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Reliability of Relative Paleointensity Recorded in Chinese Loess-Paleosol Sediments

Acta Geologica Sinica(English Edition) 2012年第5期86卷 1276-1288页

作者： YANG Tianshui LI Haiyan wu huaichun YANG Zhenyu ZHANG Shihong HYODO Masayuki State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing 100083China School of the Earth Sciences and Resources China University of GeosciencesBeijing 100083China School of Ocean Sciences and Resources China University of GeosciencesBeijing 100083China Institute of Geomechanics Chinese Academy of Geological SciencesBeijing 100081China Research Center for Inland Seas Kobe UniversityKobe 657-8501Japan

A detailed paleomagnetic and rock-magnetic investigation spanning loess L7 to paleosol S8 has been carried out at the Baoji and Xifeng sections. Results of anisotropy of magnetic susceptibility confirm that the studied loess-paleosol sediments retain primary sedimentary fabrics. Stepwise thermal demagnetization shows that two well-defined magnetization components can be isolated from both loess and paleosol specimens. A low-temperature component, isolated between 100°C and 200°C, is consistent with the present geomagnetic field direction, and a high-temperature component, isolated between 200-300°C and 620-680°C, includes clearly normal and reversed polarities. Isothermal remanent magnetization and thermomagnetic analyses indicate that characteristic remanent magnetization is mainly carried by magnetite and hematite. The Day plot, together with the stratigraphic variations of rock-magnetic parameters, shows that the uniformity of magnetic mineralogy and grain size fulfills the criteria for relative paleointensity （RPI） studies. RPI records have been constructed using natural remanent magnetization （NRM） intensity after thermal demagnetization at 300°C normalized by low-frequency magnetic susceptibility （NRM 300 /χ）. The results show that the RPI record from the Baoji section, where pedogenesis is quite weak, is compatible with the stacked PISO-1500 paleointensity record, suggesting that it might reflect the paleointensity variation of the geomagnetic field. The RPI record from the Xifeng section, where pedogenesis is rather strong, indicates a clear dissimilarity with the stacked PISO-1500 paleointensity record, implying that it does not reflect the paleointensity variation of the geomagnetic field. Our new results show that the NRM 300 /χ from the strongly pedogenetic paleosols does not completely eliminate the pedogenetic （climatic） influence, so it might be unsuitable for a reliable paleointensity study.

关键词： Chinese loess pedogenesis relative paleointensity rock magnetism geomagnetic field

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New SHRIMP U-Pb age from the wuqiangxi Formation of Banxi Group:Implications for rifting and stratigraphic erosion associated with the early Cryogenian (Sturtian) glaciation in South China

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Science China Earth Sciences 2008年第11期51卷 1537-1544页

作者： ZHANG ShiHong JIANG GanQing DONG Jin HAN YiGui wu huaichun State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesBeijing 100083China Department of Geoscience University of NevadaLas VegasNevada 89154-4010USA

In South China, the wuqiangxi Formation of the Banxi Group and its equivalents underlie the early Cryogenian (Sturtian) glacial deposits but their thickness varies from 2000 m. In the Guzhang section of western Hunan, the wuqiangxi Formation is only 152 m thick, and an ash bed 58 m below the glacial diamictite yielded a SHRIMP U-Pb age of 809.3±8.4 Ma. In contrast, 90 km south of the Guzhang section towards the basin in Zhijiang area where the wuqiangxi Formation is ～2200 m thick, an age of 725±10 Ma has been reported from the top of this unit, 300 m below the glacial diamictite. These ages provide new evidence for the regional stratigraphic correlation across the Nanhua basin, and suggest unusually large (>2 km) stratigraphic erosion potentially associated with the Sturtian glaciation in South China. The magnitude of erosion may imply significant uplifting and tectonotopography at the onset of the Sturtian glaciation.

关键词： Neoproterozoic Banxi Group SHRIMP U-Pb age Sturtian glaciation South China

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Recognition of Milankovitch Cycles in the Natural Gamma—Ray Logging of Upper Cretaceous Terrestrial Strata in the Songliao Basin

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Acta Geologica Sinica(English Edition) 2007年第6期81卷 996-1001页

作者： wu huaichun ZHANG Shihong SUI Suwen HUANG Qinghua State Key Laboratory of Geological Processes and Mineral Resources ＆ Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education China University of Geosciences Beijing 100083 School of Marine Science China University of Geosciences Beijing 10008 Exploration and Development Research Institute of Daqing Oil Field Corporation Ltd. Daqing Heilongjiang 163712

