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Geomorphologic, stratigraphic, faunistic, palynological and carbon isotope analyses were carried out in the area of the Tiber river mouth. The results depict a complex palaeoenvironmental evolution in the area of the Roman town of Ostia, ascertain the changes of the Tiber river delta over the last 6000 years and support a re-interpretation of some archaeologic issues. The wave-dominated Tiber delta evolved through three distinct phases. In the first step (5000–2700 yr BP) a delta cusp was built at the river mouth, which was located north of the present outlet. Subsequently (2700–1900 BP), an abrupt southward migration of the river mouth determined the abandonment of the previous cusp and the progradation of a new one. The third step, which is still in progress, is marked by the appearance of a complex cusp made up of two distributary channels. The transition from the first to the second evolution phase occurred in the seventh century bc and was contemporary to the foundation of Ostia, as suggested by historical accounts. However, the oldest archaeological evidence of the town of Ostia dates to the fourth century bc, when human activity is clearly recorded also by pollen data. We suggest that the first human settlement (seventh century bc) consisted of ephemeral military posts, with the aim of controlling the strategic river mouth and establishing the Ostia saltworks. Only after the fourth century bc the coastal environment was stable enough for the foundation and development of the town of Ostia. [ABSTRACT FROM PUBLISHER]

Lithostratigraphic analysis, geologic and geomorphologic surveys, and radiocarbon dating were carried out to elucidate the evolution of the Bagnoli-Fuorigrotta depression. The origin of the feature, located at the outskirts of Naples and confined between the ridge of Posillipo and the Agnano volcanic centre, was triggered by the huge volcanic-tectonic collapse, subsequent to the Tufo Giallo Napoletano emplacement (12 ka BP), which caused the Phlegrean caldera. Since then, its evolution has been controlled by the recurrent volcanic and tectonic events which occurred throughout the Phlegrean Fields as well as by sea-level rise. In particular, the tephra ejected from the vents of the Agnano centre (from 11 to 3.7 ka BP) modelled the depression by aggrading its bottom and shifting the coastline seaward. At present, a short erosion scarp, locally resembling a ‘palaeofalaise’, separates the plain reach (Coroglio plain) of the depression from the marginal Bagnoli-Fuorigrotta terrace. The depression fill consists of subaerial tephra and marine deposits with intercalations of palaeosols and transitional alluvial and lacustrine-palustrine sediments. Such an assemblage supports the inference that the depression underwent a rather complicated evolution, characterized by an overall subsidence trend in part overshadowed by the counteracting uplifting and tephra input. At Coroglio plain, the sympathetic effects of subsidence and sea-level rise were effective in preserving (apart from a few lacustrine-palustrine phases) a marine environment up to historical times. The final evolution of the plain dates back some 1.8 ka BP and depended upon the deposition of a coastal barrier capable of maintaining scattered swampy areas on the land. Since then, the plain was only affected by subsidence, at a rate inconsistent with further marine ingressions but compatible with the persistence of marshy spots until the complete reclamation of the area was accomplished in the nineteenth century. [ABSTRACT FROM AUTHOR]