Elements and mineral composition indicating the provenance of loess-like sediments in Dry-Hot Valleys of Jinsha River
YE Yulin;SU Huai;DONG Ming;MING Qingzhong;SHI Zhengtao;College of Tourism and Geography Sciences, Yunnan Normal University;Research Institute of Tourism and Culture Industry, Yunnan University of Finance and Economic;
Background, aim, and scope The dry-hot valley is a unique and important natural landscape in southwest China, however, the evolutionary history of this landscape has not been clear for a long time. The loesslike sediments widely covering the bottom of the dry-hot valley can be used as stratigraphic records for solving this problem. To do this its provenance must be understood. In this article, based on the systematical analysis of the elemental and mineral composition between the loess-like sediments and its likely source such as paleodammed lake sediments, overbank sediments and mountain red soil, the provenance of loess-like sediments has been determined in terms of composition similarity. Materials and methods The samples of loess-like sediments and their possible provenance(including paleo-dammed lake sediments, overbank sediments and mountain red soil) are collected in the reach of Jinjiangjie, Yuanmou and Qiaojia in Jinsha River. The same type samples from different river reach are mixed uniformly and sieved over 2 mm screen for measure. The major elements and trace elements of samples are measured by Magix PW2403 X-ray fluorescence spectrometer(XRF), and X'Pert3 Powder X-ray diffractometer(XRD) is used for the determination of mineral composition of samples. Results The analyze test results of major elements and trace elements indicate that among overbank sediments, mountain red soil and paleo-dammed lake sediments, which are possible provenances, the mountain red soil is the biggest difference in composition of elements from loess-like sediments in Dry-Hot Valleys of Jinsha River, while the paleo-dammed lake sediments is smallest. The X-ray diffraction pattern also shows that not only in terms of signal strength, but at the peak position, the paleo-dammed lake sediments are most similar to the loess-like sediments among the three potential sources. Discussion The results of comparative analysis of elements and minerals suggest that paleo-dammed lake sediments are major provenance of loess-like sediments in Dry-Hot Valleys of Jinsha River and the local red soil contribute little to the provenance. In fact, the similarity of element composition between paleo-dammed lake sediments and loess-like materials has been reported as early as a few years ago, but at that time the paleo-dammed lake sediments were not been regarded as major provenance due to lack of data from other area or other possible provenance, such as red soil covering the mountains on both sides of dry-hot valley, to support. In addition, the phenomena that as long as there is loess-like sediments, the paleodammed lake sediments can always be found nearby, also confirms the inherent relation between the paleodammed sediments and the loess-like materials. Conclusions Among the three-possible provenance, the paleodammed lake sediments are most similar to the loess-like sediments in Dry-Hot Valleys of Jinsha River in terms of elemental and mineral composition, which shows that paleo-dammed lake sediments may be the main source of the loess-like sediments in Dry-Hot Valleys of Jinsha River. Recommendations and perspectives Previous studies show that the loess-like sediments in Dry-Hot Valleys of Jinsha River have been deposited at last during the late Pleistocene. Determination of their provenance would benefit to reconstruct the evolutional history of dryhot valley landscape, which is a major scientific issue in south-west China and is difficult to solve by stalagmites, tree ring records in this area.