Chapter04 Marine Sediments.ppt

2/16/2014Chapter Overview Marine sediments contain a record ofEarth history. Marine sediments provide many importantresources. Marine sediments have origins from a varietyof sources.Marine SedimentsChapter Four 2014 Pearson Education, Inc.Marine SedimentsApproaching the bottom (Alvin) Provide clues to Earthhistory–––––Marine organism distributionOcean floor movementsOcean circulation patternsClimate changeGlobal extinction events 2014 Pearson Education, Inc.Marine Sediments 2014 Pearson Education, Inc.Classification of Marine Sediments Texture – size and shape of particles Sediment origins– Worn rocks– Living organisms– Minerals dissolved in water– Outer space Sediments lithify into sedimentary rock 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.1

2/16/2014Marine Sediment Collection Early exploration used dredges. Modern exploration– Cores – hollow steel tube collects sedimentcolumns– Rotary drilling – collects deep oceansediment coresDrill Ship:JOIDES Resolutionhttp://joidesresolution.org/ 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.Marine Sediment CollectionMarine Sediment Collection National Science Foundation (NSF) – formedJoint Oceanographic Institutions for DeepEarth Sampling (JOIDES) in 1963 Deep Sea Drilling Project (DSDP) – 1968– Scripps Institution of Oceanography– Rosenstiel School of Atmospheric andOceanic Studies– Lamont-Doherty Earth Observatory ofColumbia University– Woods Hole Oceanographic Institution 2014 Pearson Education, Inc.Marine Sediment Collection DSDP became Ocean Drilling Project (ODP)in 1983– JOIDES Resolution replaced GlomarChallenger Integrated Ocean Drilling Program (IODP)– Replaced ODP in 2003– Chikyu – new exploration vessel in 2007 Expedition to Japan Trench after 2011 earthquake 2014 Pearson Education, Inc.– Glomar Challenger drilling ship– Core collection in deep water– Confirmed existence of sea floor spreading Ocean floor age Sediment thickness Magnetic polarity 2014 Pearson Education, Inc.Paleoceanography and Marine Sediments Paleoceanography– study of how ocean,atmosphere, and landinteractions have producedchanges in ocean chemistry,circulation, biology, andclimate Marine sediments provideclues to past changes. 2014 Pearson Education, Inc.2

2/16/2014Marine Sediment Classification Classified by originLithogenous – derived from landBiogenous – derived from organismsHydrogenous or Authigenic – derived from waterCosmogenousg– derived from outer spacep 2014 Pearson Education, Inc.Lithogenous Sediments Small particles eroded and transported Carried to oceanLithogenous Sediments Eroded rock fragments from landAlso called terrigenousReflect composition of rock from which derivedProduced by weathering– Breaking of rocks into smaller pieces 2014 Pearson Education, Inc.Relationship of fine-grainedquartz and prevailing winds– Streams– Wind– GlaciersGl i– Gravity Greatest quantity around continental margins 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.Lithogenous Sediment Transport 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.3

2/16/2014Lithogenous Sediments Reflect composition ofrock from whichderived Coarser sedimentscloser to shore Finer sedimentsfarther from shore Mainly mineral quartz(SiO2) 2014 Pearson Education, Inc.Figure 4.3 2014 Pearson Education, Inc.Lithogenous sediments 2014 Pearson Education, Inc.Lithogenous sediments 2014 Pearson Education, Inc.Lithogenous sedimentsHawaiian Green Sand“San Diego Marina” 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.4

2/16/2014Lithogenous Quartz and Wind Transport 2014 Pearson Education, Inc.Figure 4.4dFigure 4.4c 2014 Pearson Education, Inc.Grain Size One of the most important sediment properties Proportional to energy of transportation anddeposition Classified by Wentworth scale of grain size 2014 Pearson Education, Inc.Wentworth Scale of Grain Size 2014 Pearson Education, Inc.Texture and Environment Texture indicates environmental energy– High energy (strong wave action) – largerparticles– Low energy – smaller particles Larger particles closer to shore 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.5

2/16/2014SortingSediment Distribution NeriticMeasure of grain size uniformityIndicates selectivity of transportation processWell-sorted – all same size particlePoorly sorted – different size particles mixedttogetherth– Shallow-water deposits– Close to land– Dominantly lithogenous– Typicallyypy depositedpqquicklyy Pelagic– Deeper-water deposits– Finer-grained sediments– Deposited slowly 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.Neritic Lithogenous SedimentsPelagic Deposits Beach deposits Fine-grained material Accumulates slowly on deep ocean floor Pelagic lithogenous sediment from– Mainly wave-deposited quartz-rich sands Continental shelf deposits– Relict sediments Turbidite deposits– GradedG d dbbeddingddi Glacial deposits– High-latitude continental shelf– Currently forming by ice rafting 2014 Pearson Education, Inc.Pelagic Deposits– Volcanic ash (volcanic eruptions)– Wind-blown dust– Fine-grained material transported by deepocean currents 2014 Pearson Education, Inc.Figure 4.6 (top) Abyssal Clay– At least 70% clay sized particles fromcontinents– Red from oxidized iron (Fe)– Abundant if other sediments absent 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.6

