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Deep-Sea Sediments PDF

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Elsevier Radarweg29,POBox211,1000AEAmsterdam,TheNetherlands LinacreHouse,JordanHill,OxfordOX28DP,UK #2011HeikoHu¨nekeandThierryMulder.PublishedbyElsevierB.V.Allrightsreserved. Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinany formorbyanymeans,electronic,mechanical,photocopying,recording,orotherwise,without thepriorwrittenpermissionofthepublisher. PermissionsmaybesoughtdirectlyfromElsevier’sScience&TechnologyRights Department inOxford,UK:phone:(+44)1865843830,fax:(+44)1865853333,E-mail:permissions@ elsevier.com.YoumayalsocompleteyourrequestonlineviatheElsevierhomepage(http:// elsevier.com),byselecting‘‘Support&Contact’’then‘‘CopyrightandPermission’’andthen ‘‘ObtainingPermissions.’’ LibraryofCongressCataloging-in-PublicationData AcatalogrecordforthisbookisavailablefromtheLibraryofCongress BritishLibraryCataloguing-in-PublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary ForinformationonallAcademicPresspublications visitourwebsiteatelsevierdirect.com ISBN:978-0-444-53000-4 ISSN:0070-4571 PrintedandboundinGreatBritain 11 12 13 10 9 8 7 6 5 4 3 2 1 Finally, we are particularly grateful to our families and friends whose enduring support and forbearance has sustained us over the years that “the book” has been in preparation to my parents, my wife Dagny and my children, Ragnar and Lukas (H. H.) tomyparents,mywifeClaireandmychildren,Lucy,Clothilde, Romaric and Lorraine-Marie (T. M.) C ONTRIBUTORS TorstenBickert Zentrumfu¨rMarineUmweltwissenschaften,Universita¨tBremen,Germany StevenN.Carey Graduate School of Oceanography, University of Rhode Island, Narragansett, RhodeIsland,USA Jean-ClaudeFauge`res Universite´ deBordeaux,UMRCNRS5805EPOC,TalenceCedex,France Ru¨digerHenrich Department of Sedimentology and Paleoceanography, Faculty of Geosciences, University of Bremen, klagenfurter Straße, Bremen, and Fachbereich Geowis- senschaften,Universita¨tBremen,Germany ReinhardHesse EarthandPlanetarySciences,McGillUniversity,Montreal,Quebec,Canada HeikoHu¨neke Institut fu¨r Geographie und Geologie, Universita¨t Greifswald, Jahn-Strasse 17a, D–17487Greifswald,Germany PatriceImbert Total,CSTJF,AvenueLarribau,64000Pau,France ThierryMulder Universite´ de Bordeaux, UMR CNRS 5805 EPOC, Avenue desfaculte´s, 33185 TalenceCedex,France UlrikeSchacht Australian School of Petroleum, The University of Adelaide, Adelaide, SA, Australia Jean-LucSchneider Universite´ Bordeaux 1, Observatoire Aquitain des Sciences de l’Univers, CNRS-UMREPOC,TalenceCedex,France A.Stadnitskaia DepartmentofMarineOrganicBiogeochemistry,RoyalNetherlandsInstitutefor SeaResearch(RoyalNIOZ),Texel,TheNetherlands xi xii Contributors A.Uchman Institute of Geological Sciences, Jagiellonian University, Krako´w, Oleandry 2a, Poland A.J.VanLoon Geological Institute, Adam Mickiewicz University, Mako´w Polnych 16, 61–606 Poznan,Poland HelmutWeissert DepartmentofEarthSciences,ETH-Z,Zu¨rich,Switzerland A.Wetzel Geologisch-Pala¨ontologischesInstitutderUniversita¨t,Basel,Switzerland A.J.Wheeler School of Biological, Earth & Environmental Sciences and Environmental ResearchInstitute,UniversityCollegeCork,Cork,Ireland P REFACE Therearemanyreasonsforthefast-growingunderstandingofdeep-marine sedimentary processes during the past few decades. Research has benefited greatlyfromanumberofnewlydeveloped,highlysophisticatedexploration techniques and comprehensive data sets, thanks to the immense industrial interest in deep-sea sediments. Multidisciplinary research, in addition, has shed increasingly more light on the complex biogeochemical processes driving and controlling productivity and, thus, an important part of the deep-sea sedimentation. Moreover, deep-sea sediments have been recog- nizedasarchivesofinformationaboutthechangingboundaryconditionsin the oceans’ histories and in the evolution of life. They also became of particular interest as keys for unravelling present-day climate changes, which challenge modern society. Thisbookgrewoutofourdesiretokeepupwiththisrapidlyexpanding area of knowledge and to integrate the main process-based aspects