Sedimentary Rocks - Suitable to print back to back

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Conglomerate

  • Grain Size: over 2mm (Rudaceous), matrix can be fine grained
  • Chemical Maturity: low - particles can be from a range of sources, including feldspathic
  • Textural Maturity: low - particles are rounded, but poorly sorted
    Identifying Features: looks like a pudding stone! May contain traces of graded bedding at outcrop scale
  • Geological Description: A well rounded arenaceous rock, composed of clasts from older rocks of any description. Normally moderately porous and permeable, depending on degree of compaction and the age of the rock. Pebbles can be distorted if e rock has experienced tectonic pressures. some fossil fragments have been observed but are not common as they are normally destroyed in high energy environments
  • Identifying Features: Large rounded included fragments of other rocks
  • Formation: normally found in river beds, shingle beaches, high energy environments.
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Breccia

  • Grain Size: Over 2mm (Rudaceous), matrix can be made up from smaller materials
  • Chemical Maturity: low, feldspars are a common component to breccias as well as clasts of other rocks
  • Textural Maturity: Low, fragments are angular and often large, indicating they have not travelled far from their source
    Identifying Features: The large clasts of an angular nature are the key to identifying the rock, as is the range of clasts it can contain, it is always poorly sorted and angular
  • Geological Description: An angular Rudaceous rock composed if clasts of older rocks or minerals, often no internal structure, graded bedding can be observed in outcrops.
  • Identifying Features: Large fragments of other rocks with angular edges
  • Formation: normally deposited very rapidly in high energy environments, often those wit significant variation in flow over a short period if time, for instance after flash floods, on alluvial fans and after a mass movement event
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Arkose

  • Grain Size: Between 2.0 and 0.063 mm (arenaceous), tends to be at the coarser end of this range
  • Chemical Maturity: moderate to low, the inclusion of over 25% feldspar indicates the sediment has not yet weathered to a material Stanley at surface temperatures and pressures. other common minerals are mica and quartz, as well as small rock fragments.
  • Textural Maturity: Moderate, sediment has degraded to an arenaceous grain size, but is commonly angular to sub-angular. It will bit have been transported far from it's source.
  • Identifying Features: it is commonly grey to red, it may sometimes fizz with dilute HCl as calcite cement is possible. It rarely contains fossils and often has an iron oxide cement
  • Geological Description: an areanceous rock with a low overall degree of maturity containing at least 25% feldspar
  • Formation: formed by the weathering of granites, and often deposited in cold/arid environments to prevent the decomposition of the feldspar. Often found over igneous unconformities, in an environment of rapid deposition
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Greywacke

  • Grain Size: Between 2.0 and 0.063mm (Arenaceous), often very varied within the sample
  • Chemical Maturity: Low, wackes often contain feldspathic fragments, lithic fragments and a large percentage of muds.
  • Textural Maturity: Low, over 15% of the rock will be matrix, and fragments show great variation in size and composition due to the method of deposition
  • Identifying Features: Poorly sorted, dark grey rock which can be red/earthy or black. Wide range of included fragments
  • Geological Description: A distinctive rock as it contains both sands and clays. It is immature and can display a range of sedimentary features in an outcrop. They are characterised by the wide range of minerals found within them.
  •  Formation: Turbidity currents which originate on the continental shelf descend to the deeper ocean in a thick slurry of sediment, entraining particles as they move, leading to a poorly sorted and immature deposit composed of any material that had been in the path of the turbidite.
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Example

(http://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/images/breccia3.jpg)

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Example

(http://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/images/conglomerate1.jpg)

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Example

(http://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/images/greywacke1.jpg)

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Example

(http://www.minimegeology.com/shop/images/arkose_w.gif) 

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Orthoquartzite

  • Grain Size: Between 2.0 and 0.063mm (Arenaceous)
  • Chemical Maturity: Very Mature, over 99% quartz which is stable at surface temperature and pressure
  • Textural Maturity: Very high, normally very well sorted grains, size determined by level of energy in the environment
  • Identifying Features: Usually a white/grey colour, unless stained by the presence of a coloured cement such as Haematite, which turns it a pinkish colour. Yellow and orange are also relatively common
  • Geological Description: A super mature deposit of arenaceous rock
  • Formation: Usually beach or upper shoreface environments and aeolian deposits.
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Quartz Arenite

  • Grain Size: Between 2.0 and 0.063mm (Arenaceous)
  • Chemical Maturity: Mature, the dominant mineral is quartz which is a stable substance at surface temperature and pressure, the cement normally accounts for the wide range of colours observed in arenites.
  • Textural Maturity: Moderately high, arenites are usually sub angular to rounded, and well sorted
  • Identifying Features: A wide range of sedimentary features can be seen in outcrops, including graded bedding, ripple marks, etc. They can also show a wide range of colour.
  • Geological Description: An Arenaceous rock with less than 15% matrix, and usually over 90% quartz
  •  Formation: Usually a relatively high energy environment, such as a river, beach or Aeolian dune system to account for the high degree of sorting.
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Mudstone

  • Grain Size: Less than 0.063 (Argillaceous)
  • Chemical Maturity: High, clay is stable at surface Temperature and Pressure
  • Textural Maturity: High, very fine grained and very well sorted
  • Identifying Features: Clasts are invisible to the naked eye, it is normally smooth to touch
  • Geological Description: An argillacous rock, ranging in colour from white to drak grey/black displaying few characteristics or feature, displays conchoidal fracture
  • Formation: Clays are deposited in a low energy environment and compacted over time to form mudstone. Can be made of a variety of clay minerals.
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Siltstone

  • Grain Size: Less than 0.063 and over 0.002 (Argillaceous), key is that greater than 50% have to be of silt sized particles
  • Chemical Maturity: High, clay and silt are stable at surface Temperature and Pressure
  • Textural Maturity: High, very fine grained and very well sorted
  • Identifying Features: Fine grained but lacks fissility and laminations
  • Geological Description: An argillaceous rock that can contain concretions, may appear as a clay rich fine grained sandstone.
  • Formation: Clays and silts are deposited in a low energy environment and compacted over time to form siltstone. Can be made of a variety of clay minerals.
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Example

(http://upload.wikimedia.org/wikipedia/commons/thumb/9/97/Lower_antelope_2_md.jpg/400px-Lower_antelope_2_md.jpg) (http://upload.wikimedia.org/wikipedia/commons/b/bc/Sandstone%28quartz%29USGOV.jpg)

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Example

(http://skywalker.cochise.edu/wellerr/rocks/sdrx/6sandstone-orthoquartzite135.jpg)

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Example

(http://upload.wikimedia.org/wikipedia/commons/4/42/SiltstoneUSGOV.jpg) (http://t1.gstatic.com/images?q=tbn:ANd9GcRjRhVm_nJ6DKjVu9BYJyFR5wL8RgXZWk-RNC-5vpx6O9Uzyhsa3Q)

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Example

(http://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/images/mudstone1.jpg)

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Shale

  • Grain Size: Less than 0.063 (Argillaceous)
  • Chemical Maturity: High, clay is stable at surface Temperature and Pressure.
  • Textural Maturity: High, very fine grained and very well sorted
  • Identifying Features: Clasts are invisible to the naked eye, it is normally smooth to touch, can be fissile (splits into layers)
  • Geological Description: An argillacous rock, that contains clay particles and a mix of other fragments such as sands and calcite, it is fissile (breaks easily into layers)
  • Formation: Clay particles settle out from still waters and are compacted. Often formed in lagoons, lakes and deep water where energy is very low. They can appear very dark if there is a high organic content.
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Limestone - Bioclastic/Shelly

  • Grain Size: Variable
  • Chemical Maturity: Relatively low, composed predominantly of shells or remains of marine organisms.
  • Textural Maturity: Low as grain size varies from sand to large fragments of corals/other organisms
  • Identifying Features: Clearly identifiable remains, tends to be bioclastic if the remains are broken, shelly if shells are intact or easily identifiable.
  • Geological Description: A carbonate rock formed mainly from the remains of marine life, corals, shells and ooids are common
  • Formation: A range of environments, such as the continental slope, reefs, beach deposits and lagoons.
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Limestone - Oolitic

  • Grain Size: 2.0  to 0.25mm spherical grains
  • Chemical Maturity: Relatively high, calcite is stable at surface T and P
  • Textural Maturity: Relatively high, they are normally well sorted having a high surface residence time and form slowly
  • Identifying Features: This is a distinctive rock type, composed of very spherical grains formed in a shallow marine environment. Ooids tend to be smooth grains, normally a pale cream/yellow to white.
  • Geological Description: A carbonate sedimentary rock composed of equal sized grains enclosed in plates of calcite.
  • Formation: Shallow marine environments with a low but steady energy supply which allows grains of sand or shell fragments to be enclosed in plates of calcite, making them very spherical. If they are allowed to grow beyond 2mm they are known as Pisolites. They are commonly found in sheltered carbonate platforms and are forming today in the Bahamas
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Example

(http://www.soes.soton.ac.uk/resources/collection/minerals/GY105/sediment/images/09.jpg)(http://adnams.co.uk/wp-content/uploads/2010/06/fossils-in-wall.jpg)  v    (http://www.earth.ox.ac.uk/~oesis/micro/medium/limestone-xpl_pm14-09.jpg)

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Example

(http://upload.wikimedia.org/wikipedia/en/thumb/1/18/Shale_8040.jpg/800px-Shale_8040.jpg)

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Example

(http://www.soes.soton.ac.uk/resources/collection/minerals/GY105/sediment/images/02.jpg)(http://www.soes.soton.ac.uk/resources/collection/minerals/GY105/sediment/images/02-close.jpg)(http://www.earth.ox.ac.uk/~oesis/micro/medium/limestone-oolitic-detail_pm21-38.jpg)

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