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Sedimentary rocks bs 1st year

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Awais Bakshy
Awais Bakshy

Sedimentary rocks form from the compaction and cementation of sediments. There are three main types: detrital (clastic) rocks that form from lithified rock fragments and minerals, chemical rocks that precipitate directly from solution, and organic rocks that accumulate from biological debris. Sedimentary rocks provide clues about past environments and climates based on their composition, structures like cross-bedding and ripples, and any fossil content. Important resources like coal and oil are also found within sedimentary basins.

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Sediment and Sedimentary Rocks
Intro to Sedimentary Rocks • Produced from weathering products of pre-existing rocks or accumulated biological matter – Detrital (clastic) rocks produced from rock fragments – Chemical rocks produced by precipitation of dissolved ions in water – Organic rocks produced by accumulation of biological debris, such as in swamps or bogs • Sedimentary rock types and sedimentary structures within the rocks give clues to past environments • Fossils in sedimentary rocks give clues to the history of life • Important resources (coal, oil) are found in sedimentary rocks
Sediment • Sediment - loose, solid particles originating from: – Weathering and erosion of pre-existing rocks – Chemical precipitation from solution, including secretion by organisms in water • Classified by particle size – Boulder - >256 mm – Cobble - 64 to 256 mm – Pebble - 2 to 64 mm – Sand - 1/16 to 2 mm – Silt - 1/256 to 1/16 mm – Clay - <1/256 mm
From Sediment to Sedimentary Rock • Transportation – Movement of sediment away from its source, typically by water, wind, or ice – Rounding of particles occurs due to abrasion during transport – Sorting occurs as sediment is separated according to grain size by transport agents, especially running water – Sediment size decreases with increased transport distance
• Deposition – Settling and coming to rest of transported material – Accumulation of chemical or organic sediments, typically in water – Environment of deposition is the location in which deposition occurs • Deep sea floor • Beach • Desert dunes • River channel • Lake bottom From Sediment to Sedimentary Rock
• Preservation – Sediment must be preserved, as by burial with additional sediments, in order to become a sedimentary rock • Lithification – General term for processes converting loose sediment into sedimentary rock – Combination of compaction and cementation From Sediment to Sedimentary Rock
Types of Sedimentary Rocks • Detrital (clastic) sedimentary rocks – Most common sedimentary rock type – Form from cemented sediment grains that come from pre-existing rocks • Chemical sedimentary rocks – Have crystalline textures – Form by precipitation of minerals from solution • Organic sedimentary rocks – Accumulate from remains of
 Sandstones  Conglomerate s  Breccia  Shale/mudsto nes TYPES OF SEDIMENTARY ROCKS Clastic rocks Chemical & Organic rocks Evaporitic rocks These rocks are formed due to evaporation of saline water (sea water) eg. Gypsum, Halit (rock salt) Carbonate rocks Form basically from CaCO3 – both by chemical leaching and by organic source (biochemical) eg. Limestone; dolomite Organic rocks Form due to decomposition of organic remains under temperature and pressure eg. Coal/Lignite etc.
 formed from broken rock fragments weathered and eroded by river, glacier, wind and sea waves. These clastic sediments are found deposited on floodplains, beaches, in desert and on the sea floors. CLASTIC ROCKS Clastic rockssolidify • Clastic rocks are classified on the basis of the grain size: conglomerate, sandstone, shale etc.
Gravel >256-2 mm Sand 2- 0.062 mm Clay <0.004 mm Silt 0.062-0.004 mm Boulder: >256mm Cobble: 64-256 mm Pebble: 4-64 mm Granule: 2-4mm Fine gravel
 Clastic rocks mainly comprise broken fragment of older rock – they are also know as Terrigenous rocks
Any rock fragment (size is > 4 mm=Pebble) Fine-gravel/ Granule (size <4mm) Matrix: is the finer grains or material that surrounds the larger clasts. It consist of either clay, silt and sand. Cement: dissolved substance that bounds the sediments. 1. Calcareou s 2. siliceous
Degree of roundness helps in knowing the distance of transportation •Angular clasts- short distance transport from the source •Rounded clasts- long distance transport
When clastic fragments are cemented or undergo consolidation they are called CONGLOMERATES Similarly when angular clasts undergo consolidation they are called BRECCIA
Sorting of the sediments also suggest the mode of deposition and transportation. Long distance transport= well-rounded and well-sorted sediments, Short distance transport = poorly sorted angular grains. Also helps in knowing the energy conditions of the river.
