1. Sedimentary Rocks

2. Biblical Reference
When he makes all the altar stones to be like limestone crushed to pieces, no Asherah poles or incense altars will be left standing.
Isaiah 27:9

3. Top 5 Reasons to Study Sedimentary Rocks
5) Sedimentary Rocks are the most common rocks.
4) Sedimentary Rock features help decipher Earth’s history.
3) Fossils in Sedimentary Rocks give knowledge of pre-existent life.
2) Some sedimentary rocks contain resources (water, petroleum, natural gas).

4. Top 5 (Cont’d)
Sedimentary Rocks are the most interesting of the three types of rocks!

5. Sedimentary Rocks How They are Made
Wind and water break down the earth
Bits of earth settle in lakes and rivers
Layers are formed and build up
Pressure and time turn the layers to rock

6. Types of Sedimentary Rocks
Sandstone
Limestone
Gypsum
Conglomerate
Shale

7. Sedimentary Rocks are the principal repository for Information about the Earth’s past environment.

8. Sedimentary
Sediments – Pieces of solid material that have been deposited on the Earth’s surface by:
Wind
Water
Ice
Gravity
Precipitation

9. Weathering Surface is being worn away Breaks rocks into smaller pieces
Produces Clastic (broken) rocks
Minerals remain chemically unchanged

10. Erosion & Transport 4 Main agents of Erosion
Wind  Gravity
Moving Water  Glaciers
Rocks are then transported to a new location.
Surface material is removed (eroded).

11. Deposition
When transported sediments are deposited on the ground or sink to the bottom of a body of water.
Often these are sorted with larger grains on the bottom and smaller grains on the top.
Transportation Agents determine the method of sorting.
Example: Sand dunes = fine sand
Wind too weak to carry large grains

12. Lithification
Sediments deposited in low areas (valleys or ocean basins).
As sediment piles up, increased pressure & temperature lithifies the sediment into Sedimentary Rock.
From the Greek word, lithos, which means stone.
Two Stages:
Compaction
Cementation

13. Compaction
The weight of the overlying sediment forces the grains closer together.
Mud goes from 50% - 60% to 10% - 20% water
Sand grains maintain open spaces, which can trap:
Groundwater
Oil
Natural Gas

14. Cementation
Mineral growth glues the sediment grains together into solid rock.

15. From Sediment to Sedimentary Rock

16. Environmental Clues Grain Size Rippling Rounding Sorting Bedding
Fossils
Color
Chemistry

17. Grain Size Power of Transport Medium Water Wind Glaciers Landslides
Large Particles – Fast Moving
Small Particles – Slow Moving
Wind
Can only move small grains (sand dunes)
Glaciers
Can carry all sizes equally – Unsorted particles
Landslides
Sediment moves downhill in a jumbled mess

18. Rippling Sediment is moved into small ridges by wind or waves.
Often a sign of flooding
Can be symmetrical or asymmetrical

19. Rounding When rocks break apart, the edges are sharp.
As they bump into each other or encounter weathering, the edges become rounded.
Harder rocks (quartz sand) round better than softer rocks (carbonate sand).
Sediment that travels far experiences more rounding.

20. Sorting Sediments are “sorted” by grain size Well-Sorted Poorly-Sorted
Indicates:
Energy, Rate and Duration of Deposition
Mode of Transportation
Well-Sorted
Quartz Sandstones
Shales
Poorly-Sorted
Conglomerates
Breccia

21. well-rounded, poor-sorted gravel angular, poor-sorted gravel
Rounding & Sorting
well-rounded, poor-sorted gravel
angular, poor-sorted gravel

22. Bedding Horizontal Layering Two Types:
Layers can be between a few millimeters to more than a meter thick.
Two Types:
Graded Bedding
Particle Sizes become progressively larger toward the bottom of the layer
Cross-Bedding
Inclined layers across a horizontal surface

23. Fossils Fossils are not Sedimentary Structures
Remains or traces of ancient organisms
Salt Water - Corals, Echinoderms
Heavy-Shelled Clams: Shallow, Turbulent Water
Thin-Shelled Clams: Deep, Calm Water
Filter-Feeding Organisms: Clear Seawater
Fresh Water: Insects, Amphibians
Terrestrial: Leaves, Land Animals

