The establishment and improvement of the chronological framework of the Cenozoic strata within and around the Tibetan Plateau, are very essential and significant for revealing the history of the collision, uplift and deformation of the Tibetan Plateau. It's vital to enhance the understanding of the denudation and weathering patterns varying with time and space and find out the mechanism of the uplift and deformation of the Tibetan Plateau and its relevant effects on the regional and even global environment and climate. This data set has improved or established the chronological framework of the Cenozoic strata within and around the Tibetan Plateau, based on the magnetostratigraphy and accompanied by zircon U-Pb geochronology of the volcanics/tuffs/sedimentary tuffs or detrital rocks and/or biostratigraphy. The precisely dated sedimentary sequences include a 90-m loess sequence of the Duikang section constrained as ~8.1-3.7 Ma in the Linxia basin, several fluvial and lacustrine sequences (such as the 1890-m Dayu section with a range of ~41.8-21.5 Ma in age in the Lunpola basin, the 300-m Shuanghe section dated as ~42.7-36 Ma in the Jianchuan basin, the 252-m Caijiachong section with a range of ~47-36 Ma in the Qujing basin) and a 932-m saline lacustrine sequence with gypsolyte of the Jiangcheng section in the Simao basin whose age has identified to >112-63 Ma. All relevant experiments of the above chronology results have been conducted in the Institute of Tibetan Plateau Research, Chinese Academy Sciences, Lanzhou University, Tübingen University (Germany) , University of Texas at Austin (USA). The thermal demagnetization has been implemented using a thermal demagnetization oven and measured by a cryogenic magnetometer in a magnetically shielded room. The zircon U-Pb dating has been carried out using an inductively coupled plasma mass spectrometer with an attached laser ablation system. This data set provides an important chronological foundation for the following researches on tectonic evolution, paleoenvironment and paleoclimate. It has created a series of original theoretical achievements with widespread influence.
FANG Xiaomin , FANG Xiaomin, YAN Maodu, ZHANG Weilin, ZHANG Dawen
The data includes natural remanence, thermal demagnetization and magnetic susceptibility anisotropy of paleomagnetic samples in altash section in Southwest Tarim. The data is mainly used for magnetic stratigraphy in altash section. Combined with the results of isotopic dating, the chronological framework of altash section is established according to the records of geomagnetic polarity reversal in rocks or sediments and the comparison with standard polarity columns. From 2020 to 2021, members of the research group mainly used drilling rigs to drill paleomagnetic directional samples on the profile at an interval of 1 m (back to the laboratory to be processed into a 2 cm cylinder), and collected directional hand samples in individual areas (back to the laboratory to be processed into a 2 cm * 2 cm * 2 cm cube). The paleomagnetic experimental testing instrument includes two parts: 1 Rock superconducting magnetometer is used to measure the remanence and rock magnetic parameters of paleomagnetic samples; 2. Mfk kappa bridge is used to measure the magnetic susceptibility and magnetic susceptibility anisotropy of geological samples. A total of 298 samples were selected at an interval of 10 m, of which 221 obtained stable remanence, with a success rate of 74%. According to the preliminary paleomagnetic results, the chronological framework of altash section in Southwest Tarim is established; After all the paleomagnetic results are tested, combined with the accurate isotopic age, the high-precision magnetic stratigraphic sequence in Southwest Tarim will be established.
This set of data is used to reconstruct the magnetostratigraphy of the Hoh Xil basin in the interior of the Qinghai-Tibet Plateau and the Sichuan Basinaround the eastern margin of the plateau, and then combined with other chronological methods to establish high-precision chronological scales of the two basins. All the data are thermal demagnetization data, including two parts: one is the paleomagnetic data of the strata about 1000 meters in the top of the Hoh Xil basin; The second is the paleomagnetic data of the bottom strata in Sichuan Basin. The data were measured or obtained in the State Key Laboratory of continental dynamics, Northwestern University and the laboratory of paleomagnetism and geochronology, Institute of Geology and Geophysics, Chinese Academy of Sciences. The preliminary processing results show that the data quality is high.
The data set mainly shows the magnetic lineament corresponding to different radii. The magnetic lineament is obtained by Radon transform of magnetic anomaly data, which can be used to detect more detailed individual alignments on a map, and can be compared with other anisotropic data. The dataset contains one dat file: magnetic_ lineament.dat。 The data set can be used to display the magnetic lineament with different radius in Xuhuai area and its adjacent areas. Combined with other geophysical and geological observations, the deformation mechanism of Xuhuai arc can be further discussed based on the results, .
