Calcic soils as indicators of profound Quaternary climate change in eastern Isfahan, Iran

Abstract

In the high plateau region of central Iran, there is both a lack of information on calcic soil processes and aspects of Quaternary paleoclimate. Thus, the research discussed here was undertaken as afirst step to assess the utility of calcic soil research in the region. The properties and isotope composition of calcic soils was studied on a complex of alluvial fans, located about 50 km SE of the city of Isfahan. At least three geomorphic surfaces have formed during an interval from the middle Pleistocene to the Holocene. These geomorphic surfaces contain calcareous soils and paleosols. Interpretation of the pedogenic evidence indicates that there have been multiple periods of clay formation and carbonate accumulation over time, with an overall trend of increasing environmental aridity. Microscopy shows that overprinting is a major factor responsible for the accumulation of calcrete, suggesting the impacts of climate oscillations on the calcrete formation. Stable isotope composition of pedogenic carbonates in soils of differing ages is suggestive of a decrease in plant density and an increase in evaporation as soils become younger. This research highlights the utility of the morphology and isotope chemistry of calcic soils for constraining environmental change during the Quaternary.