جستجوی مقالات مرتبط با کلیدواژه « calcrete » در نشریات گروه « زمین شناسی »

This study was done to describe and interpret the facies, the provenance of sediments, pedogenesis processes, and the model of the Abyek alluvial fan in the northern margin of Qazvin Plain, using 45 sediment samples in the form of nine profiles and nine surface samples. The facies study led to the determination of six facies grouped into two facies associations including coarse-grained lithofacies (Gms, Gcs, Gci, Gcp/Gmp, Gmg, and Glns), and calcrete facies (Plc). This alluvial fan is dominated by the episodic matrix to clast-supported gravel (interbedded with a subordinate) and red, matrix-supported gravel which were deposited by non-cohesive debris flow. The results of granulometry analysis showed that the size of the sediments of the alluvial fan shows wide variations from gravel to clay, and the texture of the sediments of this alluvial fan is mainly gravel and sandy gravel with very poorly sorting and fine skewness. The study of macromorphology and micromorphology of calcrete showed that their occurrence was controlled by pedogenic processes. Micromorphological studies also revealed alpha and beta features such as coated grains, pisoid, laminar crust and strong brecciation.

Paleosols of the study area is a part of the Eastern-Alborz Zone which is located about 50 km southeast of Azadshahr. These paleosols developed on floodplain and lacustrine facies of the Devonian Padeha Formation. Based on the field and textural evidences, two major paleosol horizons identified as A and B horizons. The A horizon consists of calcrete and noncalcrete paleosols which is located in the floodplain facies of the Padeha Formation. The B horizon identified in the lacustrine facies and consists of calcrete paleosols. Quartz, calcite, dolomite, microcline, hematite, albite, sericite, illite, chlorite and montmorilonite were identified in the paleosols. Geochemical analyses of the paleosols reveal the enrichment of immobile elements and depletion of mobile elements. Investigations of chemical alteration and effective chemical alteration indices indicate intermediate weathering in the study area. The occurrences of noncalcrete and calcrete paleosols suggest a climate change from humid to dryer condition occurred during soil formation. Combinations of textural, mineralogical and geochemical data indicate an origin of basic igneous rocks for the paleosols of the study area.