Spectrogram analysis of seven natural gamma-ray logging of Member 1 of the Qingshankou Formation （K2qn^1） and Member 1 and 2 of the Nenjiang Formation （K2n^1-2） of Late Cretaceous age in the Songliao Basin reveals sedimentary cyclicities controlled by Milankovitch climate periodicities. The recognition of Milankovitch cycles allows estimation of an average accumulation rate of ～7.55- 8.62 cm/ka for the K2qn^1 sections, and ～6.69-10.16 cm/ka for the K2n^1-2 sections. Two marine transgression events occurred during the deposition of K2qn^1 and K2n^1-2 and their ages are at ～0.74- 1.10 Ma and ～2.38-4.84 Ma, respectively. Identification of Milankoviteh cycles from fine-grained deep lake sedimentary rocks in the Songliao Basin may provide great potential for high-resolution stratigraphic subdivisions and correlations.

关键词： Songliao Basin gamma-ray logging Milankovitch cycles marine transgression events

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New paleomagnetic results from the Yangzhuang Formation of the Jixian System,North China,and tectonic implications

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Chinese Science Bulletin 2005年第14期50卷 1483-1489页

作者： wu huaichun ZHANG Shihong LI Zheng-Xiang LI Haiyan DONG Jin State Key Laboratory of Geological Processes and Mineral Resources & Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education China University of Geosciences Beijing 100083 China Tectonics Special Research Centre School of Earth and Geographical Sciences The University of Western Australia Crawley WA 6009 Australia

A paleomagnetic study was carried out on the Yangzhuang Formation (~1350 Ma) of the Jixian System in the North China Block (NCB). Detailed stepwise thermal demagnetization isolated two components. The soft compo- nent (component A) was interpreted as a remagnetization in the recent geomagnetic field. The hard component (compo- nent B) with higher unblocking-temperatures was carried by hematite. Its site-mean direction is D/I = 77.6°/-24.3° (κ = 5.4, α95 = 18.3°, N = 15 sites) before, and D/I = 72.2°/11.5° (κ = 24.6, α95 = 7.9°) after tilt correction. It passes a fold test (Mesozoic folding) at 99% confidence level and reversal test at 95% confidence level. The corresponding pole locates at 17.3°N, 214.5°E (dp = 4.1°, dm = 8.0°). A best fit of paleo- magnetic poles from the NCB, Baltica, Siberia and the ap- parent polar wander path for Laurentia suggests a long-lived connection between these paleo-continents between ~1800 and 1350 Ma.

关键词：古磁学中元古代中国岩石

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A Floating Astronomical Time Scale for the Early Late Cretaceous Continental Strata in the Songliao Basin, Northeastern China

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Acta Geologica Sinica(English Edition) 2020年第1期94卷 27-37页

作者： MA Xiaojuan wu huaichun FANG Qiang SHI Meinan ZHANG Shihong YANG Tianshui LI Haiyan WANG Chengshan Schoolof Ocean Sciences China University of GeosciencesBeijing 100083China State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing 100083China

A continuous terrestrial succession was recovered from the Songke-2(SK-2)borehole in the Songliao Basin,Northeastern *** borehole provides a unique material for further research on the continental paleoclimate during Cretaceous greenhouse period,following a series of achievements of the Songke-1(SK-1)*** this study,thorium(Th)logging data were chosen as a paleoclimate proxy to conduct a detailed cyclostratigraphic *** Th series varies quasi-periodically;power spectra and evolutionary fast Fourier transformation(FFT)analysis reveal significant cycles in the Quantou(K2 q),Qingshankou(K2 qn),Yaojia(K2 y)and Nenjiang(K2 n)*** ratio of cycle wavelengths in these stratigraphic units is approximately 20:5:2:1,corresponding to long orbital eccentricity(405 kyr),short orbital eccentricity(100 kyr),obliquity(37 kyr),and precession cycles(22.5 kyr and 18.4 kyr).The durations of the K2 n,K2 y,K2 qn and K2 q are estimated as 6.97,1.83,5.30 and 4.52 Myr,respectively,based on the constructed^18.62 Myr"floating"astronomical time scale(ATS).Comparison of the durations between the SK-1 s and SK-2 boreholes exhibits a slight difference of 0.06 Myr and 0.459 Myr for K2 qn and K2 ***,our ATS of K2 n supports the chronostratigraphic frame constructed by the CA-ID-TIMS data of the SK-1 s *** new"floating"ATS provides precise numerical ages for stratigraphic boundaries,biozones and geological events in the Songliao Basin,and can serve as a basis for correlation of strata and events between marine and terrestrial systems.

