南海中央海盆晚中新世深海火山碎屑沉积的遗迹学特征及意义
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摘要
火山碎屑沉积是南海深海沉积的重要组成部分,因记录了火山活动影响下特殊的深海环境演变过程,具有重要的科研价值.为了解火山活动期和活动间歇期底栖环境的演变过程,对IODP349航次U1431站火山碎屑岩地层的生物遗迹记录开展了研究.研究发现,在中中新世-晚中新世(12.5～7.4 Ma,主要在晚中新世)期间遗迹化石在该套地层的粉砂岩和泥岩层中广泛发育,以Zoophycos、Thalassinoides、Chondrites和Planolites为主要类型.晚中新世研究区所在南海深海海盆经历了多次火山活动期和火山活动间歇期的交替演变,研究站位遗迹化石组合特征与现代南海中央海盆遗迹化石种属相似,指示了火山活动间歇期深海环境特征,沉积速率在5～15 cm/ka范围水体平静,同时有足够的营养物质供给,适合底栖生物的生存.通过分析遗迹化石组合与地层岩性特征之间的联系,研究发现遗迹化石不仅受限于底质岩性(主要发育在粉砂岩和泥岩中),还受控于沉积物的含氧量.研究推测海底火山活动为表层海水提供营养盐,促使浮游生物发育,浮游生物死亡后沉降至海底,增加了表层沉积物有机碳的供给,但消耗大量氧气,不利于底栖生物活动;反之,在火山活动间歇期,洋底表层沉积物有机碳含量降低,溶解氧消耗减少,有利于底栖生物生存.
Volcaniclastics is one of the important compositions of deep-sea sediments produced by volcanic eruptions. It is with great research values for studies on paleoenvironmental evolution in the deep-sea volcanic environment. The purpose of this work is to reveal the pattern of the Late Miocene benthic environment revolution in the central basin of the South China Sea(SCS) by analyzing the trace fossil assemblages in the volcaniclastic sequence drilled at site U1431 during the International Ocean Discovery Program(IODP) expedition leg 349. The study shows that trace fossils were developed well in siltstone and claystone during the Middle-Late Miocene(12.5–7.4 Ma, mainly in Late Miocene), and were dominated by Zoophycos,Thalassinoides,Chondrites, and Planolites.The volcanoes in the central basin of the SCS experienced repeated alternations of eruption and quietness during Late Miocene. The trace fossil assemblage in site U1431 implies that the basin is a quiet deep-sea environment with sedimentary rate varying between 5–15 cm/ka during volcanic activity quiet periods. By analyzing the associations between the trace fossil assemblages and the lithologic stratigraphic features, the study shows that the composition of the trace fossil assemblage is limited by substrate lithology and the dissolved oxygen concentration in the water masses at the sediment/water interface. The study also suggests that during eruptions,submarine volcanic activities can potentially provide nutrients for surface seawaters, and these nutrients can promote phytoplankton growth and subsequently increase the supply of organic carbon to the seafloor. The organic carbon on the sea floor then may consume the dissolved oxygen in the sediment pore water, making it unfavorable to the activities of the benthic organisms. In contrast, during volcanic eruption quiet periods, flux of organic carbon to the seafloor possibly reduced. Consumption of the dissolved oxygen in the pore water thus reduced, and the growth of the benthic organisms subsequently developed.
Volcaniclastics is one of the important compositions of deep-sea sediments produced by volcanic eruptions. It is with great research values for studies on paleoenvironmental evolution in the deep-sea volcanic environment. The purpose of this work is to reveal the pattern of the Late Miocene benthic environment revolution in the central basin of the South China Sea(SCS) by analyzing the trace fossil assemblages in the volcaniclastic sequence drilled at site U1431 during the International Ocean Discovery Program(IODP) expedition leg 349. The study shows that trace fossils were developed well in siltstone and claystone during the Middle-Late Miocene(12.5–7.4 Ma, mainly in Late Miocene), and were dominated by Zoophycos,Thalassinoides,Chondrites, and Planolites.The volcanoes in the central basin of the SCS experienced repeated alternations of eruption and quietness during Late Miocene. The trace fossil assemblage in site U1431 implies that the basin is a quiet deep-sea environment with sedimentary rate varying between 5–15 cm/ka during volcanic activity quiet periods. By analyzing the associations between the trace fossil assemblages and the lithologic stratigraphic features, the study shows that the composition of the trace fossil assemblage is limited by substrate lithology and the dissolved oxygen concentration in the water masses at the sediment/water interface. The study also suggests that during eruptions,submarine volcanic activities can potentially provide nutrients for surface seawaters, and these nutrients can promote phytoplankton growth and subsequently increase the supply of organic carbon to the seafloor. The organic carbon on the sea floor then may consume the dissolved oxygen in the sediment pore water, making it unfavorable to the activities of the benthic organisms. In contrast, during volcanic eruption quiet periods, flux of organic carbon to the seafloor possibly reduced. Consumption of the dissolved oxygen in the pore water thus reduced, and the growth of the benthic organisms subsequently developed.
