A sequence of marine terraces near Latina (Agro Pontino, central Italy)

Abstract

A detailed physiographic soil survey has been carried out in the NW part of the Agro Pontino, near Latina. Four marine terraces and extensive eolian sand covers were found. The oldest marine terrace, the Latina complex, largely consists of augitic fine sands of marine-lagoonal origin. Towards the end of the transgression (of uncertain age) some minor sea level fluctuations occurred. The next marine terrace, the Minturno complex, is thought to date from the Tyrrhenian II transgression and was preceded by a major regression. This has the characteristics of a normal transgressive system, including late minor sea level fluctuations. The beachridge and lagoonal deposits are slightly tilted to the SW and are underlain by littoral gravels, most probably derived from the adjacent Latina complex through strong abrasion. Following a minor regression another marine terrace was formed (the Borgo Ermada complex). This terrace is considered to date from the Tyrrhenian III transgression, but has a regressive character, a phenomenon which can be explained by assuming a synformational tectonic tilting, some evidence for which is found. During a subsequent major regression (Würmian) eolian sands were repeatedly deposited, particularly on the Borgo Ermada complex. This was followed by the formation of a simple beachridge-lagoon system during the Holocene (the Terracina complex). The datings are based on correlation with sequences elsewhere, the two marine faunas studied give no clue as to their ages. Soil formation depends strongly on the texture of the parent materials and these relationships are indicated schematically. Soils in sands form a clear chronosequence, exhibiting an increased rubefaction and illuvial concentration of clay with age (Regosols — Arenosols — Luvisols). The distinction between the Borgo Ermada and Minturno complex is partly based on this chronosequence. Soils with a sandy albic E horizon, more or less abruptly overlying a stagnative clayey B horizon (Planosols and related soils) abound in intermediate materials of the Pleistocene terraces. The characteristically abrupt textural change was found to be due to the heterogeneity of the parent material (eolian sand over loam to clay) rather than to soil formation. Some attention is paid to prehistoric artefacts, in particular Pontinian type tools and observations of BLANC on the famous site of Gniff-Gnaff are reinterpreted.