Terra rossa is a soil type produced after the weathering of limestone and is quite common across the Mediterranean region. Because of its name, the red soil, people tend to generalize the terra rossa term and use it for every quaternary red clayish deposit regardless of the processes apply to soil formation.
In geoarchaeology it is very important to distinguish red sediments from paleosols as the different formation processes between them result to different information and, thus, archaeological interpretation. The necessity for a clear definition when it comes to paleosols has been stressed out from very early by Valentine and Dalrymple (1976). As it has been pointed out by van Andel (1998), paleosols represent useful stratigraphic tools: former land surfaces possibly relating with human activity. On the other hand, red sediments are ‘the oxidized residue of limestone weathering that once blanketed large regions where limestone dominates the bedrock’ (van Andel 1998, 361). However, van Andel makes a further distinction for terra rossa soils: the primary terra rossa and the re-deposited terra rossa on karst environment. Due to the existing climate, soil formation on limestone bedrocks within the Mediterranean area is very slow; because of slope wash, it is very difficult for the soil to remain in situ. In the case of a karstic peneplain, this primary terra rossa can be captured and form deposits of several meters; on this redeposited sediment, new soils can be formed.
The figure shows the evolution of loutses and poljes on a karstic peneplain (van Andel 1998, 378): ‘Time 1: Terra rossa mantle of a karstic peneplain washes into shallow surface depressions of the karst called loutses. Time 2: Compressive tectonics creates fault-bound, elongated basins of internal drainage called poljes which fill with redeposited terra rossa. Time 3: Continued uplift raises polje and streams cut into the deposits by headward erosion’.
But why do these matter?
The importance of terra rossa in archaeology lies to the fact that it is associated with many prehistoric sites in the Mediterranean area. Dating the aeolian silt that is included in the redeposited terra rossa with luminescence methods can also be possible (van Andel 1998). The type of formation associated with the archaeological finds will include different environmental information: in the case of primary terra rossa the soil were most probable exposed for a long time which indicates a low-resources dry environment. On the other hand, redeposited terra rossa yields wet environment abundant in food resources which could be the reason for an extensive human presence.
Valentine, K. W., Dalrymple, J., 1976. Quaternary Buried Paleosols: A Critical Review. Quaternary Research, 6,209-222.
van Andel, T., 1998, Paleosols, Red Sediments, and the Old Stone Age in Greece. Geoarchaeology: An International Journal, 13/4, 361–390.