Sedimentary rocks
Download
1 / 27

Sedimentary Rocks - PowerPoint PPT Presentation


  • 549 Views
  • Updated On :

Sedimentary Rocks. John Day Fossil Beds Natl. Mon.,Oregon. Sedimentary rocks  composed of sediment (particles derived by weathering). Detrital sediments  particles derived by physical weathering

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Sedimentary Rocks' - zeki


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Sedimentary rocks l.jpg

Sedimentary Rocks

John Day Fossil Beds Natl. Mon.,Oregon


Slide2 l.jpg

Sedimentary rocks composed of sediment

(particles derived by weathering)


Slide3 l.jpg

  • Detrital sediments particles derived by physical weathering

  • Non-detrital sediments minerals precipitated from solution by inorganic chem. processes or activities of organisms

    Classification of Sedimentary Particles

    SizeSediment Name

    >2 mm gravel

    1/16-2 mm sand

    1/256-1/16 mm silt

    <1/256 mm clay


Why should you study sedimentary rocks l.jpg
Why Should You Study Sedimentary Rocks?

  • Sediments are the most common Earth materials.

  • Rock Features record environmental conditions at the time sediment was deposited. (impt. in deciphering Earth history)

  • Fossils knowledge of pre-existent life preserved in sedimentary rocks

  • Some sed. rocks contain resources (i.e. water, petroleum, natural gas, etc.).


Transport deposition l.jpg
Transport & Deposition

Ice

-- carries particles of any size.

Wind

-- transports sand & smaller particles.

Water (most prolific agent)

Larger particles require more vigorous current for transport.

  • Depositional environment geographic area where sediment accumulates


Slide6 l.jpg

well-rounded, poor-sorted gravel

angular, poor-sorted gravel

  • Rounding -- abrasion during transport reduces particle size & smoothes sharp corners

  • Sorting -- variety of particle sizes present in sediment or sed. rock (influenced by transport & depositional processes)


Slide7 l.jpg

Processes (Physical, chemical, & biological) operating in the depositional environment impart distinctive charac. to accumulating sediment.


How are sediments transformed into sedimentary rocks l.jpg
How Are Sediments Transformed into Sedimentary Rocks?

Compaction

  • due to weight of overlying sediment

  • particles pack more closely & pore space is reduced

  • deposit’svolume reduced

    Cementation

  • binds one particle to anotherby chemical precipitation of minerals in sediment pore space.

  • {Common cements include quartz, calcite, & hematite.}

    Lithification

  • involves compaction & cementation

  • converts sediments to sedimentary rocks


Slide9 l.jpg

Detrital sedimentary rocks Rocks?

comprised of solid particles derived from parent material by phys. weathering

Classification of Detrital Sed. Rocks

Based on:

Sediment Size

Composition


Slide10 l.jpg

Conglomerate Rocks? = rounded gravel (>2 mm)

Breccia = angular gravel

A

B


Slide11 l.jpg

Sandstone Rocks? = sand-size (1/16 - 2 mm) particles

  • classified by mineralogy

    Quartz sandstone most common

    Arkose sandstone 25% feldspar


Slide12 l.jpg

Mudrock Rocks? any combination of silt & clay

Siltstone silt (1/16 – 1 / 256 mm)

Claystone clay (< 1 / 256 mm)

  • Shale is fissile clay. (splits along many closely spaced planes)

  • Mudrocks = most common sed. rock (quiet-water environ)

shale


Slide13 l.jpg

Chemical sedimentary rocks Rocks?

 ions taken into soln by weathering of parent material **crystalline texture (interlocking mineral grains)

Biochemical sedimentary rocks Organisms aid in the precipitation of minerals.

Classification of Chemical Sed. Rocks

Based on:

Mineral composition

Texture


Slide14 l.jpg

Evaporites Rocks? formed by precipitation of minerals from evaporating water

\

Rock salt{halite (NaCl)} (A) & Rock gypsum{gypsum (CaSO4. 2H2O)}(B) are most common.

B

A


Slide15 l.jpg

Limestones Rocks?

composed of Calcite (CaCO3)

contains much pore space

Coquina

Clastic texture

 shell fragments

Fossiliferouslimestone

skeletal fragments of marine invertebrates

-- pores filled w/ cement & mud --


Slide16 l.jpg

Coal Rocks?

crystalline texture

carbon

(compressed, altered plant remains that occupied swamps & bogs)

A

B

Chert

crystalline texture

silica

(layers of microscopic shells of marine organisms)


Sedimentary facies l.jpg

Strata Rocks? (beds)layers differ in color, texture, & comp. from rock layers above & below.

Sedimentary Facies

-- sets of sed. rock w/ distinct attributes imparted by their depositional environment

Coastal areas facies accumulate simultaneously on various areas of seafloor (w/ unique charac.).


Slide18 l.jpg

1 Rocks?

Regression(seaward shift in the shoreline)

  • Drop in sea level

    Nearshore deposits overlie offshore deposits.

2

3


Slide19 l.jpg

Transgression Rocks? (landward shift in shoreline)

  • Rise in sea level

    Nearshore seds overlie old land surfaces, & offshoreseds are stacked on top.


Determining the depositional environment l.jpg
Determining the Depositional Environment Rocks?

Grand Canyon

Muav Limestone (offshore)

Bright Angel Shale

Tapeats Sandstone (onshore)

(deposition record of laterally adjacent environ.)

Transgression Sed structures, fossils & ripple marks


Slide21 l.jpg

Sedimentary Structures Rocks?

- formed by physical processes at the time of deposition

  • Cross bedding

  • Graded bedding

  • Oscillation ripple marks

  • Current ripple marks

  • Mudcracks


Slide22 l.jpg

  • Cross bedding Rocks?

  • inclined layers w/in a bed

  • Formed by wind or water

  • slopes downward in flow direction


Slide23 l.jpg

Graded bedding Rocks?

  • upward decrease in grain size w/in a bed

    {deposits of turbidity currents}


Slide24 l.jpg

Ripple marks Rocks?

-- small ridges separated by intervening troughs

Oscillation ripple marks(A) symmetric cross-sections generated by the back-&-forth motion of waves.

A

B

Current ripple marks(B) asymmetriccross- sections record flow in one direction (i.e., streams).


Slide25 l.jpg

Mudcracks Rocks?

 shrinkage (polygonal patterns of intersecting fractures)

  • clay-rich sediment

  • depositional environ. periodic drying (i.e., a river floodplain, lake shore, or tidal flat)


Slide26 l.jpg

Fossils Rocks?are NOTSedimentary Structures.  remains or traces of ancient organisms

Morphology of organisms reveals info about environment the organisms lived in.

  • Heavy-shelled clams = shallow-water, turbulent

  • Thin, fragile-shelled clams = low-energy

  • Filter-feeding organisms (corals) = clear seawater (suspended sediment clogs their feeding organs.)


Resources in sedimentary rocks l.jpg
Resources in Sedimentary Rocks? Rocks?

  • Sand & gravel building & road construction

  • Limestone cement

  • Gypsum wallboard/plaster

  • Phosphate-bearing sedimentary rock fertilizer

  • Sand-sizedquartz glass

  • Carnotite(uranium mineral) fuels nuclear reactors [assoc w/ plant remains in sandstones formed in ancient stream channels]

  • Hematite & magnetite (banded iron formations)  iron ores


ad