of siliciclastic,biogenicandvolcaniclasticdepositsofbothmodernandancient deep-marine sedimentation into one single, unified and comprehensive text. The volume is structured to follow the various sedimentary deposi- tional processes in the deep sea, from sediment gravity flows and contour currentstopelagicsettlingandhemipelagicadvection,periplatformsettling, plankticandbenthicbioproductivity,andvolcanicactivity.Inaddition,the relationships between depositional environment and endobenthic organ- isms, as well as early-diagenetic processes at and within the deep-sea floor are dealt with. The book, finally, includes an introduction to the climatic interpretation of the various proxies that reveal global changes during the Mesozoic greenhouse and Neogene icehouse conditions, and it addresses the specific interest of the hydrocarbons industry in deep-water sediments. While each chapter is self-contained, they are interrelated, thus reflecting thecomplexityofthesubject,spanningflowtransformationofsedimentary density flows and currents, bentho-pelagic coupling, changes in sea-water chemistry, major innovations in organism evolution, and changes in external controls on sedimentation and productivity. The book is an attempt to bring together the knowledge both of scientists working in the present-day deep oceans and geologists studying ancient deposits of deep-marine environments now exposed on land. The main advantage of the actualistic point of view is, of course, that the processesdrivingtheproduction,thesupplyandthedepositionofsedimen- tary particles accumulating in the deep sea can be qualified and quantified xiii xiv Preface more or less precisely. The fossil record, on the other hand, if successfully deciphered holds valuable clues about the changing boundary conditions, controlling the sedimentation in deep-marine environments. This is important in particular where evolutionary processes are involved in the formation of deep-sea sediments. Wehaveendeavouredtoproduceawell-balancedbookwithoutimpor- tantomissions.Weattempttosummarizethecurrentfactualknowledgein thefieldofdeep-seasedimentationandtheapplicationofthisknowledgeto a variety of scientific and applied problems. We invited authors from both academiaandindustrytocontributetothisbook,thusstrivingfordifferent viewpoints on the various aspects of deep-marine sedimentation. Consid- eringtheratherbroadtopicofthebook,however,wecannotexcludethat some gaps may be found. We hope there are not too many. This book will be of interest to undergraduates taking specialist courses or simply orientating themselves with respect to the largest depositional setting on Earth: the deep sea. Postgraduates and professional geologists concerned with deep-sea research will find it useful for understanding specificaspectsofdeep-seasedimentology,orasanintroductiontoregional considerations. Oceanographers, geochemists, biologists, palaeontologists, geophysicists,palaeoclimatologistsandstructuralgeologistswillalsofindthe bookusefulasareferenceforunderstandingthesedimentologicalaspectsof the deep sea. First of all, we thank our authors, who not only kept up a very high standard of contribution, but also stuck (fairly closely) to the guidelines imposed by us. This also concerns our reviewers, chosen from various countries, who deserve considerable praise for their efforts in providing quick and fair critical comments on the contributions. The editors gratefully express their thanks also to Tom van Loon, the series editor who encouraged the publication of a volume on this rather broad topic and gave us longstanding valuable support during the prepara- tion.Itwasapleasuretoworkwithyou.WealsothankthestaffofElsevier for their help in organizing this book, in particular Anita Koch, develop- ment editor, Derek Coleman, senior developmental editor, Mageswaran BabuSivakumar, project manager, and Karishma Rathore, rights adminis- trator.Furthermore,wewouldliketo thankHeikeSengpiehl andDagmar LaufromtheGeologicalDepartmentattheUniversityofGreifswald,who did a large part of the high-quality figure drawing for many chapters. HEIKO HU¨NEKE AND THIERRY MULDER C H A P T E R 1 Progress in Deep-Sea Sedimentology Thierry Mulder,* Heiko Hu¨neke,† and A.J. Van Loon‡ Contents 1. Introduction 1 1.1. Scopeofthebook 2 2. WhatareDeep-SeaSediments? 