Quaternary Magnetostratigraphy of the Shunyi Area in Beijing Plain Using ZK12-2 Borehole Profile
详细信息
- 责任者：Zhao Yong (Beijing Institute of Geological Survey ; Beijing 100195 ; China) ; Cai Xiangmin
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(2)
- 关键词：第四纪 ; Quaternary ; 磁性地层学 ; magnetostratigraphy ; 北京 ; Beijing
- 页码：p.288-294
- 图表：illus., 1 table, 23 refs.
- 分类号：1400
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
Magnetostratigraphy was studied in detail using ZK12-2 borehole core from the Shunyi depressuib in Beijing Plain. Here we present the magnetostratigraphic results of ZK12-2 borehole (719m) located at Shunyi Depression. A total of 648 undisturbed samples were collected from ZK12-2 borehole at an interval of 0.2～0.8m except for several missing intervals during drilling. 640 samples were performed on thermal demagnetization in emperature steps until 580℃. The Brunhes/Matuyama boundary was found at the depth of 170m, the Matuyama / Gauss boundary at 706m. The Gauss normal polarity chron is shown from 706 to 719m deep in the borehole. The interval from 170m to 706m is fairly correlative with the Matuyama reversal in the geomagnetic polarity timescale with two normal polarity zones corresponding to Jaramillo (200～210m) and Olduvai(464～520m) subchrons, respectively. The OSL age of 10200 800a and 117800 590a was obtained from the sample at the depth of 9.7m and 40.5m. The lithologic section of the borehole ZK12-2 includes the entire Pleistocene and Holocene series and part of Pliocene series. According to the correlation of the polarity column, and the OSL ages from the samples,and the lithologic section,Our definition boundary for the N/Q boundary is approximately conformable with M/G boundary. We believe that the sediments below 706m depth belong to Upper Pliocenc series.The lower Pleistocene Series ranges from the depth of 170～706m,which was formed during 0.78～2.58Ma. The Middle Pleistocene Series and Upper Pleistocene Series correspond to the Brunhes normal polarity chron. Considering the sedimentation rates, the boundary between Middle and Upper Pleistocene Series is the depth of 66.5m, and the boundary of the Holocene and Upper Pleistocene Series is 10m.
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