1 / 16

SEDIMENATRY ROCKS

SEDIMENATRY ROCKS. sedimentary rocks = form when sediments become pressed or cemented together or when sediments precipitate out of solution 1. sediments = rock, minerals, and organic matter broken into fragments 2. carried away and deposited by wind, water, and ice.

ssells
Download Presentation

SEDIMENATRY ROCKS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SEDIMENATRY ROCKS sedimentary rocks= form when sediments become pressed or cemented together or when sediments precipitate out of solution 1. sediments = rock, minerals, and organic matter broken into fragments 2. carried away and deposited by wind, water, and ice

  2. 3. sediments are produced by weathering and erosion a. weathering produces clastic sediments = can be huge boulders to microscopic fragments with worn surfaces and rounded corners b. erosion = removal and movement of surface materials from one location to another c. deposition = when sediments settle down on ground or sink to bottoms of bodies of water d. sedimentary basins = depressions in Earth where sediments are usually deposited e. lithification = physical and chemical processes that transform sediments into rock

  3. Lithification Types 1. compaction = layers of sediment become compressed by weight of layers above a. pushes fragments together b. squeezes out air and water c. can reduce volume by 50% d. causes grains to interlock

  4. 2. cementation = sediments are glued together by minerals deposited between sediments a. type of cement affects the nature of rock 1) quartz cement makes toughest rocks 2) red iron oxide cement creates red sandstone b. time required depends on availability of cement and water to carry the cement

  5. 3. often form as layers a. older layers usually on bottom b. younger layers on top

  6. Features: 1. stratification = visible horizontal layering that develops as sediment is deposited a. also called bedding b. cross-bedding = arrangement of small beds lying at an angle to main sedimentary layering c. graded bedding = largest grains collect at bottom of layer and grain size decreases toward top Cross bedding

  7. 2. ripple marks = wavy features on sandstones a. formed by action of wind or water on sand 3. mud cracks = wet clay dries and contracts, filled with materials and fossilized a. result when muddy deposits dry and shrink b. usually a polygonal shape

  8. 4. fossils = remains, impressions, or any other evidence of plants and animals preserved a. most commonly found in limestone b. can also be found in shale, coal, and sandstone 5. concretions = nodules of rock with different composition of main rock body 6. geodes = ball-like objects that have small hollow where minerals grow inward from hard outer rim of silica

  9. Classification: based on kind and size of sediments that form them 1. clastic rocks = separate fragments become compacted and cemented together a. clastic particles = rock and mineral fragments that have been physically transported and deposited b. bioclastic rocks = made up of broken shells and other organic fragments (plants/animals) c. named based on shape and size of sediments d. make up more than 80% of sedimentary rocks

  10. e. coarse-grained clastics = contain gravel-size rock and mineral fragments 1) conglomerate = rounded gravel sized fragments 2) breccia = fragments are angular with sharp corners

  11. f. medium-grained clastics = contain sand-sized rock and mineral fragments 1) sandstone = lithified sand grains a) mostly rounded quartz grains b) layers useful in mapping old stream and river channels 2) porosity = percentage of open space between grains in rock a) pores through which liquids can move b) makes sandstone valuable as underground reservoir for oil, natural gas, and groundwater

  12. g. fine-grained clastics = contain silt and/or mud 1) siltstone = mostly silt-sized grains 2) shale = mostly silt and clay-sized minerals with quartz and feldspar a) makes up ~70% of all sediment rock b) usually gray to black c) contains decayed remains of plants and animals d) pressed into flat layers that easily split apart 3) rock have very low porosity → forms barriers that hinder movement of groundwater and oil

  13. 2. chemical rocks = form from minerals that have been dissolved in water a. evaporites = water evaporates leaving dissolved minerals behind Ex: halite, and gypsum b. precipitates = dissolved minerals that settle out of water due to change in temperature or chemical reaction Ex: calcite → limestone c. most commonly form in arid regions, oceans, drainage basins on continents with low water flow

  14. 3. organic rocks = forms from remains of organisms a. organic limestone = shells of marine organisms b. coal = decayed plant remains buried and compacted c. chalk = composed of tiny, one celled marine organisms

  15. d. bioclastic limestone = calcite shells compacted and cemented 1) bits and pieces of shells appear as fossils in the rock e. coquina = coarse-grained shell fragments cemented together

  16. Importance 1. used to provide geologic evidence of surface conditions in Earth’s past 2. indicate location and direction of flow of ancient rivers, wind or wave direction over lakes and deserts, and ancient shoreline positions 3. reservoir for natural resources such as oil 4. many are mined for use in industry

More Related