1. 1 Breccia Conglomerate Diamictite Sandstone Siltstone Shale New Clay Minerals Shale Clastic or Detrital Limestone Chert Diatomite Biochemical Evaporites Chert Limestone Ironstone Chemical Solution Plant Extraction Peat Coal Bitumen Resins Organic Mechanical Weathering Chemical Weathering Source Rocks Crustal, upper mantle melts Explosive Eruption Tuff, Bentonite Agglomerate Volcaniclastic EES 450: Sedimentary Geology CLASTIC, SILICICLASTIC OR DETRITAL ROCKS 70% - 80% of all sedimentary rocks Rudites

2. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Rocks are primarily classified on the basis of composition and texture. - Composition – The dominant mineral make-up of the rock (e.g., quartz, feldspar, calcite, dolomite, halite, etc.). - Texture - Refers to particle shape, size and fabric (fabric = orientation and packing of grains) (e.g., rounded vs. angular; sand-silt-clay sizes; degree of sorting, etc.). - We commonly use ternary diagrams to show composition and/or texture. EES 450: Sedimentary Geology

3. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Sedimentary Ternary Diagram (composition diagram for most sedimentary rocks). - S = Siliciclastics and volcanoclastics; usually extrabasinal. - A = Allochems (fragments of chemical, biochemical or organic origin; usually intrabasinal). - P – Precipitates, chemical or biochemical in origin; usually intrabasinal. EES 450: Sedimentary Geology S A P

4. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Composition and Texture Diagrams. - “Wacke” – “Dirty” sandstone – mixture of poorly sorted mineral and rock fragments – matrix of silt and clay size material – sandstone with matrix >10% argillaceous material – clastic rock with grains nearly equally distributed among grain sizes (sand, silt and clay). - All of the material classified below are “S” – siliciclastics from the previous slide. EES 450: Sedimentary Geology

5. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Sedimentary Ternary Diagram (composition diagram for most sedimentary rocks). - S = Siliciclastics and volcanoclastics; usually extrabasinal. - A = Allochems (fragments of chemical, biochemical or organic origin; usually intrabasinal). - P – Precipitates, chemical or biochemical in origin; usually intrabasinal. EES 450: Sedimentary Geology S A P

6. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Size matters! Size is the most important textural component in classification. How do we address size in sediments and sedimentary rocks? EES 450: Sedimentary Geology

7. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● In North America, we use the Udden-Wentworth Scale for grain size. Wentworth developed the size classes, and Udden developed the logarithmic portion of the classification. EES 450: Sedimentary Geology Reference Point Ф (phi) = –log 2 d (d = grain diameter)

8. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Grain size has potential information about energy and distance from provenance (source area). EES 450: Sedimentary Geology

9. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Other textural aspects: 1. Sorting: Grain size distribution – unconsolidated deposits or sedimentary rocks – poor sorting = mixed sediment sizes (large variance) – good sorting = similar sediment sizes (low variance). - Indication of energy involved and transport duration. Landslide? River? Deep sea? EES 450: Sedimentary Geology Vertical sorting = graded bedding Horizontal sorting = facies

10. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Other textural aspects: 1. Rounding: Used to describe the shape of the corners of a particle/grain. - Indication of distance and time in transport. Landslide? River? Deep sea? EES 450: Sedimentary Geology

11. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Other textural aspects: 1. Grain orientation: Used to describe the particular arrangement or stacking of grains. - Indication of current direction. Landslide? River? Deep sea? EES 450: Sedimentary Geology

12. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● What can you say from the look of these two outcrops? EES 450: Sedimentary Geology

13. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Textural characteristics can be used together to describe the relative maturity of a sediment. - Maturity – Relative measure of how extensively and thoroughly a siliciclastic sediment has been weathered, transported, and reworked toward its ultimate end product, quartz sand. - Maturity involves BOTH composition (changes in mineral composition) and texture (size, roundness, sorting). - Compositionally mature = sediment that has reached the ultimate mineral end member, quartz sand. - Texturally mature = sediment that is composed of perfect spheres, and sorted perfectly to size. EES 450: Sedimentary Geology

14. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Consider: How can/do textural and compositional maturity relate to short and long systems? EES 450: Sedimentary Geology

15. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Texture = the size, shapes and relationships between grains. - In sedimentary rocks, there are two common relationships between grains: (1) Crystalline = Crystals or recrystallized grains interlock. (2) Clastic = Rounded to angular grains or fragments are cemented together. EES 450: Sedimentary Geology Pennsylvanian-age limestone (crystalline) Calcite cement Calcite grains Dolomite Lower Cretaceous greensand (Bargate Stone) (clastic) Quartz grains Glauconite Silica cement

16. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Crystalline textures: (1) Chemical and biochemical rocks. (2) Cements. (3) Recrystallized grains and cements (diagenesis). EES 450: Sedimentary Geology Pennsylvanian-age limestone – Possible depositional settings? Calcite cement Shell fragments, skeletal remains Many grains have “rims”, why? What are they made of? Siderite (FeCO 3 ) – rich: Can reflect hydrothermal setting and shale and sandstone diagenesis. Chemical rock Folk Class.: Radial oograinstone (ooids + radial and spar calcite). Chemical rock

17. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Crystalline textures: (1) Chemical and biochemical rocks. - Evaporites – chlorides, sulfides, carbonates, borates, etc. - What conditions/settings do you need to form these? EES 450: Sedimentary Geology Halite-encrusted cobble from the Dead Sea. Argana Evaporites (Jurassic) – Atlas Mountains, Morocco. Playa lake, California, USA.

18. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Crystalline textures: (1) Chemical and biochemical rocks. - Limestones – ~10% of all sedimentary rocks, dominantly calcite (CaCO 3 ), but can have appreciable amounts of aragonite (calcite’s alternative crystal form) and dolomite (CaMg)(CO 3 ) 2 (diagenesis). - Tremendous variability in rock types and depositional settings. EES 450: Sedimentary Geology Travertine – Yellowstone NP, USA. Jenolan Caves, Australia. Silurian limestone outcrop – Saaremaa, Estonia.

19. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Crystalline textures: (1) Chemical and biochemical rocks. - Chert – Comprised of micro- and cryptocrystalline silica (SiO 2 ). Originates from silica derived from a) solution in water, b) biochemical sediments, or c) lava flows and volcanic ash. - Why are Diatoms and Radiolaria important? EES 450: Sedimentary Geology Radiolaria – Protozoa (zooplankton). Diatoms – Algae (phytoplankton). Typical chert hand sample.

20. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Crystalline textures: (2) Cements. - Often homogenous (contrasts with matrix). - Chemically pure and lines pores. - Often exhibits fabric (acicular, drusy, etc.). - Can be multi-phased (zoned). - Common cements include silica, calcite and iron oxides. - Rare cements include halite, gypsum, phosphates, etc. EES 450: Sedimentary Geology Acicular aragonite cement forming. Drusy calcite cement Transmitted polarized light (L) and cathodoluminesence micrograph (R) – Zoned dolomite cement.

21. CLASTIC, SILICICLASTIC OR DETRITAL ROCKS ● Crystalline textures: (3) Recrystallized grains and cements (diagenesis). EES 450: Sedimentary Geology Hard ground (cross-polarized light) from 650 m depth, Strait of Messina (Italy – Sicily). Timescale? Muscovite Biotite Recrystallized shells and cements (calcite) Quartz