1. Sediments and Diagenesis The Rock Cycle is a group of changes. It is an ongoing process. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock.

2. Sediments and Diagenesis Sediment & Diagenesis 75% of all the rocks exposed at the Earth’s land surface (only 5% of Earth’s outer 10 miles - so mostly at the surface) I. Sediment Rock fragments created by weathering and erosion Accumulates everywhere— oceans, beaches, lakes, rivers, deserts, swamps, caves, base of glaciers

3. A. Classified based on its origin. 1.Detrital: composed of transported solid fragments (detritus) of preexisting rocks 2. Chemical: forms when previously dissolved minerals either precipitate from solution or are extracted from water by living organisms and converted to shells/skeletons Sediments and Diagenesis

5. B. Sediment Transport and Deposition 1. Detrital Generally move from high ground to low ground by the pull of gravity (assisted by water, wind, or glacial ice) Deposited when the carrying material loses it’s capacity to carry the sediment 2. Chemical Ions remain in solution until there’s a change in the water’s temperature, pressure, or chemical composition and then the ions precipitate Sediments

6. C. Sediment Texture: Detrital sediment and chemical sediment are classified based on composition. 1. Grain size Grain composition - some minerals are stronger than others. a. Distance - smaller grains travel longer distances. b. Energy of the transportation medium - high energy environment moves larger grains. Sediments

8. 2. Grain shape a. Distance transported - over far distances, grained become more rounded. b. Transportation medium High energy river, wind produce rounded grains Middle of glacier, mudflow, debris flow preserve angular grains – not enough distance to round grains Sediments

9. C. Sediment Texture: detrital sediment and chemical sediment are classified based on composition. 3. Sorting Related to the carrying capacity of the transport medium Well sorted = wind Medium - well sorting = waves Medium - poor sorting = streams Poorly sorted = glaciers, debris flows Sediments

11. II. Turning sediments into rock Eventually accumulated sediment turns into rock A. Diagenesis : All the chemical, physical, and biological changes that take place after sediments are deposited. Burial Alteration by groundwater Recrystallization: regrowth of less stable minerals into more stable ones. Lithification: occurs within the upper few kilometers of the crust at temperatures < 200  C (400  F) Sediments and Diagenesis

12. II. Turning sediments into rock B. Lithification: the process by which unconsolidated sediments are transformed into solid sedimentary rocks (part of diagensis) 1.Compaction: pressure (from overlying sediment) reduces the volume of sediment— Compaction forces out air and water and packs grains together. Sediments and Diagenesis

13. II. Turning sediments into rock B. Lithification 2. Cementation Cements grains together - ions dissolved in water by chemical weathering may be deposited by groundwater circulating through the sediment. Calcium carbonate = CaCO 3 Calcium ions plus CO 2 and H 2 O Silica = SiO 2 is produced by chemical weathering of silicate igneous rocks Iron oxide = Fe 2 O 3 Sediments and Diagenesis

14. III. Types of Sedimentary rocks A. Detrital Sedimentary rocks : made of sediment that is transported as solid particles Particle size is the primary basis for distinguishing various detrital sedimentary rocks. Particle size indicates environment of deposition Water and air currents sort by size. Stronger current = larger grain sizes Sediments and Diagenesis

15. III. Types of Sedimentary rocks A. Detrital Sedimentary rocks: made of sediment that is transported as solid particles 1. Shale (mudstone, siltstone) >50% of all sedimentary rocks: Silt and clay Small grain size = settling from quiet, non-turbulent water Silt and class form in lakes, lagoons, swamps, deep ocean. Need quiet water depositional setting Sediments and Diagenesis

16. III. Types of Sedimentary rocks A. Detrital Sedimentary rocks 2. Sandstone: sand sized particles (1/16 – 2 millimeters) ~25% of all sedimentary rocks Windblown dunes, some rivers, and beaches Shape and sorting important for determining depositional environment. Sorting: well sorted = wind & waves poorly sorted = streams Shape: well rounded = water or wind transported over long distances Angular = glacier or debris flow Transported over short distances Sediments and Diagenesis

17. III. Types of Sedimentary rocks A.Detrital Sedimentary rocks 2. Sandstone : sand sized particles (1/16 – 2 millimeters) ( ~25% of all sedimentary rocks Windblown dunes, some rivers, and beaches Shape and sorting important for determining depositional environment. Sorting: well sorted = wind & waves poorly sorted = streams Shape: well rounded = water or wind transported over long distances Angular = glacier Transported over short distances Sediments and Diagenesis

18. III. Types of Sedimentary rocks A.Detrital Sedimentary rocks 2. Sandstone: sand sized particles (1/16 – 2 millimeters) ( ~25% of all sedimentary rocks Windblown dunes, some rivers, and beaches Shape and sorting important for determining depositional environment. Sorting: well sorted = wind & waves; poorly sorted = streams Shape: well rounded = transported over long distances (water) Angular = transported over short distances (glacier) Sediments and Diagenesis

21. III. Types of Sedimentary rocks A.Detrital Sedimentary rocks 3. Conglomerate and Breccia— Composed of gravels (pea to large boulders, >2 mm) Conglomerate: composed of rounded grains of difference sizes. Formed in energetic mountain streams or coasts (storm deposits) Breccia: composed of angular pieces. Did not travel far: glaciers, landslides Sediments and Diagenesis

22. III. Types of Sedimentary rocks A.Detrital Sedimentary rocks 3. Conglomerate and Breccia Composed of gravels (pea to large boulders, >2 mm) Conglomerate: composed of rounded grains of difference sizes. Formed in energetic mountain streams or coasts (storm deposits) Breccia: composed of angular pieces. Did not travel far: glaciers, landslides, (close to source) Sediments and Diagenesis