OCNG 251 Lecture 5: Marine Sediments
22 Feb 2017
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Studied by oceanographers because they are time scale of history of the earth. Over time they become lithified forming sedimentary rock. They tell us about: temperature, amount of marine life in area, water current patterns, extinction events, tectonic plate movements, nutrient supply, atmospheric winds, volcanic eruptions, climate change, mining potential. Microscopic tests sink slowly from surface of ocean to seafloor: tests= accumulation of microscopic shells, 10-50 years, tests can also be moved horizontally during descent through water column. Most biogenous tests clump together in fecal pellets: fecal pellets are large enough to sink fast (10-15 years), so most data comes from tests deposited via these pellets. Common in pelagic deposits: pelagic sediment/deposit= composed primarily of fine lithogenous and biogenous particles that is deposited slowly on deep ocean floor. Factors controlling distribution: productivity, destruction (dissolution, dilution. Grab big shovel lowered into water. Deeper samples: dredge, box core, push core (for shallow waters, deep: gravity cores, piston cores, rotary drilling.
