnetic susceptibility in the Guil Valley alluvial mire correlated with the Punic invasion of Italia in 218 BC

The enigma of Hannibal’s route across the Alps in 218 BC is one of the most enduring questions of antiquity. Many authorities, some of whom have never ventured into the mountains, have argued for various preferred crossings of the Alps. Earlier efforts to identify the route focused on the two-tier rockfall and regrouping area on the lee side of the Range, originally described by Polybius in his The Rise of the Roman Empire, by Livy in The War with Hannibal, and later by Sir Gavin de Beer who searched out the topography and stream dynamics in the area of several projected crossing routes. Recently, attention shifted to the alluvial mire in the upper Guil River after cores and sections (sites G5 and G5A, Mahaney et al., 2016a) revealed the presence of churned-up or bioturbated beds, called the Mass Animal Deposition (MAD) layer. At approximately 45 ±15 cm depth, the top of the MAD layer contains abundant bacteria belonging to the class Clostridia that are found in the mammalian gut and fecal deposits, all dated by AMS 14C to 2168 cal yr BP (i.e., 218 BC with a 95% confidence interval). Samples for magnetic susceptibility collected from three additional sections (G5B, G5C and G5D) carrying the churned-up beds reveal heightened magnetic intensity within these bioturbated sediments that is suggestive of high magnetite content, one form of iron that often was used to cast weapons in ancient times. Magnetic susceptibility levels are highest within the churned-up beds with minor exceptions in two of the three sections analyzed, possibly indicating the presence of weathered tools, implements or weapons lost or discarded. The available data is sufficient to suggest that a GPR survey of the entire mire might well lead to recovery of the first artifacts from the invasion that would shed enormous light on the culture of ancient Carthage.