东海北部外陆架EY02—1孔磁性地层研究
摘要
对长达70.20 m的东海浅钻EY02-1进行了岩石磁学和古地磁分析,证明沉积物的载磁矿物主要为低矫顽力的磁铁矿,磁性地层揭示了发生于9.62~8.58 m的磁极性事件,结合钻孔上部的AMS14C测年证明它为全新世初期的哥德堡磁极性漂移,线性外推的时间是距今12 681~10 206 Ma,为全新世开始时地磁场是否发生过短期的磁极性漂移提供了新证据;与东海高分辨率的浅地层地震剖面以及典型钻孔(中法联合东海地震调查和DZQ4钻孔)对比还揭示,在中更新世地层中也出现过两次磁倾角变化。在钻孔中下部54.00~50.94 m(2271—2151号样品)出现一段磁倾角变小甚至变成负值,但是由于该段沉积物以粗颗粒的砂为主并且负向样品并不连续,依据研究的标准不作为反磁极性事件。第二个比较连续的负向样品段出现在最底部70.20~64.31 m。虽然研究区域内不乏揭示中更新统地层的地震剖面,但至今没有足够长的钻孔在时间上予以佐证。根据东海地震相对比和沉积物中海侵和海退旋回的不同特征以及布容期以来报道的反磁极性事件发生的时间来推测下部地层的时代归属。由于钻孔最底部的沉积主要是粗颗粒的粉砂质砂和细砂,同时钻孔也穿透了倒数第二冰期的杂乱地震相地层和其下的平行透明海相层,所以推测下部的倒转可能为发生在MIS8晚期的CR0反磁极性事件(距今265~255 ka)。
Rock magnetic and paleomagnetic study is undertaken for the 70.20 m borehole in the East China Sea(ECS),showing that the main magnetic carrier is low coercivity magnetite.Magnetostratigraphy in this borehole reveals excursion at 9.62~8.58 m that is proved to be Gothenburg excursion at the beginning of Holocene with the linearly extrapolated calendar age of 12 681~10 206 a BP from AMS14C dating,which provides a new evidence for the authenticity of this excursion.The stratigraphic sequences are determined for the Late Pleistocene based on high-resolution subbottom seismic profiles and boreholes(typical seismic profiles and boreholes in the ECS)and two reversals are indicated.One is from 54.00 to 50.94 m with a shallow or negative inclination,which may be an Iceland Basin event,but this is not fully discussed because of coarse sediment(which is considered as an unreliable recorder of reversal) and discontinuous negative sample inclinations.The second continuous negative section occurs at the bottom from 70.20 to 64.31 m.Although there is seismic profile penetrating into the Middle Pleistocene sequence,real boreholes reaching such long time are absent.So the bottom age is deduced according to the seismic correlation,the cycles of transgression and regression and the time span of reversals occurring in the Brunhes chron.The sediments of the bottom reversal are mainly coarse silty sand and fine sand,and also the length of the borehole is calculated to cross the layers of the chaotic seismic phase of MIS6 and parallel stratigraphies of marine phase underneath,so it is concluded that the bottom reversal is CR0(265~255 ka BP)happened at late MIS8.
Rock magnetic and paleomagnetic study is undertaken for the 70.20 m borehole in the East China Sea(ECS),showing that the main magnetic carrier is low coercivity magnetite.Magnetostratigraphy in this borehole reveals excursion at 9.62~8.58 m that is proved to be Gothenburg excursion at the beginning of Holocene with the linearly extrapolated calendar age of 12 681~10 206 a BP from AMS14C dating,which provides a new evidence for the authenticity of this excursion.The stratigraphic sequences are determined for the Late Pleistocene based on high-resolution subbottom seismic profiles and boreholes(typical seismic profiles and boreholes in the ECS)and two reversals are indicated.One is from 54.00 to 50.94 m with a shallow or negative inclination,which may be an Iceland Basin event,but this is not fully discussed because of coarse sediment(which is considered as an unreliable recorder of reversal) and discontinuous negative sample inclinations.The second continuous negative section occurs at the bottom from 70.20 to 64.31 m.Although there is seismic profile penetrating into the Middle Pleistocene sequence,real boreholes reaching such long time are absent.So the bottom age is deduced according to the seismic correlation,the cycles of transgression and regression and the time span of reversals occurring in the Brunhes chron.The sediments of the bottom reversal are mainly coarse silty sand and fine sand,and also the length of the borehole is calculated to cross the layers of the chaotic seismic phase of MIS6 and parallel stratigraphies of marine phase underneath,so it is concluded that the bottom reversal is CR0(265~255 ka BP)happened at late MIS8.
