Sedimentary Sedimentary Petrology Petrology GEO 333 GEO 333 Lab (3) Lab (3) Clastic Sedimentary Rocks Clastic Sedimentary Rocks (Classification & (Classification & Description) Description) 2009 2009 Mansour Al-Hashim Mansour Al-Hashim
Dec 16, 2015
Sedimentary Sedimentary PetrologyPetrologyGEO 333GEO 333
Lab (3)Lab (3)Clastic Sedimentary RocksClastic Sedimentary Rocks
(Classification & Description)(Classification & Description)20092009
Mansour Al-HashimMansour Al-Hashim
Preview of Lab 2Preview of Lab 2
Classification in general Classification in general
Classification of sedimentary rocksClassification of sedimentary rocks
Clastic sedimentary rocksClastic sedimentary rocks
Chemical and biochemical Chemical and biochemical
sedimentary rockssedimentary rocks
Fundamental constituents of Fundamental constituents of
sedimentary rockssedimentary rocks
Objectives of Lab 3Objectives of Lab 3
Textures of sedimentary rocksTextures of sedimentary rocks Grain sizeGrain size Roundness and sortingRoundness and sorting MaturityMaturity ColorColor Cohesiveness (firmness)Cohesiveness (firmness) Mineral composition and sedimentary Mineral composition and sedimentary
structuresstructures Framework and matrixFramework and matrix Cements in sedimentary rocksCements in sedimentary rocks
Textures of Sedimentary Textures of Sedimentary RocksRocks
Sedimentary rocks may have Sedimentary rocks may have
1. Clastic (fragmental) texture1. Clastic (fragmental) texture Grains are stuck together. Grains are stuck together. Characteristic of clastic sedimentary rocks.Characteristic of clastic sedimentary rocks. Examples: sandstone and conglomerate.Examples: sandstone and conglomerate.
2. Non-clastic (crystalline) texture2. Non-clastic (crystalline) texture Interlocking crystals. Interlocking crystals. Characteristic of chemical sedimentary Characteristic of chemical sedimentary
rocks.rocks. Examples: limestone, dolomite, and chert.Examples: limestone, dolomite, and chert.
Grain Size (1)Grain Size (1)
Grain sizes can be determined by:Grain sizes can be determined by: Direct measurement with calipers or meter Direct measurement with calipers or meter
sticks. sticks.
For particles larger than several For particles larger than several centimeters. centimeters.
Screening and petrographic microscope. Screening and petrographic microscope.
For particles from 2 mm to about 1/16 mm.For particles from 2 mm to about 1/16 mm. Pipette or hydrometer (settling rates in Pipette or hydrometer (settling rates in
water)water)
For particles less than 1/16 mm.For particles less than 1/16 mm.
Grain Size (2)Grain Size (2)
Results of grain-size analysis can be Results of grain-size analysis can be
demonstrated as histograms, cumulative demonstrated as histograms, cumulative
curves, or frequency curves.curves, or frequency curves.
Many statistical parameters can be calculated Many statistical parameters can be calculated
(e.g., median, mean, skewness, kurtosis, etc.).(e.g., median, mean, skewness, kurtosis, etc.).
Used to characterize depositional processes Used to characterize depositional processes
and depositional environments.and depositional environments.
Udden-Wentworth grain-size scale is the most Udden-Wentworth grain-size scale is the most
widely used. widely used.
Roundness and Roundness and SortingSorting
Roundness Roundness (angularity) (angularity) Indicates how smooth or sharp the edges Indicates how smooth or sharp the edges
and corners of particles are. and corners of particles are. Usually measured with reference to a Usually measured with reference to a
comparative chart (the commonest is comparative chart (the commonest is Powers’ , 1953).Powers’ , 1953).
Sorting Sorting The degree of uniformity of grain sizes. The degree of uniformity of grain sizes.
Degrees of sortingDegrees of sorting
From Compton (1962)From Compton (1962)
* Note the standard deviation values * Note the standard deviation values between classesbetween classes
MaturityMaturity Depends on how many cycles of erosion Depends on how many cycles of erosion
and redeposition the components of a rock and redeposition the components of a rock have undergone. have undergone.
There are two types of maturity:There are two types of maturity:
1.1. Compositional maturityCompositional maturity
Compositional maturity = quartz + chert / Compositional maturity = quartz + chert / feldspars + rock fragments.feldspars + rock fragments.