2/16/2014Figure 4.6 (top)Biogenous Sediment Hard remains of once-living organisms Two major types:– Macroscopic Visible to naked eye Shells, bones, teeth– Microscopic Tiny shells or tests Biogenic ooze Mainly algae and protozoans 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.Biogenous Sediment CompositionBiogenous sediments Two most common chemical compounds:– Calcium carbonate (CaCO3)– Silica (SiO2 or SiO2·nH2O) 2014 Pearson Education, Inc.Fig. 4.5 2014 Pearson Education, Inc.Silica in Biogenous SedimentsSilica in Biogenous Sediments Diatoms Tests – shells ofmicroscopicorganisms Tests from diatomsand radiolariansgenerate siliceousooze.– Photosyntheticalgae– Diatomaceousearth Radiolarians– Protozoans– Use external food 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.7

2/16/2014Diatomaceous Earth Siliceous ooze lithifies into diatomaceous earth. Diatomaceous earth has many commercial uses.Calcium Carbonate in Biogenic Sediments Coccolithophores– Also called nanoplankton– Photosynthetic algae– Coccoliths – individualplates from deadorganismi– Rock chalk Lithified coccolith-rich ooze 2014 Pearson Education, Inc.Calcium Carbonate in Biogenic Sediments 2014 Pearson Education, Inc.Distribution of Biogenous Sediments Foraminifera– Protozoans– Use external food– Calcareous ooze Depends on three processes:– Productivity Number of organisms in surface water aboveocean floor– Destruction Skeletal remains (tests) dissolve in seawater atdepth– Dilution Deposition of other sediments decreasespercentage of biogenous sediments 2014 Pearson Education, Inc.Pelagic Deposits Siliceous ooze Accumulates in areas of high productivity Silica tests no longer dissolved by seawater whenburied by other tests 2014 Pearson Education, Inc.Neritic Deposits Dominated by lithogenous sediment, maycontain biogenous sediment Carbonate Deposits– Carbonate minerals containing CO3– Marine carbonates pprimarilyy limestone CaCO3– Most limestones contain fossil shells Suggests biogenous origin– Ancient marine carbonates constitute 25% ofall sedimentary rocks on Earth. 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.8

2/16/2014Carbonate DepositsCalcareous Ooze Stromatolites– Fine layers of carbonate– Warm, shallow-ocean, high salinity– Cyanobacteria Lived billions of years ago Modern stromatolites live near Shark Bay, Australia CCD – Calcite compensation depth– Depth where CaCO3 readily dissolves– Rate of supply rate at which the shellsdissolve Warm, shallow ocean saturated with calciumcarbonate Cool, deep ocean undersaturated withcalcium carbonate– Lysocline – depth at which a significantamount of CaCO3 begins to dissolve rapidly 2014 Pearson Education, Inc.Calcareous Ooze and the CCD 2014 Pearson Education, Inc.Calcareous Ooze and the CCD Scarce calcareous ooze below 5000 meters(16,400 feet) in modern ocean Ancient calcareous oozes at greater depths ifmoved by sea floor spreading 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.Sea Floor Spreading and SedimentAccumulationCalcareous Ooze and the Calcite Compensation Depth 2014 Pearson Education, Inc.9

2/16/2014Distribution of Modern Calcium CarbonateSediments 2014 Pearson Education, Inc.Environmental Conditions for Oozes 2014 Pearson Education, Inc.Hydrogenous Marine Sediments Minerals precipitate directly from seawater– Manganese nodules– Phosphates– Carbonates– Metal sulfidesManganese Nodules Fist-sized lumps of manganese, iron, and other metalsVery slow accumulation ratesMany commercial usesUnsure why they are not buried by seafloor sediments SmallS ll proportionti off marinei sedimentsdit Distributed in diverse environments 2014 Pearson Education, Inc.Manganese Nodules 2014 Pearson Education, Inc.Phosphates and Carbonates Phosphates– Phosphorus-bearing– Occur beneath areas in surface ocean of veryhigh biological productivity– Economically useful as fertilizer Carbonates– Aragonite and calcite– Oolites 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.10

2/16/2014Metal SulfidesEvaporites Metal sulfides Evaporites– Contain: IronNickelCopperZiZincSilverOther metals– Minerals that form when seawater evaporates– Restricted open ocean circulation– High evaporation rates– Halite (common table salt) and gypsum– Associated with hydrothermal vents 2014 Pearson Education, Inc.Evaporative Salts in Death Valley 2014 Pearson Education, Inc.Cosmogenous Marine Sediments Macroscopic meteordebris Microscopic iron-nickeland silicate spherules(small globular masses)– Tektites– Space dust Overall, insignificantproportion of marinesediments 2014 Pearson Education, Inc.K/T Boundary Core,Gulf of Mexico 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.Death Star?(look at the scale) 2014 Pearson Education, Inc.11

2/16/2014Marine Sediment Mixtures Usually mixture of different sediment types Typically one sediment type dominates in differentareas of the sea floor. 2014 Pearson Education, Inc.Pelagic and Neritic Sediment DistributionPelagic and Neritic Sediment Distribution Neritic sediments cover about ¼ of the sea floor. Pelagic sediments cover about ¾ of the sea floor. 2014 Pearson Education, Inc.Pelagic Sediment Types Distribution controlled by– Proximity to sources of lithogenous sediments– Productivity of microscopic marine organisms– Depth of water– Sea floor features 2014 Pearson Education, Inc.Sea Floor Sediments Represent SurfaceOcean Conditions 2014 Pearson Education, Inc.Worldwide Marine Sediment Thickness Microscopic tests sink slowly from surface ocean tosea floor (10–50 years) Tests could be moved horizontally Most biogenous tests clump together in fecal pellets– Fecal pellets large enough to sink quickly (10–15 days) 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.12