EES 450: Sedimentary Geology

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

2. EES 450: Sedimentary Geology 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.

3. EES 450: Sedimentary Geology S 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. A P

4. EES 450: Sedimentary Geology 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.

5. EES 450: Sedimentary Geology S 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. A P

6. EES 450: Sedimentary Geology 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?

7. EES 450: Sedimentary Geology 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. Reference Point Ф (phi) = –log2 d (d = grain diameter)

8. EES 450: Sedimentary Geology Clastic, siliciclastic or detrital rocks ●Grain size has potential information about energy and distance from provenance (source area).

9. EES 450: Sedimentary Geology 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? Vertical sorting = graded bedding Horizontal sorting = facies

10. EES 450: Sedimentary Geology 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?

11. EES 450: Sedimentary Geology 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?

12. EES 450: Sedimentary Geology Clastic, siliciclastic or detrital rocks ●What can you say from the look of these two outcrops?

13. EES 450: Sedimentary Geology 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.

14. EES 450: Sedimentary Geology Clastic, siliciclastic or detrital rocks ●Consider: How can/do textural and compositional maturity relate to short and long systems?

15. EES 450: Sedimentary Geology Calcite cement 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. Quartz grains Silica cement Calcite grains Dolomite Glauconite Lower Cretaceous greensand (Bargate Stone) (clastic) Pennsylvanian-age limestone (crystalline)

16. EES 450: Sedimentary Geology Siderite (FeCO3) – rich: Can reflect hydrothermal setting and shale and sandstone diagenesis. Chemical rock Calcite cement Clastic, siliciclastic or detrital rocks ●Crystallinetextures: (1) Chemical and biochemical rocks. (2) Cements. (3) Recrystallized grains and cements (diagenesis). Shell fragments, skeletal remains Many grains have “rims”, why? What are they made of? Pennsylvanian-age limestone – Possible depositional settings? Folk Class.: Radial oograinstone (ooids + radial and spar calcite). Chemical rock

17. EES 450: Sedimentary Geology Clastic, siliciclastic or detrital rocks ●Crystallinetextures: (1) Chemical and biochemical rocks. - Evaporites – chlorides, sulfides, carbonates, borates, etc. - What conditions/settings do you need to form these? Playa lake, California, USA. ArganaEvaporites (Jurassic) – Atlas Mountains, Morocco. Halite-encrusted cobble from the Dead Sea.

18. EES 450: Sedimentary Geology Clastic, siliciclastic or detrital rocks ●Crystallinetextures: (1) Chemical and biochemical rocks. - Limestones – ~10% of all sedimentary rocks, dominantly calcite (CaCO3), but can have appreciable amounts of aragonite (calcite’s alternative crystal form) and dolomite (CaMg)(CO3)2 (diagenesis). - Tremendous variability in rock types and depositional settings. Jenolan Caves, Australia. Silurian limestone outcrop – Saaremaa, Estonia. Travertine – Yellowstone NP, USA.

19. EES 450: Sedimentary Geology Clastic, siliciclastic or detrital rocks ●Crystallinetextures: (1) Chemical and biochemical rocks. - Chert – Comprised of micro- and cryptocrystalline silica (SiO2). 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? Radiolaria – Protozoa (zooplankton). Typical chert hand sample. Diatoms – Algae (phytoplankton).

20. EES 450: Sedimentary Geology Acicular aragonite cement forming. Clastic, siliciclastic or detrital rocks ●Crystallinetextures: (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. Drusy calcite cement Transmitted polarized light (L) and cathodoluminesence micrograph (R) – Zoned dolomite cement.

21. EES 450: Sedimentary Geology Muscovite Quartz Clastic, siliciclastic or detrital rocks ●Crystallinetextures: (3) Recrystallized grains and cements (diagenesis). Biotite Recrystallized shells and cements (calcite) Hard ground (cross-polarized light) from 650 m depth, Strait of Messina (Italy – Sicily). Timescale?