引文
①国家海洋局第一海洋研究所,青岛海洋地质研究所.东海晚第四纪以来古环境演化.2002.
②上海海洋石油局.东海和黄海地质浅钻补充调查技术设计书.2000.
③国家海洋局第一海洋研究所,青岛海洋地质研究所.东黄海典型过井浅地层剖面地质解释图说明书.2003.
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[4]YOO D G,LEE C W,KI MS P,et al.Late Quaternary transgressive and highstand systemtransacts in the northern East China Sea midshelf[J].Marine Geology,2002,187:313—328.
[5]刘振夏,夏东兴.中国近海潮流沉积沙体[M].北京:海洋出版社,2004:125—126.
[6]唐保根.东海陆架第四纪地层[M]//杨子赓.中国第四纪地层与国际对比.北京:海洋出版社,1996:56-75.
[7]唐保根,陈裕迅,张异彪,等.黄海、东海晚第四纪地层划分、特征及其沉积环境演化的研究[C]//我国专属经济区和大陆架勘测研究论文集.北京:海洋出版社,2002:178—191.
[8]LI UJian,ZHU Ri-xiang,LI Guang-xue,et al.Rock magnetic properties of the fine-grained sedi ment onthe East China Sea:i mplicationforprovenance[J].Marine Geology,2003,193:195—206.
[9]刘振夏,BERNE S.中更新世以来东海陆架的古环境[J].海洋地质与第四纪地质,1999,2:1—9.
[10]向荣,杨作升,SAITO Y,等.近2 300 a来环境敏感粒度组分记录的东亚冬季风变化[J].中国科学(D辑)2006,36(7):654—662.
[11]朱日祥,黄保春,潘永信,等.岩石磁学与古地磁实验室简介[J].地球科学进展,2003,18(2):177—181.
[12]MACRO S.Late Pleistocene paleomagnetic secular variation fromthe Sea of Galilee,Israel[J].Geophys Res Lett,2002,29(21):2015.
[13]CHAMPION D E,LANPHERE M A.Evidence for a newgeomagnetic reversal fromlava flows in Idaho:discussion of short polarity re-versals in the Brunhes and late Matuyama polarity chrons[J].J Geophys Res,1988,93(B10):11667—11680.
[14]LANGEREIS G C G,DEKKERS MJ,LANGE GJ,et al.Magnetostratigraphy and astronomical calibration of the last 1.1 Myr fromaneastern-Mediterranean core and dating of short events in the Brunhes[J].Geophys J Int,1997,129:75—94.
[15]MORNER N A,LANSERJ P.Gothenburg magnetic‘flip’[J].Nature,1974,251:408—409.
[16]庄丽华,李铁刚,常凤鸣,等.东海中陆架晚第四纪底栖有孔虫定量分析[J].海洋地质与第四纪地质,2004,24(1):43—50.[17〗陈俊仁.雷州半岛田洋火山湖盆磁学地层学的研究[J].海洋地质与第四纪地质,1988,8(1):73—84.
[18]马醒华,孙知明,胡守云.哥德堡极性事件在湖泊沉积物中的记录[J].第四纪研究,1994,2:175—180.
[19]ZHU Ri-xiang,GU Zhao-yan,HUANG Bao-chun,et al.Geomagnetic secular variation and cli matic changes since 15 000 a BP,Beijing re-gion[J].Sci in China(Ser B),1994,37(8):984—990.
[20]ZHU Ri-xiang.COE R S,ZHAO Xi-xi.Sedi mentary record of two geomagnetic excursions within the last 15 000 years in Beijing,China[J].Geophys Res,1998,103(B12):30323—30333.
[21]李培英,王永吉,刘振夏.冲绳海槽年代地层与沉积速率[J].中国科学(D辑),1999,29(1):50—55.
[22]CHANNELL J E T.Geomagnetic paleointensity and directional secular variation at ocean drilling program(ODP)Site 984(Bjom Drift)since 500 ka:comparisons with ODP Site 983(Gardar Drift)[J].J Geophys Res,1999,104(B10):22937—22951.
[23]STONERJ S,CHANNELLJ E T,HODELL D A,et al.A580 kyr paleomagnetic record fromthe sub-Antarctic South Atlantic OceanDrilling ProgramSite 1089[J].J Geophys Res,2003,108(B5):EPM5-1.
