Small-scale seismic stratigraphy and paleogeographical evolution of the continental shelf facing the SE Elba Island (northern Tyrrhenian Sea, Italy)

Approximately 200 naut. mi. of high-resolution, single-channel seismic reflection profiles from the SE Elba continental shelf were analyzed. The analysis included a detailed three-dimensional reconstruction of the upper 100 m of shelf sediments. Six depositional sequences were identified, with an average thickness of less than 10 m. These sequences were bounded by unconformities which were mostly erosional and which extended over the entire area. Commonly used exploration seismology methods were applied; they included an analysis of the configurations of reflectors inside each sequence and their terminations against the basal unconformity. The lower five sequences experienced a similar history. They appear to represent coastal environments which developed at more than 100 m below the present sea level during Pleistocene sea level changes. The uppermost sequence was correlated with the muddy shelf sedimentation of the present highstand. The recurrert distribution in the five lower seismic sequences can be explained by the fact that, during rises of sea level, sedimentation was largely controlled by local paleogeography and paleotopography. During such periods, the investigated area was located at the apex of a wide gulf connecting Elba Island to the mainland. In this area, progradations were mostly controlled by the slope of the paleocoast, that is, by the structural constraint represented by the Monte Calamita headland. The paleoenvironmental interpretation for the upper sequences was largely substantiated by seafloor cores. Cores were collected from relict transgressive littoral deposits below a mud interval related to the present eustatic environment.