Page 5 - Tesi_dottorato_Polizzi_Sabrina

The evolution of the continental shelf of the Egadi Islands, has been influenced by the different
phases of the glacial-eustatic variation of sea level. During the low stationary phase (lowstand), the
sea level was about 120 m lower than at present, and the the continental shelf was emergent . This
phase (Wurm glacial phace), was followed by a progressive phase of flooding, such that the
continental shelf was affected by alternating conditions of erosion and sediment accumulation,
which were the main morpho-genetic processes that have characterized the area in the late
Quaternary age.
The sedimentary structures present in the Egadi Islands, have erosiional and depositional origin.
Differences in the size, the variety of depth and the different orientations that are found, suggest that
the sedimentary structures were generated in different hydrodynamic environments and at different
times.
Channalized structures, such as moat drifts and sediment drifts that are found both along the
Marettimo channel, respectively oriented NW-SE and WNW-ESE, show that these areas are
affected by bottom currents that create the conditions for the development of erosive sedimentary
structures, as contourite drift.
The areas in question are part of an area that is home to important exchanges between maior water
masses in the Mediterranean Sea (MAW, LIW and MDW), which may give rise to local phenomena
of bottom currents with high speed. Infact, the contour currents that are channeled inside the
Marettimo Channel follow the trend of the LIW, that in the area of the Mediterranean Sea central
ranges from S to N. Here they encroach a very shallow-water sill and a narrow passags and undergo
a strong acceleration, creating the conditions to form sedimentary structures with both depositional
and erosional character.
The interaction between these currents and the sediment progradation of the margin during fall the
level of the sea has influenced the evolution of the margin by limiting the accretion front.
In addition to the sedimentary structures generated by the current "density", numerous sedimentary
structures are scattered along the seabed of the continental shelf, generated by tractive currents
induced by waves during major storms and storm surges. Among the latter, some appear to have
been generated by marine weather events of exceptional intensity, higher than the highest record of
the instrumental time series.

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