Guided by the theory of plate tectonics, paleogeography, petroliferous basin analysis and sedimentary basin dynamics, we have collected a large number of data and achievements of geological research and petroleum geology in recent years, including strata, sedimentation, paleontology, paleogeography, paleoenvironment, paleoclimate, structure, oil and gas (potash) geology and other basic materials, especially paleomagnetism, Paleogene Based on the data of detrital zircon and geochemistry, combined with the results of typical measured stratigraphic sections, the lithofacies and climate paleogeographic pattern of Cretaceous were restored and reconstructed, and two lithofacies paleogeographic maps of early and late Cretaceous of Pan tertiary and two climate paleogeographic maps of early and late Cretaceous of Pan tertiary were obtained, aiming at discussing the influence of paleogeography, paleostructure and paleoclimate In order to reveal the geological conditions and resource distribution of oil and gas formation, and provide scientific basis and technical support for China's overseas and domestic oil and gas exploration deployment.
The development of the southern piedmont of the Himalayan margin and its depositional setting have changed since the tectonic uplift of the Himalaya due to the continental collision of India with Asia, in which the marine- and terrestrial-facies sediments recorded the tectonic deformation and environmental evolution of the front edge of continental collision. To better understand the deformation mechanism of the southern Himalayan margin and constrain the continental collision age, we selected the well an exposed outcrop profile from late Cretaceous to middle Eocene strata in the western Nepal and carried on detailed paleomagnetic studies. At present, all the samples for the Butwal section with depth of 315 m had been performed on the stepwise alternating field demagnetization (AFD) with high-resolution declination and inclination.
Paleomagnetism has played an important role in quantifying the Mesozoic evolution of “Proto-Tibet”. We present here our recent paleomagnetic data from five Middle-Upper Jurassic sedimentary sequences of the eastern North Qiangtang Terrane at Yanshiping. The new paleomagnetic results from 99 sites, 1,702 samples and reveal paleopoles at 79.1°N/306.9°E (dp=3.9°, dm=6.3°) for Quemo Co Fm, 68.9°N/313.8°E (dp=2.1°, dm=3.7°) for Buqu Fm, 66.1°N/332.1°E (dp=2.7°, dm=4.6°) for Xiali Fm, 72.4°N/318.6°E (dp=3.9°, dm=6.7°) for Suowa Fm, and 76.9°N/301.1°E (dp=7.9°, dm=13.2°) for Xueshan Fm, respectively. These results indicate that Yanshiping experienced latitudinal changes from ~24.5° N to ~22.0º N over the time interval 171.2 - <157.5 Ma, accompanied by clockwise (CW) rotations of ~19.8±9.4º between ~171.2 and 161.7 Ma and counterclockwise (CCW) rotations of ~15.4±13.4º between ~161.7 and <157.2 Ma. We attribute the change in rotation sense at approximately ~161.7 Ma to the initial collision of the Lhasa and Qiangtang terranes. Using this and other paleomagnetic data from the Lhasa, Qiangtang and Tarim terranes, as well as other geological evidence, such as tectonism-related sedimentary sequences, volcanism, and HP metamorphism, we propose a new conceptual evolution model for the Mesozoic QT and Tethyan Oceans, including 3 intra-continental collisions (South-North Qiangtang, Qiangtang-Songpan-Ganzi and Lhasa-Qiangtang) and post collisional extensions.
The Simao Basin is located in the south of the Yunnan province and the southeast of the Qinghai-Tibet plateau. It is classified as the Sanjiang tectonic domain belongs to the eastern part of Tethyan tectonic domain. The thick and continuous Early Cenozoic strata preserved in the basin is thought to be an ideal achieve to reconstruct the history of tectonic evolution in this area as well as on the southeastern plateau. The most complete Early Cenozoic strata in the Simao Basin are located in Xiaojinggu Town, Jinggu County, which mainly includes the sedimentary strata of the Mengyejing Formation, the Denghei Formation and the Mengla Formation. Previously, the chronological study of sedimentary strata in the Simao Basin is mainly concentrated in the Mengyejing Formation with potassium salt. However, scholars still have significant controversy about the deposition time of this group at this stage. Further, a complete sedimentary profile containing the middle and lower part of the Mengyejing Formation could not obtain due to vegetation cover and village construction. Through the systematic thermal demagnetization analysis of the 361.86-meter-thick borehole that encompasses the entire Mengyejing Formation, a Paleocene-Cretaceous high-resolution magnetic chronology results were obtained in this area initially.
