Development of quaternary calcrete in the Tensift Al Haouz area, Central Morocco: Characterization and environmental significance

This study utilizes features of calcrete to elucidate the main environmental factors that affect its formation and distribution in the Tensift Al Haouz area, Central Morocco, one of semi arid regions where calcrete is ubiquitous and occurs in a variety of forms. More than hundred calcretes profiles were examined and described by field observations. Selected samples were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), X-ray Diffraction (XRD), and chemical analysis (XRF). Two types of evolution and genesis are evidenced: 1) calcrete of pedogenic origin in the central and eastern part of the studied area, developed in the vadose zone with an upward gradational maturity pattern, ranging from incipient, nodular, to concretionary and to hardpan. 2) Combination of groundwater and pedogenic origin in the western part; the paired calcrete profiles consist from bottom to top of massive calcrete suggested to have a groundwater origin; it might be formed under wet to semi-arid climatic conditions and the gravel hardpan situated at the top suggested to have developed in the vadose zone by pedogenic processes under arid climate. In this study, we conclude that the vertical and lateral distribution of calcrete is related to differences in the topography, the nature of the bedrock, the texture of parent material and the climate.