1. SEDIMENTARY ROCKS

3. Sedimentary Rocks
80 % of Earth’s surface is covered with sediments and Sedimentary Rocks

5. What is sediment???? Broken pieces of rocks called CLASTS
Chemical precipitates ( dissolved solids come out of solution)
Organic fragments – shells, decayed plant matter – this is called BIOCLASTIC

6. Source of Sediment
When Igneous, Metamorphic Rocks, and Sedimentary Rocks are uncovered and exposed to the atmosphere and hydrosphere they start to break down
Weathering is the general term for all actions that break down or wear away rock
Erosion is the carrying away of the sediment

7. Sedimentary Rocks form when after weathering and erosion sediments/clasts are …
Deposited in horizontal layers called beds or strata
Buried
Compacted – particles forced extremely close together because of the pressure of the overlying layers and water
Cemented – glued together

9. Cementing Material (Glue)
Minerals precipitate out of solution to cement particles together.
Cementing material is often quartz, calcite, and hematite

10. Most Sedimentary Rocks form under large bodies of water, such as lakes, seas, and oceans

11. Horizontal layers deposited under water

12. Classification of Sedimentary Rocks
We classify sedimentary rocks depending whether the sediments are
LAND DERIVED
CHEMICALLY - ORGANICALLY DERIVED

13. INORGANIC LAND DERIVED
Main source of clasts are from pre-existing igneous, metamorphic or other sedimentary rocks that have been weathered.

14. CHEMICAL Sedimentary Rocks Sediment From Solution
All liquid water contains dissolved minerals.
These minerals precipitate (dissolved solids come out of solution/water)
Usually happens because of evaporation

16. ORGANIC Sedimentary Rocks Bioclastic Sediment
LIMESTONE AND CORALS
Dissolved minerals taken out of solution by marine organisms for their hard parts (shells) can pile up on the seafloor when they die.
These fossil remains accumulate into a thick enough layer to form an “organic” sedimentary rock
Cement is commonly calcite ( bubbles with acid)
COAL
Decayed plant remains

20. Identifying Sedimentary Rocks
To identify Sedimentary Rocks, we ask ourselves 2 questions:
Where does it come from? Look at the composition
Where was it put together? Look at the texture or grain size.

22. Composition of Inorganic Land-Derived Sedimentary Rocks
Sediment is from pre-existing older rocks
What type of minerals make up igneous and metamorphic rocks?
Silicate minerals

23. Composition of Inorganic Land Derived Sedimentary Rocks
Silicate Minerals
Quartz – highly resistant (remember Moh’s scale)
Feldspars
Clay minerals (form when feldspars weather in water)
HOW USEFUL IS COMPOSITION FOR CLASSIFYING THESE ROCKS?

24. WHERE WAS IT PUT TOGETHER???
Let’s see if 2nd question helps us.
Texture or grain size
What do you notice about grain size?
Is there a range of sizes within each category?

25. Let’s look at Sand

26. Sand Composition Varies
BLACK SAND HAWAII – BASALTIC MINERALS
GREEN SAND – HAWAII – OLIVINE
WHITE SAND – GYPSUM
PINK SAND - CORALS

27. HOW DO WE KNOW THE SEDIMENT IS SAND??
To be considered sand the range of grain sizes is from 0.2 cms. to cms.
COMPOSITION MAY VARY – BUT ALL SAND CONTAINS SILICATE MINERALS

28. NAMING INORGANIC LAND DERIVED SEDIMENTARY ROCKS
WE CANNOT NAME INORGANIC LAND-DERIVED SEDIMENTARY ROCKS BY THEIR COMPOSITION BECAUSE ALL CONTAIN SILICATE MINERALS
WE CAN NAME BY THEIR GRAIN SIZE

30. Sediments are pebbles, cobbles, and boulders
rounded
Breccia
angular

31. Silt (0.006 to cms.
SILTSTONE
Sand (0.2 to cms.)
SANDSTONE
Clay (less than cms.)
SHALE

32. IDENTIFYING CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS
WE ASK SAME 2 QUESTIONS:
Where was it put together? Look at the texture or grain size.
Where does it come from? Look at the composition

33. 2 TYPES OF TEXTURE CRYSTALLINE FOR CHEMICALLY FORMED SEDIMENTARY ROCKS
BIOCLASTIC FOR ORGANICALLY FORMED SEDIMENTARY ROCKS
HOW USEFUL IS GRAIN SIZE????

