The Yixian Formation is a series of volcanic-sedimentary rocks in Biepiao area of Liaoning Province. It is mainly composed of basic and intermediate-basic volcanic lava,pyroclasts and terrestrial sedimentary rocks. Ba...The Yixian Formation is a series of volcanic-sedimentary rocks in Biepiao area of Liaoning Province. It is mainly composed of basic and intermediate-basic volcanic lava,pyroclasts and terrestrial sedimentary rocks. Based on the regularity of volcanic activity,the Yixian Formation was divided by the present authors into four members in ascending order:the first member is of basal conglomerate,basic and intermediate-basic volcanic rocks; the second member is of lake phrase sedimentary rocks,or in another word,precious fossil-rich sedimentary beds; the third is of basic volcanic rocks; and the fourth is of upper conglomerate. Field mapping and comprehensive study also indicate that there are abundant vertebrate fossils (mainly of Psittacosaurus) in the first member of the Yixian Formation,and the Jehol Biota (including Sinosauropterxy,Confuciusorns sanctus,Archaefructus,etc.) is yielded in the second member of Yixian Formation. From west to east,the volcanic activity of Yixian Formation changed regularly from early to late,and from basic and intermediate-basic to acid (alkali).展开更多
It has been debated whether there was southward movement of the South China Block （SCB） during the Cretaceous. In this study, a paleomagnetic investigation was carried out on the Late Cretaceous volcanic rocks （-88...It has been debated whether there was southward movement of the South China Block （SCB） during the Cretaceous. In this study, a paleomagnetic investigation was carried out on the Late Cretaceous volcanic rocks （-88 Ma） of the Shimaoshan Group in Yongtai County, Fujian Province. Rock magnetic experiments showed that magnetite in pseudo-single-domain and multi-domain grain and hematite were predominant magnetic phases. Stepwise thermal demagnetization successfully isolated characteristic directional components at high-temperature interval （〉 500℃） from 383 specimens in 19 sites, which yielded a paleomagnetic pole for the studied section at 83.1°N, 152.6°E （N = 19, A95 = 3.9°）, and the scatter SB = 9.0. The Fisher distri- bution of virtual geomagnetic poles （VGPs） and the consistence of S8 with the expected value at the 95% confidence level in- dicate that the yielded paleomagnetic pole is free of paleomagnetic secular variation influence. The new pole, which is well consistent with that from the Eurasian apparent polar wander path （APWP） curve, suggests no obvious southward movement of the sampling site during the Cretaceous.展开更多
文摘The Yixian Formation is a series of volcanic-sedimentary rocks in Biepiao area of Liaoning Province. It is mainly composed of basic and intermediate-basic volcanic lava,pyroclasts and terrestrial sedimentary rocks. Based on the regularity of volcanic activity,the Yixian Formation was divided by the present authors into four members in ascending order:the first member is of basal conglomerate,basic and intermediate-basic volcanic rocks; the second member is of lake phrase sedimentary rocks,or in another word,precious fossil-rich sedimentary beds; the third is of basic volcanic rocks; and the fourth is of upper conglomerate. Field mapping and comprehensive study also indicate that there are abundant vertebrate fossils (mainly of Psittacosaurus) in the first member of the Yixian Formation,and the Jehol Biota (including Sinosauropterxy,Confuciusorns sanctus,Archaefructus,etc.) is yielded in the second member of Yixian Formation. From west to east,the volcanic activity of Yixian Formation changed regularly from early to late,and from basic and intermediate-basic to acid (alkali).
基金supported by National Natural Science Foundation of China (Grant Nos. 40634024 and40821091)
文摘It has been debated whether there was southward movement of the South China Block （SCB） during the Cretaceous. In this study, a paleomagnetic investigation was carried out on the Late Cretaceous volcanic rocks （-88 Ma） of the Shimaoshan Group in Yongtai County, Fujian Province. Rock magnetic experiments showed that magnetite in pseudo-single-domain and multi-domain grain and hematite were predominant magnetic phases. Stepwise thermal demagnetization successfully isolated characteristic directional components at high-temperature interval （〉 500℃） from 383 specimens in 19 sites, which yielded a paleomagnetic pole for the studied section at 83.1°N, 152.6°E （N = 19, A95 = 3.9°）, and the scatter SB = 9.0. The Fisher distri- bution of virtual geomagnetic poles （VGPs） and the consistence of S8 with the expected value at the 95% confidence level in- dicate that the yielded paleomagnetic pole is free of paleomagnetic secular variation influence. The new pole, which is well consistent with that from the Eurasian apparent polar wander path （APWP） curve, suggests no obvious southward movement of the sampling site during the Cretaceous.
