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Dating and genesis of the upper Weihe river terraces in Longxi basin,China

Progress in Natural Science:Materials International 2007年第11期17卷 1334-1340页

作者： Pan Baotian, Liu Xiaofeng, Gao Hongshan, Wang Yong and Li Jijun(Key Laboratory of Western China’s Environmental System, Ministry of Education, Lanzhou University, Lanzhou 730000, China) Key Laboratory of Western China's Environmental System Lanzhou University Lanzhou 730000 China

Seven terraces along the Weihe river in Longxi basin have been investigated. These terraces all consist of archetypal duality in structure, namely the floodplain deposits and the layer of gravels overlaid by varying thickness of the loess. By resorting to various dating approaches such as palaeomagnetic, optically stimulated luminescenece (OSL), 14C and loess-paleosol sequence, we provide preliminary timing of these seven terraces along upper Weihe river. Analysis on sedimentation characteristics and dating of these terraces showed that seven terraces may be jointly generated by tectonic uplifts and climatic changes. Tectonic uplifts may accommodate initial river incision, and climatic change may be responsible for processes of subsequent channel widening and aggradation. Aggradation normally occurs during glacial periods, in contrast to down-cuttings during transitions from glacial to interglacial period. Moreover, on the basis of the timings and heights of these terraces, we infer that the long-term rate of river incision was determined to be 0.2 m/kyr during the last 870 kyr, which differs from other river incision rates. This discrepancy may reflect spatio-temporal differentiation of tectonic activities in the Qinling orogenic belt during the Pleistocene.

关键词： loess stratigraphy river terraces climate change Upper Weihe river

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FORMATION OF river terraces AND EVOLUTION OF DRAINAGE SYSTEM IN THE MIDDLE REACHES OF THE YELLOW river

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Journal of Geographical Sciences 1993年第4期3卷 50-62页

作者： Zhu Zhaoyu Guangzhou Institute of Geochemistry CAS

On the basis of field data and by the"paleosol-dating method",it is concluded that the Yellow river of this segment and its main tributaries were formed 1670-1450 ka ago,afterwhich six terraces and two valley flats have *** ages(ka BP)are as follows:T6,1670-850;T5,850-470;T4,470-100;T3,100-10;T2,10-0.7;T1,0.-0.3;the upper valley flat,0.3-0.15;and the lower valley flat,*** evolution of this drainage system may be divided into four stages and nine substages.

关键词： middle reaches of the Yellow river river terraces evolution of the drainage system paleosol dating

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THE GENESIS OF terraces IN THE THREE GORGE VALLEY OF THE YANGTZE river

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Journal of Geographical Sciences 1991年第2期2卷 14-20页

作者： Yang Dayuan Department of Geo.& Ocean Sciences Nanjing University

There are several levels of terraces in the Three Gorge Valley of the Yangtze *** on field survey,chemical and mineral analyses,archaeological data,radiocarbon dates,and pollen diagram,a hypothesis is presented that the rock planes of terraces and their overlying gravels and fine flood sediments were developed in different environmental conditions of different *** rock planes were the old channel beds and were developed in underwater *** coarse gravel layers between bedrocks and fine flood sediments are the relics from *** fine flood sediments overlying the gravels were deposited in high waterlevel periods of the Yangtze river in the past interglacial periods or in the middle ***,the genetic mechanism of terrace deposits in the mountainous region may be very different from that of the binary structure of terrace deposits in the plain region.

关键词： Three Gorges Yangtze river river terraces flood plain deposits

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Geological Study of Dasht-e-Top Sedimentary Basin, Wardak Province, Afghanistan

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International Journal of Geosciences 2021年第6期12卷 531-540页

作者： Hafizullah Rasouli Shekeb Shamal Mohammad Hasib Sarwari Department of Geology Geoscience Faculty Kabul University Kabul Afghanistan

This study is conducted to investigate the occurrence of various geological features, and to study the geology and soil characteristics of the study area. To achieve the objective of this research collection, different samples from different locations in study area were collected, analyzed in laboratory, and the results are compared with each other. The main rock types found in the study area were metamorphic rock (Gneiss) and igneous rock (Granite), and the main soil types found were Loam, sandy and silty soils with different soil structures (e.g. crumbling, platy, single grain, granular and prismatic). Calcium carbonate, Iron oxides and different sizes of sediments were also seen in the soil profile, where the size of sediments were changing as it was course size sediments and gravels near the mountain range and as going far from the mountain it was changed to fine size sediments like sand, silt and clay. The river terraces present in the area cover different geological structures such as angular and erosional unconformities, thinning o

关键词： Petrography Sediment Size Soil Structure river terraces Tectonic Structures Geomorphology Calcium Carbonate

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