干旱区生态环境知识资源中心

Late Miocene (Messinian) alluvial and lacustrine deposits characterize the so-called Kizilbayir Formation of the Aktoprak Basin (central Turkey) and consist of conglomerate, sandstone, mudstone, limestone, marl, and dolomite units. These sediments are composed mainly of feldspar, quartz, hornblende, diopside, olivine, serpentine, calcite, and dolomite With Subordinate palygorskite, chlorite, smectite, and illite. Studies by scanning electron microscopy indicate that calcite and dolomite show both meniscus and micrite-sparite-type cements, characteristic of both vadose and phreatic zones. Chlorite, smectite, and illite are products of the alteration of the underlying Guney Formation with Subsequent transportation by local streams into the Kizilbayir Formation, and therefore these are considered to be reworked materials. Authigenic palygorskite and dolomite formed as a result of the calcretion of mudstone-carbonate units under alkaline conditions, with high Si, Ca, and Mg activity, and low Al, originated from ophiolitic and carbonate units based on the increase in Ni and Co. The paragenesis and textural features of the minerals of the alluvial fan and lacustrine sediments determined in the study area indicate that precipitation probably occurred due to climate fluctuations ranging front and and semi-arid to wet conditions.