Geochemistry of quaternary sediments of Haji-Arab river catchment, Qazvin Plain, Northwestern Iran: provenance and source rock weathering.

Quaternary sediments of the Haji Arab River catchment located in Qazvin Plain, northwestern Iran, were studied in terms of sedimentology and geochemistry to determine the sedimentary environment and rock weathering. Discrimination diagrams show that the source rock of these sediments is granite and their tectonic setting is the active continental margin. These rocks show a negative Eu anomaly and a high ratio of light rare earth elements to heavy rare earth elements, suggesting that these sediments are originated due to the weathering of felsic rocks. Regarding the descending trend of chemical index of weathering, chemical index of alteration values, and the increase in coarse-grained particles, it was concluded that the sediments from the depth of 6 to 2.6 m formed under arid and high-energy conditions; however, this trend for sediments from 2.6 m depth to surface changes slightly toward semi-humid up to semiarid climate. Hence, it can be stated that the conditions of sedimentation environments in the Haji Arab basin are not constant at least in the Upper Holocene (Schmidt et al. in Holocene, 2011. https://doi.org/10.1177/0959683610385961) and this has led to changes in river sedimentation. These results indicate the changes in river regime conditions probably because of the changes in weather conditions during the Quaternary. [ABSTRACT FROM AUTHOR]