PEDOGENIC CARBONATE δ13C AND ENVIRONMENTAL PRECIPITATION CONDITIONS

Abstract

Carbon isotopic analysis is a useful tool for investigating paleoenvironments, as the pedogenic carbonate δ 13 C is related to δ 13 C SOM and to the proportions of C 3 /C 4 plants. In this work we interpreted the paleoenvironmental conditions at the time of carbonate precipitation in soils formed under different climates and during different geological ages. Samples were taken from a Bk (PR1, Holocene) and from two Bkm horizons (PR2 and PR3, Pleistocene). When the mean δ 13 C plant values and the most plausible paleotemperatures were used in the evaluation, PR1 showed a lower percentage of C 4 plants (48%) than Pleistocene soils (~53%), in agreement with paleoclimate changes. When instead the δ 13 C values of current plants were used for PR1, C 4 plants ranged from 59 (12°C) to 66% (18°C), suggesting two possible interpretations: either plant species changed during the Holocene, or the plant mean values normally used in the literature are not suitable for Pleistocene reconstructions