Calcium Carbonate Pendants as a Record of Climate Change in Semiarid Soils of Rashkan Region, Urmia, Iran

Abstract

Accumulation of secondary calcium carbonates in arid and semiarid regions is а valuable tool in evaluating thе degree of soil evolution, soil age, paleoenvironmental reconstruction, soil classification and land use. In particular, laminated pedogenic calcium carbonate pendants can provide some evidence about local environmental and climatic changes. In this study, pedogenic calcium carbonate pendants from Rashakan region of Urmia - Iran were investigated micromorphologicaly. Carbonatic pendants occuar as mammillary to botryoidally stalactite-like masses (segregation), which grow downwards from the bottom of coarse fragments. Pendants аrе multilayered аnd composed оf two to five light and dark colored layers indicating the differences in conditions of calcite precipitation. The sequences of lightand dark colored laminae in pendants probably can represent climatic changes. We suggest that light colored laminae with relatively pure calcite have been precipitated in dry periods that climatic conditions were not favorable for biological activity. Whereas, the dark colored laminae, composed of calcite and some organic impurities, have been formed in relatively wet periods with better conditions for biological activity. Thus, the sequence of light and dark colored laminae can bee used as a tool for paleoclimate and paleoenvironmental research.