关键词： Late Cretaceous SK-2 borehole cyclostratigraphy astronomical time scale Songliao Basin northeastern China

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High-precision geochronology of the Early Cretaceous Yingcheng Formation and its stratigraphic implications for Songliao Basin,China

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Geoscience Frontiers 2022年第4期13卷 89-97页

作者： Tiantian Wang Chengshan Wang Jahandar Ramezani Xiaoqiao Wan Zhiqiang Yu Youfeng Gao Huaiyu He huaichun wu State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing 100083China Institute of Earth Sciences China University of GeosciencesBeijing 100083China School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China Department of Earth Atmospheric and Planetary SciencesMassachusetts Institute of TechnologyCambridgeMA 02139United States Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China College of Earth Sciences Jilin UniversityChangchun 130061China School of Ocean Sciences China University of GeosciencesBeijing 100083China

The Songliao Basin in Northeast Asia is the largest and longest-lived rift basin and preserves a nearcontinuous continental succession of the most of the Cretaceous period,providing great material to investigate the adaption of the terrestrial systems to the Cretaceous greenhouse climate and tectonic ***,the paucity of precise and accurate radioisotopic ages from the Early Cretaceous strata of the Songliao Basin has greatly held back the temporal and causal correlation of the continental records to the global Early Cretaceous *** tuff layers intercalated in the Yingcheng Formation have been intercepted by the SK-2 borehole,which offer excellent materials for radioisotopic dating and calibration of the chronostratigraphy of the Lower Cretaceous sequence of Songliao ***,the Yingcheng Formation recorded the largest and the last of the two major volcanic events in Songliao Basin,which also represents a turning point in the basin evolution history of Songliao from syn-rift stage to post-rift *** we report high-precision U–Pb zircon geochronology by the CA-ID-TIMS technique on three tuff samples from the Yingcheng Formation of the SK-2 borehole in the Songliao Basin to construct a greatly improved,absolute age framework for the Yingcheng Formation and provide crucial age constraints for the Songliao Lower Cretaceous *** new CA-ID-TIMS geochronology constrained the Yingcheng Formation at 102.571+0.320/-2.346 Ma to ca.113 Ma,correlating to the Albian *** with the previous published Songliao geochronology,the Quantou Formation is constrained to between 96.442+0.475/-0.086 Ma and 91.923+0.475/-0.086 Ma;the Denglouku Formation is constrained to between 102.571+0.320/-2.346 Ma and 96.442+0.475/-0.086 Ma;the age of the Shahezi Formation is estimated at ca.113 Ma to ca.118 Ma,which could extend to ca.125 Ma in some locations in Songliao *** major unconformity between the Yingcheng Formation and the Denglouku Formation

关键词： U–Pb geochronology Songliao Basin Early Cretaceous Yingcheng Formation China

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Cyclostratigraphic Calibration of the Upper Ordovician(Sandbian-Katian) Pagoda and Linhsiang Formations in the Yichang Area,South China

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Acta Geologica Sinica(English Edition) 2019年第S01期93卷 177-180页

作者： ZHONG Yangyang CHEN Dongyang FAN Junxuan wu huaichun FANG Qiang SHI Meinan State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing 100083China School of Ocean Sciences China University of GeosciencesBeijing 100083China Jiangsu Huohe Information Technology Co. LtdNanjing 210000JiangsuChina School of Earth Sciences and Engineering Nanjing UniversityNanjing 210023China

1 Introduction The Sandbian-Katian is a critical period for the transition from"hot-house"in the Lower Ordovician to"ice-house"in the end-Ordovician(Trotter et al.,2008).During this interval,the South China Block was located in the equatorial region(Torsvik and Cocks,2016),with the widespread accumulation of Pagoda and Linhsiang formations(Zhan and Jin,2007).

关键词： cyclostratigraphy time-series analysis astronomical time scale duration

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High-frequency polarity swings during the Gauss-Matuyama reversal from Baoji loess sediment

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Science China Earth Sciences 2014年第8期57卷 1929-1943页

作者： YANG TianShui Masayuki HYODO YANG ZhenYu ZHANG ShiHong Toshiaki MISHIMA wu huaichun LI HaiYan LI Yi SHI XingAn WANG Kan MA YiMing State Key Laboratory of Biogeology and Environmental Geology China University of Geosciences School of the Earth Sciences and Resources China University of Geosciences Research Center for Inland Seas Kobe UniversityKobe 657-8501 Japan Institute of Geomechanics Chinese Academy of Geological Sciences Henan Institute of Nonferrous Metal Exploration

