Chapter 5 Slides

Chapter 5 Slides - Geology 1001 PHYSICAL GEOLOGY Chapter 5...

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Unformatted text preview: Geology 1001 PHYSICAL GEOLOGY Chapter 5 Sedimentation: Rocks Formed by Surface Processes Sedimentary Rocks Are composed of sediments: Solid material that has settled from suspension. Sediments In General: All sediments have a source where they are created. All sediments are transported by surface processes. All sediments are deposited as they settle from suspension in an environment. 1 2 3 Types of Sediment: Clastic Clastic Sediments produced by weathering of prepreexisting rocks. rocks. Types of Sediment: Clastic Physical Weathering: big rocks mechanically fragmented or broken into smaller particles. 4 Types of Sediment: Clastic Chemical Weathering: components of rocks are chemically altered or dissolved. Type of Sediments: Clastic Erosion by wind, water, ice, or gravity mobilizes the particles. Type of Sediments: Clastic Particles are deposited in a sink they settle out of suspension. 5 Type of Sediments: Clastic Type of Sediments: Clastic Sediment source is outside of the basin of deposition Classified by grain size, sorting, and roundness. size, 6 Grain size is determined by current strength. strength. Grain size is determined by current strength. Grain size is determined by current strength. 7 Grain size is determined by current strength. Classified by grain size, sorting, and roundness. sorting, Sorting: Size distribution of sediments. Sorting: Grain sorting is determined by transport distance. Poorly sorted Moderately sorted Well sorted 8 Roundness is determined by transport distance Grains: Trends Size decreases away from the source area. Sorting increases away from the source area. Roundness increases away from the source area. Types of Sediment: Chemical Chemical Sediments produced by precipitation of dissolved solids. solids. Most commonly associated with evaporation. 9 Types of Sediment: Chemical Sediment source is within the basin of deposition Classified by the chemical composition of sediments Halite, NaCl Gypsum, CaSO4 * 2H2O Types of Sediment: Biological Biological Sediments secreted by biological activity. activity. 10 Types of Sediment: Biological Sediment source is within the basin of deposition Classified by the chemical composition and/or the size of sediments. sediments. Silica: SiO2 Calcite & Aragonite: CaCO3 11 The agent of transport (wind, water, air) and its strength (strong, moderate, weak). The type (fresh vs. salt) and amount of water. Topography (mountain, lowland, coastal plain, shallow ocean, deep ocean). 12 Biological Activity (Reef formers, shell producers) Climate (arid, humid, polar, etc.) Sedimentary Environments: 3 general types Continental or nonmarine: land and freshwater nonmarine: environments. Marine: ocean (saltwater) environments. Marine: Shoreline or transitional: separate continental transitional: and marine environments. 13 Continental Environments: Topography and Climate Lakes: Arid or Humid 14 Continental Environments: Topography and Climate Alluvial: River-transported sediments River- 15 Continental Environments: Topography and Climate Desert: Wind-blown sediments Wind- 16 Continental Environments: Topography and Climate Glacial: Ice-transported sediments Ice- 17 Sediment types: generalizations Clastic sedimentary environments: land-derived landsediments or terrigenous sediments Chemical sedimentary environments: arid (evaporites) or swamps (coals) evaporites) Biological Sedimentary: organic Carbonate (CaCO3) and siliceous (SiO2) remains 18 Shoreline environments: Ocean vs. River Deltaic Environments 19 Shoreline environments: Ocean vs. River Tidal Flat Environments Pacific Coast of South America Persian Gulf (border of Kuwait and Saudi Arabia) ) 20 Shoreline environments: Ocean vs. River Beach Environments 21 Marine Environments: Depth, distance from shore Shelf Environments Clastic (SiO2) shelf Carbonate (CaCO3) shelf 22 Marine Environments: Depth, distance from shore Organic Reefs 23 Marine Environments: Depth, distance from shore Deep Sea Environment 24 From Sediment to Rock Heat, Pressure, and Time From Sediment To Rock Diagenesis: Sum of physical and chemical Diagenesis: changes that converts sediments to rock Lithification: hardening of soft sediment into Lithification: rock. Deposition is the starting point. 25 From Sediment To Rock Some sediments are lithified at shallow depths From Sediment To Rock or lithified at significant depth Compaction Weight of overlying sediments Compaction 5060% water HEAT ROCK 1020% water 26 Cementation WATER & MINERALS ROCK Clastic Sedimentary Rocks: know them! Carbonate Sedimentary Rocks Warm: Tropical or subtropical 20N - 20 S latitude 20 27 Carbonate Sedimentary Rocks Shallow, Clear: Within the photic zone, up to 200 m. Great Bahama Bank 28 Carbonate Sedimentary Rocks Limestone: Composed of CaCO3, either Limestone: calcite or aragonite. Carbonate Sedimentary Rocks Dolostone: Composed of recrystallized Dolostone: CaCO3, called dolomite (CaMg(CO3)2. Chemical Sedimentary Rocks Evaporites: Evaporites: Halite, NaCl & Gyprock, CaSO4 * 2H2O Gyprock, 29 "Other" Sedimentary Rocks Other" Chert/Flint: Composed of siliceous sediment SiO2 Chert/Flint: "Other" Sedimentary Rocks Other" Chert/Flint: Composed of siliceous sediment SiO2 Chert/Flint: "Other" Sedimentary Rocks Other" Mesabi Iron District, Northern Minnesota. 30 "Other" Sedimentary Rocks Other" Iron Formations: Fe-Oxide accumulations. Fe- "Other" Sedimentary Rocks Other" Coal: Composed of altered plant material Carbon "Other" Sedimentary Rocks Other" Coal (in Tons) produced by County 31 ...
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