Formation mechanisms of megadunes and lakes in the Badain Jaran Desert, Inner Mongolia

Abstract

Field observations demonstrate that calc-sinters occurred in the lakes of Badain Jaran Desert. 87 Sr/ 86 Sr ratios, 14 C, δ 13 C and mineral compositions of calc-sinters, and 3 He/ 4 He, 4 He/ 20 Ne, δ 18 O, δ D, pH and TDS of water from springs and lakes are analyzed in detail. The results indicate that the lake water is supplied through deep fault zone. The "kernel" of stabilized dunes in the Badain Jaran Desert perhaps consists of calc-sinters and calcareous cementation layers. Deep-seated groundwater effuses from this "kernel" and recharges to lakes in desert. Precipitation and snowmelt water from the Qinghai-Tibet Plateau is fed into the Badain Jaran Desert, Gurinai, Wentougaole and Ejinqi areas through the Xigaze-Langshan Fault zone. The isotopic compositions of groundwater in the Alax Plateau are abnormal due to the strong evaporation of the Gyaring and Ngoring lake water in the headstream of the Yellow River. Groundwater dissolves dissoluble fractions of rocks during its transportation through the fault zone and flows out of the mouth of spring in the Badan Jaran Desert. The dissoluble fractions are finally developed into calc-sinters and calcareous cementation layers around the spring. Calci-sinters are gradually largened and eventually emerge on the surface of lake water. Eolian sands accumulate on the surfaces of calc-sinters and calcareous cementation layers, and eventually develop into dunes. Invasion of magma causes an increase in the temperature of groundwater within the faults. Groundwater evaporation provides water vapor for the formation of humid stabilized dunes during its upwelling. Rhizoconcretions found in Yihejigede indicate that the dune was formed and remained immovable 4700 years ago. The height of the megadunes is proportional to thermal quantity carried by the groundwater.

Comment on “Origin of water in the Badain Jaran Desert, China: new insight from isotopes” by Wu et al. (2017)

“…Recent work (Wang and Chen, 2018) found considerable overestimation of the groundwater age by the 14 C dating method due to neglect of dead carbon brought on by deep CO 2 emission. In contrast to the fossil groundwater hypothesis, the detectable tritium activities as shown by Wu et al (2017) and many others (Chen et al, 2006;Gates et al, 2008;Yang and Williams, 2003) indicate a modern precipitation source of the BJD groundwater. This suggests that the Qilian Mountains-sourced groundwater flows through hundreds of kilometers over only tens of years.…”

“…This suggests that the Qilian Mountains-sourced groundwater flows through hundreds of kilometers over only tens of years. We suggest that, due to geological activities, various southwest-northeast deep fault systems exist between the Qilian Mountains and the desert (Chen et al, 2006). Based on the geological conditions and geochemical evidence (helium results), these large deep fault systems are hypothesized to act as a quick passage for the groundwater (Chen et al, 2006(Chen et al, , 2004(Chen et al, , 2012, which explains the detectable tritium in the groundwater.…”

“…They suggested that the BJD groundwater is derived primarily from modern meteoric water from local areas, including the southeastern adjacent small mountains. Based on isotopic evidence, the authors ruled out other hypotheses on the groundwater source, including fossil groundwater (Gates et al, 2008;Ma and Edmunds, 2006;Wang et al, 2015; and snowmelt from the Qilian Mountains, 500 km (center-to-center distance) southwest of the desert (Chen et al, 2004(Chen et al, , 2006.…”

Geomorphological evolution revealed by aeolian sedimentary structure in Badain Jaran Desert on Alxa Plateau, Northwest China

“…The mean annual wind speed ranges from 2.8 m/s to 4.6 m/s, increasing from the south to the north, with the strongest winds in April and May. The mean annual air temperature ranges from 9.5℃ to 10.3℃, increasing from the south to the north as the elevation decreases (Dong et al, 2004;2009), and the highest air temperature can reach 41℃, while the surface temperature is over 70℃ (Zhu et al, 1980;1992;Chen et al, 2006;Zhao et al, 2010).…”

Hydrochemical Characteristics and Water Quality Assessment of Surface Water at Xiahe County in Tibetan Plateau Pastoral of China

“…As for water will become, oil and an important controlling component in restricting the development of the global economy and society of the 21 st century [4,5] .Although climate warming has caused to increasing amounts of meltwater on the Tibetan Plateau, but much of this water can't used, reducing the water available for downstream areas and limiting the water consumption of these areas [1,[6][7][8] .There is a lack of understanding and knowing concerning the water quality of these water resource except its importance, Barnett and Huang found that the resultant changes in hydrological conditions on the quality and availability of the water from the Plateau. In recent years, a great many survives have been demonstrated runoff [9] , precipitation, etc, on the water cycle components of the plateau [3] , alpine lake water environment changes on the Tibetan Plateau [10] . But for surface water, only Zheng carried out the Tibetan surface water in 1956 which studies mainly focused on major ions in saline lakes on the Tibetan Plateau is the most comprehensive study [11] and surface water quality of Yangtze Estuary [12] .…”