Stratigrafia e paleogeografia del “lacus timavi” (Friuli Venezia Giulia)

Abstract

Marocco R. & Melis R., Stratigraphy and palaeogeography of the “Lacus Timavi” area (Friuli Venezia Giulia). (IT ISSN
0394-3356, 2009).
A litho-biostratigraphic study of the immediate subsoil of Lisert area (Monfalcone) has been carried out. This marshy area, located at
the foot of the Karst near the mouth of the Timavo river, is rich in evidence of the Roman culture. This research focuses on the paleogeographic reconstruction of the territory that previous studies have only outlined, starting from the Holocene until the Roman settlement, testified by numerous archaeological sites and several literary quotations (Insulae Clarae, Lacus Timavi, etc. ..).
The stratigraphic sequence identified in different analyzed cores, reveals that at least from 4370 ÷ 4220 yrs B.C. the Lisert territory was
covered by a large lagoon which incorporates the Insulae Clarae limestone outcrops (now smooth) and also extended to the south of
the same for several kilometres.
Subsequently there was a transgression that led to a progressive widening of the lagoon basin, but at the same time a probable river
diversion has led to the emergence of south Insulae.
The marginal vegetate settings of this basin, characterized by sandy-pelite sediments, include the exclusive presence of Ammoscalaria
ruinana (HERON-ALLEN & EARLAND), little agglutinated foraminifer that currently lives in the European high-latitude mud flats and has not been reported in the Adriatic Sea.
In the Roman period the lagoon environment had gradually expanded toward the southern margins of Insulae Clarae. This configuration of the southern coast was probably determined by the immediate west occurrence of the mouth of an Isonzo river branch.
The paralic deposits of the Lisert plain fall into the range of variability of the depth - age curve of all the other similar dated deposits
located along the Venetian-Friulian coast. This makes it impossible to define the contribution of tectonics in the determination of the
coastal field of Monfalcone, although there are strong indications of its activity.