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Types of Sedimentary Rocks. Chapter 6.2. Classifications . Sedimentary rocks are classified by their mode of formation Clastic Chemical Biochemical . Clastic Sedimentary Rocks. C lassified according to size of their particles Coarse grained rocks Medium grained rocks
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Types of Sedimentary Rocks Chapter 6.2
Classifications • Sedimentary rocks are classified by their mode of formation • Clastic • Chemical • Biochemical
Clastic Sedimentary Rocks • Classified according to size of their particles • Coarse grained rocks • Medium grained rocks • Fine grained rocks
Coarse grained rocks • Gravel sized rock and mineral fragments
Conglomerates rock
Medium grained rocks • Sand sized rocks • Sandstone • Ripple marks and cross-bedding help geologists map out ancient rivers • Quartz and rock fragments • High porosity
Sandstone rock
Fine-grained rocks • Consist of silt and clay sized particles • Siltstone and shale • Environments like swamps and ponds • Still or slow moving • Accumulate in thin horizontal layers • Low porosity • Form barriers that hinder the movement of groundwater and oil
Siltstone and Shale rock
Chemical Sedimentary Rocks • Involves the processes of evaporation and precipitation of minerals • Evaporation • Minerals are left behind • Arid areas – high evaporation rates can increase concentration of dissolved minerals in bodies of water • Great Salt Lake • -common in arid regions
Biochemical • Formed from the remains of once living organisms • Limestone • Primarily calcite • Common in shallow water • Around coral reefs • May include fossils • Siliceous ooze solidifies • Coal
Limestone rock
Chert • Fine grained quartz
Calcareous tufa • Calcite