Chemical-petrographic and isotopic characterization of the volcanic pavement along the ancient Appia route at the Aurunci Mountain Pass, Italy. Insights on possible provenance

The ancient Appia route was built across central-southern Italy between the fourth and second century before the common era (B.C.E.). At the Aurunci Mountain Pass, the route crosses carbonate ridges that provided the raw material used to pave the road in the first century C.E. This material was replaced with lava blocks of unknown origin in the third century C.E. The study area is at least 50 km from the main volcanic centers along the peri-Tyrrhenian side of Italy, such as the Colli Albani, Roccamonfina, and Middle Latin Valley volcanoes. The main objective of this research was the chemical–petrographic and isotopic characterization of rock samples from the Appia flagstones to unravel their possible provenance. The analytical procedure included scanning electron microscope and electron microprobe analyses and 87Sr/86Sr–143Nd/144Nd isotopic measurements. Samples taken from unknown quarries found in the Middle Latin Valley volcanic field underwent the same analyses. After comparing the analysis results with data from the literature, the most likely source area was identified with the Roccamonfina precaldera ultrapotassic sequence. The availability and use of volcanic resources for the construction and maintenance of the ancient Appia route in the investigated territories are only outlined in this work and deserve further study.