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1. Formation of
Sedimentary Rocks
Understanding the processes that transform loose sediments into solid
rock through weathering, transportation, and deposition.

2. What Are Sediments?
Definition
Loose solid particles from
Latin sedimentum meaning "to
settle" - material settling from
water or air.
Origin
Formed by breaking apart of
older rocks through
weathering and erosion
processes.
Coverage
Form surface layers on bedrock ranging from practically non-
existent to several kilometers thick.

3. Why Study Sedimentary Rocks?
Energy Resources
Most valuable sources of oil, gas, and
coal. Fossil fuels derive from organic
matter in sediments.
Earth's History
Mount Everest's fossiliferous limestone
reveals it was once ocean floor, showing
geological evolution.
Life Evolution
Fossils preserved in sedimentary rocks
provide knowledge of life's evolution on
Earth.

4. Types of Sedimentary Particles
1
Terrigenous Particles
Fragments of pre-existing rocks
worn down by weathering. Include
gravel, sand, silt, clay, and volcanic
materials like ash and lapilli.
2
Chemical Precipitates
Materials transported in solution
but grow as solids through
chemical precipitation. Examples:
carbonate rocks and evaporites.
3
Organic Materials
Plant and skeletal remains or
biological secretions. Examples:
coal deposits, coquina, and
fossiliferous limestone.

5. Classification of Sedimentary Rocks
Clastic Rocks
• Derived from disintegration of pre-existing rocks
• Variable grain sizes: clay to boulder
• Transported by gravity, water, wind, glaciers
• Examples: conglomerate, sandstone, shale
Non-Clastic Rocks
• Chemical precipitates from evaporation
• Biochemical from organic accumulation
• Examples: limestone, dolomite, coal
• Formed by crystallization processes

6. Physical Weathering Processes
Frost Action
Water freezes in cracks, expands 9%, creating pressure that
fractures rocks into angular pieces.
Exfoliation
Pressure release causes outer rock surfaces to expand and
break into sheets parallel to surface.

7. Chemical Weathering
Reactions
Carbonation
Carbonic acid reacts with calcite in limestone, forming
caves through dissolution processes.
Oxidation
Oxygen reacts with iron to form iron oxide, giving rocks
reddish-brown coloration and weakening structure.
Hydrolysis
Water breaks down silicate minerals like feldspar,
converting them into clay minerals plus dissolved ions.

8. Sediment Transportation Methods
01
Dissolved Load
Material carried in solution as part of moving water. Amount depends on temperature and
saturation point.
02
Suspended Load
Silt and fine sand remain suspended by upward turbulent currents generated at river bed.
03
Saltation Load
Sand-size particles bounce along stream bed through impact of other bouncing particles.
04
Bed Load
Larger particles rolled, bounced, and slid along bottom, fully supported by channel bed.

9. From Sediment to Rock:
Lithification
Burial
More sediments pile onto existing layers, creating pressure and
causing basin subsidence.
Compaction
Weight of overlying material reduces pore spaces, expelling
water and creating tighter packing.
Cementation
Minerals precipitate in pore spaces, binding grains together
with silica, calcite, or iron oxide cement.

10. Diagenesis: Post-Depositional Changes
Conditions
Occurs at temperatures below 250°C
and pressures below 2 kilobars, up
to 5000m depth.
Processes
Physical, chemical, and biological
changes during and after
lithification but before
metamorphism.
Effects
Mineral composition changes, new
mineral formation, dissolution, and
element mobilization.