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Lecture 7 Sediments and Sedimentary Rocks Physical Geology Lecture Outline I A) B) Definitions Sediment Transportation i. ii. iii. Fluid Dynamics Modes of Transport Transport-Related Properties C) D) Deposition Lithification A) Clastic Rocks II Sedimentary Rocks i. ii. iii. Breccia and Conglomerate Sandstone Fine-Grained Clastic Rocks i. ii. Carbonates Evaporites B) Chemical Sedimentary Rocks C) Organic Sedimentary Rocks A) B) C) Source Area Depositional Environment Plate Tectonics and Sedimentary Rocks III IV Sedimentary Structures Interpretation of Sedimentary Rocks Physical Geology Definitions sediment - solid fragmental material transported and deposited by wind, water, or ice, chemically precipitated from solution, or secreted by organisms, that forms in layers in loose, unconsolidated form. unconsolidated material - A sediment that is loosely arranged or unstratified, or whose particles are not cemented together, occurring either at the surface or at depth. sedimentary rock - A layered rock resulting from the consolidation of sediment. Physical Geology Grain Size Udden-Wentworth Scale Physical Geology Sediment Transport Water Wind Gravity Ice Physical Geology Sediment Transport Fluid Dynamics Physical Geology Sediment Transport Modes of Transport Dissolved Load Suspended Load Bed Load •Saltation •Rolling (Surface Creep) Physical Geology Sediment Transport Transport-Related Properties Physical Geology Deposition of Sediment deposition - the laying-down of rock-forming material by any natural agent deposit - Earth material of any type that has accumulated through the activities of water, wind, ice, or other agents, such as precipitation. depositional environment - the location in which deposition occurs Physical Geology Deposition of Sediment Progressive Sorting Physical Geology Lithification of Sediment lithification - the conversion of newly deposited sediment into a solid rock. It may be concurrent with, soon after, or long after deposition. Cementation Compaction Crystallization Physical Geology Lithification of Sediment Compaction compaction - reduction in bulk volume or thickness of fine-grained sediments, owing to increasing weight of overlying material that is continuously being deposited, or to pressures resulting from earth movements. Tighter packing of sedimentary particles results in a decrease in porosity. Physical Geology Lithification of Sediment Cementation cementation - the process by which clastic sediments are converted into rock by precipitation of a mineral cement among the grains of the sediment. cement - chemically precipitated mineral material that occurs in the spaces among the grains of a sedimentary rock, thus binding the grains into a rigid mass. The most common cements are silica, carbonates, and iron oxides. Physical Geology Lithification of Sediment Crystallization crystallization - the development and growth of crystals by precipitation from solution at or near the Earth's surface. Physical Geology Sedimentary Rocks Clastic Chemical Organic Physical Geology Sedimentary Rocks Clastic Rocks Physical Geology Sedimentary Rocks Clastic Sedimentary Rocks - Examples conglomerate sandstone siltstone graywacke shale breccia Physical Geology Sedimentary Rocks Chemical Sedimentary Rocks Carbonates Evaporites Physical Geology Sedimentary Rocks Chemical Sedimentary Rocks - Carbonates (Bioclastic Limestones) coquina chalk coralline limestone Physical Geology Sedimentary Rocks Chemical Sedimentary Rocks - Carbonates (Inorganic Limestones) travertine oolitic limestone tufa Physical Geology Sedimentary Rocks Chemical Sedimentary Rocks - Evaporites rock salt NaCl anhydrite CaSO4 rock gypsum CaSO4. H2O Physical Geology Sedimentary Rocks Organic Sedimentary Rocks peat lignite coal Physical Geology Sedimentary Structures Definitions sedimentary structure - a feature in sedimentary rock, formed either contemporaneously with deposition (primary structure) or by later sedimentary processes (secondary structure) bedding - the arrangement of sedimentary rock in layers bedding plane - division plane that separates each successive sedimentary layer or bed from the one above or below. It commonly marks a visible change in lithology or color. formation - a body of rock strata that consists dominantly of a certain lithologic type or combinations of types. It is the fundamental lithostratigraphic unit. Formations may be combined into groups and subdivided into members. Physical Geology Sedimentary Structures Stratification Internal Structures Bedding Plane Structures Geopetal Structures Physical Geology Sedimentary Structures Stratification stratification - the arrangement of sedimentary rocks in strata; bedding. It may be indicated by differences in texture, cementation, color, or composition. Physical Geology Sedimentary Structures Stratification - Principle of Superposition Physical Geology Sedimentary Structures Stratification - Principle of Original Horizontality Physical Geology Sedimentary Structures Internal Structure graded bedding cross-stratification Physical Geology Sedimentary Structures Cross-Bedding Physical Geology Sedimentary Structures Graded Beds Physical Geology Sedimentary Structures Bedding Plane Features Mudcracks Ripples Fossils Physical Geology Bedding Plane Sedimentary Structures Ripples Lecture 7 III.F Physical Geology Bedding Plane Sedimentary Structures Mudcracks mudcrack - an irregular fracture in a crudely polygonal pattern, formed by the shrinkage of clay, silt, or mud, generally in the course of drying under surface conditions. Physical Geology Bedding Plane Sedimentary Structures Fossils Physical Geology Sedimentary Structures Geopetal Structures geopetal - pertaining to any rock feature that indicates the relation of top to bottom at the time of formation of the rock symmetric ripple marks included fragments cross-bedding graded bedding mud cracks bed surface marks scour marks fossils Physical Geology Interpretation of Sedimentary Rocks Grain Size Lecture 7 IV Physical Geology Interpretation of Sedimentary Rocks Color Physical Geology Depositional Environment Continental Transitional Marine Physical Geology Plate Tectonics and Sedimentary Rocks Passive Margin Physical Geology Plate Tectonics and Sedimentary Rocks Volcanic Island Arcs Physical Geology Plate Tectonics and Sedimentary Rocks Continental Collision
