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Stable isotopes of pedogenic carbonates from the Somma–Vesuvius area, southern Italy, over the past 18 kyr: palaeoclimatic implications
Author(s) -
Zanchetta G.,
Vito M. Di,
Fallick A. E.,
Sulpizio R.
Publication year - 2000
Publication title -
journal of quaternary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.142
H-Index - 94
eISSN - 1099-1417
pISSN - 0267-8179
DOI - 10.1002/1099-1417(200012)15:8<813::aid-jqs566>3.0.co;2-z
Subject(s) - pedogenesis , geology , carbonate , holocene , δ18o , geochemistry , stable isotope ratio , isotopes of carbon , organic matter , radiocarbon dating , paleontology , soil water , total organic carbon , soil science , chemistry , environmental chemistry , physics , organic chemistry , quantum mechanics
Stable isotopes were measured in the carbonate and organic matter of palaeosols in the Somma–Vesuvius area, southern Italy in order to test whether they are suitable proxy records for climatic and ecological changes in this area during the past 18000 yr. The ages of the soils span from ca. 18 to ca. 3 kyr BP. Surprisingly, the Last Glacial to Holocene climate transition was not accompanied by significant change in δ 18 O of pedogenic carbonate. This could be explained by changes in evaporation rate and in isotope fractionation between water and precipitated carbonate with temperature, which counterbalanced the expected change in isotope composition of meteoric water. Because of the rise in temperature and humidity and the progressive increase in tree cover during the Holocene, the Holocene soil carbonates closely reflect the isotopic composition of meteoric water. A cooling of about 2°C after the Avellino eruption (3.8 ka) accounts for a sudden decrease of about 1‰ in δ 18 O of pedogenic carbonate recorded after this eruption. The δ 13 C values of organic matter and pedogenic carbonate covary, indicating an effective isotope equilibrium between the organic matter, as the source of CO 2 , and the pedogenic carbonate. Carbon isotopes suggest prevailing C 3 vegetation and negligible mixing with volcanogenic or atmospheric CO 2 . Copyright © 2000 John Wiley & Sons, Ltd.