CHAPTER 4: Marine Sediments at ECC Dr. C. Dong 03/16/10 CHAPTER 4: Marine Sediments at ECC Dr. C. Dong

Marine sediments Eroded rock particles and fragments Dr. C. Dong 03/16/10 Marine sediments Eroded rock particles and fragments Transported to ocean Deposit by settling through water column Oceanographers decipher Earth history through studying sediments Dr. C. Dong

Classification of marine sediments Dr. C. Dong 03/16/10 Classification of marine sediments Classified by origin Lithogenous (derived from land) Biogenous (derived from organisms) Hydrogenous (derived from water) Also known as Authigenic Cosmogenous (derived from outer space) Dr. C. Dong

Features of marines sediments Dr. C. Dong 03/16/10 Features of marines sediments Origin Distribution Texture Composition Dr. C. Dong

Distribution of sediments Dr. C. Dong 03/16/10 Distribution of sediments Neritic Shallow water deposits Close to land Dominantly lithogenous Typically deposited quickly Pelagic Deeper water deposits Finer-grained sediments Deposited slowly Dr. C. Dong

Distribution of neritic and pelagic marine sediments Dr. C. Dong 03/16/10 Distribution of neritic and pelagic marine sediments Neritic sediments cover about ¼ of sea floor Pelagic sediments cover about ¾ Dr. C. Dong

Distribution of neritic and pelagic marine sediments Dr. C. Dong 03/16/10 Distribution of neritic and pelagic marine sediments Fig. 4.19 Dr. C. Dong

Lithogenous Sediments Origin Dr. C. Dong 03/16/10 Eroded rock fragments from land Reflect composition of rock from which derived Transported from land by Water (e.g., river-transported sediment) Wind (e.g., windblown dust) - aolian transport Ice (e.g., ice-rafted rocks) Gravity (e.g., turbidity currents) Dr. C. Dong

Lithogenous Sediments Texture Dr. C. Dong 03/16/10 Lithogenous Sediments Texture Fig. 4.5 Dr. C. Dong

Sediment texture Grain size Dr. C. Dong 03/16/10 Sediment texture Grain size Proportional to energy of transportation and deposition Table 4.2 Dr. C. Dong

Lithogenous Sediments Distribution Dr. C. Dong 03/16/10 Lithogenous Sediments Distribution Most lithogenous sediments at continental margins Coarser sediments closer to shore Finer sediments farther from shore Mainly mineral quartz (SiO2) Dr. C. Dong

Relationship of fine-grained quartz and prevailing winds Dr. C. Dong 03/16/10 Relationship of fine-grained quartz and prevailing winds Fig. 4.6b Dr. C. Dong

Neritic lithogenous sediments Dr. C. Dong 03/16/10 Neritic lithogenous sediments Beach deposits Mainly wave-deposited quartz-rich sands Continental shelf deposits Relict sediments Turbidite deposits Glacial deposits High latitude continental shelf Dr. C. Dong

Pelagic lithogenous sediments Dr. C. Dong 03/16/10 Pelagic lithogenous sediments Sources of fine material: Volcanic ash (volcanic eruptions) Wind-blown dust Fine-grained material transported by deep ocean currents Abyssal clay (red clay) Oxidized iron Abundant if other sediments absent Dr. C. Dong

Dr. C. Dong 03/16/10 Exe 09 - 01 1. How many types of marine sediments we have in terms of their orgin? 2. What features of marine sediments do we study? 3. Do we expect finer lithogenous sediments near Continental Margins or Deep-Ocean Basin?Why? Dr. C. Dong

Biogenous marine sediments (origin) Dr. C. Dong 03/16/10 Hard remains of once-living organisms Shells, bones, teeth Macroscopic (large remains) Microscopic (small remains) Tiny shells or tests settle through water column Biogenic ooze (30% or more tests) Mainly algae and protozoans Dr. C. Dong

Biogenous marine sediments (composition) Dr. C. Dong 03/16/10 Biogenous marine sediments (composition) Commonly either calcium carbonate (CaCO3) or silica (SiO2 or SiO2·nH2O) Usually planktonic (free-floating) Dr. C. Dong

Silica in biogenic sediments Dr. C. Dong 03/16/10 Silica in biogenic sediments Diatoms (algae) Photosynthetic Diatomaceous earth Radiolarians (protozoans) Use external food Siliceous ooze Fig. 4.7b Dr. C. Dong

Distribution of biogenous sediments Dr. C. Dong 03/16/10 Distribution of biogenous sediments Most common as pelagic deposits Factors controlling distribution Productivity Destruction (dissolution) Dilution Dr. C. Dong

Carbonate deposits Stromatolites Dr. C. Dong 03/16/10 Carbonate deposits Limestone (lithified carbonate sediments) Stromatolites Warm, shallow- ocean, high salinity Cyanobacteria Fig. 4.10a Dr. C. Dong

Dr. C. Dong 03/16/10 Exe 09-02 1. What is the origin of biogeonous sediments? 2. Where can majority of biogeonous sediments found? 3. What are major chemical compositions of biogeoneous sediments? Dr. C. Dong

Dr. C. Dong 03/16/10 Hydrogenous marine sediments: derived from the dissolved material in water Minerals precipitate directly from seawater Manganese nodules Phosphates Carbonates Metal sulfides Small proportion of marine sediments Distributed in diverse environments Dr. C. Dong

Iron-manganese nodules Dr. C. Dong 03/16/10 Iron-manganese nodules Fist-sized lumps of manganese, iron, and other metals Very slow accumulation rates Why are they on surface sea floor? Fig. 4.15a Dr. C. Dong

Cosmogenous marine sediments Dr. C. Dong 03/16/10 Cosmogenous marine sediments Macroscopic meteor debris Microscopic iron-nickel and silicate spherules Tektites Space dust Overall, insignificant proportion of marine sediments Dr. C. Dong

Mixtures of marine sediments Dr. C. Dong 03/16/10 Mixtures of marine sediments Usually mixture of different sediment types For example, biogenic oozes can contain up to 70% non-biogenic components Typically one sediment type dominates in different areas of the sea floor Dr. C. Dong

Marine sediments often represent ocean surface conditions Dr. C. Dong 03/16/10 Temperature Nutrient supply Abundance of marine life Atmospheric winds Ocean current patterns Volcanic eruptions Major extinction events Changes in climate Movement of tectonic plates Dr. C. Dong

Exe. 09-03 What is the origin of hydrogenous sediments? Dr. C. Dong 03/16/10 Exe. 09-03 What is the origin of hydrogenous sediments? What is the origin of cosmogenous sediments? List at least five ocean surface condition can be represented by marine sediments Dr. C. Dong