Paleoecological changes in the Northeastern Iran, signals from carbon isotopic composition of pedogenic carbonates in loess derived soils

Abstract

Stable isotopes in pedogenic carbonates can provide information for geomorphic <br><br>evolution of landscapes, past atmospheric CO2 partial pressure fluctuations, <br><br>paleotemperatures and local and global vegetation changes. Loess/paleosol <br><br>sequences and loess derived soils in the north and Northeastern Iran ar ean <br><br>excellent archive for Quaternary environmental changes and have been studied by <br><br>many authors during recent years but there is no information about carbon stable <br><br>isotopic composition of pedogenic carbonates in the loess derived soils of the north <br><br>and northeastern Iran. The objective of this study was to determine the carbon <br><br>isotopic composition of pedogenic carbonates from loess derived soils of southern <br><br>Mashhad for quantitative reconstruction of paleovegetation. Carbon and oxygen <br><br>isotopic composition of pedogenic carbonates in Btk horizon of last interglacial <br><br>period and Bk horizons of Holocene were measured by a mass spectrometer. <br><br>Results indicated the higher precipitation and environmental moisture during <br><br>interglacial periods of MIS5 and MIS1 compared w ith the glacial periods and <br><br>present time. Carbon isotopic composition of pedogenic carbonates revealed the <br><br>dominance of C3 plants during MIS1 and MIS5 periods in northeastern Iran. It <br><br>seems that changes in partial pressure of atmospheric CO2 and air temperature <br><br>were the main factors influencing vegetation type during late Quaternary in the <br><br>northeastern Iran.