Petrochemical Identification and Insights on Chronological Employment of the Volcanic Aggregates Used in Ancient R oman Mortars

Through the assistance of trace element and petrographic analyses on 14 samples of mortar aggregates from R oman monuments, including the Porticus Aemilia , the T emple of Concordia, the T emple of the D ioscuri, T emple B and other structures of the Area Sacra di Largo A rgentina, and the Villa di Livia, we establish the source area and we investigate the chronological employment of the volcanic materials used in ancient R ome's masonry. In contrast to previous inferences, the petrochemical data presented here show that systematic exploitation of the local ‘ P ozzolane R osse’ pyroclastic deposit has occurred since the early development of concrete masonry, at the beginning of the second century bc , through the early Imperial age. Subsequently, exploitation was extended to the overlying P ozzolane N ere and P ozzolanelle deposits. Only during the early phase of development of the concrete masonry in R ome, volcaniclastic sediments outcropping near the construction sites were mixed with the sieved remains of the tuff employed as the coarse aggregate, to produce the fine aggregate. The results of the study on the investigated monuments suggest the possibility of establishing the chronological identification of three different types of mortars, as a function of the composition of the volcanic material employed in the fine aggregate, which, when implemented by future studies, may contribute to the dating of monuments and archaeological structures.