saline lakes
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2021 ◽  
Author(s):  
Xiao‐Yan Li ◽  
Fang‐Zhong Shi ◽  
Yu‐Jun Ma ◽  
Shao‐Jie Zhao ◽  
Jun‐Qi Wei

Author(s):  
Jennifer L. Bentz ◽  
Ronald C. Peterson

ABSTRACT The mudflats of saline lakes are amenable to authigenic clay formation due to the high ionic strength of the solutions driven by evaporative concentration and due to the fluctuating wet/dry cycles. However, the mudflats of saline lakes have received relatively little study given the challenges in sampling unstable sediments coupled with post-depositional alterations that make direct relationships to the climate difficult. In an effort to gain a better understanding of the authigenic phyllosilicates present, the mudflats of 17 sulfate-rich saline lake basins across southern Saskatchewan were sampled. The <2 μm fraction was separated from the sediments and analyzed utilizing X-ray diffraction (XRD), scanning electron microscopy, bulk chemical analysis via digestion and inductively coupled optical emission spectroscopy, and visible and near-infrared reflectance spectroscopy. The mudflat sediments were characterized as highly variable and were classified based on particle size into sediment classes A (clay-rich), B (unsorted till), and C (sand). Despite the high variability in sorting and thickness of the sedimentary layers, the phyllosilicates were distinctive within each class independent of the basin. Phyllosilicates in sediment class A were characterized by well-crystalline dioctahedral (Al) clays similar to the surrounding soils with smectite > illite > kaolinite > chlorite. Phyllosilicates from sediment class B displayed highly variable characteristics ranging between classes A and C. Clays from sediment class C were dominated by illite with decreasing proportions of smectite, kaolinite, and chlorite. The illite in the sand lenses was poorly formed, with broad reflections in the XRD patterns indicative of small crystallite size or high disorder, which is consistent with an authigenic nature. The clays in class C were rich in iron (Fe) and magnesium (Mg) and displayed lath-like morphologies common with authigenic illite forming in sandy porous sediments. The sand lenses of mudflats represent viable targets for finding authigenic clay minerals in detrital-rich sediments to use in understanding past climates on Earth and Mars.


2021 ◽  
Vol 9 ◽  
Author(s):  
Pu Zhang ◽  
Chenyang Cao ◽  
Xiangzhong Li ◽  
Xuezheng Pei ◽  
Chi Chen ◽  
...  

The dissolved uranium (U) content in the water column of saline lakes varies little between ice-free seasons throughout the whole water column. Such uniformity allows for the potential absolute dating and/or paleohydrologic interpretations of lake sediments and biogenic shell materials using U isotopes. Before using these methods in cold regions, however, it is necessary to evaluate the effects that ice freeze-thaw processes have on the distribution of U isotopes in saline lake waters, and to determine the amount of variation in U isotopic values when such processes occur. In this paper, we collected ice and dissolved water samples from six lakes with variable salinity in February 2021. Five groundwater and three water samples from rivers into Qinghai Lake were sampled in November 2020. The sampled water was analyzed for dissolved concentrations of 238U and the activity ratio of 234U/238U ([234U/238U]AR). The results show that the 238U concentration of ice samples was less than that of the underlying water. The [234U/238U]AR of ice in the five saline lakes was similar to that of the underlying water with less than a 10‰ variation, suggesting no observable fractionation between ice and dissolved water. Thus, the ice freeze-thaw processes have almost no effect on the uranium content and [234U/238U]AR of the sampled saline lakes, which were characterized by a limited recharge volume from surface runoff, groundwater, and ice volume, namely the close saline lake in arid alpine background. The results from the indoor freeze-thaw experiments also showed that the U isotopic composition of Qinghai Lake waters and ice were similar with the 238U concentration of the ice was about 40% of that of the dissolved lake water, supporting the data obtained from natural saline lakes. The above results provide important insights into whether it is feasible to use U isotopes for absolute dating and/or paleohydrologic analysis of lake sediments or biogenic shell materials. In addition, the results are important for evaluating the [234U/238U]AR and uranium concentrations in seawater when there exists a process of melting polar ice, and for determining the initial delta 234U variations needed for dating of coral and other fossil materials.


iScience ◽  
2021 ◽  
pp. 103439
Author(s):  
Chengxiang Gu ◽  
Yantao Liang ◽  
Jiansen Li ◽  
Hongbing Shao ◽  
Yong Jiang ◽  
...  

Author(s):  
María del Pilar Alvarez ◽  
Eleonora Carol ◽  
Inés Eymard ◽  
Andrés Bilmes ◽  
Daniel Ariztegui

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