Red soil at São Brás de Alportel (Portugal). Credit A. Jordán (http://personal.us.es/ajordan).
The term “terra rossa” comes from the Italian for “red soil” or “red earth”. Although terra rossa exists in other places in the world, these soils are common in areas with Mediterranean-type climates: alternation of a rainy and cool-to warm-dry season.
The terra rossa soil is heavy and clay-rich (silty-clay to clayey) soil, strongly reddish, developed on limestone or dolomite. It is a colloquial way to refer to land included within the Rhodustalfs (but also other sub-orders included in Alfisols, Inceptisols, Mollisols and Ultisols of the Soil Taxonomy), Chromic Luvisols (but also other soil types inside Cambisols, Luvisols and Phaeozems of the WRB) or modal fersiallitic red soils (French classification).
Lorena, while sampling a red soil in São Brás de Alportel, Faro, Portugal. Credit A. Jordán (http://personal.us.es/ajordan).
There are several theories about the formation of terra rossa. The first one, traditionally accepted, states that it derives from the insoluble residue of the underlying limestone. Following dissolution of calcium carbonate by rain, clay contained in limestone sediments with other insoluble substances or rock fragments, forming discontinuous residual layers variable in depth. Under oxidizing conditions iron oxides appear, which produces the characteristic red color. According to this theory, terra rossa is a polygenetic relict soil, formed during the Tertiary and subjected to hot and humid periods during the Quaternary.
Karstic landscape (Cerro del Hierro, Sevilla, Spain). Credit A. Jordán (http://personal.us.es/ajordan).
A more recent theory is based on the geochemical composition of the soil, and suggests that these soils would have formed about 12.000 to 25.000 years from wind transported sediments over long distances.
Prof. Nicolás Bellinfante (Univ. of Sevilla), talking about the genesis of red calcareous soils. Credit A. Jordán (http://personal.us.es/ajordan).
However, although in this case soil material is considered to be allochthonous (eg, aeolian dust from the Sahara), formation of the Mediterranean terra rossa is closely related to the properties of the limestone substrate.
Despite their clayey, red soils are usually well drained, due to the strong development of its structure, which allows agricultural use.
Dust from the Sahara? Credit A. Jordán (http://personal.us.es/ajordan).
Know more
Banerjee, A., Merino, E. 2011. Terra rossa genesis by replacement of limestone by kaolinite. III. dynamic quantitative model. Journal of Geology 119, 59-274. DOI: 10.1086/659146.
Boero, V., Schwertmann, U. 1989. Iron oxide mineralogy of terra rossa and its genetic implications. Geoderma 44, 319-327. DOI: 10.1016/0016-7061(89)90039-6.
Colombo, C., Torrent, J. 1991. Relationships between aggregation and iron oxides in Terra Rossa soils from southern Italy. Catena 18, 51-59. DOI: 10.1016/0341-8162(91)90006-J.
Durn, G. 2003. Terra Rossa in the Mediterranean region: Parent materials, composition and origin. Geologia Croatica 56, 83-100. DOI: 10.4154/GC.2003.06.
Durn, G., Ottner, F., Slovenec, D. 1999. Mineralogical and geochemical indicators of the polygenetic nature of terra rossa in Istria, Croatia. Geoderma 91, 125-150. DOI: 10.1016/S0016-7061(98)00130-X.
Iacoviello, F., Martini, I. 2012. Provenance and geological significance of red mud and other clastic sediments of the Mugnano Cave (Montagnola Senese, Italy). International Journal of Speleology 41, 317-328. DOI: 10.5038/1827-806X.41.2.17.
Iacoviello, F., Martini, I. 2013. Clay minerals in cave sediments and terra rossa soils in the Montagnola Senese karst massif (Italy). Geological Quarterly 57, 527-536. DOI: 10.7306/gq.1111.
Lucke, B., Kemnitz, H., Bäumler, R., Schmidt, M. 2014. Red mediterranean soils in Jordan: New insights in their origin, genesis, and role as environmental archives. Catena 112, 4-24. DOI: 10.1016/j.catena.2013.04.006.
Madrau, S., Zucca, C., Akşit, I., Fiori, V. 2013. Stress features in Terra Rossa soil under traditional olive cultivation: A micromorphological and mineralogical characterization. Turkish Journal of Earth Sciences 22, 391-397. DOI: 10.3906/yer-1112-13.
Merino, E., Banerjee, A. 2008. Terra rossa genesis, implications for karst, and eolian dust: A geodynamic thread. Journal of Geology 116, 62-75. DOI: 10.1086/524675.
Muhs, D.R., Budahn, J., Avila, A., Skipp, G., Freeman, J., Patterson, D. 2010. The role of African dust in the formation of Quaternary soils on Mallorca, Spain and implications for the genesis of Red Mediterranean soils. Quaternary Science Reviews 29, 2518-2543. DOI: 10.1016/j.quascirev.2010.04.013.
Šušteršič, F., Rejšek, K., Mišič, M., Eichler, F. 2009. The role of loamy sediment (terra rossa) in the context of steady state karst surface lowering. Geomorphology 106, 35-45. DOI: 10.1016/j.geomorph.2008.09.024.
Simone Priori
I would introduce two papers on “Terra Rossa”, written by my research group:
– Priori S., Costantini E.A.C., Capezzuoli E., Protano G., Hilgers A., Sauer D., Sandrelli F. (2008): Pedostratigraphy of Terra Rossa and Quaternary geological evolution of a lacustrine limestone plateau in central Italy. Journal of Plant Nutrition and Soil Science 171,509–523.
– Capezzuoli E., Priori S., Costantini E.A.C., Sandrelli F. (2009). Stratigraphic and paleopedological aspects from the Middle Pleistocene continental deposits of the southern Valdelsa Basin. Italian Journal of Geosciences, 128, 2, 395-402.