北京大兴凸起南部PGZ05钻孔剖面第四纪磁性地层学
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摘要
对北京大兴凸起南部PGZ05孔(孔深255 m)全孔岩心进行了磁性地层、岩石地层、AMS14C测年研究,在系统性的古地磁样品采集(440块岩样)、处理和测试基础上,分析认为255 m的岩心记录了布容正向极性时(Brunhes)、贾拉米洛(Jaramillo)极性亚时、奥尔都维(Olduvai)极性亚时和高斯正极性时(Gauss)。在此磁性年代框架上,结合AMS14C测年及岩性特征,对PGZ05钻孔剖面进行第四纪地层划分,确定下更新统、中更新统、上更新统和全新统的分布深度及年代,将更新统的底界(Q/N)定位于181. 35 m处,亦为一重要岩性(棕红色半固结黏土)界限,中更新统、上更新统、全新统的底界分别定位于75. 60 m、57. 20 m、17. 35 m处。研究成果为大兴凸起南部第四纪地层划分与对比、古地理环境演变及区域地层研究提供了可靠的地层年代学框架,具有重要地质意义。
Quaternary deposits in the southern Daxing uplift in the Beijing Plain provide an important archive for Quaternary stratigraphic changes. Here we present the magnetostratigraphic results of borehole PGZ05( 255 m). A total of 440 undisturbed samples were collected from the borehole at a 0. 2-0. 5 m interval except for the sand and gravel lay. The results show that the Brunhes/Matuyama and Matuyama/Gauss boundaries occur at75. 60 m and 181. 35 m deep,respectively. The Gauss normal polarity chron occurs at 181. 35 to 255. 00 m deep. The 75. 60 to 181. 35 m interval is fairly correlative with the Matuyama reversal in the geomagnetic polarity timescale,with two normal polarity zones corresponding to the Jaramillo( 90. 90-100. 60 m) and Olduvai( 149. 70 ～ 165. 50 m) subchrons,respectively. The AMS14 C age of( 2,370 ± 30) a BP and( 23,190 ±100) a BP were obtained from the samples at 12. 20 m and 31. 45 m deep. The lithologic section of the borehole PGZ05 includes the entire Pleistocene and Holocene sequences and part of the Pliocene sequence. According to the M/G boundary and lithologic section of the borehole,we suggest that the N/Q boundary is located at 181. 35 m deep,and it represents an important lithological interface. We propose that the sediments be-low 181. 35 m depth belong to the Upper Pliocene series. The Lower Pleistocene sequence occurs at 75. 60-181. 35 m deep and were deposited during 0. 78-2. 58 Ma. The boundary between the Middle and Upper Pleistocene sequence is located at 57. 20 m deep,whilst the Holocene-Upper Pleistocene boundary is located at 17. 35 m deep.
Quaternary deposits in the southern Daxing uplift in the Beijing Plain provide an important archive for Quaternary stratigraphic changes. Here we present the magnetostratigraphic results of borehole PGZ05( 255 m). A total of 440 undisturbed samples were collected from the borehole at a 0. 2-0. 5 m interval except for the sand and gravel lay. The results show that the Brunhes/Matuyama and Matuyama/Gauss boundaries occur at75. 60 m and 181. 35 m deep,respectively. The Gauss normal polarity chron occurs at 181. 35 to 255. 00 m deep. The 75. 60 to 181. 35 m interval is fairly correlative with the Matuyama reversal in the geomagnetic polarity timescale,with two normal polarity zones corresponding to the Jaramillo( 90. 90-100. 60 m) and Olduvai( 149. 70 ～ 165. 50 m) subchrons,respectively. The AMS14 C age of( 2,370 ± 30) a BP and( 23,190 ±100) a BP were obtained from the samples at 12. 20 m and 31. 45 m deep. The lithologic section of the borehole PGZ05 includes the entire Pleistocene and Holocene sequences and part of the Pliocene sequence. According to the M/G boundary and lithologic section of the borehole,we suggest that the N/Q boundary is located at 181. 35 m deep,and it represents an important lithological interface. We propose that the sediments be-low 181. 35 m depth belong to the Upper Pliocene series. The Lower Pleistocene sequence occurs at 75. 60-181. 35 m deep and were deposited during 0. 78-2. 58 Ma. The boundary between the Middle and Upper Pleistocene sequence is located at 57. 20 m deep,whilst the Holocene-Upper Pleistocene boundary is located at 17. 35 m deep.
