Two Red Clay profiles near Xi' an and Xifeng were investigated in an attempt to determine magne-tostratigraphic and palaeoclimatic records. The results show that aeolian dust accumulation and the related East Asia...Two Red Clay profiles near Xi' an and Xifeng were investigated in an attempt to determine magne-tostratigraphic and palaeoclimatic records. The results show that aeolian dust accumulation and the related East Asia palaeomonsoon system had begun by 6.5 Ma, and it is deduced that the Tibetan Plateau had reached a significant elevation at that time. The late Tertiary palaeoclimatic history of the Red Clay as reflected by magnetic susceptibility is reconstructed during the period of 6.5-2.5 Ma. Stepwise increase in susceptibility of aeolian dust accumulation appears to have a close correlation to the uplift processes of the Tibetan Plateau. The remarkable increase of aeolian dust accumulation at 3.2 Ma appears to be due to the influence of global ice volume on the East Asia monsoon. Palaeomonsoon variation during the late Tertiary as recorded in the Red Clay sequences from the Chinese Loess Plateau can be regarded as the product of a number of interacting factors, such as uplift of the Tibetan Plateau, solar radiation, global ice volume, etc.展开更多
Rock-magnetic and palaeomagnetic studies have been carried out on the interval of famous fossil-bearing sedimentary rocks and its overlying basalts and underlying basalts at the Sihetun section, West Liaoning Province...Rock-magnetic and palaeomagnetic studies have been carried out on the interval of famous fossil-bearing sedimentary rocks and its overlying basalts and underlying basalts at the Sihetun section, West Liaoning Province. Normal polarity was obtained for the sedimentary interval and the underlying basalts, while reversed polarity was found in the overlying basalts. Taking account of the new 40Ar/39Ar ages (Swisher et al., 1999), we classified the fossil-bearing sedimentary interval into the Barremian M3n zone (Early Cretaceous age). Several abnormal horizons on magnetic properties, probably corresponding to the tuffs, were observed in the fossil-bearing sedimentary interval. This implies that the massive bio-extinction may link to dramatic environmental changes that were caused by volcanic eruptions.展开更多
基金Project supported by the National Natural Science Foundation of China and the Foundation of Xi'an Laboratory of Loess and Quatemary Geology,Chinese Academy of Sciences
文摘Two Red Clay profiles near Xi' an and Xifeng were investigated in an attempt to determine magne-tostratigraphic and palaeoclimatic records. The results show that aeolian dust accumulation and the related East Asia palaeomonsoon system had begun by 6.5 Ma, and it is deduced that the Tibetan Plateau had reached a significant elevation at that time. The late Tertiary palaeoclimatic history of the Red Clay as reflected by magnetic susceptibility is reconstructed during the period of 6.5-2.5 Ma. Stepwise increase in susceptibility of aeolian dust accumulation appears to have a close correlation to the uplift processes of the Tibetan Plateau. The remarkable increase of aeolian dust accumulation at 3.2 Ma appears to be due to the influence of global ice volume on the East Asia monsoon. Palaeomonsoon variation during the late Tertiary as recorded in the Red Clay sequences from the Chinese Loess Plateau can be regarded as the product of a number of interacting factors, such as uplift of the Tibetan Plateau, solar radiation, global ice volume, etc.
基金the National Natural Science Foundation of China (Grant No. 49834001) and the National Key Basic Research Program (Grant No. G1999075509) and the CAS (Grant No. KZ951-A1-401).
文摘Rock-magnetic and palaeomagnetic studies have been carried out on the interval of famous fossil-bearing sedimentary rocks and its overlying basalts and underlying basalts at the Sihetun section, West Liaoning Province. Normal polarity was obtained for the sedimentary interval and the underlying basalts, while reversed polarity was found in the overlying basalts. Taking account of the new 40Ar/39Ar ages (Swisher et al., 1999), we classified the fossil-bearing sedimentary interval into the Barremian M3n zone (Early Cretaceous age). Several abnormal horizons on magnetic properties, probably corresponding to the tuffs, were observed in the fossil-bearing sedimentary interval. This implies that the massive bio-extinction may link to dramatic environmental changes that were caused by volcanic eruptions.
