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Sedimentary Rocks

Sedimentary Rocks. Sedimentary rock is formed by erosion Sediments are moved from one place to another Sediments are deposited in layers, with the older ones on the bottom

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Sedimentary Rocks

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  1. Sedimentary Rocks • Sedimentary rock is formed by erosion • Sediments are moved from one place to another • Sediments are deposited in layers, with the older ones • on the bottom • The layers become compacted and cemented together http://www.fi.edu/fellows/payton/rocks/create/sediment.htm

  2. Sedimentary Rock • Sedimentary Rocks are formed at or near the Earth’s surface • No heat and pressure involved • Strata – layers of rock • Stratification – the process in which sedimentary rocks are arranged in layers

  3. Sediments -pieces of material left by: *wind *ice *chemical precipitation *water *gravity Step 1: WEATHERING Chemical- minerals are chemically broken down

  4. * Physical – minerals remain chemically unchanged

  5. Step 2: EROSION * transporting weathered materials to another location * Wind, water, gravity and glaciers transport

  6. Step 3: DEPOSITION * sediments are deposited and sorted

  7. Step 4: BURIAL * deposited into depressions called “sedimentary basins” * the deeper it gets, the more pressure on it til…… 2 ROCK BURIAL

  8. Step 5 : LITHIFICATION (FYI – lithos: Greek for stone) * physical and chemical process that changes it to sedimentary rock 1st Compaction 2ndCementation & Solidification new minerals precipitate more of the same type around existing ones crystallize around existing ones

  9. FEATURES OF SEDIMENTARY ROCKS BEDDING – *horizontal layers *if sorted, graded bedding CROSS-BEDDING - *inclined layers move forward like sand dunes

  10. RIPPLE MARKS * when sediment is moved into small ridges by wind or wave action * back & forth waves yield symmetrical waves * currents, (like in rivers) asymmetrical waves Sand dune – ripple marks from wind

  11. Asymmetrical ripple marks

  12. FOSSILS *animals die, buried, lithified * some plants replaced by other minerals * shells, bones, etc. could leave impressions

  13. CONCRETIONS * lumps of fine grained silica * called chert *also called nodules CHERT

  14. MUD CRACKS *wet clay dries and contracts * cracks later fill with sediment

  15. TYPES OF SEDIMENTARY ROCKS CLASTIC formed by lithifications Coarse Medium Fine gravel sand silt & mud some rocks sandstone siltstone conlglomerates mudstone POROSITY * percent of open space between grains of sand *good reservoirs for oil, natural gas, and H2O * permeable if water can pass through

  16. Porous Rock

  17. 2. CHEMICAL a. rocks formed by evaporation - called evaporites ex: calcite, halite & gypsum S DEAD SEA SALT CALCITE

  18. b. organic sedimentary rock -formed from the remains of living things - most abundant is limestone (mostly calcite) CaCO3 from shells if shells are high in silica, they form siliceous ooze - Coal – from remains of plant material…almost entirely carbon Siliceous ooze CALCAREOUS OOZE

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