3 3. ToolsUsedforDeep-SeaSedimentInvestigations 5 3.1. Geophysics 5 3.2. Geotechnictools 11 3.3. Sedimentsampling 12 3.4. Submersiblesystems 14 3.5. Currentmetersandparticletraps 14 3.6. Laboratoryanalyses 14 4. StructureoftheBook 16 References 22 1. Introduction Inthisbook,allmarinedomainsextendingseawardoftheshelfbreak are considered as deep-sea. This domain represents 63.6 % of the Earth’s surface (the ocean in its entirety covers 361(cid:1)106 km2 or 70.8% of the Earth’s surface, including continental shelves). From a stricter geological point of view, the oceanic domain would begin at the boundary between the high-density (3.25 on average), usually thin (5 km in average) oceanic crust and the thick (30 km on average) low-density (2.7 in average) continental crust. A transitional crust may exist in between. Thestudyofdeep-seasedimentsbenefitedgreatlyfromrecentimprove- mentsintechnologies.Theseimprovementshavebeendrivenbyacademic needs (most of the sea floor remains unexplored in detail and most of the topography of abyssal plains has not been mapped with accurate tools) and * Universite´deBordeaux,UMRCNRS5805EPOC,AvenuedesFaculte´s,33185TalenceCedex,France { Institutfu¨rGeographieundGeologie,Universita¨tGreifswald,Jahn-Strasse17a,D–17487Greifswald { GeologicalInstitute,AdamMickiewiczUniversity,Mako´wPolnych16,61–606Poznan,Poland DevelopmentsinSedimentology,Volume63 #2011ElsevierB.V. ISSN0070-4571,DOI:10.1016/S0070-4571(11)63001-X Allrightsreserved. 1 2 ThierryMulderetal. byeconomicneeds,suchasthedemandformineraldeposits(metal-bearing nodules, exploration of ultra-deep offshore oil). These newly-developed technologiesbenefitedfrombothinsitudatacollectionanddatainterpreta- tion in laboratory. In terms of data collection, this includes: – Sea-floor morphology (multibeam bathymetry), – subsurface investigation (seismic tools), – high-resolution echosounders, – 3-D tools, – sampling gear (interface corer). In terms of data interpretation in the laboratory, this includes: – core scanners for measurement of geotechnical and physical properties, X-ray, geochemistry, – thedevelopmentofbiologicaltracersandbiomarkersforpalaeoenviron- mental reconstruction, – the improvement and development of stratigraphic tools and dating methods based on radiogenic and non-radiogenic elements (especially for the Quaternary), the development of micro-lithostratigraphy (IRD, tephra recognition) and magnetostratigraphy. 1.1. Scope of the book The chapters of this book have the following objectives: – to explain the formation and supply of sedimentary particles by conti- nentalerosion(riverload,iceorwindtransport),coastalerosion,current- induced winnowing, through volcanic and authigenic processes, and by means of biogenic productivity; – to describe the way the sediments are transported from the source area (continental edge, slope, surface water) to the accumulation zone in the deep-sea; – topresenttheearlygeochemicaltransformationsaffectingtheparticlesin the water column or the sediments as soon as they are produced and accumulate on the sea floor; – toshowhowsedimentsarepreservedontheseafloordespiteerosionand dissolution; – to present the characteristic features and main changes in worldwide ocean sedimentation with focus on “modern” oceans that have been formed since the disintegration of Pangaea (Mesozoic-Cenozoic); – to discuss major changes in biogenic productivity, sea-water chemistry, and external controls of deep-sea sedimentary processes, depending on long-term trends in ocean history; ProgressinDeep-SeaSedimentology 3 – topresenttheacademic(e.g.,palaeoclimaticstudies),societal(e.g.,natu- ral hazards) and industrial interests (e.g., the exploration for mineral resources) in the study of deep-sea sediments. 