2.2. Textural maturityTextural maturity
Textural (structural) maturity = sorting and Textural (structural) maturity = sorting and roundness of sand-sized grains.roundness of sand-sized grains.
ColorColor
Organic matter, sulfides, and some iron Organic matter, sulfides, and some iron
oxides give rocks a dark color.oxides give rocks a dark color. Indicating deposition in a reducing Indicating deposition in a reducing
environment.environment.
Some iron oxides give rocks red or Some iron oxides give rocks red or
yellowish color.yellowish color. Indicating deposition in an oxidizing Indicating deposition in an oxidizing
environment.environment.
Color IndicationsColor Indications
Black - organic matter FeSBlack - organic matter FeS Yellowish - pyrite, markasite FeSYellowish - pyrite, markasite FeS22
Yellowish or bluish - sulphates, Yellowish or bluish - sulphates, carbonates, and chloridescarbonates, and chlorides
Yellowish to brownish - limonite, Yellowish to brownish - limonite, goethite FeO(OH)goethite FeO(OH)
Reddish - iron oxides FeO Reddish - iron oxides FeO
Cohesiveness (firmness)Cohesiveness (firmness)
The degree to which the particles The degree to which the particles stick together.stick together.
Cohesiveness can be described as: Cohesiveness can be described as:
1.1. FragileFragile
2.2. Soft Soft
3.3. Intermediate Intermediate
4.4. Hard Hard
5.5. Very hard Very hard
Mineral CompositionMineral Composition The most common minerals in The most common minerals in
sedimentary rocks are:sedimentary rocks are:1.1. QuartzQuartz2.2. Clay mineralsClay minerals3.3. FeldsparsFeldspars4.4. Carbonates (calcite and dolomite)Carbonates (calcite and dolomite)5.5. Rock fragmentsRock fragments Small amounts of amphibole, Small amounts of amphibole,
pyroxene, and mica. pyroxene, and mica.
Sedimentary Sedimentary StructuresStructures
Some common sedimentary structures Some common sedimentary structures include:include:
1.1. Bedding (stratification)Bedding (stratification)2.2. Lamination Lamination 3.3. Graded BeddingGraded Bedding4.4. Cross-BeddingCross-Bedding5.5. Ripple MarksRipple Marks6.6. Mud CracksMud Cracks7.7. Raindrop Impressions Raindrop Impressions Nodules, concretions, geodes, and Nodules, concretions, geodes, and
Stromatolites.Stromatolites.
Framework and MatrixFramework and Matrix The grains in a sand-sized or coarser grained The grains in a sand-sized or coarser grained
sedimentary rock are known as the framework. sedimentary rock are known as the framework.
These grains are either: These grains are either:
1.1. In contact with each otherIn contact with each other
2.2. Surrounded by empty spaces Surrounded by empty spaces (pore spaces)(pore spaces)
3.3. Surrounded by finer grained sediment Surrounded by finer grained sediment
(matrix)(matrix)
4.4. Cemented together by a bonding material Cemented together by a bonding material
(cement)(cement)
Cements in Cements in Sedimentary RocksSedimentary Rocks
The most common cements in The most common cements in sedimentary rocks are: sedimentary rocks are:
1.1. Silica (quartz, opal, or chalcedony)Silica (quartz, opal, or chalcedony)
2.2. Carbonates (calcite, dolomite, or Carbonates (calcite, dolomite, or siderite)siderite)
3.3. Iron oxides (hematite)Iron oxides (hematite) Recognition of matrix and cement Recognition of matrix and cement
is not always possible in hand is not always possible in hand specimens.specimens.
References References
Compton, 1962. Manual of field geology.Compton, 1962. Manual of field geology. Folk, 1974. Petrology of sedimentary rocks.Folk, 1974. Petrology of sedimentary rocks. Folk, 1951. Stages of textural maturity in Folk, 1951. Stages of textural maturity in
sedimentary rocks: Journal of Sedimentary sedimentary rocks: Journal of Sedimentary Petrology, v. 21.Petrology, v. 21.
Immenhauser, 2002. Sedimentology for master Immenhauser, 2002. Sedimentology for master students. students.
Tucker, 2001. Sedimentary petrology: an Tucker, 2001. Sedimentary petrology: an introduction to the origin of sedimentary rocks. introduction to the origin of sedimentary rocks. Blackwell Science, London, UK. Blackwell Science, London, UK.
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