| 渭南阎村W7孔岩心样品的古地磁学研究 |
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| 引用本文： | 葛同明,樊利民,徐行,李素珍,郑洪瑞.渭南阎村W7孔岩心样品的古地磁学研究[J].海洋地质与第四纪地质,1991(4). |
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| 作者姓名： | 葛同明 樊利民 徐行 李素珍 郑洪瑞 |
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| 作者单位： | 地质矿产部广州海洋地质局
(葛同明，樊利民，徐行)，地质矿产部水文地质工程地质研究所
(李素珍)，地质矿产部水文地质工程地质研究所(郑洪瑞) |
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| 摘 要： | 对渭南阎村W7孔岩心地层样品的磁性地层学研究,确定了黄土组、三门组地层的时代。这一地区的黄土/古土壤层形成始于松山反极性时晚期,约为1.1MaB.P.。按照地层样品的剩磁特征和岩性特征对黄土/古土壤层作更精细地划分,这一地区的黄土/古土壤层相当于马兰黄土、离石黄土层,缺失午城黄土。地层的剩磁极性资料表明,三门组地层形成于高斯极性时晚期—松山极性时中期,按照奥尔都维正极性亚时为第四纪下限的年代准则,确定三门组地层的时代为晚上新世。 W7孔岩心的地层样品的剩磁极性序列与已有的地磁极性年代表的磁极性序列大体相当,本项研究也揭示了二个短周期极性事件的存在,位于第5黄土层的安比拉事件(Emperor)发生的年代约为0.445—0.458Ma B.P.。位于第9黄土层的后期哈拉米洛事件(Post-Jaramillo)发生的年代约为0.77—0.81MaB.P.。 磁性地层学研究表明这一地区在松山反极性时中晚期出现过沉积间断,持续时约0.5Ma。 根据W7孔的地层学研究认为,选择以奥尔都维正极性亚时末期的年代(1.60MaB.P.)作为第四纪下限是有利于第四纪地层的划分和对比的。
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| 关 键 词： | 地层时代 沉积间断 第四纪下限 |
MAGNETOSTRATIGRAPHIC STUDY FOR BOREHOLE W7 FROM YANCUN, WEINAN |
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| Ge Tongming,Fan Limin,Xu Xing.MAGNETOSTRATIGRAPHIC STUDY FOR BOREHOLE W7 FROM YANCUN, WEINAN[J].Marine Geology & Quaternary Geology,1991(4). |
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| Authors: | Ge Tongming Fan Limin Xu Xing |
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| Abstract: | The ages of Huangtu Formation and Sanmen Formation were determined by magnetostratigraphic study for Borehole W7 from Yancun, Weinan. In the area, loess and paleosoil layers were deposited after late Matuyama Chron (about 1.1 Ma). Based on the results of paleomagnetism and lithologicc chara-ters, loess and paleosoil layers could be classified exactly and they were equal to Malan Loess and Lishi Loess, and Wucheng Loess was not deposited. The paleomagnetical data revealed that Sanmen formation was deposited from late Gauss to middle Matuyama Chron. Because Olduvai Chron is the lower limitation of Quaternary, the age of Sanmen Formation is Late Pliocene.
The magnetic polarity of Borehole W7 is approximately equal to that of previous geomagnetic polarity time scale. The study also reveals the existence of two polarity events. Emperor Event, located in the fifth layer of loess, is about 0.445-0.458 Ma, and Post-Jaramillo Event, located in the ninth layer, is about 0.77-0.81 Ma.
The magnetostratigraphic study shows that there was a sedimentation gap during middle-late Matuyama Chron in this area. The duration of the gap was about 0.5 Ma.
According to the stratigraphic imformation, the lower limitation of Quaternary determined by the end of Olduvai Subchron (about 1.6 Ma) is beneficial to stratigraphic classification and correlation for Quaternary. |
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| Keywords: | formation age sedimentation ap lower limitation |
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