1. Sedimentary Rocks

2. Sedimentary Rocks
Sedimentary rocks cover most of the outer surface of the Earth
Sedimentary rocks form from consolidation of material weathered from other rocks
Pieces of preexisting rocks

3. Formation of Sedimentary Rocks
Weathering and Erosion
Whenever rock is exposed at Earth’s surface, it is continuously being broken down by weathering.
Sediments: small pieces of rock that are moved and deposited by water, wind, glaciers, and gravity.
When sediments become “glued” together, they form sedimentary rocks

4. Weathering Weathering produces rock fragments (sediments)
Sediments range in size from huge boulders to microscopic particles
Chemical Weathering: minerals in a rock are dissolved or otherwise chemically changed
Physical Weathering: Minerals remain chemically unchanged
Breaking rock into smaller pieces
No change in composition

5. Weathering

6. Effects of Weathering
Chemical weathering – limestone or marble (calcite) building materials dissolve from rain

7. Erosion Erosion: the removal and transport of sediment
Four main agents of erosion:
Moving Water
Wind
Glaciers (Ice)
Gravity

8. Energy of transporting agents
Water:
Fast-moving water can transport large particles better than slow-moving water
As water slows down, largest particles settle out first
Wind:
Can only move small grains
Glaciers:
Move all materials with equal ease
Dumps materials in unsorted piles as the glacier melts
Deposits similar to landslides

9. Transport Rounding: Sorting: Effects of transport:
Grinding away sharp edges and corners during transport
Angular: irregular, sharp shape grains
Sorting:
Sediment is organized by size by transporting agent (speed)
Assortment starts off poorly, then becomes well assorted after process of transportations

10. Close to Source
Far from Source

11. Deposition Transported sediments are dropped
Sediments in nature are deposited when transport stops
Particles will settle out forming layers with the largest grains at the bottom

12. Lithification
As sediment is deposited, the bottom layers are subjected to increasing pressure and temperature causing lithification
Lithification: the physical and chemical processes that transform sediments into sedimentary rocks
Lithify: Greek word lithos meaning stone

13. Lithification Compaction 2. Cementation
The weight of overlying sediments forces the sediment grains closer together
Water, oil and natural gas is usually found in the pore space
2. Cementation
Occurs when mineral growth glues sediment grains together into solid rock
Usually calcite or iron oxide

14. Sedimentary Features Bedding Graded Bedding Cross-Bedding
Sediment is deposited in horizontal layering
Oldest beds on the bottom, youngest on top
Horizontal in nature because thing will settle to the lowest position
Graded Bedding
Progressive change in grain size from bottom to top (coarse on bottom, fine grains on top)
Cross-Bedding
Form as flowing water or air move sand grains

15. Bedding

16. Sedimentary Features Fossils Ripple Marks
From as water or wind pass over the top of loose sand or silt
Happen whenever a current is occurring
Fossils
Traces of plants or animals preserved in rock
Hard parts (shells, bones) more easily preserved as fossils

17. Types of Sedimentary Rocks
Clastic (Detrital): form from cemented sediment grains that come from pre-existing rocks
Chemical: form by precipitation of minerals from solution
Biochemical (Organic): accumulate from remains of organisms

18. Clastic Sedimentary Rocks
Most common sedimentary rock
Classified according to the sizes of their particles
Gravel: 2mm Conglomerate or breccia
Sand: 1/16 to 2mm (like sandpaper) Sandstone
Silt: 1/256 to 1/16 mm (gritty on teeth) Siltstone
Clay: up to 1/256mm (slick on teeth) Shale/Claystone

20. Conglomerate/Breccia
Breccia: angular grains
Conglomerate: rounded grains

21. Chemical Sedimentary Rocks
During weathering, minerals can be dissolved and carried into lakes and oceans. As water evaporates, the dissolved minerals are left behind.
Crystal grains precipitate out of solution and settle on the bottom. As a result, layers of chemical sedimentary rocks form, most which are called evaporates.
Evaporites: crystals form from evaporating water
Examples: rock gypsum and rock salt

22. Biochemical Sedimentary Rocks
Formed from the remains of once-living organisms.
Limestone: composed mainly of calcite (fizz with HCl)
Only formed in the tropical area
Coal: compaction of partially decayed plant material
Rapid plant growth and deposition in water
Rapid burial
Only occurs where you have a lot of plants
Usually form in swampy areas

24. Uses of Sedimentary Rocks
Ceramics
Claystone, shale
Building Material
Limestone
Sandstone
Fossil fuels
Coal
Petroleum forms in sedimentary rocks