The relationship between paleogeographic pattern and sedimentary differentiation of evaporite-carbonate symbiotic system is examined based on logging,core and thin section data,by taking the sixth sub-member of fifth ...The relationship between paleogeographic pattern and sedimentary differentiation of evaporite-carbonate symbiotic system is examined based on logging,core and thin section data,by taking the sixth sub-member of fifth member of Ordovician Majiagou Formation(M56)in the central-eastern Ordos Basin as an example.(1)Seven sub-geomorphic units(Taolimiao west low,Taolimiao underwater high,Taolimiao east low,Hengshan high,East salt low,North slope and Southwest slope)developed in the study area.(2)The“three lows”from west to east developed dolomitic restricted lagoon,evaporite evaporative lagoon and salt evaporative lagoon sedimentary facies respectively,the"two highs"developed high-energy grain beach and microbial mound,and the north and south slopes developed dolomitic flats around land.(3)The paleogeographic pattern caused natural differentiation of replenishment seawater from the northwest Qilian sea,leading to the eccentric sedimentary differentiation of dolomite,evaporite and salt rock symbiotic system from west to east,which is different from the classic“bull's eye”and“tear drop”distribution patterns.(4)As the Middle Qilian block subducted and collided into the North China Plate,the far-end compression stress transferred,giving rise to the alternate highland and lowland in near north to south direction during the sedimentary period of M56 sub-member.(5)Taolimiao underwater high and Hengshan high developed favorable zones of microbial mounds and grain shoals in south to north strike in M56 sub-member,making them favorable exploration areas with great exploration potential in the future.展开更多
A possible approach to assess the fine grain OSL dating is discussed through comparison of equivalent dose (DE) values and ages obtained by IRSL and GLSL of fine grains for 31 sediment samples from North China. The IR...A possible approach to assess the fine grain OSL dating is discussed through comparison of equivalent dose (DE) values and ages obtained by IRSL and GLSL of fine grains for 31 sediment samples from North China. The IRSL and GLSL were measured with the same aliquots for each sample, i.e. shine-down was by 100 s of IRSL (880 nm) followed by 100 s of GLSL (514 nm) on the same discs. The DE values and ages found by IRSL are in good agreement with those by GLSL within 1-2σ for 80% samples, especially for aeolian loess samples. Considering that IRSL from feldspar differs obviously from GLSL dominated from quartz in dose response, thermal stability and optical bleaching characteristic, the agreement between the DE values may be taken as evidence that the two clocks of IRSL and GLSL had been well reset during deposition. The consistent ages of IRSL and GLSL, in turn, may be referred to an indicator to evaluate the fine grain OSL dating of sediments.展开更多
基金Supported by the Fundamental Project of China National Petroleum Corporation(2021DJ0501).
文摘The relationship between paleogeographic pattern and sedimentary differentiation of evaporite-carbonate symbiotic system is examined based on logging,core and thin section data,by taking the sixth sub-member of fifth member of Ordovician Majiagou Formation(M56)in the central-eastern Ordos Basin as an example.(1)Seven sub-geomorphic units(Taolimiao west low,Taolimiao underwater high,Taolimiao east low,Hengshan high,East salt low,North slope and Southwest slope)developed in the study area.(2)The“three lows”from west to east developed dolomitic restricted lagoon,evaporite evaporative lagoon and salt evaporative lagoon sedimentary facies respectively,the"two highs"developed high-energy grain beach and microbial mound,and the north and south slopes developed dolomitic flats around land.(3)The paleogeographic pattern caused natural differentiation of replenishment seawater from the northwest Qilian sea,leading to the eccentric sedimentary differentiation of dolomite,evaporite and salt rock symbiotic system from west to east,which is different from the classic“bull's eye”and“tear drop”distribution patterns.(4)As the Middle Qilian block subducted and collided into the North China Plate,the far-end compression stress transferred,giving rise to the alternate highland and lowland in near north to south direction during the sedimentary period of M56 sub-member.(5)Taolimiao underwater high and Hengshan high developed favorable zones of microbial mounds and grain shoals in south to north strike in M56 sub-member,making them favorable exploration areas with great exploration potential in the future.
基金the National Natural Science Foundation of China (Grant No. 49872062) by the Chinese Academy of Sciences (Grant No. KZ951-A 1-402-07).
文摘A possible approach to assess the fine grain OSL dating is discussed through comparison of equivalent dose (DE) values and ages obtained by IRSL and GLSL of fine grains for 31 sediment samples from North China. The IRSL and GLSL were measured with the same aliquots for each sample, i.e. shine-down was by 100 s of IRSL (880 nm) followed by 100 s of GLSL (514 nm) on the same discs. The DE values and ages found by IRSL are in good agreement with those by GLSL within 1-2σ for 80% samples, especially for aeolian loess samples. Considering that IRSL from feldspar differs obviously from GLSL dominated from quartz in dose response, thermal stability and optical bleaching characteristic, the agreement between the DE values may be taken as evidence that the two clocks of IRSL and GLSL had been well reset during deposition. The consistent ages of IRSL and GLSL, in turn, may be referred to an indicator to evaluate the fine grain OSL dating of sediments.