2. What are Deep-Sea Sediments? The sea-water environment can be subdivided into shallow (epicon- tinental) seas and deep seas. The morphology of modern oceans and mar- ginal seas is based on the water depth and on changes in the slope gradient (Fig. 1.1). Using a classical cross-section through a passive continental margin, the shallowest environment is the continental shelf (or platform), which extends in the continental domain from the shoreline to the shelf break.Itrepresents26(cid:1)106km2(7.2%ofthemarinearea).Inthisarea,the sea-floor gradient is < 0.5(cid:3). In offshore direction, the water depth extends downto100–110msuchasonthenorth-westernAfricanmargin(Seibold andHinz,1974)or200monmostofthecontinentalmargins,includingthe northern European and the North-American Atlantic margins. Its extent canbefromseveralhundredsofkilometres(1500kmfortheSiberianshelf, >600kmforthesouthernArgentina–PatagonianShelf)toafewkilometres (off Nice in the Mediterranean). Active continental margins, such as the South-American Pacific margin, are usually only a few kilometres wide. The continental shelf is exposed to numerous oceanographic processes that are absent in deep seas. Most of them are related to atmospheric processes. They include swell and storm waves that generate oscillatory motions in the water column (producing specific sedimentary structures such as hummocky cross-stratifications), tides, shallow contour currents, as well as shelf and coastal currents, including littoral drift. The continental shelf is separated from the continental slope by the shelf break, which is defined by a change in the slope gradient. The slope steepens from a gradient<1(cid:3) ontheshelfto3–5(cid:3) inaveragealongtheslope,tosometimes (cid:3) more than 20 in areas where canyons are incised the slope and the shelf. Further downslope, it passes into the continental rise at a water depth of about 2500 m. The continental slope corresponds approximately to the bathyal zone (200–3000 m). On the rise, the slope gradient decreases (cid:3) to 1–2 and the relief becomes smoother. Because of this change, the continental rise is the preferential area for final deposition of terrigenous sediment that bypassed the shelf and slope area. Together, the continental shelf,slopeandriseformthecontinentalmargin.Themargincanbepassive andtectonicallyquiescent(NorthAtlanticmargin)oractiveandtectonically dynamic (circum-Pacific margins). At about 5000 m water depth, the rise passes into the abyssal plain. Abyssal plains represent the largest oceanic domains with a mean water 4 ThierryMulderetal. deep sea littoral zone bathyal zone abyssal zone hadal zone coastline shelf 0m slope 2000m average ocean depth rise ridge 4000m abyssal plain 6000m 8000m 10,000m trench active margin passive margin ocean continent continent LITHOSPHERE oceanic crust continental crust mantle Figure 1.1 Cross-section through an ocean, showing the various deep-sea environ- mentsanddomains.Lithosphere includesupperpartofuppermantleplusoceanicor continentalcrust.(Amulti-colourversionofthisfigureisontheincludedCD-ROM.) depth of (cid:4) 3800 m. Abyssal plains are “flat” at a large scale. A closer look reveals, however, that their “flatness” is disrupted by tectonic and volcanic features: transform faults at different scales and strike-like faults with hang- ingwallsofseveralhundredsofmetresorevenseveralkilometresinheight andrelatedlocalsedimentarybasins.Thereare,inaddition,hot-spot-related volcanic mounds and islands, volcano alignments forming the oceanic ridges, channels and thick and extensive accumulations of sediments form- ing drifts, and levees, gypsum diapirs; there are also dissolution structures. Thecontinentalriseandabyssalplainsconstitutetheabyssaldomain(3000– 6000 m). Only 2% of the total ocean surface is deeper than 6000 m (hadal domain).Insubductionareas,thepresenceofasubductiontrenchgenerates the deepest oceanic environments, down to 11,020 m (Mariana Trench). There,thepresenceofanaccretionaryprismcangenerateimportantrelief- formingprocesses,suchasmuddiapirsandvolcanoes(whichmayberelated to the upward motion of deep fluids) and pockmarks, which are due to liquefaction related to fluid escape. Thesedimentsinthedeep-seaconsistof(1)clasticparticlesderivedfrom erodedrocks andsediments outcroppingeither on the emerged continents or previously deposited in a marine environment, (2) particles formed by

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