Page 7 - valerio agnesi - geographical-phisical aspect Sicily

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2.2 From Pleniglacial to Tardiglacial (75,000-10,000 years B.P.)

During the highest glacial expansion phase, Sicily had a geographic outline significant-
ly different than today’s. In fact, the eustatic lowering, that during glacial acme reached -
130 m level compared to today’s, uncovered large portions of the sea floor, especially
along the south coast. The Hyblaean area stretched south, joining the Maltese islands, and
the western cusp of Sicily pushed out towards west, including the Favignana and Levanzo
islands, that were just reliefs imposing from the large surrounding plain. The coastal sec-
tor between Mazara and Sciacca stretched south-west too, generating a vast promontory
and, because of the contemporaneous expansion of Africa’s north coast, the present Canale
di Sicilia was only a narrow sea strait ensuring difficult continuity between west and east
Mediterranean; such two seas were considered two marine basins with different oceano-
graphic features.

The widespread lowering of the base level determined an increase in the erosion of the
stream floors causing thus a deeper hydrographic net of the island and a stress in slopes
dynamics processes. Temperature decrease and the following reduction of snow limits
brought about periglacial conditions on the highest reliefs, favouring physicalweathering
processes . Therefore, slopes became seat of weathering processes that were feeding the
great debris found, with a certain continuity, along the piedmont strip of major reliefs;
analogous side deposits are also located below the actual sea level, as seen in the subma-
rine reliefs of the Aegadi archipelago (Agnesi & al. 1993). Perhaps, taking into account the
existence of Würmian glaciers on Mt. Pollino and in Sila, the highest reliefs have, for some
time, welcomed glaciers.

Along the northern coast, dominant winds were able to move sandy sediments of sea
floors uncovered by Würmian Regression, to deposit them at the base of the reliefs. This
mechanism explains the genesis of powerful and spread aeolian deposits that are found
along northern slopes of Trapani and Palermo Mounts. Perhaps, many of these deposits
formed during the Upper Pleniglacial. The strong dune-like formations that cover the
north-west side of Mt. Palmeto (Terrasini) are veiled by side deposits, typical of a more
humid climate, most likely originated during the Tardiglacial period and deeply altered and
cemented during the hot-humid climatic phase of the Early Holocene. Generally, the exis-
tence of colder phases spaced out by phases of milder climate (interstage), is witnessed by
the alternation of aeolian deposits and debris, at time, at levels alternating different granu-
lometry (èboulis ordonnès); these cover, in various locations, beach deposits of the
Eutyrrhenian, well known in the Aegadi islands and in the Palermo Mounts (Agnesi & al.
1993; Hugonie 1982).

The phase of glacial acme and the Tardiglacial, including deglaciation, are important
faunal exchanges between Sicily and Italy. During this period human populations of
Epigravettian culture and open environment animals reached the island. Among these ani-
mals there was the wild donkey (Equus hydruntinus), animal common in the Italian penin-
sula during the Tardiglacial period that preferred shrubby steppe and well tolerated even
moderate arboreous covers (Abbazzi & al. 1996).

The strips emerged from the platform, perhaps lacking trees, were probably used by
such animals to enter the island. The founding of abundant remains of Terricola savii, a