Clastic Process
Examples of clastic sedimentary rocks include CONGLOMERATE BRECCIA SANDSTONESHALE
Clastic Sedimentary Rocks • Breccia and Conglomerate – Coarse-grained clastic sedimentary rocks – The individual grains are larger than 2 mm – Sedimentary breccia composed of coarse, angular rock fragments cemented together – Conglomerate composed of rounded gravel cemented together • Sandstone – Medium-grained clastic sedimentary rock – The individual grains of sandstone ranges from 0.062 to 2 mm – Types determined by composition • Quartz sandstone - >90% quartz grains • Arkose - mostly feldspar and quartz grains • Graywacke - sand grains surrounded by dark, fine- grained matrix, often clay-rich
Clastic Sedimentary Rocks • Shale – Fine-grained clastic sedimentary rock – Splits into thin layers (fissile) – Silt- and clay-sized grains – Sediment deposited in lake bottoms, river deltas, floodplains, and on deep ocean floor • Siltstone – Slightly coarser-grained than shales – Lacks fissility • Claystone – Predominantly clay-sized grains; non- fissile • Mudstone – Silt- and clay-sized grains; massive/blocky
2. Non-Clastic contain 2 types: chemical and biochemical CHEMICAL Sedimentary Rocks are made from mineral crystals that formed from chemicals dissolved in water. Here’s How They Form: •The water in the oceans, lakes, and underground is often full of dissolved minerals like halite and calcite. •Water evaporates leaving the solids behind: rock salt is formed when salt is left after evaporation and limestone is formed when calcite is left behind
Limestone Cave Chemical Sedimentary Rocks are also formed in caves where mineral-rich water drips from the ceiling, creating stalactites and stalagmites made out of limestone Limestone Examples of chemical sedimentary rocks include limestone and rock salt
BIOCHEMICAL OR ORGANIC Sedimentary Rocks are made from remains of once-living plants or animals (organic matter) COQUINA Made from shells CHALK Made from dead animals Biochemical sedimentary rocks include: coquina, chalk, coal and limestone •this is the sedimentary rock type with the most fossils •will be found near areas of lots of biological activity COAL Made from dead plants LIMESTONE with fossils in it
Chemical Sedimentary Rocks • Carbonates – Contain CO3 as part of their chemical composition – Limestone is composed mainly of calcite • Most are biochemical, but can be inorganic • Often contain easily recognizable fossils • Chemical alteration of limestone in Mg-rich water solutions can produce dolomite • Chert – Hard, compact, fine-grained, formed almost entirely of silica – Can occur as layers or as lumpy nodules within other sedimentary rocks, especially limestones • Evaporites – Form from evaporating saline waters (lake, ocean) – Common examples are rock gypsum, rock salt
Organics in Sedimentary Rocks • Coal – Sedimentary rock forming from compaction of partially decayed plant material – Organic material deposited in water with low oxygen content (i.e., stagnant) • Oil and natural gas – Originate from organic matter in marine sediment – Subsurface “cooking” can change organic solids to oil and natural gas – Can accumulate in porous overlying rocks
Sedimentary Structures • Bedding • Cross-bedding • Ripple marks • Graded bedding • Mud cracks • Sedimentary structures – Features within sedimentary rocks produced during or just after sediment deposition – Provide clues to how and where deposition of sediments occurred
• Bedding • Layers in sedimentary rocks, caused by changes in composition or grain size.
Sedimentary Structures • Cross-bedding – Series of thin, inclined layers within a horizontal bed of rock – Common in sandstones – Indicative of deposition in ripples, bars, dunes, deltas
• Ripple marks – Small ridges formed on surface of sediment layer by moving wind or water
• Graded bedding – Progressive decrease in grain size from bottom to top of a bed
• Mud cracks – Polygonal cracks formed in fine grained muddy sediments when they dried. – They are preserved when new sediments are deposited in these cracks
Sedimentary Rock Interpretation • Sedimentary rocks give important clues to the geologic history of an area • Source area – Locality that eroded and provided sediment – Sediment composition, shape, size and sorting are indicators of source rock type and relative location • Depositional environment – Location where sediment came to rest – Sediment characteristics and sedimentary structures (including fossils) are indicators – Examples: glacial valleys, alluvial fans, river channels and floodplains, lakes, deltas, beaches, dunes, shallow marine, reefs, deep marine
Plate Tectonics and Sedimentary Rocks • Tectonic setting plays key role in the distribution of sedimentary rocks • Occurrence of specific sedimentary rock types can be used to reconstruct past plate- tectonic settings • Erosion rates and depositional characteristics give clues to each type of tectonic

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Sedimentary rocks bs 1st year

  • 2. Intro to Sedimentary Rocks • Produced from weathering products of pre-existing rocks or accumulated biological matter – Detrital (clastic) rocks produced from rock fragments – Chemical rocks produced by precipitation of dissolved ions in water – Organic rocks produced by accumulation of biological debris, such as in swamps or bogs • Sedimentary rock types and sedimentary structures within the rocks give clues to past environments • Fossils in sedimentary rocks give clues to the history of life • Important resources (coal, oil) are found in sedimentary rocks
  • 3. Sediment • Sediment - loose, solid particles originating from: – Weathering and erosion of pre-existing rocks – Chemical precipitation from solution, including secretion by organisms in water • Classified by particle size – Boulder - >256 mm – Cobble - 64 to 256 mm – Pebble - 2 to 64 mm – Sand - 1/16 to 2 mm – Silt - 1/256 to 1/16 mm – Clay - <1/256 mm
  • 4. From Sediment to Sedimentary Rock • Transportation – Movement of sediment away from its source, typically by water, wind, or ice – Rounding of particles occurs due to abrasion during transport – Sorting occurs as sediment is separated according to grain size by transport agents, especially running water – Sediment size decreases with increased transport distance
  • 5. • Deposition – Settling and coming to rest of transported material – Accumulation of chemical or organic sediments, typically in water – Environment of deposition is the location in which deposition occurs • Deep sea floor • Beach • Desert dunes • River channel • Lake bottom From Sediment to Sedimentary Rock
  • 6. • Preservation – Sediment must be preserved, as by burial with additional sediments, in order to become a sedimentary rock • Lithification – General term for processes converting loose sediment into sedimentary rock – Combination of compaction and cementation From Sediment to Sedimentary Rock
  • 7. Types of Sedimentary Rocks • Detrital (clastic) sedimentary rocks – Most common sedimentary rock type – Form from cemented sediment grains that come from pre-existing rocks • Chemical sedimentary rocks – Have crystalline textures – Form by precipitation of minerals from solution • Organic sedimentary rocks – Accumulate from remains of
  • 8.  Sandstones  Conglomerate s  Breccia  Shale/mudsto nes TYPES OF SEDIMENTARY ROCKS Clastic rocks Chemical & Organic rocks Evaporitic rocks These rocks are formed due to evaporation of saline water (sea water) eg. Gypsum, Halit (rock salt) Carbonate rocks Form basically from CaCO3 – both by chemical leaching and by organic source (biochemical) eg. Limestone; dolomite Organic rocks Form due to decomposition of organic remains under temperature and pressure eg. Coal/Lignite etc.
  • 9.  formed from broken rock fragments weathered and eroded by river, glacier, wind and sea waves. These clastic sediments are found deposited on floodplains, beaches, in desert and on the sea floors. CLASTIC ROCKS Clastic rockssolidify • Clastic rocks are classified on the basis of the grain size: conglomerate, sandstone, shale etc.
  • 10. Gravel >256-2 mm Sand 2- 0.062 mm Clay <0.004 mm Silt 0.062-0.004 mm Boulder: >256mm Cobble: 64-256 mm Pebble: 4-64 mm Granule: 2-4mm Fine gravel
  • 11.  Clastic rocks mainly comprise broken fragment of older rock – they are also know as Terrigenous rocks
  • 12. Any rock fragment (size is > 4 mm=Pebble) Fine-gravel/ Granule (size <4mm) Matrix: is the finer grains or material that surrounds the larger clasts. It consist of either clay, silt and sand. Cement: dissolved substance that bounds the sediments. 1. Calcareou s 2. siliceous
  • 13. Degree of roundness helps in knowing the distance of transportation •Angular clasts- short distance transport from the source •Rounded clasts- long distance transport
  • 14. When clastic fragments are cemented or undergo consolidation they are called CONGLOMERATES Similarly when angular clasts undergo consolidation they are called BRECCIA
  • 15. Sorting of the sediments also suggest the mode of deposition and transportation. Long distance transport= well-rounded and well-sorted sediments, Short distance transport = poorly sorted angular grains. Also helps in knowing the energy conditions of the river.
