The Tertiary basins are distributed in the eastern margin of the Tibetan Plateau along the large\|scale arc\|shaped strike\|slip belt of the Qiangtang—Hengduan Shan—Jinshajiang—Red River belt. Most of basins were c...The Tertiary basins are distributed in the eastern margin of the Tibetan Plateau along the large\|scale arc\|shaped strike\|slip belt of the Qiangtang—Hengduan Shan—Jinshajiang—Red River belt. Most of basins were controlled by regional northwest\| and south\|north treading faults, and a few basins were constrained by northwest\| or north\|north\|east\|treading local faults.The detailed field mapping and sedimentologic observations for 6 typical Tertiary basins in eastern Tibet show that their types include depressive basins, rifting basins, pull\|apart and extensional basins related to strike\|slip faulting, and erosion\|residual basins. Recently, most of them are controlled by compression\| or thrust\|related margin faults in single side or double laterals of these basins. Not\|well\|developed strata in the Tertiary basins were deformed to form various tight folds and thrusts. High\|K magma intruded widely into the basins. The tectono\|sedimentary evolution of the Tertiary basins appears tempo\|spatially inhomogeneous. The preliminary model to interpret the Tertiary basin evolution is described as below.展开更多
The results of the granulometrical and sequential analysis supported by micropaleontological dating using the foraminifera as well as chemico-ponderous and X-ray diffraction analysis,confirmed the contemporaneity of t...The results of the granulometrical and sequential analysis supported by micropaleontological dating using the foraminifera as well as chemico-ponderous and X-ray diffraction analysis,confirmed the contemporaneity of the Burdigalian outcrops of the two studied zones(Ain Sidi Salah zone in the northeast and Fedj El Behim zone in the southwest), both located at the north of the city of Ouenza in展开更多
To contribute to the understanding of the ages of large sedimentary basins in northern Tibet, and the Cenozoic tectonic history of Asia in general, we conducted an integrated paleomagnetic and stratigraphic study on t...To contribute to the understanding of the ages of large sedimentary basins in northern Tibet, and the Cenozoic tectonic history of Asia in general, we conducted an integrated paleomagnetic and stratigraphic study on the sedimentary sequences of the Hoh Xil basin, north of the Qinghai\|Tibet Plateau. Red sedimentary sections from the Fenghuoshan and Yaxicuo Groups have recorded a pattern of magnetic polarity reversals that correlates well with the known magnetic polarity time scale for the past 56Ma. Reliable magnetostratigraphy for the Fenghuoshan and Yaxicuo Groups suggests that the sediment ages for these two groups are about 56～29Ma and 29～25Ma, respectively.We collected more than 1000 paleomagnetic samples from 335 sites distributed in 3 sections of the Hoh Xil basin. Detailed litholostratigraphic, petrologic, and sedimentologic studies have also been carried out on these sections during the past three field sessions. Magnetic directions in these sites were obtained by progressive alternating\|field and thermal demagnetization experiments. Most samples exhibit two components of magnetization. The lower unblocking temperature component is an overprint resembling the geocentric axial dipole field direction at the sampling locality. The most stable, characteristic remanence (ChRM) appears to be an early chemical remanent magnetization residing mainly in hematite. Curie temperature determinations, acquisition of isothermal remanent magnetization (IRM) and backfield demagnetization of saturation IRM, hysteresis loop parameters, and low\|temperature demagnetization on representative samples all corroborate demagnetization behavior. The positive results of fold and reversal tests indicate that the ChRM is a record of the paleomagnetic field close to the time of formation of these sediments. Further evidence that the magnetization of these sediments was acquired close to their time of deposition is the fact that patterns of magnetic reversals have been identified, which can be matched with the established polarity time scale.展开更多
文摘The Tertiary basins are distributed in the eastern margin of the Tibetan Plateau along the large\|scale arc\|shaped strike\|slip belt of the Qiangtang—Hengduan Shan—Jinshajiang—Red River belt. Most of basins were controlled by regional northwest\| and south\|north treading faults, and a few basins were constrained by northwest\| or north\|north\|east\|treading local faults.The detailed field mapping and sedimentologic observations for 6 typical Tertiary basins in eastern Tibet show that their types include depressive basins, rifting basins, pull\|apart and extensional basins related to strike\|slip faulting, and erosion\|residual basins. Recently, most of them are controlled by compression\| or thrust\|related margin faults in single side or double laterals of these basins. Not\|well\|developed strata in the Tertiary basins were deformed to form various tight folds and thrusts. High\|K magma intruded widely into the basins. The tectono\|sedimentary evolution of the Tertiary basins appears tempo\|spatially inhomogeneous. The preliminary model to interpret the Tertiary basin evolution is described as below.
文摘The results of the granulometrical and sequential analysis supported by micropaleontological dating using the foraminifera as well as chemico-ponderous and X-ray diffraction analysis,confirmed the contemporaneity of the Burdigalian outcrops of the two studied zones(Ain Sidi Salah zone in the northeast and Fedj El Behim zone in the southwest), both located at the north of the city of Ouenza in
文摘To contribute to the understanding of the ages of large sedimentary basins in northern Tibet, and the Cenozoic tectonic history of Asia in general, we conducted an integrated paleomagnetic and stratigraphic study on the sedimentary sequences of the Hoh Xil basin, north of the Qinghai\|Tibet Plateau. Red sedimentary sections from the Fenghuoshan and Yaxicuo Groups have recorded a pattern of magnetic polarity reversals that correlates well with the known magnetic polarity time scale for the past 56Ma. Reliable magnetostratigraphy for the Fenghuoshan and Yaxicuo Groups suggests that the sediment ages for these two groups are about 56～29Ma and 29～25Ma, respectively.We collected more than 1000 paleomagnetic samples from 335 sites distributed in 3 sections of the Hoh Xil basin. Detailed litholostratigraphic, petrologic, and sedimentologic studies have also been carried out on these sections during the past three field sessions. Magnetic directions in these sites were obtained by progressive alternating\|field and thermal demagnetization experiments. Most samples exhibit two components of magnetization. The lower unblocking temperature component is an overprint resembling the geocentric axial dipole field direction at the sampling locality. The most stable, characteristic remanence (ChRM) appears to be an early chemical remanent magnetization residing mainly in hematite. Curie temperature determinations, acquisition of isothermal remanent magnetization (IRM) and backfield demagnetization of saturation IRM, hysteresis loop parameters, and low\|temperature demagnetization on representative samples all corroborate demagnetization behavior. The positive results of fold and reversal tests indicate that the ChRM is a record of the paleomagnetic field close to the time of formation of these sediments. Further evidence that the magnetization of these sediments was acquired close to their time of deposition is the fact that patterns of magnetic reversals have been identified, which can be matched with the established polarity time scale.