引文
Bromley,R.G.,Ekdale,A.A.,1984.Chondrites:A Trace Fossil Indicator of Anoxia in Sediments.Science,224:872-874.
Dorador,J.,Wetzel,A.,Rodriguez-Tovar,F.J.,2016.Zoophycos in DeepSea Sediments Indicates High and Seasonal Primary Productivity:Ichnology as a Proxy in Palaeoceanography during GlacialInterglacial Wariations.Terra Nova,28:323-328.
Ekdale,A.,Mason,T., 1988.Characteristic Trace-Fossil Associations in Oxygen-Poor Sedimentary Environments. Geology,16:720-723.
Knaust,D.,2013.The Ichnogenus Rhizocorallium:Classification,Trace Makers,Palaeoenvironments and Evolution. Earth Science Reviews, 126:1-47.
Lei,C.,Ren,J.Y.,Zhang,J.,2015.Tectonic Province Divisions in the South China Sea:Implications for Basin Geodynamics.Earth Science,40(4):7 44-7 62(in Chinese with English abstract).
Li,C.F.,Lin,J.,Kulhanek,D.K.,et al.,2015.South China Sea Tectonics:Opening of the South China Sea and Its Implications for Southeast Asia Tectonics,Climates,and Deep Mantle Processessince the Late Mesozoic.Proceedings of the International Ocean Discovery Program Volume 349 Publications(Site U1431), College Station, Texas A&M University, 1-54.
Li,W.B.,Wang,R.J.,2016.Mechanism of Sea Level Change at the Earth Orbital Parameter Cycles during the Last 2 Ma BP.Earth Science,41(5):742-756(in Chinese with English abstract).
Miller, W.,2007.Trace Fossils:Concepts,Problems,Prospects.Elsevier,New York.
Sun,C.Q.,You,H.T.,Liu,J.Q.,et al.,2016.Differences between Whole Rock and In Situ Analysis on Tephra:Evidence from the1 600 a cal.BP Eruption of Jinlongdingzi Volcano. Earth Science,41(1):97-104(in Chinese with English abstract).
Taylor,A.M.,Goldring,R., 1993.Description and Analysis of Bioturbation and Ichnofabric Journal of Geological Society,150:141-148.
Wang,G.H.,Xie,S.P.,Qu,T.,et al.,2011.Deep South China Sea Circulation.Geophysical Research Letters,38:1-6.
Wang,X.J.,Wu,M.Q.,Liang,D.H.,et al.,1984.Some Geochemical Characteristics of Basalts in the South China Sea. Geochemica,4(4):332-340(in Chinese with English abstract).
Wang,Y.J.,Han,X.Q.,Luo,Z.H.,et al.,2009. Late Miocene Magmatism and Evolution of Zhenbei-Huangyan Seamount in the South China Sea:Evidence from Petrochemistry and Chronology. Acta Oceanologica Sinca,31(4):93-102(in Chinese with English abstract).
Wetzel,A.,2002.Modem Nereites in the South China SeaEcological Association with Redox Conditions in the Sediment.Palaios, 17:507-515.
Wetzel,A.,2008.Recent Bioturbation in the Deep South China Sea:A Uniformitarian Ichnologic Approach.Palaios,23:601-615.
Wetzel,A.,Tjallingii,R.,Wiesner,M.G.,2011.Bioturbational Structures Record Environmental Changes in the Upwelling Area off Vietnam(South China Sea)for the Last 150 000 Years. Palaeogeography,Palaeoclimatology,Palaeoecology,311:256-267.
Yang,S.F.,Zhang,J.P.,Yang,M.F.,2004.Trace Fossils in China. Science Press,Beijing(in Chinese).
Zhao,Q.H.,Wang,P.X., 1999.Process in Quaternary Paleoceanography of the South China Sea:A Reiew.Quaternary Sciences,19(6):481-501(in Chinese with English abstract).
雷超,任建业,张静,2015.南海构造变形分区及成盆过程.地球科学,40(4):744-762.
李文宝,王汝建,2016.近2 Ma BP以来地球轨道参数周期上全球海平面变化机制.地球科学,41(5):742-756.
孙春青,游海涛,刘嘉麒,等,2016.火山灰全岩与原位分析差异:以四海龙湾记录的1 600年前金龙顶子火山喷发为例.地球科学,41(1):97-104.
王贤觉,吴明清,梁德华,等,1984.南海玄武岩的某些地球化学特征.地球化学,4(4):332-340.
王叶剑,韩喜球,罗照华,等,2009.晚中新世南海珍贝—黄岩海山岩浆活动及其演化:岩石地球化学和年代学证据.海洋学报,31(4):93-102.