引文
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[14]王强,张玉发,袁桂邦,等. MIS3阶段以来河北黄骅北部地区海侵期与气候期的对比[J].第四纪研究,2008,28(1):79-95.
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[16]高秀林,王强,李玉德,等.从天津P8孔看中更新世末期以来海侵期、气候期对比问题[J].海洋地质与第四纪地质,1986,6(1):53-65.
[17]张世红,李海燕.地磁学、古地磁学和环境磁学的研究新进展——第32届国际地质大会学科总结和评述[J].现代地质,2004,18(4):415-422.
[18]赵勇,王强,李瑞杰,等.北京平原区南部PGZ01孔第四纪地层划分及其环境意义[J].古地理学报,2018,20(2):337-348.
[19]蔡向民,郭高轩,栾英波,等.永定河形成时代研究[J].第四纪研究,2010,30(1):167-174.
[2]李龙吟,陈华慧.北京怀柔HR88-1钻孔剖面磁性地层学研究[J].地层学杂志,1994,18(1):39-44.
[3]栾英波,郭高轩,黄骁.北京山前冲洪积缓倾斜平原晚新生代沉积物磁性地层学研究[J].城市地质,2008,3(2):17-20.
[4]栾英波,蔡向民,郭高轩,等.北京平原区新5孔岩心特征及地层初步划分[J].中国地质,2011,38(2):495-503.
[5]蔡向民,郭高轩,栾英波,等.永定河形成时代研究[J].第四纪研究,2010,30(1):167-174.
[6]赵勇,蔡向民,王继明,等.北京平原顺义ZK12-2钻孔剖面第四纪磁性地层学研究[J].地质学报,2013,87(2):288-294.
[7]赵勇,蔡向民,王继明,等.北京平原构造断块划分及微断块第四纪活动性探讨[J].中国地质,2015,42(6):1876-1884.
[8]白凌燕,张磊,蔡向民,等.磁性地层年代对北京平原顺义断裂第四纪活动性的约束[J].现代地质,2014,28(6)1234-1242.
[9]张磊,张晓亮,白凌燕,等.北京平原沙河凹陷第四纪磁性地层学研究及其新构造运动的沉积响应[J].中国地质,2016,43(3):1076-1084.
[10]白凌燕,李潇,秦浩敏,等.平原南口—孙河断裂南段第四纪活动性及其构造意义[J].现代地质,2018,32(2):270-278.
[11]张磊,白凌燕,蔡向民,等.北京南口—孙河断裂北西段综合物探剖面定位及其活动性研究[J].现代地质,2014,28(1):234-242.
[12] SINGER B S. A Quaternary geomagnetic instability time scale[J]. Quaternary Geochronology,2014,24(1):29-52.
[13]王强,吕金福.海面变化与海岸线变迁[M]//李汉鼎,吕金福,王强.中国北方沿海泥炭和环境.北京:海洋出版社,1995:109-128.
[14]王强,张玉发,袁桂邦,等. MIS3阶段以来河北黄骅北部地区海侵期与气候期的对比[J].第四纪研究,2008,28(1):79-95.
[15]卢海峰,王金艳,王瑞.河北省衡水地区第四纪中—晚期标准地层剖面的建立及其地质含义[J].现代地质,2014,28(5):962-970.
[16]高秀林,王强,李玉德,等.从天津P8孔看中更新世末期以来海侵期、气候期对比问题[J].海洋地质与第四纪地质,1986,6(1):53-65.
[17]张世红,李海燕.地磁学、古地磁学和环境磁学的研究新进展——第32届国际地质大会学科总结和评述[J].现代地质,2004,18(4):415-422.
[18]赵勇,王强,李瑞杰,等.北京平原区南部PGZ01孔第四纪地层划分及其环境意义[J].古地理学报,2018,20(2):337-348.
[19]蔡向民,郭高轩,栾英波,等.永定河形成时代研究[J].第四纪研究,2010,30(1):167-174.
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