Terra rossa (Italian for 'red soil') is a well-drained, reddish,clayey tosilty soil with neutralpH conditions and is typical of theMediterranean region. The reddish color of terra rossa is the result of the preferential formation ofhematite overgoethite. This soil type typically occurs as a discontinuous layer that ranges from a few centimeters to several meters in thickness that coverslimestone anddolomitebedrock inkarst regions. The high internal drainage and neutral pH conditions of terra rossa are a result of the karstic nature of the underlying limestone and dolomite.[1][2][3] Terra rossa is also found associated withMediterranean climates and karst elsewhere in the world.[4]
Compared to most clay rich soils, terra rossa has surprisingly good drainage characteristics.[1] This makes it a popular soil type forwine production. Among other wine regions, it is found inLa Mancha inSpain and theCoonawarra,Fleurieu,Wrattonbully andBarossa Valley growing areas inAustralia.[5]
The origin of terra rossa, its parent material, and its relationship to underlying limestones and dolomites has been greatly debated over recent decades by geologists, geomorphologists, and soil scientists.[3][6] One group of scientists argue that terra rossa likely developed from dissolution of the underlying carbonate rocks and the concentration of insoluble sediment and chert within it as the parent material of terra rossa.[7][8] Another group of scientists argues that terra rossa cannot have been formed exclusively from the insoluble residue of underlying limestone and dolomite. Instead they propose that terra rossa is polygenetic in origin and that, depending on their geographic location, their parent material, which has been altered bypedogenesis, contains exotic sediments fromvolcanic ash; non-limestone and non-dolomite; andaeolian sources.[4][9] A final group of scientists argues that terra rossa was formed bymetasomatic replacement processes.[3][10]
Inpedology,red Mediterranean soil, also known asterra rossa (Italian for "red soil") is asoil classification that has been formally superseded by the formal classifications of systems such as theFAO soil classification, but that is still in common use. The terra rossa classification was still, as of 1997, a part of the national soil classifications of countries such asIsrael andItaly. TheUNESCO/FAO World map equivalents are thechromic luvisols (a sub-order of theluvisols), and theUSDA soil taxonomy equivalent is therhodustalfs (a sub-order of theustalfs).[11]
The classification denotes red-coloured soils (sometimes called "redrendzinas") which develop in or on thekarstic landscape of thelimestones of theMiocene and earlier periods, as well ascalcretes in regions where the modernMediterranean climate is predominant. The most accelerated development of red Mediterranean soils occurred from theMiocene to theLate Pleistocene, due to the large amount of climate fluctuation in those periods.[12][13]
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