杨式溥,张建平,杨美芳,2004.中国遗迹化石.北京:科学出版社.
赵泉鸿,汪品先,1999.南海第四纪古海洋学研究进展.第四纪研究,19(6):481-501.
Dorador,J.,Wetzel,A.,Rodriguez-Tovar,F.J.,2016.Zoophycos in DeepSea Sediments Indicates High and Seasonal Primary Productivity:Ichnology as a Proxy in Palaeoceanography during GlacialInterglacial Wariations.Terra Nova,28:323-328.
Ekdale,A.,Mason,T., 1988.Characteristic Trace-Fossil Associations in Oxygen-Poor Sedimentary Environments. Geology,16:720-723.
Knaust,D.,2013.The Ichnogenus Rhizocorallium:Classification,Trace Makers,Palaeoenvironments and Evolution. Earth Science Reviews, 126:1-47.
Lei,C.,Ren,J.Y.,Zhang,J.,2015.Tectonic Province Divisions in the South China Sea:Implications for Basin Geodynamics.Earth Science,40(4):7 44-7 62(in Chinese with English abstract).
Li,C.F.,Lin,J.,Kulhanek,D.K.,et al.,2015.South China Sea Tectonics:Opening of the South China Sea and Its Implications for Southeast Asia Tectonics,Climates,and Deep Mantle Processessince the Late Mesozoic.Proceedings of the International Ocean Discovery Program Volume 349 Publications(Site U1431), College Station, Texas A&M University, 1-54.
Li,W.B.,Wang,R.J.,2016.Mechanism of Sea Level Change at the Earth Orbital Parameter Cycles during the Last 2 Ma BP.Earth Science,41(5):742-756(in Chinese with English abstract).
Miller, W.,2007.Trace Fossils:Concepts,Problems,Prospects.Elsevier,New York.
Sun,C.Q.,You,H.T.,Liu,J.Q.,et al.,2016.Differences between Whole Rock and In Situ Analysis on Tephra:Evidence from the1 600 a cal.BP Eruption of Jinlongdingzi Volcano. Earth Science,41(1):97-104(in Chinese with English abstract).
Taylor,A.M.,Goldring,R., 1993.Description and Analysis of Bioturbation and Ichnofabric Journal of Geological Society,150:141-148.
Wang,G.H.,Xie,S.P.,Qu,T.,et al.,2011.Deep South China Sea Circulation.Geophysical Research Letters,38:1-6.
Wang,X.J.,Wu,M.Q.,Liang,D.H.,et al.,1984.Some Geochemical Characteristics of Basalts in the South China Sea. Geochemica,4(4):332-340(in Chinese with English abstract).
Wang,Y.J.,Han,X.Q.,Luo,Z.H.,et al.,2009. Late Miocene Magmatism and Evolution of Zhenbei-Huangyan Seamount in the South China Sea:Evidence from Petrochemistry and Chronology. Acta Oceanologica Sinca,31(4):93-102(in Chinese with English abstract).
Wetzel,A.,2002.Modem Nereites in the South China SeaEcological Association with Redox Conditions in the Sediment.Palaios, 17:507-515.
Wetzel,A.,2008.Recent Bioturbation in the Deep South China Sea:A Uniformitarian Ichnologic Approach.Palaios,23:601-615.
Wetzel,A.,Tjallingii,R.,Wiesner,M.G.,2011.Bioturbational Structures Record Environmental Changes in the Upwelling Area off Vietnam(South China Sea)for the Last 150 000 Years. Palaeogeography,Palaeoclimatology,Palaeoecology,311:256-267.
Yang,S.F.,Zhang,J.P.,Yang,M.F.,2004.Trace Fossils in China. Science Press,Beijing(in Chinese).
Zhao,Q.H.,Wang,P.X., 1999.Process in Quaternary Paleoceanography of the South China Sea:A Reiew.Quaternary Sciences,19(6):481-501(in Chinese with English abstract).
雷超,任建业,张静,2015.南海构造变形分区及成盆过程.地球科学,40(4):744-762.
李文宝,王汝建,2016.近2 Ma BP以来地球轨道参数周期上全球海平面变化机制.地球科学,41(5):742-756.
孙春青,游海涛,刘嘉麒,等,2016.火山灰全岩与原位分析差异:以四海龙湾记录的1 600年前金龙顶子火山喷发为例.地球科学,41(1):97-104.
王贤觉,吴明清,梁德华,等,1984.南海玄武岩的某些地球化学特征.地球化学,4(4):332-340.
王叶剑,韩喜球,罗照华,等,2009.晚中新世南海珍贝—黄岩海山岩浆活动及其演化:岩石地球化学和年代学证据.海洋学报,31(4):93-102.
杨式溥,张建平,杨美芳,2004.中国遗迹化石.北京:科学出版社.
赵泉鸿,汪品先,1999.南海第四纪古海洋学研究进展.第四纪研究,19(6):481-501.