1. Sedimentary Rocks

2. Standards Classify matter in a variety of ways
Describe the composition and structure of Earth’s materials, including:
the major rock types (i.e., sedimentary, igneous, metamorphic) and their formation

3. Sedimentary Rocks Cover 75% of Earth’s surface
Make up only 5% of the crust by volume
Form by burial and lithification of sediments
lithification = the process of turning sediments into sedimentary rock by compaction &/or cementation
Compaction = grains squeezed together by overlying sediments
Cementation = minerals precipitate around sediments and bind them together

4. Lithification of Sediments
Loose Sediments
Sedimentary Rock
Photo: Windows to the Universe
link=/earth/geology/sed_lithification.html

5. 3 Types of Sedimentary Rocks
Clastic
Chemical
Organic

6. Clastic Sedimentary Rocks
Are formed from fragments of other rocks by the following process:
Weathering breaks rocks into fragments
Physical weathering occurs by:
Water
Wind (also called eolian)
Gravity, or
Freezing
Chemical weathering occurs by:
Chemical reactions

7. Clastic Sedimentary Rocks
The rock fragments are eroded and transported to new locations by water or wind
The rock fragments are deposited – called sedimentation

8. Clastic Sedimentary Rocks
4. The rock fragments are buried and turned into rock (lithification).
Cementing agents are sometimes present and help turn the sediments into rock.
Types of cementing agents are lime, iron and silica

9. Deposition of Sediments
As sediments are transported from their source, the largest fragments get deposited first (i.e., closest to the source).
This happens because the current that is carrying the sediments slows, and therefore can no longer carry the larger particles.
This means that large sediments get deposited in high energy environments and small sediments get deposited in low energy environments.
Examples: boulders are deposited in mountain streams, sand is deposited on beaches, and clay is deposited in the ocean

10. Naming Clastic Sedimentary Rocks
Clastic sedimentary rocks are named according to the size of the fragments that make them.
Fragment mm Fragments Rock
Size Names
Coarse – pebbles conglomerates
gravel breccia
Medium – 1/16 sand sandstone
Fine to 1/16 – 1/ silt siltstone
Very fine clay shale

11. Pebbles to Conglomerate
Photo: Aradon, Australia
Photo:
images/pebbles.jpg
Photo: USGS
terraces.html

12. Sand to Sandstone Photo: http://www. mccullagh.org/db9/
1ds-4/sahara-desert-
sand-dune.jpg
Photo:
mark.com/cgi-
bin/getpic.cgi?
id=233
Photo: Zion National Park
zioninfo/photos/photos.htm

13. Clay to Shale Photo: http://www.saraarts. com/alaska/shale.html
arikah.com/commons
/en/2/2c/Clay-ss-2005
.jpg
Photo:

14. Grain Sorting
The size of grains in a sedimentary rock will be either well-sorted (all near the same size) or poorly-sorted (lots of different sizes).
Well-sorted sediments have been transported farther than poorly-sorted sediments.
Wind-transported sediments are more well-sorted than water transported sediment.
Poorly-sorted
Well-sorted

15. Grain Rounding
Grains in a sedimentary rock will be either rounded or angular, depending on how far they have been transported.
Grains that have been transported further get abraded longer and are thus more rounded.
Rounded
Angular

16. Chemical Sedimentary Rocks
Chemical sedimentary rocks are formed by:
Precipitation out of a solution (a solid comes out of solution)
Evaporation
Chemical action

17. Names of Chemical Sedimentary Rocks
Limestone – made of calcite &/or tiny sea creatures
Rock salt (halite) – formed by evaporation
Rock gypsum – formed by evaporation
Silicates – microcrystalline (or cryptocrystalline) quartz
exs: agate, chalcedony

18. Types of Chemical Sedimentary Rocks
5. Concretions – nodules (clumps) of silica in limestone with quartz or calcite crystals in center (geodes)
Petrification – replacement of plant and animal remains by
another mineral = fossil
Ex: petrified wood: wood
is replaced by
microcrystalline quartz

19. Organic Sedimentary Rocks
Organic sedimentary rocks are formed from plants and animals.
Organic material dies, gets buried and turns into sedimentary rock.

20. Names of Organic Sedimentary Rocks
Some limestone
Coquina – made of
shells and limestone
3. Coal – made of plants,
peat
4. Chalk – made of
microorganisms
Photo: Chalk Cliffs, Dorset
uk/P005814_chalk_cliffs_dorset.jpg

21. Sedimentary Structures
Sedimentary structures – features that are formed in sedimentary rocks when the sediments are deposited (i.e., before the sediments are turned into rock)
They include:
- bedding
- cross-bedding
- graded bedding
- ripples
- bioturbation structures

22. Bedding Also called stratification.
Occurs when layers of different grain sizes or compositions are deposited on top of one another. Can be from millimeters to meters thick.

23. Cross-Bedding
Sets of bedded material inclined at angles to each other.
Occurs when sediments are deposited on steeper, downcurrent slopes of sand dunes or sandbars.

24. Cross-Bedding Photo: Zion National Park http://www.earth.
northwestern.edu/grad/

25. Cross-Bedding
Photo: Cross Beds in Jemez Red Rocks
L. Brown

26. Graded Bedding
Progression of a bedding layer from coarse-grained at the bottom to fine- grained at the top.
Indicates a
weakening of
the current
carrying the
sediment.

27. Ripples
Low narrow ridges.
Symmetrical or asymmetrical.

28. Symmetrical Ripples
Formed by back and forth motion of waves.

29. Asymmetrical Ripples
Formed by currents moving in one direction.

30. Bioturbation Structures
Tubes and other structures left by burrowing organisms

31. Sedimentary Rocks are Economically Important
Coal is a major energy resource
Limestone is used as building material, stone and an ingredient in cement
Ores and native elements such as copper, lead, zinc, iron, gold & silver are all concentrated in sedimentary rock
Fossils are found in sedimentary rocks