The opinions vary on the secondary remagnetization mechanisms of carbonate rocks. The prevalent interpretations of magnetic remanences are either chemical in origin that invoked the large scale migration of orogenic f...The opinions vary on the secondary remagnetization mechanisms of carbonate rocks. The prevalent interpretations of magnetic remanences are either chemical in origin that invoked the large scale migration of orogenic fluids, or thermoviscous magnetization involved burial diagenetic processes. The paleomagnetic study carried out in northwestern part of Henan Province (north of the Qinling orogenic belt) reveals that 90% of carbonate rocks have suffered from the secondary remagnetization. On the basis of rock magnetic experiments, the assemblage of the magnetic minerals, remanent carriers and its formation process, and the possible mechanisms of remagnetization in these carbonate rocks are discussed.展开更多
It has been proposed that paleoclimatic changes and tectonic events strongly affect hominoid evolution. The Zhupeng section at Yuanmou Basin, southwestern China, with the hominoid-bearing fluvial-lacustrine sediments,...It has been proposed that paleoclimatic changes and tectonic events strongly affect hominoid evolution. The Zhupeng section at Yuanmou Basin, southwestern China, with the hominoid-bearing fluvial-lacustrine sediments, is an ideal natural laboratory to test this hypothesis. This study provided an integrated magnetic study, including low-fre- quency susceptibility, the anisotropy of magnetic susceptibil-ity, temperature-dependent susceptibility, hysteresis loops, isothermal remanent magnetization, and anhysteretic rema-nent magnetization, on samples from the Baozidongqing section at Zhupeng. Results show that the dominant mag-netic carrier is hematite, with minor amount of magnetite. Both the composition and concentration of magnetic miner-als strongly correlate with the lithostratigraphy. At least eight short-term events defined by higher concentrations of magnetite were identified. These short events reflect that the subtropical dry-hot climate is similar to today’s climate. Basing on the lithostratigraphic and rock magnetic results, we suggest that Yuanmou Basin was in a steady deposition environment from about 11 to 7 Ma, which is characterized by alternating of long-term torrid-humid climate and short-term dry-hot climate. Our study provides invaluable environment information for understanding the climate shift and the relationship between paleoenvironment and homi-noid evolution in southwestern China during late Miocene.展开更多
文摘The opinions vary on the secondary remagnetization mechanisms of carbonate rocks. The prevalent interpretations of magnetic remanences are either chemical in origin that invoked the large scale migration of orogenic fluids, or thermoviscous magnetization involved burial diagenetic processes. The paleomagnetic study carried out in northwestern part of Henan Province (north of the Qinling orogenic belt) reveals that 90% of carbonate rocks have suffered from the secondary remagnetization. On the basis of rock magnetic experiments, the assemblage of the magnetic minerals, remanent carriers and its formation process, and the possible mechanisms of remagnetization in these carbonate rocks are discussed.
基金We thank Prof.Gao Feng for advice on the field work.This work was supported by the National Natural Science Foundation of China(Grant No.40221402).
文摘It has been proposed that paleoclimatic changes and tectonic events strongly affect hominoid evolution. The Zhupeng section at Yuanmou Basin, southwestern China, with the hominoid-bearing fluvial-lacustrine sediments, is an ideal natural laboratory to test this hypothesis. This study provided an integrated magnetic study, including low-fre- quency susceptibility, the anisotropy of magnetic susceptibil-ity, temperature-dependent susceptibility, hysteresis loops, isothermal remanent magnetization, and anhysteretic rema-nent magnetization, on samples from the Baozidongqing section at Zhupeng. Results show that the dominant mag-netic carrier is hematite, with minor amount of magnetite. Both the composition and concentration of magnetic miner-als strongly correlate with the lithostratigraphy. At least eight short-term events defined by higher concentrations of magnetite were identified. These short events reflect that the subtropical dry-hot climate is similar to today’s climate. Basing on the lithostratigraphic and rock magnetic results, we suggest that Yuanmou Basin was in a steady deposition environment from about 11 to 7 Ma, which is characterized by alternating of long-term torrid-humid climate and short-term dry-hot climate. Our study provides invaluable environment information for understanding the climate shift and the relationship between paleoenvironment and homi-noid evolution in southwestern China during late Miocene.
