ISEA reversed event in the Cretaceous Normal Super-chron (CNS): ^(40)Ar/^(39)Ar dating and paleomagnetic results  

作　　者：SHIRuiping HEHuaiyu ZHURixiang PANYongxin 

机构地区：[1]InstituteofGeologyandGeophysics.ChineseAcademyofSciences.Beijing100029,China

出　　处：《Chinese Science Bulletin》2004年第9期926-930,共5页

摘　　要：In order to provide the age for the ISEA (one reversed event in the CNS) a combined rock magnetic, pa-leomagnetic and geochronologic study has been conducted on two Cretaceous andesitic basalt lava flows from Sanbaoying, Liaoning Province of northeastern China. Rock magnetic investigations show that pseudo-single domain (PSD) ti-tanomagnetite with poor-Ti content is the dominant mag-netic mineral in Sanbaoying lava flows. Detailed systematic thermal demagnetization allowed us to isolate two rema-nence components after removing a low temperature com-ponent at 100℃/150℃; an intermediate temperature com-ponent with normal polarity at 150℃/200℃—380℃/400℃ and the characteristic remanence component (ChRM) with reversed polarity above 400℃/450℃. 40Ar/39Ar dating results show that Sanbaoying rocks were erupted at 116.0±0.3 Ma. Combination of paleomagnetic results and 40Ar/39Ar dating indicates that the reversed event recorded in Sanbaoying lavas corresponds to the ISEA event in the CNS. Our age determination for ISEA reversed event provides chronologi-cal evidence to study the relevance between global geological events that occurred in the CNS and geodynamo processes.In order to provide the age for the ISEA (one reversed event in the CNS) a combined rock magnetic, pa-leomagnetic and geochronologic study has been conducted on two Cretaceous andesitic basalt lava flows from Sanbaoying, Liaoning Province of northeastern China. Rock magnetic investigations show that pseudo-single domain (PSD) ti-tanomagnetite with poor-Ti content is the dominant mag-netic mineral in Sanbaoying lava flows. Detailed systematic thermal demagnetization allowed us to isolate two rema-nence components after removing a low temperature com-ponent at 100℃/150℃; an intermediate temperature com-ponent with normal polarity at 150℃/200℃—380℃/400℃ and the characteristic remanence component (ChRM) with reversed polarity above 400℃/450℃. 40Ar/39Ar dating results show that Sanbaoying rocks were erupted at 116.0±0.3 Ma. Combination of paleomagnetic results and 40Ar/39Ar dating indicates that the reversed event recorded in Sanbaoying lavas corresponds to the ISEA event in the CNS. Our age determination for ISEA reversed event provides chronologi-cal evidence to study the relevance between global geological events that occurred in the CNS and geodynamo processes.

关 键 词：ISEA 白垩纪 岩石磁性 古地磁 ^40AR/^39AR 年代测定 辽宁西部地区 

分 类 号：P318.44[天文地球—固体地球物理学] P597[天文地球—地球物理学]