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Red algae

This type of algae (figure 4.3b) is an important builder of carbonate reefs or platforms. Red algae
appearance can be dated back to Cambrian period. In the form of Rhodoliths they can be quite abundant.
This special occurrence of red algae is discussed somewhat later in this section.

Foraminifera

Foraminifera are uni-cell organisms of generally less than one millimetre in size, which can be made
of CaCO3 or agglutinated particles from the substrate. Several hundreds of thousands of species are
known, and they can be split up in two main types. Benthic foraminifera live on the sea floor, however
larger species need to be in the photic zone in order to survive. Therefore the presence of these type
of foraminifera can possibly indicate a shallow sedimentary environment. Planktonic foraminifera are
suspended in the water column during their life. They are possible indicators of more deep marine
environments. The Favignana calcarenite contains approximately twice as much benthic as planktonic
forams. Figures 4.3c and 4.3d show examples of both types.

Rhodoliths

Rhodoliths are a group of coralline red algae that live in the benthic zone, drifting over the sea floor
forming sphere shaped structures. Figures 4.4a and 4.4b show respectively a close up of a rhodolith
encapsulating a particle and a collection of rhodoliths in calcarenite.

Molluscs

Molluscs are invertebrate animals, in a some cases showing an external skeleton. In the outcrops of
Favignana they are represented in the form of bivalve shells, mostly pelecypods and scallops (figure 4.4c),
and occasionally in the form of pinna (figure 4.4d) or oyster shells (figure 4.5b). Preservation is generally
good, and makes it easy to find almost intact clams in outcrops. In thin sections fragments are observed,
as figure 4.3e illustrates.

Echinoids

Echinoids are sea urchins, featuring a crest of several centimetres in diameter generally covered with
numerous spines. In some cases the whole skeleton is preserved — for example in figures 4.4e and 4.4f —
showing the typical fivefold symmetry. On the top of the skeleton, five equal parts are radiating out to
the sides. In addition, fragments of both the skeleton and the spines are observed in thin sections (figure
4.3e).

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