Data di Pubblicazione:
2012
Abstract:
Stable isotope C analysis is the most reliable method used for the distinction and understanding of soil car-
bonates origin. However, in soils with a complex geological setting the carbonate !13C signature could lead
to incorrect interpretations if used alone. Thus coupling this technique to other methods may be necessary.
In this work we evaluated advantages and disadvantages of several methods, some of which are well
known while others are still unused, to distinguish among carbonates of different origins in a soil developed
on “Valle Versa Chaotic Complex”, a marly geological formation in North-western Italy. For a better evalua-
tion of their potentialities the methods were also applied to simpler situations used as a reference for carbon-
ate of pedogenic and lithogenic origins. Thin sections analysis revealed the presence of three kinds of
carbonates in the investigated complex soil: one was pedogenic, while two showed clear lithogenic origin.
The lithogenic carbonate that showed a low !13C (about −9‰) was interpreted as freshwater while isotopic
signature increased up to −4‰ with the presence of marls, thus no evidence of pedogenic precipitations
could be obtained with isotopic analysis. The mean crystallite domain (L104) was highly variable and related
to the amounts of co-precipitated impurities in the carbonates. Thus these methods provided important in-
formation about the formation environment. These rarely used techniques permitted to distinguish between
pedogenic and lithogenic material in simple systems, but did not adequately support the presence of pedo-
genic carbonates in the complex soil. Surface areas and porosity evaluated by N2 adsorption are particularly
influenced by the processes occurring during calcification such as the development of coatings and pore
infillings. The comparison between additive models and measured specific surface area, indeed allowed us
to observe the effect of pedogenic carbonate on the physical properties, although it did not permit any quan-
tification. These results indicated that, although all the methods were able to distinguish between pedogenic
and lithogenic origins in simple systems, only micromorphology and N2 adsorption techniques allowed for
the identification of pedogenic carbonate in a more complex soil system.
Tipologia CRIS:
03A-Articolo su Rivista
Elenco autori:
Catoni M.; Falsone G.; Bonifacio E.
Link alla scheda completa:
Link al Full Text:
Pubblicato in: