sedimentary rocks fossils - wou...
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Sedimentary RocksFossils
Sedimentary rocks
Two main types
Rocks formed by deposition of sedimentClastic
Rocks formed by precipitation from waterChemical (includes rocks formed by organisms)
Clastic Sediment Grains
Particle loosened from pre‐existing rock
Transported to place of deposition
Shape, size, and sorting of grains can tell about the environment of deposition
Lithification
Process of becoming stone Burial and compaction
Precipitation of cementp
Each reduces ‘pore space’
Cement
Brought in by water
Mineral material between grains
Fills in pore spaces
Commonly calcite, silica, and sometimes iron oxide
Bedding and bedding planes
STRATA• http://www.birdandhike.com/Hike/General_Info/Glossary/Gloss4.htm
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Types of Clastic Rocks
Shale (most abundant)
Sandstone
Conglomerate
Fossils
Traces or remains of prehistoric life
Are the most important inclusions
Help determine past environments p p
Used as time indicators
Used for matching rocks from different places
Shale with plant fossilsShale
Composed of very fine grained sediment
Shows obvious tendency to split along planes (fissile)
Usually gray
Most common type of sedimentary outcrop
Sandstone Sandstone
Composed of sand‐size particles Between 1/16 mm and 2 mm diameter
Particles may be individual mineral grains or rock fragments
Q f i Quartz most common type of grain
Environments include
•Beach,
•river,
•shallow sea,
•sand dunes
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Conglomerate Conglomerate
Composed of particles larger than 2 mm
Usually particles are rock fragments
Clastic rocks
•Shale is the most common one
•Made from solid particles
•Classified by particle size y p
Chemical rocks
Material was once in solution and precipitates to form sediment
•Directly precipitated as the result of physical processes or physical processes, or
•Through life processes (biochemical origin)
Chemical rocksLimestone
Composed of the mineral calcite (calcium carbonate)
Much of this calcite was precipitated by organisms
Considered an ‘organic chemical sediment’ if from gorganisms
Most common type of chemical rock—
second most common type of sedimentary rock
Chalk
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Fossiliferous limestoneCoquina
Close up of coquina Chemical rocksDirect mineral precipitation from water
Evaporites such as rock salt or gypsum
Microcrystalline quartz (precipitated quartz) known as chert, flint, jasper, opal or agate
Travertine (calcite) and sinter (silica) from hotspring deposits
Travertine
• http://njminerals.org/travertine.html
• http://www.gonomad.com/destinations/0409/hot_springs_of_the_sierras.html
• http://www.cis.nctu.edu.tw/~whtsai/World%20Highlights/New%20Side%20Show%20Webpages/imagepages/Turkey%202001‐‐‐Travertine%20stones%20and%20water%20in%20Pamukale.html
Evaporites
• http://www.bonnevillehealeyclub.org/
• http://www.img.uni‐karlsruhe.de/925.php
• http://www.paintersflat.net/saltflat.html• http://www.nv.blm.gov/Winnemucca/blackrock/BRHR_Planning.htm
• http://www.pitt.edu/~cejones/GeoImages/1Minerals/2SedimentaryMineralz/Gypsum.html
• http://www.flickr.com/photos/snogun/191723596/
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Rock salthttp://geomaps.wr.usgs.gov/sfgeo/geologic/stories/marin_sedimentary.html
• http://www.mii.org/Minerals/photochert.html
Chert
• http://homestake.sdsmt.edu/Photos/Surface_geology_photos.htm
Classification of sedimentary rocks Features of sedimentary
rocks Porosity
Permeability
Sedimentary rocks
Economic importance
• Coal
• Petroleum and natural gas
• Precipitation of iron and aluminum
• Deposition of gold and tin
• Sand, gravel, clay
Fossils: evidence of past life
Remains or traces of prehistoric life
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Petrified
Cavities and pores are filled with precipitated mineral matter
Petrified
Formed by replacement
Cell material is removed and replaced with mineral matter
Mold
Shell or other structure is buried and then dissolved by underground water
Shape is preserved in the surrounding sediment http://www.ammonoid.com/Manning.html
Cast
Hollow space of a mold is filled with mineral matter
Carbonization
Organic matter becomes a thin residue of carbon. This is a
f‘compression’ of the original organism
Impression
Replica of the fossil's surface preserved in ffine‐grained sediment
http://www.lfbuffalo.org/exhibitions/map/t/
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Preservation in amber
Hardened resin of ancient trees surrounds an organism
Indirect Evidence Includes
Tracks
Burrows
Coprolites
fossil dung and stomach contents
Gastroliths
stomach stones used to grind food by some extinct reptiles
Tracks
Dinosaur footprint in fine‐grained limestone near Tuba City, Arizona.