24. Color & Chemistry Red Beds - Often Terrestrial
Black Shale - Often Deep Water
Dark or Black – Organic Material
Different layers can have very different colors
Oxygen Poor - Often Deep Water
Evaporites – Arid Climates
Iron-Rich – Red, Brown or Pink

25. Types of Sedimentary Rocks

26. Relative Abundance of Sediments

27. Formation of Sedimentary Rocks
Clastic Rocks
Made of Fragmentary Material
Deposited by
Water (Most Common)
Wind
Glacial Action
Gravity
Biochemical Rocks
Evaporation
Precipitation
Biogenic Sediments

28. Clastic Sedimentary Rocks
Most Common Sedimentary Rocks
Greek Word klastos – “broken”
Made up of broken pieces of pre-existing rocks
Could be Igneous or Metamorphic in origin
Three types categorized by grain size:
Coarse-Grained
Medium-Grained
Fine-Grained

29. Coarse-Grained Clastic Rocks
Usually gravel-sized rock & mineral fragments
Rarely boulder-sized (see below)
Two Main Types:
Conglomerates
Breccias

30. Conglomerate = rounded gravel (>2 mm)
Conglomerates
Gravel Transported by High Energy Water
Mountain Streams
Flooding Rivers
Ocean Waves
Well-Rounded
Lithification Compacts & Cements these fragments into Rocks
Conglomerate = rounded gravel (>2 mm)

31. Breccias Angular, Gravel-Sized Particles
Particles transported short distances from their sources
Did not have time to become rounded
Breccia = angular gravel

32. Medium-Grained Clastic Rocks
Sand-sized sediments in streams, rivers, deserts and beaches
Sandstone
Ripple Marks and Cross-Bedding indicate direction of current flow
High Porosity – Open spaces allow liquid to travel
Valuable as underground reservoirs of oil, natural gas, and water

33. Sandstone Sand-size (1/16 mm – 2 mm particles)
Classified by Minerology
Most Common: Quartz Sandstone
Arkose Sandstone = 25% Feldspars
Feels Rough & Gritty

34. Fine-Grained Clastic Rocks
Consist of Silt or Clay-sized particles
Typically found near swamps or ponds
Still or slow-moving water
Poor Porosity which forms a barrier to the movement of groundwater
Three Main Types
Siltstone
Claystone
Shale

35. Fine-Grained Clastic Rocks
Siltstone
Made from Silt
1/256 mm to 1/16 mm
Three times stronger than most bricks
Claystone
Made from Clay
< 1/256 mm
Shale
Made from Fissile Clay
Splits along closely spaced planes

36. Clastic rocks

37. Sediment Sizes and Clastic Rock Types
Shale
Clay
Siltstone
Silt
Sandstone
Sand
Conglomerate
Gravel
Sedimentary rocks made of silt- and clay-sized particles are collectively called mudrocks, and are the most abundant sedimentary rocks.

38. Chemical Sedimentary Rocks
Ions are taken into solution by the parent weathering material
Evaporation in arid locations leaves chemically enriched crystals, which solidify into rock
Other conditions for Evaporites:
Fresh water supply is low
No connect to an open sea
Usually are light-colored

39. Common Chemical Rocks Dolostone Flint Rock Gypsum
Magnesium ions bonded to CaCO3
Flint
Formed from Silica in Sea Beds
Rock Gypsum
Sulfate-based
Very soft
Used to construct the Egyptian pyramids

40. Bio-Chemical Sedimentary Rocks
Formed from remains of once-living organisms
Many contain fossils
Evidence of their biological origins
Falls of the Ohio fossil beds are made of limestone

41. Common Bio-Chemical Rocks
Limestone
Predominately CaCO3
Formed from skeletal fragments of marine invertebrates
Chert
Silica-based
Layers of microscopic shells
Coal
Carbon-based
Compressed, altered plant remains from bogs & swamps

42. Francis John Turner

43. Pop Quiz
During which process does the weight from layers of sediment force out fluids and decrease the space between grains?
A. cementation
B. crystallization
C. compaction
D. evaporation

44. Pop Quiz
Which types of rocks are sedimentary rocks made up of broken pieces of minerals and rock fragments?
chemical
biochemical
fragmented
clastic

45. Pop Quiz
Chemical rocks form when minerals crystallize directly from which of these?
A. gas
B. water
C. sediment
D. magma