[24]ODA H,NAKAMURA K,IKEHARA K,et al.Paleomagnetic record from Academician Ridge,Lake Baikal:a reversal excursion at thebase of marine oxygenisotope stage 6[J].Earth and Planetary Science Letters,2002,202(1):117—132.
[25]CHANNELL J E T,MAZAUD A,STONER J S.IODP expedition 303(North Atlantic):excursions and reversals in the Brunhes andMatuyama chrons(Abstract).EOS Trans.AGU86(52).Fall Meet.Supp1.2005,San Francisco,5-9 December.2005.
[26]刘青松,朱日祥,潘永信,等.极性转换期间地球磁场快速倒转的统计模型[J].中国科学(D辑),1999,29(1):56—61.
[27]秦蕴珊,赵一阳,陈丽蓉,等.黄海地质[M].北京:海洋出版社,1989:84—89.
[28]周墨清,葛宗师.黄海及其邻近地区松散沉积物的磁性地层[J].海洋地质与第四纪地质,1990,10:21—32.
[29]SAITO Y,KATAYAMA H,IKEHARA K,et al.Transgressive and highstand systems tracts and post-glacial transgression,the EastChina Sea[J].Sedi mentary Geology,1998,122:217—232.
[30]刘振夏,BERNE S,L’ATLANTE科学考察组.东海陆架的古河道和古三角洲[J].海洋地质与第四纪地质,2000,20(1):9—14.
[31]葛淑兰,石学法,朱日祥,等.南黄海EY02—2磁性地层及古环境意义[J].科学通报,2005,50(22):2531—2540.
[32]ROBERTS AP,WI NKLHOFER M.Why are geomagnetic excursions not al ways recordedin sedi ments?Constraint frompost-depostion-al remanent magnetization lock-in modeling[J].Earth and Planetary Science Letters,2004,227:345—359.
[33]MARTI NSON D G,PISI AS N G,HAYSJ D,et al.Age dating andthe orbital theory of theice ages:development of a high-resolution 0—300 000-year chrono-stratigraphy[J].Quaternary Res,1987,27:1—29.
②上海海洋石油局.东海和黄海地质浅钻补充调查技术设计书.2000.
③国家海洋局第一海洋研究所,青岛海洋地质研究所.东黄海典型过井浅地层剖面地质解释图说明书.2003.
[1]刘忠臣,陈义兰,丁继胜,等.东海海底地形分区特征和成因研究[J].海洋科学进展,2003,21(2):160—173.
[2]LI U Zhen-xia,BERNE S,SALTO Y,et al.Quaternary seismic stratigraphy and paleoenvironments on the continental shelf of the EastChina Sea[J].J Asian Earth Sciences,2000,18:441—452.
[3]BERNE S,VAGNER P,GUICHARD F,et al.Pleistocene forced regressions andtidal sand ridgesinthe East China Sea[J].Marine Geo-logy,2002,3193:1—23.
[4]YOO D G,LEE C W,KI MS P,et al.Late Quaternary transgressive and highstand systemtransacts in the northern East China Sea midshelf[J].Marine Geology,2002,187:313—328.
[5]刘振夏,夏东兴.中国近海潮流沉积沙体[M].北京:海洋出版社,2004:125—126.
[6]唐保根.东海陆架第四纪地层[M]//杨子赓.中国第四纪地层与国际对比.北京:海洋出版社,1996:56-75.
[7]唐保根,陈裕迅,张异彪,等.黄海、东海晚第四纪地层划分、特征及其沉积环境演化的研究[C]//我国专属经济区和大陆架勘测研究论文集.北京:海洋出版社,2002:178—191.
[8]LI UJian,ZHU Ri-xiang,LI Guang-xue,et al.Rock magnetic properties of the fine-grained sedi ment onthe East China Sea:i mplicationforprovenance[J].Marine Geology,2003,193:195—206.
[9]刘振夏,BERNE S.中更新世以来东海陆架的古环境[J].海洋地质与第四纪地质,1999,2:1—9.
[10]向荣,杨作升,SAITO Y,等.近2 300 a来环境敏感粒度组分记录的东亚冬季风变化[J].中国科学(D辑)2006,36(7):654—662.
[11]朱日祥,黄保春,潘永信,等.岩石磁学与古地磁实验室简介[J].地球科学进展,2003,18(2):177—181.
[12]MACRO S.Late Pleistocene paleomagnetic secular variation fromthe Sea of Galilee,Israel[J].Geophys Res Lett,2002,29(21):2015.
