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Sedimentary Rocks

Sedimentary Rocks. Chapter 3 Section 3. SEDIMENTARY ROCKS. Sedimentary  sedimentum Latin for ‘settling’ Rock formed from compressed or cemented layers (DEPOSITS) of sediment. Sometimes fossils accumulate and are compacted/cemented together.

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Sedimentary Rocks

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  1. Sedimentary Rocks Chapter 3 Section 3

  2. SEDIMENTARYROCKS • Sedimentary  sedimentum Latin for ‘settling’ • Rock formed from compressedorcementedlayers (DEPOSITS) of sediment. • Sometimes fossils accumulate and are compacted/cemented together. • Contain fragments of older rocks from weathering. Canyonlands Nat. Park, Utah

  3. SEDIMENTARY FORMATION WITHIN ROCK CYCLE

  4. Formation of Sedimentary Rocks • Weathering, Erosion, and Deposition • Weathering= breaks rocks into sediments; first step in formation of sedimentary rocks (mechanical and chemical) • Erosion= water, wind, ice, gravity move weathered sediments • Deposition= when agents of erosion (listed above) lose energy sediments stop moving  deposition • Deposited according to size—largest first • Compaction and Cementation • After sediments deposited become lithified (turned to rock) • Compaction= squeezes, or compacts, sediments; caused by weight of sediments • Cementation= dissolved minerals are deposited in the tiny spaces among the sediments Conglomerate rounded pebbles cemented together • Sandstone • grains are • cemented

  5. Classifying Sedimentary Rocks Breccia: quartz; clastic • Classified into two main groups according to the way they form: • Clastic: made of weathered bits of rocks and minerals • Most common minerals found in clastic = clay (most abundant product) of chemical weathering and quartz (durable and resistant to chemical weathering • Grouped according to size of sediments: • Conglomerate = larger pebbles • Sandstone = sand sized grains • Shale = most common sed. rock; fine grained

  6. Classifying Sedimentary Rocks • Chemical/Biochemical: form when dissolved minerals precipitate (deposit in solid form) from water solutions • Precipitation generally occurs when H2O evaporates or boils off leaving solid product. • Limestone = calcite and aragonite; clear, shallow marine waters accumulation of shell coral, algal and fecal debris or CaCO3 from water • Coquina=type of limestone biochemical – sediments of shells and skeletal remains settle • Rock salt = halite (mineral form of NaCl); evaporation • Rock Gypsum = evaporation in shallow sea basins or salt lakes gypsum precipitates Coquina Rock Salt

  7. Features • Unique features of sedimentary rocks that are clues to how, when, and where they formed. • Layers law of superposition • Ripple marks: beach or stream bed • Fossils

  8. Classification of Major Sedimentary Rocks

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