Chapter_4

Chapter_4 - Chapter 4 Marine Sedimentation Sediment in the...

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Chapter 4 Marine Sedimentation
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Classification of marine sediment Factors that control sedimentation We will consider the: Sedimentologists inspecting a sediment core onboard the drilling ship, Resolution . Sediment in the sea
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Marine sediments are classified based on The size of the particles The mode of formation of the particles Sediment in the sea Studying a sediment core
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Sediment Size The geologists’ grain-size scale Most of the sediment particles in the ocean are sand, silt, and clay sizes. Silt- and clay-size particles mixed together are called mud . Diameters (mm) Name > 256 Boulder 256-64 Cobble 64-4 Pebble 4-2 Granule 2-1 Very coarse sand 1-1/2 Coarse sand 1/2-1/4 Medium sand 1/4 -1/8 Fine sand 1/8 -1/16 Very fine sand 1/16 -1/256 Silt < 1/256 Clay
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Sediment Origins Based on origin, sediments are one of five types. Terrigenous Biogenic Authigenic Volcanogenic Cosmogenous
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Terrigenous sediments are derived from the land (terra). Rocks weather to small particles. These particles are transported to the ocean by both wind and rivers. Weathering and transport are called erosion . Much terrigenous sediment is deposited in river deltas. Arial view of the Atchafalaya River delta, LA.
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Biogenic particles are the skeletal remains of living organisms. Foraminifer: calcium carbonate Radiolarian: silica
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Four of the most common are: Coccolithophorids foraminifera foraminifera Radiolarians Diatoms Foraminifera
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Authigenic particles are precipitated from the water. The most common are ferro- manganese nodules. These have large potential economic value (Mn, Co, Ni, Cu, and other trace metals). Nodules are normally fist size.
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Volcanic eruptions produce volcanogenic particles. Mostly found near volcanoes Can be transported LARGE distances by wind. Major eruptions can affect sediments on a global scale.
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Chapter_4 - Chapter 4 Marine Sedimentation Sediment in the...

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