The Qujing Basin is located in the eastern part of Yunnan Province, is a long and narrow rift basin with north-south trend in shape. The Basin preserves thick and continuous Cenozoic sediments, which can be divided into Xiaotun Formation, Caijiachong Formation and Ciying Formation from bottom to top. These thick Cenozoic sediments deposited are ideal achieves used to explore the history of local deformation process affected by the collision of the Indian-Eurasian plate as well as the evolution of the Indian monsoon in the Cenozoic. Previously, the macrochronological framework of these stratum was mainly defined by biological fossils, but high-resolution chronology with precise chronological control has not been carried out, thus limiting the understanding of tectonic evolution and climate and environmental changes since the Eocene in Yunnan. Based on the paleomagnetic test performed on the 300-meters thick boreholes drilled in the Qujing Basin as well as the U-Pb age (35.49 ± 0.78 Ma) results of volcanic tuff zircon collected from the top of the Caijiachong Formation, we then present the preliminary results of a precise chronological controlled high-resolution magnetic chronology record.
The thick Cenozoic sediments deposited in Yunnan are ideal achieves used to explore the history of local deformation process affected by the collision of the Indian-Eurasian plate as well as the evolution of the Indian monsoon in the Cenozoic. However, due to the lack of precise age control, the early Neogene strata in Yunnan are poorly constrained. The Qujing Basin in the northern part of Yunnan Province preserves thick and continuous Cenozoic sediments, which can be divided into the Xiaotun Formation, the Caijiachong Formation and the Ciying Formation from bottom to top. Through the combination of the field outcrop profile and the borehole core, the research team obtained the stratified stratum of the Xiaotun Formation and the Caijiachong Formation with a total thickness of 251 m in the Qujing Basin. The U-Pb geochronology of the top volcanic tuff layer (35.49 ± 0.78 Ma), Caijiachong mammal fossil group (late Eocene) as well as magnetic stratigraphy collectively reveals that the age at the bottom of the Xiaotun Formation is 46.2 Ma, the top of the Caijiachong Formation should be < 36.2 Ma, and the epoch line of the two groups is 41.2 Ma. However, due to the weak influence of tectonic activities in the late Cenozoic and the small deformation of the formation, the terrain in the middle of the basin is relatively flat, resulting in the inability to obtain the top of the continuous Caijiachong Formation and the upper Ciying Formation samples. A total of 320.1 meter core covering the entire Ciying Formation and the Caijiachong Formation was obtained through the continuous drilling mission carried out in the center of the basin. Among them, the overall lithology of the core of the Ciying Formation (0-216.3 m) is dominated by gray mudstone and siltstone, and several layers of coal seams are intercalated; while the lower Caijiachong Formation (216.3-305.5 m) is grayish and grayish green mudstone. The lithology of the Xiaotun Formation (305.5-320.1 m) is mainly dominated by red mudstone.
The most complete Early Cenozoic strata in the Simao Basin are located in Xiaojinggu Town, Jinggu County, which mainly includes the sedimentary strata of the Mengyejing Formation, the Denghei Formation and the Mengla Formation. Due to the tectonic uplifting of the mountain in the late Cenozoic, the syncline structure caused the top of the Mengyejing Formation, the Denghei Formation and the Mengla Formation to be exposed to the surface. However, a complete sedimentary profile containing the middle and lower part of the Mengyejing Formation could not be obtained due to vegetation cover and village construction. The chronological study of sedimentary strata in the Simao Basin is mainly concentrated in the Mengyejing Formation with potassium salt. However, there still has significant controversy about the deposition time of this group at this stage. Recently, a continuous and complete high-resolution sequence (361.86 m in thickness) of the Mengyejing Formation was obtained through the continuous drilling. Among them, the Mengyejing Formation (0-353.3 m) is mainly a set of purple-red muddy silt and mudstone combination, while the underlying Mangang Formation (353.3-361.86 m) is a set of gray-white sandstone.
This data set contains a deep drilling paleomagnetic age data near the open sea in the middle reaches of Heihe River. The borehole is located at 99.432 E and 39.463 n with a depth of 550m. The samples of paleomagnetic age were taken at the interval of 10-50 cm. The paleomagnetic test was carried out in the Key Laboratory of Western Ministry of environmental education of Lanzhou University. The primary remanence of the samples was obtained by alternating demagnetization and thermal demagnetization, and the whole formation magnetic formation was obtained by using the primary remanence direction of each sample, and then the sedimentary age of the strata was obtained by comparing with the standard polarity column. The results show that the bottom boundary of the borehole is about 7 Ma and the top boundary is 0 ma.
HU Xiaofei, PAN Baotian
This data set contains two shallow drilling data near Heiquan in the middle reaches of Heihe River: 140 meters and 68.2 meters deep respectively. Paleomagnetic age samples were taken at 10-50 cm intervals from the two boreholes, and the magnetostratigraphic sequences of the two boreholes were obtained by testing these samples.
HU Xiaofei, PAN Baotian