  • 17. Examples of clastic sedimentary rocks include CONGLOMERATE BRECCIA SANDSTONESHALE
  • 18. Clastic Sedimentary Rocks • Breccia and Conglomerate – Coarse-grained clastic sedimentary rocks – The individual grains are larger than 2 mm – Sedimentary breccia composed of coarse, angular rock fragments cemented together – Conglomerate composed of rounded gravel cemented together • Sandstone – Medium-grained clastic sedimentary rock – The individual grains of sandstone ranges from 0.062 to 2 mm – Types determined by composition • Quartz sandstone - >90% quartz grains • Arkose - mostly feldspar and quartz grains • Graywacke - sand grains surrounded by dark, fine- grained matrix, often clay-rich
  • 19. Clastic Sedimentary Rocks • Shale – Fine-grained clastic sedimentary rock – Splits into thin layers (fissile) – Silt- and clay-sized grains – Sediment deposited in lake bottoms, river deltas, floodplains, and on deep ocean floor • Siltstone – Slightly coarser-grained than shales – Lacks fissility • Claystone – Predominantly clay-sized grains; non- fissile • Mudstone – Silt- and clay-sized grains; massive/blocky
  • 20. 2. Non-Clastic contain 2 types: chemical and biochemical CHEMICAL Sedimentary Rocks are made from mineral crystals that formed from chemicals dissolved in water. Here’s How They Form: •The water in the oceans, lakes, and underground is often full of dissolved minerals like halite and calcite. •Water evaporates leaving the solids behind: rock salt is formed when salt is left after evaporation and limestone is formed when calcite is left behind
  • 21. Limestone Cave Chemical Sedimentary Rocks are also formed in caves where mineral-rich water drips from the ceiling, creating stalactites and stalagmites made out of limestone Limestone Examples of chemical sedimentary rocks include limestone and rock salt
  • 22. BIOCHEMICAL OR ORGANIC Sedimentary Rocks are made from remains of once-living plants or animals (organic matter) COQUINA Made from shells CHALK Made from dead animals Biochemical sedimentary rocks include: coquina, chalk, coal and limestone •this is the sedimentary rock type with the most fossils •will be found near areas of lots of biological activity COAL Made from dead plants LIMESTONE with fossils in it
  • 23. Chemical Sedimentary Rocks • Carbonates – Contain CO3 as part of their chemical composition – Limestone is composed mainly of calcite • Most are biochemical, but can be inorganic • Often contain easily recognizable fossils • Chemical alteration of limestone in Mg-rich water solutions can produce dolomite • Chert – Hard, compact, fine-grained, formed almost entirely of silica – Can occur as layers or as lumpy nodules within other sedimentary rocks, especially limestones • Evaporites – Form from evaporating saline waters (lake, ocean) – Common examples are rock gypsum, rock salt
  • 24. Organics in Sedimentary Rocks • Coal – Sedimentary rock forming from compaction of partially decayed plant material – Organic material deposited in water with low oxygen content (i.e., stagnant) • Oil and natural gas – Originate from organic matter in marine sediment – Subsurface “cooking” can change organic solids to oil and natural gas – Can accumulate in porous overlying rocks
  • 25. Sedimentary Structures • Bedding • Cross-bedding • Ripple marks • Graded bedding • Mud cracks • Sedimentary structures – Features within sedimentary rocks produced during or just after sediment deposition – Provide clues to how and where deposition of sediments occurred
  • 26. • Bedding • Layers in sedimentary rocks, caused by changes in composition or grain size.
  • 27. Sedimentary Structures • Cross-bedding – Series of thin, inclined layers within a horizontal bed of rock – Common in sandstones – Indicative of deposition in ripples, bars, dunes, deltas
  • 28. • Ripple marks – Small ridges formed on surface of sediment layer by moving wind or water
  • 29. • Graded bedding – Progressive decrease in grain size from bottom to top of a bed
  • 30. • Mud cracks – Polygonal cracks formed in fine grained muddy sediments when they dried. – They are preserved when new sediments are deposited in these cracks
  • 31. Sedimentary Rock Interpretation • Sedimentary rocks give important clues to the geologic history of an area • Source area – Locality that eroded and provided sediment – Sediment composition, shape, size and sorting are indicators of source rock type and relative location • Depositional environment – Location where sediment came to rest – Sediment characteristics and sedimentary structures (including fossils) are indicators – Examples: glacial valleys, alluvial fans, river channels and floodplains, lakes, deltas, beaches, dunes, shallow marine, reefs, deep marine
  • 32. Plate Tectonics and Sedimentary Rocks • Tectonic setting plays key role in the distribution of sedimentary rocks • Occurrence of specific sedimentary rock types can be used to reconstruct past plate- tectonic settings • Erosion rates and depositional characteristics give clues to each type of tectonic