1. Sediments and Sedimentary Rocks
Types of Sediments
Lithification and Diagenesis
Common types of Sed. Rock
Environmental Clues in Sed. Rocks

2. Sedimentary Rocks Controlled by the processes that occur at surface
Water
Wind
Ice
gravity

3. Sedimentary Rocks
Records conditions at the surface at the time of deposition

4. River Bluffs 450 million years ago St. Peter Sandstone
Pure quartz sand
Beach deposit
Platteville Limestone
Deep water deposit

5. Sedimentary Rocks
Contain the Fossil Record

6. Sedimentary Rocks
Contains all the
Fossil Fuel Supplies

7. Sedimentary Rocks Clastic sediments Chemical sediments weathering
Small rock fragments
Clastic sediments
Na+, Cl-, ions
Chemical sediments

8. Sedimentary Rocks Transport Wind, water Ice, gravity weathering
Small rock fragments
Transport
Wind, water
Ice, gravity
Na+, Cl-, ions

9. Sedimentary Rocks weathering Transport Wind, water Ice, gravity
Small rock fragments
Transport
Wind, water
Ice, gravity
Na+, Cl-, ions
Deposition of
sediment

10. Sedimentary Rocks weathering Transport Wind, water Ice, gravity
Small rock fragments
Transport
Wind, water
Ice, gravity
Na+, Cl-, ions
Deposition of
sediment
Burial & Lithification
Sedimentary Rock

11. Turning Sediment into Rock
Diagenesis
All chemical, physical, and biological changes after sediment is deposited
Upper few kilometers of Earth’s Crust
Temperatures < 100 C

12. Turning Sediment into Rock
Lithification: processes transform sediments into rock
Cement agent
Pore space
Compaction
Cementation
After deposition
Precipitation- Crystals precipitate directly from solution.

13. Stratification (Strata)
Distinct layering
Beds
Sedimentary Rock
Bed 1
Bed 2
Different thicknesses
Color, & other characteristics

14. Figure 7.1

15. All sediment is derived from preexisting rocks and can be classified as
Clastic Sediments
Form from the combination of rock fragments.
Chemical Sediments
Comprised of mineral crystals precipitated from solution.
Biogenic Sediments
Composed of remains of dead organisms, seashells, plant fragments, and carbon.

16. Clastic Sediments and Clastic Sedimentary Rocks
A. Sediments
B. Sedimentary Rocks

17. Well sorted and well rounded
Features of Clastic Sediments

18. Sorting Shape Roundness Fluctuations in Energy of Transport
Distance of transport
Shape
Roundness

19. Varieties of layerings
Horizontal (rhythmic)
Sediment Cycles (Varves)

20. Varieties of layerings
Cross-bedding
Direction of wind or current
Cross beds
Particles drop out of flowing water or wind

21. Varieties of layerings
Graded Bedding
Particles are sorted according to size
fine
top
Mudflow from Mt. St. Helens
Coarse
bottom

22. Varieties of layerings
Non sorted Sediments
Tillite, Ancient glacial deposit (S. Afrcia)

23. Chemical Sediments
Form by precipitation of minerals from solution in water.
Inorganic reactions in the water.
Evaporites
The most important salts that precipitate from seawater are
halite(rock salt: NaCl)
gypsum (CaSO4.2H2O).

24. Carbonate shelf in the Bahamas
Inorganic precipitation of Limestone (CaCO3, calcite)
S. C. Porter

25. Chemical Sediment Banded Iron Formation Layers of iron oxide and SiO2
Some of the Earth’s most important iron concentrations
Formed ~ billion years ago

26. Iron Formations and the Chemistry of the Ancient Atmosphere

27. Banded Iron Formations are a distinctive type of rock often found in old sedimentary rocks. The structures consist of repeated thin layers of iron oxides, either magnetite or hematite, with bands of shale and chert. Some of the oldest known rock formations dated around 3,000,000,000 years before present, 3000MA, include banded iron layers, and the banded layers are a common feature in sediments for much of the Earth's early history. Banded iron beds are less common after 1800MA although some are known that are much younger. The conventional concept is that the banded iron layers are the result of oxygen released by photosynthetic cyanobacteria, combining with dissolved iron in Earth's oceans to form insoluble iron oxides. The banding is assumed to result from cyclic peaks in oxygen production. It is unclear whether these were seasonal or followed some other cycle. It is assumed that initially the Earth started out with vast amounts of iron dissolved in the world's seas. Eventually, as photosynthetic organisms pumped out oxygen, all the available iron in the Earth's oceans was precipitated out as iron oxides. The atmosphere became oxygenated.
Water flowing over iron rich beds
Until fairly recently, it was assumed that the rare later banded iron deposits represent unusual conditions where oxygen was depleted locally and iron rich waters could form then come into contact with oxygenated water. An alternate explaination of these later rare deposits is undergoing much research as part of the Snowball Earth hypothesis — wherein it is believed that an early equatorial supercontinent (Rodinia) was totally covered in an ice age (implying the whole planet was frozen at the surface to a depth of several kilometers) which corresponds to evidence that the earth's free oxygen may have been nearly or totally depleted during a severe ice age circa 750 to 580 million years ago (mya) (See Cryogenian period, from 800 million years ago (mya, boundary defined chronometrically) to approximately 635 mya) prior to the Cambrian Explosion wherein the earliest multicellular lifeforms appear. Alternatively, some geochemists suggest that BIFs could form by direct oxydation of iron by autotrophic (non-photosynthetic) microbes. The total amount of oxygen locked up in the banded iron beds is estimated to be perhaps 20 times the volume of oxygen present in the modern atmosphere. Banded iron beds are an important commercial source of iron ore.

28. Biogenic Sedimentary Rocks
Sediment produced by the physiological activity of organisms
Calcium Carbonate (CaCO3)
Foraminifera

29. Biogenic Sedimentary Rocks
Limestone (CaCO3)
The most important biogenic rock.
limestone accounts for a major proportion of the carbon dioxide CO2 stored in the Earth’ crust.
If all the CO2 in limestone was
released into atmosphere
Like Venus
Venus
CO2-rich atmosphere
greenhouse gas
surface T about
400oC (750oF)
above value
without CO2

30. Green River Oil Shale, Colorado
Biogenic Sedimentary Rocks
Remains of plant material
Coal
Oil shale
Green River Oil Shale, Colorado
Fig. 6.17

31. Environmental Clues in Sedimentary Rocks
Grains size
shape
composition

32. Environmental Clues in Sedimentary Rocks
Grains size
shape
composition
“BB”-sized spheres
Mars
???

33. Environmental Clues in Sedimentary Rocks
Features on Bedding planes
Footprints
Mudcracks
Ripple marks

34. Fossils

36. Depositional Environments

37. Sedimentary Facies Reflect
Depositional Environments

38. End

39. Turning sediments into rocks
Lithification occurs by
burial
when additional sediment accumulates on top
compaction
reduction of the amount of pore space between particles
because of the weight of overlying sediment
cementation
precipitation of minerals within pores
binds sediment together
calcium carbonate (CaCO3) cement is common
silica (SiO2) cement is common
iron oxide (Fe2O3) cement is less common

40. Turning Sediment into Rock
Lithification: processes transform sediments into rock
Compaction: sediments get compressed and compacted
Cementation: Small crystals precipitate and act as glue that holds the rock together
Precipitation- Crystals precipitate directly from solution.

41. Size
Rounding
Sphericity
Sorting