Types of fossils
Petrified
Formed by replacement
Carbonization
Impression
i ireplacement
Mold
Cast
Preservation in amber
Indirect evidence
Conditions favoring preservation
Rapid burial
Possession of hard parts
Fossils and correlation
Principle of faunal succession
Index fossils
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Principle of faunal succession
Proposed by William Smith –late 1700s
Fossil organisms succeed one another in a definite and d bl d h fdeterminable order, therefore any geologic time interval can be recognized by its fossil content
http://www.lfbuffalo.org/exhibitions/map/a/
Geologic Time Scale
Archean through Devonian
http://rst.gsfc.nasa.gov/Sect2/Sect2_1b.html
Carboniferous through Quaternary
http://rst.gsfc.nasa.gov/Sect2/Sect2_1b.html
Cambrian Marine Life
http://www.handprint.com/PS/GEO/geoevo.html
Trilobite
http://www.ststephens.it/biology/fossils.html
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Crinoid—380 ma
http://www.lsa.umich.edu/exhibitmuseum/exhibits/temporary_exhibits/
Ordovician sea floor
http://www.uwsp.edu/geo/faculty/hefferan/Geol106/CLASS6/MAIN%20PAGE.htm
Ordovician Invertebrates
http://www.handprint.com/PS/GEO/geoevo.html
Silurian reef
Silurian Reefhttp://hoopermuseum.earthsci.carleton.ca/camex/1rpaleoreef.html
Silurian Landscape
http://www.nasa.gov/worldbook/earth_worldbook.html
Devonian Sea
http://www.handprint.com/PS/GEO/geoevo.html
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Mid Paleozoic
http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/text/text_bio_4.html
Late Paleozoic
http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/text/text_bio_4.html
Carboniferous Fern Forests
http://www.handprint.com/PS/GEO/geoevo.html
Permian Sea
http://www.handprint.com/PS/GEO/geoevo.html
Permian Reptiles
http://www.handprint.com/PS/GEO/geoevo.html
Permian Extinction
Link to hypotheses of the Permian Extinction
80‐95% of marine species died out
70%+ of terrestrial vertebrates
Largest extinction episode in geologic record
http://en.wikipedia.org/wiki/Permian_extinction
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Geologic Time Scale Mesozoic
http://geography.berkeley.edu/ProgramCourses/CoursePagesFA2002/Geog40/Geog40.Week7.html
Mesozoic
http://serc.carleton.edu/introgeo/earthhistory/dinosaur.html
Mesozoic
http://geography.berkeley.edu/ProgramCourses/CoursePagesFA2002/Geog40/Geog40.Week7.html
Mesozoic
http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/text/text_bio_4.html
Archeopteryx
http://www.researchcasting.ca/sculpt%20miami.htm
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Mesozoic Mammal
Eomaia
http://www.amnh.org/exhibitions/dinosaurs/diorama/
Mesozoic Mammal
Repenomamus
http://www.amnh.org/science/papers/mesozoic_mammal.php
Jurassic
http://www.worldbook.com/features/dinosaurs/html/world_mesozoic.html
Cretaceous
http://www.worldbook.com/features/dinosaurs/html/world_mesozoic.html
Mesozoic Sea
http://geography.berkeley.edu/ProgramCourses/CoursePagesFA2002/Geog40/Geog40.Week7.html
Mesozoic sea
http://www.uky.edu/AS/Geology/webdogs/time/mesozoic/mesozoic.htm
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Cretaceous Extinction
Perhaps 60% of species died
Result of radical change in environment
Perhaps Earth encountered a large meteorite—
10 km in diameter
90,000 km/hr
Equivalent to 100 megatons of TNT exploding
Cenozoic mammals
http://www.handprint.com/PS/GEO/geoevo.html
Cenozoic
http://www.handprint.com/PS/GEO/geoevo.html
Cenozoic
http://www.uky.edu/AS/Geology/webdogs/time/cenozoic/cenozoic.htm
Cenozoic
http://www.copyrightexpired.com/Heinrich_Harder/cenozoic.html
Geologic Time Scale