GLOSSARY

a) Fossil guide = in terms of age (Trilobiti-Graptoliti-Ammoniti-Nummuliti…)= Fossil specie that characterizes a certain horizon with its plenitude (even if this isn’t restricted at that horizon in the time).

b) Fossil of zone = fossil specie that characterizes a certain horizon with a limited distribution in the time.

c) Fossil of facies = fossil of ambient (specie or fauna fossil closed to a particular sedimentary ambient)

d) Climatic fossils = hot fauna and cold fauna (Strombus bubonius e Cyprina islandica)

e) Remodelled fossil = organism discovered in a younger rock than the one where the fossil had originally laid himself, because of phenomena of natural denudation and redeposition. This can be also skeletal organic material, accumulated during a certain period of time, which has suffered rolling and abrasion more or less in situ before its burial. The possible high concentration of fossils (trough = erosion channel) is due to both the sediment shortage and the action of the current that obstructs the deposition of the sediments. [Many osseous layers (bone breccia) are just due to these mechanisms].

f) Erosion channels = they develop in conditions of shallow waters, in marshlands, as delta, marshy costs, lagoons and not very deep lakes. They have usually filled with a material that contains fragments of the eroded layers (they can be used as polarity methods).

g) Sedimentary environment = in this place certain animals or plants live; for example dens, sand, not very deep water, sea or tropical environment. The environment can be continental or marine [littoral, nephritic, pelagic (planktonic, nektonic and benthonic, of the fotica and afotica zone), of continental shelf, continental, bathyal and abyssal slope].

h) Continental environment = it can be both terrestrial (dry land) and aquatic. The terrestrial environments are differentiated on the basis of climatic zones, while the aquatic environments are differentiated on:

1)fluvial environment=of estuary,delta,fresh water and brackish water;

2) marshy = ponds and marshes;

3) paralico = of lacustral environment polluted by marine conditions;

4) lacustral, limnico = lakes;

5) lagoon = lagoons, of brackish water.

i) Horizon = surface-time recognizable in the rocks by means of some their characteristics as flora, fauna and lithology.

j) Horizon guide = it is a rocky level (usually sedimentary, but also pyroclastic or constituted by lava) which is easily identifiable for the lithological characteristics, the structure and the floro-fauna content. This thin level is not DIACRONO and represents, therefore, an exact moment of the geological era. The horizons guide are very important in the stratigraphic correlations and in the study of the structures; in particular when they are in successions having a reduced thickness and characterized by levels not fossiliferous or by uniform lithology. Sometimes the term horizon guide is related to the contact between two relatively thin levels (of course this is not a precise terminology). The horizon guide concept has been extended to the stratified igneous structures.

k) Diacrono = (literally through the time) - opposed to synchronous, it is a term applied to lithological units (for example an arenaceous level, a bioconstructed horizon and so on) that seem continuos but actually represent the development of same FACIES in various areas and different times, or rather the lithological unit intersects the time lines. Sometimes it talks about diacroni fossils, but it is not an appropriate use of the term.

l) Facies = (continental, marine, of marsh, of delta, lagoon) – It’s the sum of all the characteristics of a kind of a sedimentary rock for example as the fossils content that characterize a sediment deposited in a certain environment. Facies characterized by a particular lithological kind, are named litofacies, while those characterized by the fauna, are named biofacies. It is important to note that a particular litofacies can be diacrona and this it is possible to establish only if the fossiliferous content is adequate. The study of the facies distribution allows to execute paleographic reconstructions.

m) Fossil signs = These are sedimentary structures due to the biological activity. The fossil signs include:

1) Dens and other types of excavations;

2) Sign of shifting, furrows, marks, footprints, habitation structures (domichnia);

3) Nourishment structures (pascichnia);

4) Coproliti (fossil excrement, faecal pellets).

These structures can keep both as a model (internal and external) and as contramark. The signs left by the shells that roll or bounce off the soft sediments are not included with this term.

In the last years a remarkable importance has acquired the study of the fossil signs (Ichnology), in particular in the field of the paleoecology. Even if it’s unusual to go back to the organism responsible for a special mark, the fossil signs are almost exclusively fossil of facies. In fact, they are related to a well limited environment. Moreover they are useful in order to determinate the polarity of the layers.

Even if marks and models are commonly put in relation with the conservation of the fossils, they can also preserve casts and other three-dimensional structures, as marks of rain, rollings and ripples due to the current (ripple marks).

n) Polarity = Any geological phenomenon that allows to determine the original orientation of a rocky mass. The most important use of these criterions is the determination of the succession in the stratified rocks; unless the succession has not been turned over by tectonic events or the layers are vertical, it is possible to apply the superposition principle. Also the layers with a rich fossil fauna can usually be correlated to a well-known succession and so their orientation can be determined. The fossils in life position, as the corals, the sponges, the roots of the plants and so on, can be used. Some kinds of shells, even though they do not grow with a fixed position, tend to be on the sea floor according to their more stable position. For instance the Brachiopodi or the isolated valve of a Lamellibranco lie on the bedding planes with their convex surfaces turned toward up.