[13]CHAMPION D E,LANPHERE M A.Evidence for a newgeomagnetic reversal fromlava flows in Idaho:discussion of short polarity re-versals in the Brunhes and late Matuyama polarity chrons[J].J Geophys Res,1988,93(B10):11667—11680.
[14]LANGEREIS G C G,DEKKERS MJ,LANGE GJ,et al.Magnetostratigraphy and astronomical calibration of the last 1.1 Myr fromaneastern-Mediterranean core and dating of short events in the Brunhes[J].Geophys J Int,1997,129:75—94.
[15]MORNER N A,LANSERJ P.Gothenburg magnetic‘flip’[J].Nature,1974,251:408—409.
[16]庄丽华,李铁刚,常凤鸣,等.东海中陆架晚第四纪底栖有孔虫定量分析[J].海洋地质与第四纪地质,2004,24(1):43—50.[17〗陈俊仁.雷州半岛田洋火山湖盆磁学地层学的研究[J].海洋地质与第四纪地质,1988,8(1):73—84.
[18]马醒华,孙知明,胡守云.哥德堡极性事件在湖泊沉积物中的记录[J].第四纪研究,1994,2:175—180.
[19]ZHU Ri-xiang,GU Zhao-yan,HUANG Bao-chun,et al.Geomagnetic secular variation and cli matic changes since 15 000 a BP,Beijing re-gion[J].Sci in China(Ser B),1994,37(8):984—990.
[20]ZHU Ri-xiang.COE R S,ZHAO Xi-xi.Sedi mentary record of two geomagnetic excursions within the last 15 000 years in Beijing,China[J].Geophys Res,1998,103(B12):30323—30333.
[21]李培英,王永吉,刘振夏.冲绳海槽年代地层与沉积速率[J].中国科学(D辑),1999,29(1):50—55.
[22]CHANNELL J E T.Geomagnetic paleointensity and directional secular variation at ocean drilling program(ODP)Site 984(Bjom Drift)since 500 ka:comparisons with ODP Site 983(Gardar Drift)[J].J Geophys Res,1999,104(B10):22937—22951.
[23]STONERJ S,CHANNELLJ E T,HODELL D A,et al.A580 kyr paleomagnetic record fromthe sub-Antarctic South Atlantic OceanDrilling ProgramSite 1089[J].J Geophys Res,2003,108(B5):EPM5-1.
[24]ODA H,NAKAMURA K,IKEHARA K,et al.Paleomagnetic record from Academician Ridge,Lake Baikal:a reversal excursion at thebase of marine oxygenisotope stage 6[J].Earth and Planetary Science Letters,2002,202(1):117—132.
[25]CHANNELL J E T,MAZAUD A,STONER J S.IODP expedition 303(North Atlantic):excursions and reversals in the Brunhes andMatuyama chrons(Abstract).EOS Trans.AGU86(52).Fall Meet.Supp1.2005,San Francisco,5-9 December.2005.
[26]刘青松,朱日祥,潘永信,等.极性转换期间地球磁场快速倒转的统计模型[J].中国科学(D辑),1999,29(1):56—61.
[27]秦蕴珊,赵一阳,陈丽蓉,等.黄海地质[M].北京:海洋出版社,1989:84—89.
[28]周墨清,葛宗师.黄海及其邻近地区松散沉积物的磁性地层[J].海洋地质与第四纪地质,1990,10:21—32.
[29]SAITO Y,KATAYAMA H,IKEHARA K,et al.Transgressive and highstand systems tracts and post-glacial transgression,the EastChina Sea[J].Sedi mentary Geology,1998,122:217—232.
[30]刘振夏,BERNE S,L’ATLANTE科学考察组.东海陆架的古河道和古三角洲[J].海洋地质与第四纪地质,2000,20(1):9—14.
[31]葛淑兰,石学法,朱日祥,等.南黄海EY02—2磁性地层及古环境意义[J].科学通报,2005,50(22):2531—2540.
[32]ROBERTS AP,WI NKLHOFER M.Why are geomagnetic excursions not al ways recordedin sedi ments?Constraint frompost-depostion-al remanent magnetization lock-in modeling[J].Earth and Planetary Science Letters,2004,227:345—359.
[33]MARTI NSON D G,PISI AS N G,HAYSJ D,et al.Age dating andthe orbital theory of theice ages:development of a high-resolution 0—300 000-year chrono-stratigraphy[J].Quaternary Res,1987,27:1—29.
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