1. Unit 3 - Rock Types
Sedimentary Rocks

2. Basic Rock Classifications
Igneous
Sedimentary
Metamorphic

3. Make up 5% of Earth’s outer 16 km and 75% of continental crust.
Sedimentary Rocks
Make up 5% of Earth’s outer 16 km and 75% of continental crust.
Originate from sediment produced from:
(i) physical breakdown of pre-existing rock
(ii) chemical weathering followed by precipitation of dissolved materials.

4. Weathering: The break up of existing rocks
Sedimentary Rocks
Sediment becomes eroded then deposited in water or air and later lithified into a solid mass.
Weathering: The break up of existing rocks
Two Types: Chemical and Mechanical
Erosion: The movement of eroded rock material
Agents: water, ice, and wind
Over geological time, sediments transform into sedimentary rock.

5. Lithification - pg. 158
Lithification: The process of when sediments form into rock
Two sub processes
Compaction
Cementation

6. Lithification: Compaction
Compaction: Occurs when sediments get buried deep underground
pressure from the burial solidifies material into rock.
This results in reduced porosity (less space) and permeability.

7. Lithification: Cementation
Cementation: Minerals precipitate from groundwater and fill the spaces between sediments
It is crystallization of minerals in the pore space.
Reduces porosity and permeability
Precipitates include: Silica, calcite, iron oxide

8. Cementation

12. Classes of Sedimentary Rocks
Sedimentary Rocks are classified in three ways:
Clastic (formed from weathering)
Chemical (formed from precipitates)
Biochemical (formed from living material)

13. Clastic/Detrital Rocks
Formed from mechanical weathering of preexisting rocks
e.g., shale, siltstone, sandstone, conglomerate, breccia

14. Clastic/Detrital Rocks
Clastic rocks are classified based on:
Grain size
Grain Shape
Sorting

15. Clastic Sedimentary Rock classification: grain size
Shale
Clay (very fine) - shale
Silt (fine) - siltstone
Sand - sandstone
Sandstone
Siltstone

16. Grain Shape Angular gravel particles - Breccia
Rounded gravel particles- Conglomerate
Conglomerate
Breccia

17. Sorting
Is the degree of similarity in particle size in a sedimentary rock
“well sorted” sediment: all the particles are the same size
wind blown,
transported a great distance,
deposited slowly

18. Sorting “poorly sorted” sediment: show variation in size and shape
wave action,
turbulent streams,
transported a short distance,
deposited rapidly

19. Sorting
Degree of rounding indicates the distance or time involved in transportation in air or water
Size of sediment indicates strength of current/wind

20. Sorting
The faster flowing the wind/water the finer the sediment and more rounded
High Velocity Low Velocity
Breccia, Conglomerate → Sandstone → Siltstone → Shale
COARSE FINE

21. Horizontal Sorting Vertical Sorting

23. What can we tell from grain size/shape?
Large grain size = (less current velocity) closer to source
Smaller grain size = (more current velocity) father from source
Angular grains = (less current velocity) closer to source
Rounded grains = (more current velocity) farther from source

24. Clastic Depositional Environments
Sedimentary rock types form in specific places
Fluvial (Rivers/streams) – Conglomerate, Breccia, Sandstone, Siltstone, Shale
Lagoonal/Bays – Siltstone, Shale
Beaches – Conglomerate, Sandstone

25. Clastic Depositional Environments
Deep Marine – Conglomerate, Sandstone, Siltstone, Shale,
but is dominated by chemical sedimentary rocks.
Shallow Marine – Conglomerate, Sandstone, Siltstone, Shale

26. Beach
Fluvial
Fluvial
Shallow Marine

27. Chemical Sedimentary Rocks
2 Types of Chemical sedimentary rocks:
1) Evaporites
2) Precipitates

28. Chemical Sedimentary Rocks types
1) Evaporites
When water evaporates dissolved minerals are left behind
e.g., halite (rock salt), gypsum, sylvite
Salt flats

29. Chemical Sedimentary Rocks types
2) Precipitates
Due to Changes in Environmental conditions.
E.g., Temperature change, chemical change, concentration change.
Chemical weathering – dissolving of chemicals
e.g., compact limestone, travertine, dolomite, nodular chert

30. Chemical Depositional Environments:
1. Shallow Marine
e.g., gypsum, halite, sylvite, limestone and
dolomite
2. Deep Marine
e.g., limestone, dolomite and nodular chert
3. Cave - Stalactites and stalagmites

31. Stalactites and stalagmites
StalaCtites: are icicle-like pendants that hang from the Ceiling. Water seeps through cracks in the ceiling of the cave.
StalaGmites: form from the Ground.
The precipitated limestone that makes up
stalactites and stalagmites is called travertine.

32. Stalactites and Stalagmites

33. Biochemical Sedimentary Rocks
Biochemical: Rocks that are formed from living material

34. Biochemical Sedimentary Rock Examples
Coquina – forms from the build-up, compaction, and cementation of shells from dead organisms (mostly on beaches).

35. Biochemical Sedimentary Rock Examples
Chaulk – forms from the accumulation, compaction, and cementation of microscopic marine organisms such as formaminifera (i.e. deep marine)

36. Biochemical Sedimentary Rock Examples
Chert – forms from the accumulation of microscopic marine organisms, such as radiolaria and diatoms, that form a very hard rock consisting of microcrystalline silica.
E.g. of chert include jasper, flint, and agate (i.e. deep marine)

37. Biochemical Sedimentary Rock Examples
Coral limestone – accumulations of coral can be compacted and cemented into coral limestone (i.e. shallow marine)

38. What are corals?
Corals: organisms that are capable of creating large quantities of marine limestone from their shells and external skeletons which are composed of calcium carbonate.

39. Biochemical Sedimentary Rock Examples
Coal – formed from the accumulation of plant material, which is buried and chemically altered over millions of years.

40. The Formation of Coal - Swamps
There are 4 stages of coal formation:
Peat – earliest stage of plant accumulation. Contains large amounts of volatiles. (PEAT IS NOT A ROCK).
Lignite – decreased levels of volatiles.
Bituminous – higher grade of coal than lignite.
Anthracite – final stage of coal formation. It is classified as a metamorphic rock due to heat, pressure, and hot chemical fluids. It burns cleaner. Small amount available world-wide.
Increasing Grade

43. Depositional Environments
Swamp – Coal
Shallow Marine – Coquina, Limestone (Coral)
Beach – Coquina
Deep Marine – Chaulk, Chert
Think about the concept of systems. How do biochemical sedimentary rocks and coral represent interaction of the spheres?

48. Core Lab 3 – Sedimentary Rocks
Concept Map for rocks
Next class – Metamorphic Rocks