Chapter Overview Marine Sediments Marine Sediment Classification
Chapter Overview Marine Sediments Marine Sediment Classification
Chapter Overview Marine Sediments Marine Sediment Classification
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
CHAPTER 4<strong>Marine</strong> <strong><strong>Sediment</strong>s</strong>Paleoceanography and <strong>Marine</strong><strong><strong>Sediment</strong>s</strong>• Paleoceanography – study of how ocean,atmosphere, and land interactions haveproduced changes in ocean chemistry,circulation, biology, and climate– <strong>Marine</strong> sediments provide clues to pastchanges.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.<strong>Chapter</strong> <strong>Overview</strong>• <strong>Marine</strong> sediments contain a record ofEarth history.• <strong>Marine</strong> sediments provide a variety ofimportant resources.• <strong>Marine</strong> sediments have a variety of origins.<strong>Marine</strong> <strong>Sediment</strong> <strong>Classification</strong>• Classified by origin• Lithogenous – derived from land• Biogenous – derived from organisms• Hydrogenous or Authigenic – derivedfrom water• Cosmogenous – derived from outerspace© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.<strong>Marine</strong> <strong><strong>Sediment</strong>s</strong><strong>Marine</strong><strong><strong>Sediment</strong>s</strong>• Eroded rock particlesand fragments– Transported to ocean• Deposit by settlingthrough watercolumn• Oceanographersdecipher Earthhistory throughstudying sediments.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.
Lithogenous <strong><strong>Sediment</strong>s</strong>• Eroded rock fragmentsfrom land• Also called terrigenous• Reflect composition ofrock from which derived• Produced byweathering– Breaking of rocksinto smaller piecesLithogenous <strong><strong>Sediment</strong>s</strong>• Reflect composition ofrock from which derived• Coarser sedimentscloser to shore• Finer sediments fartherfrom shore• Mainly mineral quartz(SiO 2 )© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Lithogenous <strong><strong>Sediment</strong>s</strong>• Small particles eroded and transported• Carried to ocean– Streams–Wind– Glaciers–Gravity• Greatest quantity around continentalmarginsLithogenous Quartz and WindTransport© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Lighogenous <strong>Sediment</strong>TransportGrain Size• Proportional to energy of transportation anddeposition© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.
<strong>Sediment</strong> Texture• Grain size sorting– Indication of selectivity of transportationand deposition processes• Textural maturity– Increasing maturity if• Clay content decreases• Sorting increases• Non-quartz minerals decrease• Grains are more rounded (abraded)Pelagic Deposits• Fine-grained material• Accumulates slowly on deep ocean floor• Pelagic lithogenous sediment from– Volcanic ash (volcanic eruptions)– Wind-blown dust– Fine-grained material transported by deepocean currents© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.<strong>Sediment</strong> Distribution• Neritic– Shallow-water deposits– Close to land– Dominantly lithogenous– Typically deposited quickly• Pelagic– Deeper-water deposits– Finer-grained sediments– Deposited slowlyPelagic Deposits• Abyssal Clay– At least 70% clay sized particles fromcontinents– Red from oxidized iron (Fe)– Abundant if other sediments absent© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Neritic Lithogenous <strong><strong>Sediment</strong>s</strong>• Beach deposits– Mainly wave-deposited quartz-rich sands• Continental shelf deposits– Relict sediments• Turbidite deposits– Graded bedding• Glacial deposits– High latitude continental shelf– Currently forming by ice raftingBiogenous <strong>Sediment</strong>• 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© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.
Biogenous <strong>Sediment</strong>Composition• Two most common chemical compounds:– Calcium carbonate (CaCO 3 )– Silica (SiO 2 or SiO 2·nH 2 O)Calcium Carbonate in Biogenic<strong><strong>Sediment</strong>s</strong>• Coccolithophores– Also callednannoplankton– Photosynthetic algae– Coccoliths – individualplates from deadorganism– Rock chalk• Lithified coccolithrichooze© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Silica in Biogenous <strong><strong>Sediment</strong>s</strong>•Diatoms– Photosyntheticalgae– Diatomaceousearth• Radiolarians– Protozoans– Use externalfoodCalcium Carbonate in Biogenic<strong><strong>Sediment</strong>s</strong>• Foraminifera– Protozoans– Use externalfood– Calcareous ooze© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Silica in Biogenous <strong><strong>Sediment</strong>s</strong>• Tests from diatomsand radiolariansgenerate siliceousooze.• Siliceous ooze lithifiesinto diatomaceousearth.Distribution of Biogenous<strong><strong>Sediment</strong>s</strong>• Depends on three processes:– Productivity– Destruction– Dilution© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.
Neritic Deposits• Dominated by lithogenous sediment, maycontain biogenous sediment• Carbonate Deposits– Carbonate minerals containing CO 3– <strong>Marine</strong> carbonates primarily limestone –CaCO 3– Most limestones contain fossil shells• Suggests biogenous origin– Ancient marine carbonates constitute 25% ofall sedimentary rocks on Earth.Calcareous Oozeand theCCD© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Carbonate Deposits• Stromatolites– Fine layers ofcarbonate– Warm, shallow-ocean,high salinity– CyanobacteriaCalcareous 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© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Calcareous Ooze and the CCD• CCD – Calcite compensation depth– Depth where CaCO 3 readily dissolves– Rate of supply = rate at which the shellsdissolve• Warm, shallow ocean saturated withcalcium carbonate• Cool, deep ocean undersaturated withcalcium carbonate– Lysocline – depth at which a significantamount of CaCO 3 begins to dissolve rapidly© 2011 Pearson Education, Inc.Sea Floor Spreading and <strong>Sediment</strong>Accumulation© 2011 Pearson Education, Inc.
Cosmogenous <strong>Marine</strong><strong><strong>Sediment</strong>s</strong>• Macroscopicmeteor debris• Microscopic ironnickeland silicatespherules (smallglobular masses)– Tektites– Space dust• Overall,insignificantproportion ofmarine sediments© 2011 Pearson Education, Inc.Pelagic and Neritic <strong>Sediment</strong>Distribution• Distribution controlled by– Proximity to sources of lithogenoussediments– Productivity of microscopic marineorganisms– Depth of water– Sea floor features© 2011 Pearson Education, Inc.<strong>Marine</strong> <strong>Sediment</strong> Mixtures• Usually mixture of different sediment types• Typically one sediment type dominates in different areasof the sea floor.Pelagic <strong>Sediment</strong> Types© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Pelagic and Neritic <strong>Sediment</strong> Distribution• Neritic sediments cover about ¼ of the sea floor.• Pelagic sediments cover about ¾ of the sea floor.Sea Floor <strong><strong>Sediment</strong>s</strong> RepresentSurface Ocean Conditions• Microscopic tests sinkslowly from surfaceocean to sea floor(10-50 years)• Tests could bemoved horizontally• Most biogenoustests clump togetherin fecal pellets– Fecal pellets largeenough to sinkquickly (10-15 days)© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.
Worldwide <strong>Marine</strong> <strong>Sediment</strong> ThicknessDistribution of ManganeseNodules© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Resources from <strong>Marine</strong><strong><strong>Sediment</strong>s</strong>• Energy resources– Petroleum• Mainly from continental shelves– Gas hydrates• Sand and gravel (including tin, gold, andso on)• Evaporative salts• Phosphorite• Manganese nodules and crusts© 2011 Pearson Education, Inc.End of CHAPTER 4<strong>Marine</strong> <strong><strong>Sediment</strong>s</strong>© 2011 Pearson Education, Inc.Mining Sea Salt© 2011 Pearson Education, Inc.