Focusing on the objective of estimating the total amount of unconsolidated sediments in the Yarlung Tsangpo River Basin (YTRB), we marked a series of Quaternary sections of unconsolidated sediments in the whole basin to measure their thickness. The dataset presents a collection of field photos of unconsolidated sediments obtained in the scientific expedition in YTRB in 2020. Specifically, this dataset comprises of 16 composite first–class sub basins, from upstream to downstream, including Dangque–Laiwu Tsangpo, Resu–Lierong Tsangpo, Chaiqu–Menqu, Xiongqu–Wengbuqu, Jiada Tsangpo, Pengji Tsangpo–Sakya Chongqu, Duoxiong Tsangpo, Shabu–Danapu, Nianchu River, Xiangqu–Wuyuma, Manqu, Nimuma–Lhasa River, Gonggapu–Luoburongqu, Niyang River, Yigong Tsangpo–Palong Tsangpo, and Xiangjiang River Basin. A total of 584 sites of unconsolidated sediments were marked. The atlas displays different types of unconsolidated sediments, such as alluvium, eluvium, diluvium, colluvium, eolian, lacustrine and moraine deposits, showing their spatial distribution in hillsides, foothills, floodplains, terraces, alluvial–diluvial fans and glacier fronts. With a scale of 1m benchmarking, it shows the significant difference in distribution of thickness. Generally, the thickness of the eluvium on the upper part of the hillside is about 0.3–2.5m, and the thickness of the alluvium is difficult to bottom out. The thickness of diluvium in the gentle area of the piedmont with steep slope is usually between 5 and 10 m, while the thickness of the deposit at the piedmont gully mouth is related to the scale of the pluvial fan, which can reach tens of meters thick and only 3 to 4 meters thin. From the upstream to the downstream, the thickness of alluvium varies greatly. The bedrock in the canyon area is exposed, and the thickness is almost 0. However, the thickness of alluvium in the upstream river valley is large and difficult to see the bottom interface; The maximum thickness of measured moraine deposits can reach more than 20 m. Aeolian deposits are common in the middle and upper reaches, with a wide range of thickness, ranging from a few meters to more than 20 meters. The dataset provides a wide variety of in–suit photos and measurements of unconsolidated sediments covering the whole basin, showing their characteristics of spatial distribution and genetic types, which lays a material foundation and prior knowledge for further detailed characterization and investigation of unconsolidated sediments. This work presents data for estimating the total accumulation of solid debris deposited in the YTRB, and provides a basis for assessing the risk of natural disasters related to unconsolidated sediments and formulating scientific preventive measures.
LIN Zhipeng, WANG Chengshan , HAN Zhongpeng, BAI Yalige, WANG Xinhang, HU Taiyu
The considerable amount of solid clastic material in the Yarlung Tsangpo River Basin (YTRB)) is one of the important components in recording the uplift and denudation history of the Tibet Plateau. Different types of unconsolidated sediments directly reflect the differential transport of solid clastic material. Revealing its spatial distribution and total accumulation plays an important value in the uplift and denudation process of the Tibet Plateau. The dataset includes three subsets: the type and spatial distribution of unconsolidated sediments in theYTRB, the thickness spatial distribution, and the quantification of total deposition. Taking remote sensing interpretation and geological mapping as the main technical method, the classification and spatial distribution characteristics of unconsolidated sediments in the whole YTRB (16 composite sub-basins) were comprehensively clarified for the first time. Based on the field measurement of sediment thickness, the total accumulation was preliminarily estimated. A massive amount of sediment is an important material source of landslide, debris flow and flood disasters in the basin. Finding out its spatial distribution and total amount accumulation not only has theoretical significance for revealing the key information recorded in the process of sediment source to sink, such as surface environmental change, regional tectonic movement, climate change and biogeochemical cycle, but also has important application value for plateau ecological environment monitoring and protection, flooding disaster warning and prevention, major basic engineering construction, and soil and water conservation.
LIN Zhipeng, WANG Chengshan , HAN Zhongpeng, BAI Yalige, WANG Xinhang, ZHANG Jian, MA Xinduo, HU Taiyu, ZHANG Chenjin
The Wuyu Basin is bounded by the Gangdese Mountains to the north and the Yarlung Tsangpo River to the south, and is a representative basin to study the Cenozoic tectonism of the southern Tibet. The sedimentary strata in the Wuyu Basin include the Paleocene-Eocene Linzizong Group volcanics and the Oligocene Rigongla Formation (Fm.) volcanics, the Miocene lacustrine sediments of the Mangxiang Fm. and Laiqing Fm. volcanics, the late Miocene-Pliocene Wuyu Fm., and the Pleistocene Dazi Fm. Five sandstone samples from the Mangxiang Fm., Wuyu Fm. and Dazi Fm. and one modern Wuyu reiver sand sample were collected for detrital zircon U-Pb dating using the LA-ICP-MS method. Detrital zircon U-Pb ages in the Mangxiang Fm. show a large cluster at 45-80 Ma; those in the Wuyu Fm. show a large cluster at 8-15 Ma and a subsidiary cluster at 45-70 Ma; those in the Dazi Fm. show three large clusters at 45-65 Ma, 105-150 Ma and 167-238 Ma; and those in modern Wuyu river show a large cluster at 8-15 Ma and a subsidiary cluster at 45-65 Ma (Figure 1). Late Cretaceous-early Eocene zircons in all samples are consistent with the most prominent stage of magmatism of the Gangdese Mountains; the 8-15 Ma zircons in the Wuyu Fm. and modern Wuyu river are consistent with the magmatism of the Laiqing Fm.; and the Triassic-Jurassic zircons in the Dazi Fm. are consistent with the magmatism of the central Lhasa terrane. The results of detrital zircon U-Pb ages and sedimentary facies analyses in the Wuyu Basin indicate that the southern Tibetan Plateau suffered multi-stage tectonism-magmatism since the India-Asia collision: (1) Paleogene Linzizong Group-Rigongla Fm. volcanics; (2) tectonism-magmatism at ~15 Ma ended the lacustrine sediments of the Mangxiang Fm. and resulted in volcanism of the Laiqing Fm.; (3) tectonism at ~8 Ma resulted in the volcanic rocks of the Laiqing Fm. becoming one of the main provenances for the overlying Wuyu Fm.; (4) the Wuyu Basin formed braided river and received sediments from the central Lhasa terrane to its north at ~2.5 Ma. The geomorphic pattern of the southern Tibet has gradually formed since the Quaternary.
MENG Qingquan MENG Qingquan
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