Types of Sedimentary Rocks Section 6.2

Clastic Most common Most common Form from abundant sediments at Earth’s surface Form from abundant sediments at Earth’s surface Klastos means broken Klastos means broken Further classified by size Further classified by size

Coarse-Grained Rocks Includes gravel-sized rocks and mineral fragments Includes gravel-sized rocks and mineral fragments Gravel has to be transported by high- energy water or glaciers Gravel has to be transported by high- energy water or glaciers During transport they become well- rounded (beach and river gravel) During transport they become well- rounded (beach and river gravel) Lithification turns these sediments into conglomerates with rounded gravel sized paticles Lithification turns these sediments into conglomerates with rounded gravel sized paticles

Coarse-Grained Rocks Breccias consist of angular, gravel-sized particles Breccias consist of angular, gravel-sized particles Particles transported a short distance and deposited close to the source Particles transported a short distance and deposited close to the source Do not have time to become rounded Do not have time to become rounded

Medium-Grained Rocks Contain sand-sized rock and mineral fragments Contain sand-sized rock and mineral fragments Sandstone can indicate the direction of current flow; used to map ancient stream and river channels Sandstone can indicate the direction of current flow; used to map ancient stream and river channels High porosity - % of open spaces between grains in rock High porosity - % of open spaces between grains in rock Valuable for oil, natural gas, and ground water Valuable for oil, natural gas, and ground water

Fine-Grained Rocks Consist of silt and clay-sized particles Consist of silt and clay-sized particles Includes siltstone and shale Includes siltstone and shale Develop in still or slow-moving water Develop in still or slow-moving water Low porosity Low porosity Hinders the movement of groundwater and oil Hinders the movement of groundwater and oil

Chemical Formation involves the evaporation and precipitation of minerals Formation involves the evaporation and precipitation of minerals Minerals dissolved into lakes and oceans are left behind when water evaporates Minerals dissolved into lakes and oceans are left behind when water evaporates Example: The Great Salt Lake Example: The Great Salt Lake

Chemical Sedimentary Rocks Evaporites are layers of chemical sedimentary rocks that settle to the bottom of a body of water Evaporites are layers of chemical sedimentary rocks that settle to the bottom of a body of water Little freshwater flows into these areas causing the concentration of dissolved minerals to remain high Little freshwater flows into these areas causing the concentration of dissolved minerals to remain high

Biochemical Biochemical SR are formed from the remains of once-living organisms Biochemical SR are formed from the remains of once-living organisms Limestone is most common (mainly calcite); found in shallow water environments Limestone is most common (mainly calcite); found in shallow water environments What is siliceous ooze? What is siliceous ooze?