© 2016 Cengage Learning. All Rights Reserved. 5 Oceanography, An Invitation to Marine Science | 9e Tom Garrison Sediments

© 2016 Cengage Learning. All Rights Reserved. Sediments are loose accumulations of particulate material The depth and composition of marine sediments tell us of relatively recent events in the ocean basin The most abundant sediments are terrigenous (from land) and biogenous (from once-living things) Key Concepts

© 2016 Cengage Learning. All Rights Reserved. Marine sediments have been uplifted and exposed on land (e.g., The Grand Canyon) Because marine sediments are usually subducted along with the seabed on which they lie, the oldest sediments are relatively young—rarely older than 180 million years Key Concepts

© 2016 Cengage Learning. All Rights Reserved. Particles of organic or inorganic matter that accumulate in a loose, unconsolidated form that vary according to: –Size –Source –Location –Color 5.1 Ocean Sediments Vary Greatly in Appearance

© 2016 Cengage Learning. All Rights Reserved. 5.2 Sediments Are Classified By Particle Size

© 2016 Cengage Learning. All Rights Reserved. Sediments Are Classified By Particle Size

© 2016 Cengage Learning. All Rights Reserved. 5.3 Sediments May Be Classified By Source

© 2016 Cengage Learning. All Rights Reserved. Terrigenous sediments come from land –Erosion and deposition Sediments May Be Classified By Source

© 2016 Cengage Learning. All Rights Reserved. Biogenous sediments form from the remains of marine organisms Hydrogenous sediments precipitate directly from seawater Cosmogenous sediments come from space Marine sediments are usually a combination –Terrigenous and biogenous most common Sediments May Be Classified By Source

© 2016 Cengage Learning. All Rights Reserved. Sediments May Be Classified By Source

© 2016 Cengage Learning. All Rights Reserved. Neritic – on the continental shelf Most neritic sediments are terrigenous –Currents distribute sediments along the coast –Wave action –Glacial deposits Lithification –Sediments converted to sedimentary rock Pressure-induced compaction Cementation 5.4 Neritic Sediments Overlie Continental Margins

© 2016 Cengage Learning. All Rights Reserved. Turbidites – deposited by turbidity currents Clays – most easily transported terrigenous sediment Oozes – remains of living creatures –Calcareous Foraminifers and coccolithophores Cannot exist below the CCD, dissolve –Siliceous Radiolarians, diatoms 5.5 Pelagic Sediments Vary in Composition and Thickness

© 2016 Cengage Learning. All Rights Reserved. Pelagic Sediments Vary in Composition and Thickness

© 2016 Cengage Learning. All Rights Reserved. Pelagic Sediments Vary in Composition and Thickness

© 2016 Cengage Learning. All Rights Reserved. Hydrogenous sediments precipitate out of seawater –Manganese nodules Evaporites –Include many salts Oolite sands –Form when calcium carbonate precipitates from seawater Pelagic Sediments Vary in Composition and Thickness

© 2016 Cengage Learning. All Rights Reserved. 5.6 Researchers Have Mapped the Distribution of Deep-Ocean Sediments

© 2016 Cengage Learning. All Rights Reserved. Clamshell sampler Piston corer 5.7 Geologists Use Specialized Tools to Study Ocean Sediments

© 2016 Cengage Learning. All Rights Reserved. Stratigraphy – analysis of layered deposits Paleoceanography – study of the ocean’s past –Microfossils –Dating deep-sea sediments –Relative analysis of stable isotopes 5.8 Sediments Are Historical Records of Ocean Processes

© 2016 Cengage Learning. All Rights Reserved. Components of building materials Crude oil and natural gas Sand and gravel Manganese nodules 5.9 Marine Sediments Are Economically Important

© 2016 Cengage Learning. All Rights Reserved. Sediments covering nearly all of the seafloor are parts of the great cycles of formation and destruction assured by Earth’s hot interior The position and nature of sediments provide important clues to Earth’s recent history, and valuable resources can sometimes be recovered from them Chapter in Perspective

© 2016 Cengage Learning. All Rights Reserved. What’s the relationship between deep-sea animals and the sediments on which they live? Why are flights cancelled when there’s just a hint of volcanic smoke in the air? Some Questions from Students