1 / 31

Sedimentary Petrology GEO 333

This Sedimentary Petrology lab-course focuses on the classification, description, and fundamental constituents of clastic and chemical sedimentary rocks. It covers grain size analysis, roundness, sorting, maturity, color, cohesiveness, mineral composition, sedimentary structures, framework, cements, and more.

jeremyrichardson
Download Presentation

Sedimentary Petrology GEO 333

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. Sedimentary PetrologyGEO 333 Lab (3) Clastic Sedimentary Rocks (Classification & Description) 2009 Mansour Al-Hashim

  2. Preview of Lab 2 • Classification in general • Classification of sedimentary rocks • Clastic sedimentary rocks • Chemical and biochemical sedimentary rocks • Fundamental constituents of sedimentary rocks

  3. Objectives of Lab 3 • Textures of sedimentary rocks • Grain size • Roundness and sorting • Maturity • Color • Cohesiveness (firmness) • Mineral composition and sedimentary structures • Framework and matrix • Cements in sedimentary rocks

  4. Textures of Sedimentary Rocks Sedimentary rocks may have 1. Clastic (fragmental) texture • Grains are stuck together. • Characteristic of clastic sedimentary rocks. • Examples: sandstone and conglomerate. 2. Non-clastic (crystalline) texture • Interlocking crystals. • Characteristic of chemical sedimentary rocks. • Examples: limestone, dolomite, and chert.

  5. Clastic (fragmental) Texture From eos.ubc.ca

  6. Non-clastic (crystalline) Texture From eos.ubc.ca

  7. Grain Size (1) Grain sizes can be determined by: • Direct measurement with calipers or meter sticks. For particles larger than several centimeters. • Screening and petrographic microscope. For particles from 2 mm to about 1/16 mm. • Pipette or hydrometer (settling rates in water) For particles less than 1/16 mm.

  8. Grain Size (2) • Results of grain-size analysis can be demonstrated as histograms, cumulative curves, or frequency curves. • Many statistical parameters can be calculated (e.g., median, mean, skewness, kurtosis, etc.). • Used to characterize depositional processes and depositional environments. • Udden-Wentworth grain-size scale is the most widely used.

  9. Wentworth grade scale

  10. Modified Udden-Wentworth grain-size Scale

  11. Simplified grain-size scale

  12. Roundness and Sorting Roundness (angularity) • Indicates how smooth or sharp the edges and corners of particles are. • Usually measured with reference to a comparative chart (the commonest is Powers’ , 1953). Sorting • The degree of uniformity of grain sizes.

  13. Categories of roundness From Tucker (2001)

  14. Degrees of sorting From Compton (1962) * Note the standard deviation values between classes

  15. Visual estimation of sorting From Tucker (2001)

  16. Maturity • Depends on how many cycles of erosion and redeposition the components of a rock have undergone. • There are two types of maturity: 1.Compositional maturity Compositional maturity = quartz + chert / feldspars + rock fragments. 2.Textural maturity Textural (structural) maturity = sorting and roundness of sand-sized grains.

  17. Textural Maturity From Folk (1951)

  18. Color • Organic matter, sulfides, and some iron oxides give rocks a dark color. • Indicating deposition in a reducing environment. • Some iron oxides give rocks red or yellowish color. • Indicating deposition in an oxidizing environment.

  19. Color Indications • Black - organic matter FeS • Yellowish - pyrite, markasite FeS2 • Yellowish or bluish - sulphates, carbonates, and chlorides • Yellowish to brownish - limonite, goethite FeO(OH) • Reddish - iron oxides FeO

  20. From eos.ubc.ca

  21. Cohesiveness (firmness) • The degree to which the particles stick together. • Cohesiveness can be described as: • Fragile • Soft • Intermediate • Hard • Very hard

  22. Mineral Composition • The most common minerals in sedimentary rocks are: • Quartz • Clay minerals • Feldspars • Carbonates (calcite and dolomite) • Rock fragments • Small amounts of amphibole, pyroxene, and mica.

  23. Sedimentary Structures • Some common sedimentary structures include: • Bedding (stratification) • Lamination • Graded Bedding • Cross-Bedding • Ripple Marks • Mud Cracks • Raindrop Impressions • Nodules, concretions, geodes, and Stromatolites.

  24. Framework and Matrix • The grains in a sand-sized or coarser grained sedimentary rock are known as the framework. These grains are either: • In contact with each other • Surrounded by empty spaces (pore spaces) • Surrounded by finer grained sediment (matrix) • Cemented together by a bonding material (cement)

  25. Framework and Matrix From Immenhauser (2002)

  26. Cements in Sedimentary Rocks • The most common cements in sedimentary rocks are: • Silica (quartz, opal, or chalcedony) • Carbonates (calcite, dolomite, or siderite) • Iron oxides (hematite) • Recognition of matrix and cement is not always possible in hand specimens.

  27. Assignment 3

  28. References • Compton, 1962. Manual of field geology. • Folk, 1974. Petrology of sedimentary rocks. • Folk, 1951. Stages of textural maturity in sedimentary rocks: Journal of Sedimentary Petrology, v. 21. • Immenhauser, 2002. Sedimentology for master students. • Tucker, 2001. Sedimentary petrology: an introduction to the origin of sedimentary rocks. Blackwell Science, London, UK. • eos.ubc.ca

  29. The End

More Related