Paleomagnetic records of the Gauss-Matuyama reversal were obtained from two loess sections at Baoji on the Chinese Loes Plateau. Stepwise thermal demagnetization shows two obvious magnetization components. A low-temperature component iso lated between 100 and 200–250？C is close to the present geomagnetic field direction, and a high-temperature component iso lated above 200–250？C reveals clearly normal, reversed, and transitional polarities. Magnetostratigraphic results of both sec tions indicated that the Gauss-Matuyama reversal consists of a high-frequency polarity fluctuation zone, but the characteristic remanent magnetization directions during the reversal are clearly inconsistent. Rock magnetic experiments demonstrated tha for all the specimens with normal, reversed, and transitional polarities magnetite and hematite are the main magnetic carriers Anisotropy of magnetic susceptibility indicates that the studied loess sediments have a primary sedimentary fabric. Based on virtual geomagnetic pole latitudes, the Gauss-Matuyama reversal records in the two sections are accompanied by 14 short-lived geomagnetic episodes（15 rapid polarity swings） and 12 short-lived geomagnetic episodes（13 rapid polarity swings）, respec tively. Our new records, together with previous ones from lacustrine, marine, and aeolian deposits, suggest that high-frequency polarity swings coexist with the Gauss-Matuyama reversal, and that the Gauss-Matuyama reversal may have taken more than11 kyr to complete. However, we need more detailed analyses of sections across polarity swings during reversals as well a more high-resolution reversal records to understand geomagnetic behavior and inconsistent characteristic remanent magnetiza tion directions during polarity reversals.

关键词： polarity reversals geomagnetic episodes Gauss-Matuyama loess

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New Zircon SHRIMP U-Pb Ages of the Langjiu Formation Volcanic Rocks in the Shiquanhe Area,Western Lhasa Terrane and their Implications

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Acta Geologica Sinica(English Edition) 2017年第2期91卷 737-738页

作者： BIAN Weiwei YANG Tianshui SHI Yuruo MA Yiming JIN Jingjie GAO Feng PENG Wenxiao ZHANG Shihong wu huaichun LI Haiyan State Key Laboratory of Biogeology and Environmental Geology China University of Geosciences School of Earth Sciences and Resources China University of Geosciences Beijing SHRIMP Center Institute of GeologyChinese Academy of Geological Sciences Guangzhou Institute of Geochemistry Chinese Academy of Sciences

Objective The potassic and ultrapotassic rocks relating to the India-Eurasia collision and continual plate convergence are widely distributed in the Lhasa terrane. These rocks are very important to understand the deep processes of the India-Eurasia collision and the uplift and evolution of the Tibetan Plateau. Although high-potassic volcanic rocks are also exposed in the western Lhasa terrane, their formation time is still uncertain for the lack of reliable dating. We carried out zircon U-Pb geochronological study on the Langjiu Formation volcanic rocks, which are part of the Early Cretaceous Zenong group volcanic rocks based on 1：250000 scale Shiquanhe regional geological survey report, in the Shiquanhe area of the western Lhasa terrane. These new age data not only offer chronological basis for the regional stratigraphic correlation and classification, but also provide an essential opportunity for revealing signatures of magmatic pulses hidden in the deep crust of the Lhasa terrane.

关键词： SHRIMP Pb New Zircon SHRIMP U-Pb Ages of the Langjiu Formation Volcanic Rocks in the Shiquanhe Area,Western Lhasa Terrane and their Implications

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Magnetic susceptibility variations of the Edicaran cap carbonates in the Yangtze platform and their implications for paleoclimate

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Chinese Journal of Oceanology and Limnology 2005年第3期23卷 291-298页

作者： wu huaichun ZHANG Shihong JIANG Ganqing LI Haiyan State key Laboratory of Geological Processes and Mineral Resources Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of EducationChina University of Geosciences Beijing 100083China Department of Geoscience University of NevadaLas VegasNV 89154-4010USA

Magnetic susceptibility(MS)data were obtained from 11 sections of the Doushantuo(Edicaran)cap carbonate that directly overlies the Nantuo glacial diamictite in the southeastern margin of the Yangtze *** MS data revealed two regionally correlatable peaks at the bottom and top of the cap carbonate,sepa-rated by an interval of low *** lower MS peak coincides with high percentage of insoluble siliciclastic residues that are compositionally identical to the matrix of the underlying diamictite,suggesting its origin con-trolled mainly by detrital components during the first phase of cap carbonate deposition at the end of the *** upper MS peak is associated with high clay content and iron sulfides,and can be interpreted as either derived from enhanced greenhouse weathering that could have brought more terrigenous components into the ocean,or the result of ocean anoxia at the late stage of cap carbonate deposition that could led to formation of abundant iron *** regionally consistent MS curves from the cap carbonates provided the first geo-physical record for the rapid climate change from icehouse to greenhouse conditions in the aftermath of the Neoproterozoic“snowball Earth”event.

关键词： Yangtze platform Doushantuo Formation cap carbonates magnetic susceptibility(MS) paleocli-mate

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