THE second volume of Baron Ferdinand von Richthofen's great work on China has just appeared. Five years have elapsed since the publication of the first volume, and two additional volumes are promised to complete the work, which when its maps and full index have been supplied, will be a great storehouse of observations in almost every department of Geology. Few geologists have enjoyed such opportunities of extended travel as have fallen to the Baron's lot. Already familiar with the rocks of a large part of Central Europe, he carried his knowledge and experience to the far west of North America, and did admirable service there as a pioneer to those who have Jcome after him. Subsequently he set himself to explore the geological structure of the Chinese Empire, and he is now laboriously collecting and arranging the vast materials which he amassed in his wanderings through the almost unknown geological formations of that wide region. China: Ergebnisse eigener Reisen und darauf gegrundeter Studien. Von F. Freiherrn von Richthofen. Zweiter Band. (Berlin: Reimer, 1882.)

The Geology of China

The UlanBuh Desert reach belongs to the upper reaches of the Yellow River located in Inner Mongolia Autonomous Region (China), which has developed a sandy bed. This reach that flows across aeolian dunes field of the UlanBuh Desert has caused large lateral infusion of aeolian sands into riverbed, an abrupt addition of the bedload and a sharp channel widening, forming a typical braided channel. In addition to traditional driving factors such as discharge, suspended sediments and slope, here we also focus on the lateral infusion of aeolian sands into the Yellow River, which may have a significant impact on channel form. To further recognize the desert braided channel change, here based on a long-time series of field dataset from 1966 to 2013, results show that lateral infusion of aeolian sand is the same as discharge as a significant factor to channel form, which is mainly controlled by aeolian activity and discharge conditions. Before the early-1990s, higher discharge and greater intensity of aeolian activity caused a frequent lateral movement and large lateral inputs of aeolian sands into river; this reach showed an unsteady and wider braided channel with a higher braiding intensity. From the early-1990s to 2013, a reduced discharge that caused a decreasing lateral movement, coupled with the decreasing aeolian activity, have resulted in the main flow of the Yellow River far away from sand dunes, which led to a reduction in lateral inputs of aeolian sands. Thus, the braided channel of the UlanBuh Desert reach presented a shrinkage state, gradually changing from a wider and unsteady braided channel to a narrower and relative steady channel form.

Responses of the braided channel to reduced discharge and lateral inputs of aeolian sand in the Ulan Buh Desert Reach of the Upper Yellow River

Sediment records of Yellow River channel migration and Holocene environmental evolution of the Hetao Plain, northern China

Identifying the provenance of sediments carried by modern rivers can provide information on earth surface processes and help us to interpret geological history more clearly. The types and distribution patterns of surface sediments deposited in river systems are determined mainly by the fluvial flux and weathering of the proximal source rocks. In this paper, analysis of the heavy mineral content of 99 surface sediment samples was used to identify the source of the sediments carried by the Dan River in China. The objectives of this study are to: (1) determine the characteristics and distribution of the sediments, and (2) identify and classify the various depositional areas according to their differing source areas. The Dan River is divided into the lower, middle, and upper reaches to investigate the spatial distribution of heavy minerals. The main minerals detected were amphiboles, pyroxene, epidote, garnet, tourmaline, zircon, apatite, rutile, sphene, anatase, pyrite, and ilmenite. Generally, ilmenite (0.7% to 69.1%), amphibole (0% to 93.6%), epidote (0% to 53.3%), garnet (0% to 36.7%) and pyroxene (0% to 42.0%) were the most frequent detrital heavy minerals in the studied river sections. The Dan River and its tributaries are characterized with respect to their heavy mineral assemblages and heavy mineral indexes. Six depositional areas are distinguished and classified as Depositional area A (the Laoguan, Qi, and Xian rivers), Depositional area B (the Qingyou and Wuguan rivers), Depositional area C (the Laojun River), Depositional area D (the upper reaches of the Dan River), Depositional area E (the Yinhua River), and Depositional area F (the Tao River). The provenance study indicated that the sediments were derived mainly from the proximal exposed rocks. Sediments in the middle reaches of the Dan River were derived from Depositional areas B, C, and E, whereas sediments in the lower reaches were derived mainly from the local rocks along the river. Similar heavy mineral assemblages were obtained from Danjiangkou Reservoir and Depositional area A, especially for the Laoguan River, indicating the significant influence of Depositional area A on the reservoir.

Heavy mineral analysis to identify sediment provenance in the Dan River drainage, China

The Jamuna is one of the world’s most heavily sediment-laden braided river. Despite a major host for heavy mineral resources, the sediments of the Jamuna river are sparsely studied. A mineralogical and SEM-EDS investigation has been carried out in the middle part (along Sirajganj and Jamalpur district of Bangladesh) of the Jamuna river to appraise the grain size parameter, texture, depositional environment, heavy mineral distribution, and elemental composition of the heavy minerals. The results show that sediment samples are very fine to fine sand, moderate to well sorted, near symmetrical to strongly fine skewed, and mesokurtic to very leptokurtic. Uniform to graded suspension mechanisms are the processes for sediment deposition. Heavy minerals accumulation ranges from 0.5% to 9.33%, and the assemblages are predominantly marked by epidote, amphibole, followed by opaque (magnetite and ilmenite), garnet, zircon, sillimanite, apatite, tourmaline, rutile, kyanite, staurolite, monazite, chlorite, and titanite. The percentage of amphibole, garnet, and zircon decreases downstream and epidote increases in the same direction. The calculated zircon-tourmaline-rutile index (ZTR) varied between 3 to 13%, average apatite-tourmaline index (ATi), garnet-zircon index (GZi), rutile-zircon index (RuZi) and staurolite-zircon index (SZi) values are 54.55%, 75%, 38.68%, and 30% respectively. The Brahmaputra-Jamuna river sediments are derived from mixed-source regions (e.g., Shillong Plateau, Indo-Burman Ranges, and the Himalayas). The abundance of sub-angular to angular, high relief heavy mineral grains with sharp edges on the surface, conchoidal fractures, deep troughs, and breakage blocks infer that the provenance is close to the depositional area. The presence of rounded to sub-rounded, smoother surface with adhering particles, arcuate steps, and low to medium relief indicate the long-distance transportation of heavy mineral grains through fluvial environment.

Heavy Mineral Analysis of Jamuna River Sediments, Bangladesh

Siltation of coarse sediment in the river channel is the main cause of flooding and dike burst on China’s Yellow River, and the loess are thought as the coarse sediment sources of the lower reach of the Yellow River. The Ningxia-Inner Mongolia reaches of the Yellow River flow through an extensive area of aeolian desert, with flood events occurring frequently in this region. In this paper, we investigate the trace element contents of the coarse sediment in the Ningxia-Inner Mongolia reaches of the Yellow River. The main chemical components of the coarse sediments consist of 28 trace elements. Correlation analysis and factor analysis of 21 of these trace elements indicates that Ti and Zr are stable indicators of the coarse sediment sources. Comparing the spatial distribution of some of the main trace elements to major sources and riverbed sediment of the main reaches of the Yellow River suggests that the coarse sediments deposited in the Ningxia-Inner Mongolia reaches are mostly controlled by the local sediment sources. The results of R-factor analysis further proved that desert sand, riverbank material, and the Ten Tributaries are the primary sources of the coarse sediment in the Ningxia-Inner Mongolia reaches of the Yellow River.

Xiaopeng Jia

Papers

Sources and trace element geochemical characteristics of the coarse sediment in the Ningxia-Inner Mongolia reaches of the Yellow River