Clay-carbonate aggregation in alluvial calcareous soils, Central Anatolia, Turkey

Abstract

An unexpectedly high infiltration capacity was determined for heavy-textured, clayey alluvial calcareous soils (Calcic Haploxerepts) in central Anatolia, Turkey, presumably due to the specific mineralogical contents. In order to unravel the phenomenon, clay mineralogy and morphology, soil microaggregate composition, and carbonate accumulations were studied in these soils via X-ray diffractometry, scanning electron microscopy, and energy-dispersive analyses. Calcite and layered minerals were the principal components of the fine fraction. The percentages of clay, silt, and sand were 45, 54, and 1%, respectively. Illites were dominant in the clay fraction – 43–49%, whereas the content of smectites was rather small – 4– 6%. The results indicated that the principal factors of the high hydraulic capacity of the soils were (1) illitization, a process that is typical for arid and semi-arid soils, and (2) microaggregation involving pedogenic calcite, resulted in the formation of clay–calcite ultra-microaggregates maintaining elongated 3–10 μm in diameter micropores.