34. WHERE DOES IT COME FROM –COMPOSITION???
Comments
ROCK NAME
Halite
Crystalline
Rock Salt
Gypsum
Rock Gypsum
Dolomite
Dolostone
Calcite
Cemented shells or precipitates
Limestone
Carbon
Plant remains
Coal

35. ROCK SALT
Intergrown crystals of just 1 mineral
DOLOSTONE
ROCK GYPSUM

36. Characteristics of Chemically Formed Sedimentary Rocks
They are monominerallic – consisting of intergrown crystals of just 1 mineral.
Uniform color
Form in shallow seas

37. CHEMICALLY PRECIPITATED LIMESTONE
BIOCLASTIC LIMESTONE
COAL

38. Summary
Inorganic Land-Derived Sedimentary Rocks are identified by Texture or Grain Size
Chemically and/or Organically Formed Sedimentary Rocks are identified by Composition

39. ENVIRONMENT OF FORMATION
How does the natural environment affect the formation of Sedimentary Rocks????
What conditions control which Sedimentary Rock is formed?????
Why are certain rocks formed at different locations???

40. THE SIZE OF THE GRAIN IS DETERMINED BY THE ENVIRONMENT OF FORMATION
HIGH ENERGY ENVIRONMENT
Large particles
Fast moving water – rivers, ocean waves
LOW ENERGY ENVIRONMENT
Small particles
Slow moving water – lake, bay, swamp

42. DETERMINE THE STREAM VELOCITY NEEDED TO TRANSPORT A 1. 0 CM
DETERMINE THE STREAM VELOCITY NEEDED TO TRANSPORT A 1.0 CM. SIZE PEBBLE

43. SEDIMENTARY ROCK WHERE IT WAS PUT TOGETHER CONGLOMERATE BRECCIA
HIGH ENERGY
SANDSTONE
MEDIUM ENERGY
SILSTONE
LOW ENERGY
SHALE
VERY LOW ENERGY

44. HIGH ENERGY
LOW ENERGY

45. Environment of Formation Ocean Derived Sedimentary Rocks
help us understand our past
geologic history
There is evidence of climate
change as well as lost species
of plants and animals in

46. During the Cretaceous Period (about 120 mya) a shallow inland sea split North America.
We know this by the Sedimentary Rocks deposited in the former shallow sea
KANSAS AND KENTUCKY HAVE A GREAT DEAL OF CHALK – TELLS ME ONCE UNDERWATER
WHITE CLIFFS OF DOVER – ENGLAND UNDER WATER
DURING CRETACEOUS PERIOD 120 MYA, LATIN FOR CHALK – A GREAT DEAL OF CHALK WAS FORMED DURING THIS PERIOD. CLIMATE WAS VERY MILD, ICE FREE POLAR REGIONS
1/3 OF NORTH AMERICA WAS FLOODED – NO MODERN GULF OF MEXICO

48. Cretaceous Limestone Deposits in Kansas

49. New York's salt deposits occur layered with shale, dolomite, and anhydrite in the lower part of the Silurian-aged Salina group. The Salina group outcrops in an east-west band from near Buffalo and Rochester through Syracuse to Herkimer County. At the southern edge of the state the salt is 3,000 feet deep.

50. SALT AND GYPSUM EVAPORATION
Bedrock of Salt and Gypsum around Buffalo
What type of environment would cause salt and/or gypsum to evaporate?
Ocean environment with hot temperatures
KANSAS AND KENTUCKY HAVE A GREAT DEAL OF CHALK – TELLS ME ONCE UNDERWATER
WHITE CLIFFS OF DOVER – ENGLAND UNDER WATER
DURING CRETACEOUS PERIOD 120 MYA, LATIN FOR CHALK – A GREAT DEAL OF CHALK WAS FORMED DURING THIS PERIOD. CLIMATE WAS VERY MILD, ICE FREE POLAR REGIONS
1/3 OF NORTH AMERICA WAS FLOODED – NO MODERN GULF OF MEXICO

51. CHARACTERISTICS OF SEDIMENTARY ROCKS
Horizontal layers called beds or strata
Clasts are rounded and sorted because they have been moved by water
Ripple Marks
Mud Cracks
Fossils
Interconnected mineral crystals of 1 mineral (monominerallic)

52. HORIZONTAL LAYERS

53. A. SHALLOW WATER B. LOW ENERGY C. DIRECTION OF FLOW

54. MUDCRACKS
ALTERNATING WET AND DRY CONDITIONS

55. Limestone - FOSSILS