Bonifacio, Eleonora

Catoni, Marcella

D&apos

Zanini, Ermanno

English

D'Amico, Michele

Institutional Research Information System University of Turin

Geophysical Research AbstractsVol. 16, EGU2014-PREVIEW, 2014EGU General Assembly 2014© Author(s) 2014. CC Attribution 3.0 License.Contrasting environmental memories by ancient soils on different parentrocks in the South-western Italian AlpsMichele D’Amico (1), Marcella Catoni (2), Eleonora Bonifacio (2), and Ermanno Zanini (1)(1) Torino, DISAFA - Natrisk, Grugliasco (To), Italy (ecomike77@gmail.com), (2) Torino, DISAFA, Grugliasco (To), ItalyAncient soils (pre-Holocenic paleosols and vetusols) are uncommon on the Alps, because of the extensivePleistocenic glaciations which erased most of the previously existing soils, the slope steepness and climaticconditions favoring soil erosion. However, in few sites, particularly in the outermost sections of the Alpine range,Pleistocene glaciers covered only small and scattered surfaces because of the low altitude reached in the basins,and ancient soils could be preserved for long periods of time on particularly stable surfaces.We described and sampled soils on 11 stable surfaces in the Upper Tanaro valley, Ligurian Alps (SouthwesternPiemonte, Italy). The sampling sites were characterized by low steepness and elevation between 600 to 1600m, under present day lower montane Castanea sativa/Ostrya carpinifolia forests, montane Fagus sylvatica andPinus uncinata forests or montane heath/grazed grassland, on different substrata. In particular, we sampled soilsdeveloped on dolomite, limestone, quartzite, gneiss and shales.The soils were always well representative of the pedogenic trends active on the respective parent materials, i.e.the skeletal fraction in each soil was always composed of just one rock type, despite the proximity of lithologicalboundaries and the small dimensions of the different outcrops, often coexisting on the same stable surface.All the considered profiles showed signs of extremely long pedogenesis and/or different phases of intensepedogenesis interrupted by the deposition of periglacial cover beds in the steepest sites. Up to four phases ofintense pedogenesis were recognized where cover beds were developed, presumably during cold Pleistocenephases, as present-day climate is not cold enough to create such periglacial morphologies. In such cases, eachcover bed underwent similar pedogenesis, strongly dependent on the parent material: on quartzite, podzols withthick E horizons and well developed placic ones were formed in all phases except the most superficial one (i.e.Holocene phase), where non cemented spodic horizons or weakly cemented ortstein were formed; placic horizonswere never found in Holocene soils. On limestone, each cover bed separated soils with extremely hard petrocalcichorizons overlaid by argillic ones.Where no cover beds were observed, podzols with extremely thick E horizons (up to more than 2 m thick) and avery hard, very thick ortstein were formed on quartzite. Red Nitisols-like or reddish brown Luvisols were formedon limestone and dolomite, while red, extremely acidic Alisols, with or without fragipan horizons were formed onshales. Very large stone circles and other large patterned ground features, which can be interpreted as evidence ofpast permafrost conditions, were preserved on coarse quartzitic conglomerate.These soils represent excellent pedo-signatures of different specific past climatic or environmental conditions,as a response of different lithologies to specific soil-forming environments, which range from warm and humidclimates typical of red Luvisols and Nitisols, to cool and wet climates leading to the formation of Podzols withplacic or ortstein horizons, to extremely cold and dry ones characterizing permafrost sites and often associatedwith fragipan formation, to warm and dry leading to the cementation of petrocalcic horizons. The precise datingand interpretation of these soils are intriguing.

Contrasting environmental memories by ancient soils on different parent rocks in the South-western Italian Alps

https://iris.unito.it/bitstream/2318/147705/1/EGU2014-0.pdf

Contrasting environmental memories by ancient soils on different parent rocks in the South-western Italian Alps

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