| 南京附近地区一些新生代玄武岩组的古地磁学研究及对其地质时代的初步认识 |
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| 引用本文： | 刘椿,程国良,叶素娟,朱湘元,林金录,李素玲.南京附近地区一些新生代玄武岩组的古地磁学研究及对其地质时代的初步认识[J].地球物理学报,1976,19(2):125-137. |
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| 作者姓名： | 刘椿 程国良 叶素娟 朱湘元 林金录 李素玲 |
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| 作者单位： | 中国科学院地质研究所 |
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| 摘 要： | 中国东部广泛分布着新生代的玄武岩,其地质时代始终是一个争议的问题。本文作者对南京附近地区的两个标准玄武岩组剖面进行了古地磁学研究,使用交变场退磁法检验了样品,证明它们的剩磁稳定性良好,测得江宁方山玄武岩组的I,平均值为8.1×10-4CGSM,Dr=195°29′、Jr=-54°9′,古地磁南极位置为λP=192°35′E、ΦP=76°47′N;六合灵岩山玄武岩组的l,平均值为26.4×10-4CGSM,Dr=354°44′,Jr=42°12′,古地磁北极位置为λP=329°38′E、Φp=80°36′N,并得出如下结论: （1）六合灵岩山玄武岩组和江宁方山玄武岩组的极性截然不同,灵岩山玄武岩组的岩石磁性全系正向,可能相当于布容期（Brunhes epoch）,方山玄武岩组的岩石磁性全属反向,可能相当于松山期（Matuyama epoch）; （2）灵岩山玄武岩组测得的古北极相距现今的北极要比方山玄武岩组的近一些,清晰地表明它们的形成时间绝非同一时期,而是灵岩山玄武岩组要晚,方山玄武岩组要早; （3）灵岩山玄武岩组和方山玄武岩组形成时期的岩石产地所处的古纬度都是中纬度地区,属亚热带气候; （4）对比世界各地区一些有关时代的岩石古地磁学数据,参照这两套玄武岩组的上下地层中所含有的古生物化石及岩石学特征,六合灵岩山玄武岩组的地质时代似应为Q2-Q3,江宁方
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| 关 键 词： | 新生代玄武岩 灵岩山 地质时代 方山 古地磁学研究 古地极 附近地区 天然剩余磁化强度 初步认识 江宁 |
THE PALEOMAGNETIC STUDY ON SOME CAINOZOIC BASALT GROUPS IN VICINITY OF NANKING AND THE PRELIMINARY DETERMINATION OF ITS GEOLOGICAL AGES |
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| LIU CHUN,CHENG GUO-LIANG,YE SU-JUAN,ZHU XIANG-YUAN,LlN JlN-LU,LI SU-LING.THE PALEOMAGNETIC STUDY ON SOME CAINOZOIC BASALT GROUPS IN VICINITY OF NANKING AND THE PRELIMINARY DETERMINATION OF ITS GEOLOGICAL AGES[J].Chinese Journal of Geophysics,1976,19(2):125-137. |
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| Authors: | LIU CHUN CHENG GUO-LIANG YE SU-JUAN ZHU XIANG-YUAN LlN JlN-LU LI SU-LING |
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| Institution: | Institute of Geology, Academia Sinica |
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| Abstract: | In eastern China Cainozoic basalts are widely distributed, but its gelogical ages are still a problem and discussed among geologists. For that reason two typical sec-tions of basalts located nearby Nanking have been studied by the a. c. demagnetizing technique of rock samples. It is shown that their remanent magnetism seems to be very stable. The rock samples collected from the Fangshan basalt group in district Jiangning give the mean direction of Dr = 195°29', J = - 54°9' with a mean inten-sity of magnetization 8.1 × 10-4 CGSM, corresponding to a palaeomagnetic polar position of λp= 192°35' E, φp = 76°47' N; and the rock samples collected from the Lingyanshan basalt group in district Liuhe give the mean direction of Dr = 354°44', Jr = 42°12' with a mean intensity of magnetization 26.4 × 10-4 CGSM, corresponding to a palaeomagnetic: polar position of λp= 329°38' E, φp = 80°36' N. Based on the above results some conclusions may be obtained as follows:1. The polarity of rocks from the Lingyanshan basalt group is distinctly dif-ferent from that of the Fangshan basalt group. The polarity of the former is nor-mal, possibly comparable with the Brunhes epoch; whereas the polarity of the latter is reversed, comparable with the Matuyama epoch.2. The paleomagnetic polar position obtained from rocks of the Lingyanshan basalt group appears to be nearer to the present geographic pole than that from the Fangshan group, showing the difference of their time eruption, the former was younger than the latter.3. The paleolatitudes in which both the Lingyanshan and Fangshan basalt groups were formed are considered as intermediate latitudes with sub-tropical climate.4. Comparing with the paleomagnetic data for rock ages from various regions of the world and referring to the animal fossils contained in the underlying and overlying beds of this two basalt groups and also the petrological properties, it is more reasonable to consider the geological ages of the Lingyanshan basalt group and the Fangshan basalt group as Q2-Q3 and N2-Q1, respectively. |
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