1. What is a sedimentary rock?
Sedimentary rocks result from mechanical and chemical weathering
Comprise ~ 5% of Earth’s upper crust
Contain evidence of past environments
Record how sediment is transported
Often contain fossils

2. Fossil Fish - 50 Million Year Old Lakes in southern Wyoming
Sediment is fine-grained mudstone

3. Turning sediment into rock
Changes occur in sediment after it is deposited
Diagenesis – chemical and physical changes that take place after sediments are deposited

4. Turning sediment into rock
Diagenesis
Recrystallization – growth of stable minerals from less stable ones
Lithification – loose sediments is transformed into solid rock by compaction and cementation
Natural cements include calcite, silica, and iron oxide

5. Types of sedimentary rocks
Detrital rocks – transported sediment as solid particles
Chemical rocks – sediment that was once in solution

6. Detrital sedimentary rocks
Constituents of detrital rocks can include
Clay minerals
Quartz
Feldspars
Micas
Particle size is used to distinguish among the various types of detrital rocks

7. Detrital sedimentary rocks
Common detrital sedimentary rocks
Shale
Mud-sized particles deposited in thin layers called laminae

8. Detrital sedimentary rocks
Sandstone

9. Detrital sedimentary rocks
Conglomerate and breccia
Both composed of particles > 2mm in diameter
Conglomerate consists largely of rounded clasts
Breccia is composed of large angular particles

10. Chemical sedimentary rocks
Precipitated material once in solution
Precipitation of material occurs two ways:
Inorganic processes
Organic processes (biochemical origin)

11. Chemical sedimentary rocks
Common chemical sedimentary rocks
Limestone
Most abundant chemical rock
Made of the mineral calcite
Marine biochemical limestones form as coral reefs, coquina (broken shells), and chalk (microscopic organisms)
Inorganic limestones include travertine and oolitic limestone

12. Coquina

13. Fossiliferous limestone
Note shells and lime matrix

14. Chalk Outcrops in SE USA
Hand Specimen

15. Travertine forming in Hot Spring
Hand Specimen

16. Chemical sedimentary rocks
Common chemical sedimentary rocks
Dolostone
Typically formed secondarily from limestone
Common in ancient rocks, rare today
Chert
Made of microcrystalline quartz
Usually deposited as siliceous ooze in deep oceans (can be diatomaceous)
chert
Diatomaceous chert

17. Chemical sedimentary rocks
Common chemical sedimentary rocks
Evaporites
Evaporation triggers deposition of chemical precipitates
Examples include rock salt and rock gypsum

18. Chemical sedimentary rocks
Common chemical sedimentary rocks
Coal
Different from other rocks because it is composed of organic material

19. Metamorphic Rocks
The transformation of rock by temperature and pressure
Metamorphic rocks are produced by transformation of:
Igneous, sedimentary and igneous rxs

20. Metamorphism Metamorphism progresses from low to high grades
Rocks remain solid during metamorphism

21. Metamorphism Three types of metamorphic settings:
Contact metamorphism – from a rise in temperature within host rock
Hydrothermal metamorphism – chemical alterations from hot, ion-rich water
Regional metamorphism -- Occurs in the cores of mountain belts and makes great volumes of metamorphic rock

22. Metamorphic Environments
Metamorphic grade
A group of minerals that form in a particular P-T environment
Zeolite (really low T,P; <200C)
Greenschist (low T, P; C, km)
Blueschist (low T, high P - subduction zones)
Amphibolite (high T, P; C, km)
Granulite (super high T, P; >700C, >25km)

23. What are metamorphic textures?
Texture refers to the size, shape, and arrangement of mineral grains within a rock
Foliation – planar arrangement of mineral grains within a rock

24. Common metamorphic rocks
Nonfoliated rocks
Quartzite
Formed from a parent rock of quartz-rich sandstone
Forms in intermediate T, P conditions

25. Common metamorphic rocks
Nonfoliated rocks
Marble
Coarse, crystalline
Parent rock usually limestone
Composed of calcite crystals
Fabric can be random or oriented

26. Common metamorphic rocks
Foliated rocks
Slate
Very fine-grained
Made by low-grade metamorphism of shale

27. Common metamorphic rocks
Foliated rocks
Phyllite
Grade of metamorphism between slate and schist
Composed mainly of muscovite and/or chlorite

28. Common metamorphic rocks
Foliated rocks
Schist
Medium- to coarse-grained
Comprised of platy minerals (micas)
The term schist describes the texture

29. Common metamorphic rocks
Foliated rocks
Gneiss
Banded appearance
High-grade metamorphism
Composed of light-colored feldspar layers with bands of dark mafic minerals

30. Outcrop of foliated gneiss

31. The rock cycle

32. The rock cycle
- Series of processes by which rocks changes into other types of rocks
Illustrates various processes and paths as earth materials change both on the surface and inside the Earth
- What are the three main rocks ?
1- Igneous
2- Metamorphic
3- Sedimentary

33. The rock cycle

34. Fundamental Rock Types
Igneous Rocks: solidify from melt, e.g. lava (extrusive) or magma (intrusive)
Sedimentary Rocks: are made at the Earth’s surface from particle and chemical remnants of other rocks
Metamorphic rocks: form when other rocks are heated, squeezed, and deformed.