Reconstructed, with an innovative methodology, the geological history of Rome and the surrounding area by a team of experts in geochronology, paleontology, archeology, volcanology and seismology. A study, signed by INGV and ISPRA, published in Quaternary International, takes a snapshot of the situation
Oscillations in sea level during the succession of glacial periods, volcanic and tectonic activity, alternating action of deposition and erosion of the Tiber and its tributaries, are the factors that have drawn over time the current landscape of the Eternal City, with its characteristic necks. This scenario was reconstructed by the study A review of the stratigraphy of Rome (Italy) according to evidence from geochronologically and paleomagnetically constrained aggradational successions and tephrostratigraphic data, carried out by the National Institute of Geophysics and Volcanology (INGV) and the Istituto Superiore per the Protection and Environmental Research (ISPRA) and published on Quaternary International
(link: 10.1016/j.quaint.2017.01.044).
"The work, which traces the history of studies on the geology of Rome", explains Fabrizio Marra, INGV researcher and corresponding author of the article, "intends to provide an updated tool for reading and interpreting the geology of Rome, which account of both the advances made in the knowledge of stratigraphy and of the mechanisms that determined the succession of sediments, thanks to multidisciplinary studies conducted by INGV over the last twenty years in collaboration with Italian and international researchers".
Thanks to its particular geographical and geological characteristics, the Roman area, in fact, represents a real natural laboratory, in which it is possible to study global phenomena, such as climatic variations and sea oscillations.
"The presence of a large watercourse and the proximity of the coast have meant that the depositional phenomena, in the last million years, have been regulated and marked by the oscillations of the sea, induced by the alternation of glacial and interglacial periods" continues Marra.
Furthermore, the eruptive activity of two large volcanic districts on the outskirts of the city, the Monti Sabatini to the northwest and the Colli Albani to the southeast, strongly interacted with these processes, providing, at the same time, the key to reconstructing their history.
"Moreover, the volcanic deposits of this region", adds the researcher, "being rich in radioactive minerals containing Argon, allow very precise dating to be made".
In fact, thanks to the collaboration between INGV, the University of Berkeley and the Berkeley Geochronology Center, at the end of the XNUMXs it was possible to date, with the Argon isotope method, the products of the Roman volcanoes, interspersed in the sedimentary deposits of the Tiber. In addition to providing a key to reconstructing the ages of the ice ages and better understanding the mechanisms that are at the origin, radiometric dating, integrated with the paleomagnetic analysis of clayey sediments, have made it possible to reconstruct in detail the sedimentary cycles in this region .
"The conceptual model of aggradational succession has been developed to demonstrate the direct correlation between the deposition of sediments of the Tiber and the rise in sea level during the glacial terminations, due to the sudden melting of the ice that covered most of the land". continued Marra.
This model has made it possible to re-determine not only the age of the sedimentary deposit which housed the two skulls of Homo neanderthalensis of Saccopastore, but also to demonstrate that the remains found in the locality of the Aniene Valley constituted the most ancient evidence of the presence of this hominid in Italy, in addition to the growth of knowledge on the stratigraphy and eruptive history of the volcanoes of Rome. Finally, the new knowledge on volcanic products has given rise to various geo-archaeological applications, such as studies on the origin of the volcanic materials used in the building of Ancient Rome, through a long and fruitful collaboration with the various Archaeological Superintendencies.
"Hence the idea", concludes Marra, "to update the geological cartography of Rome in order to support those planning interventions on the territory made indispensable by various factors such as climate change and the increasing attention to the environmental impact".
Extended
A critical review of the studies conducted on the geology of Rome since the first half of the 20th century, aimed at presenting an updated state of the art on the stratigraphy of this area, is presented in the paper entitled "A review of the stratigraphy of Rome (Italy) according to evidence from geochronologically and paleomagnetically constrained aggradational successions and tephrostratigraphic data", by Gian Marco Luberti, Fabrizio Marra, and Fabio Florindo.
Following an introductory summary, a complete reconstruction of the geological evolution and the resulting chronostratigraphic setting of the greater area of Rome is presented, according to a series of works that in the last 20 years have adopted an innovative methodological approach based on the conceptual model of aggradational successions deposited in response to sea-level rise during the glacial terminations, and on the strict geochronologic constraints to the sedimentary record achieved by paleomagnetic investigation of clay sections and 40Ar/39Ar dating of interbedded volcanic materials. A complete overview on the chronostratigraphy of the two volcanic districts of Colli Albani and Monti Sabatini, located SE and NW of Rome respectively, is presented, which has been achieved integrating the field work with the large number of radiometric ages provided in these years on their eruptive products. Moreover, a revised stratigraphic column to compare the most recent official 1:50,000 and 1:10,000 geologic mapping of Rome is proposed, which is intended as a tool of correlation for an international audience of Quaternary scientists to approach the study of this area. A detailed discussion of the proposed revisions is also provided as supplementary information to the paper. 10.1016/j.quaint.2017.01.044
The Campidoglio, like the other famous hills of Rome, is formed by a succession of semi-lithoid volcanic deposits (tuffs), interspersed with the sedimentary formations of the Tiber and its tributaries. The latter are the so-called "aggradational successions", deposited during the phases of sea level rise at the end of the glacial periods which have occurred over the last million years. The alternation of glacial periods, combined with a progressive volcanic-tectonic uplift of the Roman area, has produced the erosion of the land and the origin of the characteristic hilly conformation of the territory.
The Capitoline Hill, like the other famous hills of Rome, is constituted by a succession of semi-lithified volcanic deposits (tuffs), in which the sedimentary formations of the Tiber River and its tributaries are intercalated. These latter are the so-called "aggradational successions", deposited in response to sea-level rise during the glacial terminations in the last million years.
The alternating glacial periods, in combination with a volcano-tectonic uplift affecting the Roman area, produced the erosion of the terrains, shaping the characteristic hilly landscape.