摘要
根据古地磁测试数据在兰州西固以西、柴家川以北的下白垩统河口群中下岩段（厚约３９４ｍ）中划分出１９个正向极性段和１８个反向极性段，其底界对应于国际古地磁极性年表中Ｍ１６正向极性时的底界，顶界对应于Ｍ２正向极性时的顶界，时限约为至今１４３－１２８Ｍａ．古地磁资料还表明当时研究区古纬度约为２５°Ｎ．
Based on paleomagenetic measurements of samples from Lower Cretaceous redbeds,the so-called Hekou Group, near the city of Lanzhou,this study distinguishes 19 magnetostratigraphic members of normal polarity and 18 ones of reversed polarity from Chaijiachuan Section about 394m thick.The lowest member of normal polarity corresponds to the bottom of M16 normal interval of the International Palemagenetic Time Scale and the upmost correspondS to the top of M2. This indicates that the sampled beds were deposited during a period of 143-128Ma B.P.In addition,paleomagnetic data suggest that this area was situated in subtrogical zone during that time.The Paleobtitude was about 25°N.
出处
《地球物理学报》
SCIE
EI
CSCD
北大核心
1994年第A02期342-347,共6页
Chinese Journal of Geophysics
基金
中国科学院院长基金资助
美国国家科学基金
