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the excavations. The elevation of the lowest quarried part never drops below sea level. An explanation
might be found in groundwater problems, because of the highly permeable rock. Secondly, the worst
quality rock is often left behind, i.e. not quarried. In a lot of fractured areas this can be observed, because
fractures decrease the ability to serve as building material.

Outcrop quality in these quarries varies considerably. Depending in the age and the degree of weathering
the ability to observe sedimentary structures varies. A too young quarry still shows the cuts made by
mining equipment, and sedimentary structures were not able to become visible on the outcrop rock face.
The result is a — for the human eye — homogeneous wall with a regular grid of cuts. On the other side,
some very old quarries with exposure to seawater are weathered, colouring the rock to a blackish surface.
In the perfect conditions the quarries are old enough for the wind to erode part of the wall, exposing
sedimentary structures, and not too close to a source of water to develop a high degree of weathering.

2.3 Geological setting

The geological setting of Favignana is geometrically related to the same geological history which affected
the larger island of Sicily, southern Italy. In the Mesozoic, the African and the Eurasian plates were
bounded by a passive continental margin. The African plate moves north and collides with the European
continent, creating several mountain ranges in the Mediterranean area, including the Apennines, the Alps
and the Pyrenees. An overview of all the Tertiary structures as a result of the Alpine orogeny is given in
figure 2.3.

During this Alpine orogeny stage different thrust sheets developed, superposing each other. The island
of Sicily is therefore characterised by a fairly complex structural setting of folds and east-west trending
thrust belts (see figure A.1 for a geological map of the onshore part of western Sicily). The structurally
interesting part of Favignana can be subdivided into two main tectonic units; the Monte Santa Caterina
unit and the Punta Faraglione unit (Incandela, 1996; Tavarnelli et al., 2003). A simplified geological map
— see figure 2.4a — shows the position of both units.

The Monte Santa Caterina unit consists of upper Triassic to Lower Jurassic platform carbonates.
They show a grading upward trend to the middle Jurassic - Eocene limestones and marls. The
latter are pelagic — or deep marine — deposits. An unconformity follows with on top Miocene
limestones deposited in relatively shallow depths. The youngest sediments in this unit are Tortonian
and Messinian marls and clays.

The Punta Faraglione unit superposes the Monte Santa Caterina unit and is basically built up with
the same stratigraphic column.

The Monte Santa Caterina unit overthrusted the Punta Faraglione unit on the most western part of
the island, as shown in figure 2.4a. The mountain of Monte Santa Caterina itself consists mainly of a

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