1. Sedimentary Rocks

2. What is a Sedimentary Rock?
Sedimentary rock is formed by
deposition and consolidation of sediment and organic material
precipitation of minerals from solution

3. Where does sediment come from?
Weathering is the process that reduces solid rock to rubble
Two types
Physical: solid rock to rubble without changing chemical composition
Chemical: altering or dissolving minerals in a rock

4. Moving Rocks “Au Naturel”
Direction of transport
Erosion: transportation of sediment/ions
streams, wind, glaciers
super-strong hikers…
Water is the most efficient natural transporter
~27 billion tons annually)

5. Grain Size and Distance
It’s the size that counts…
Sediment far removed from its place of origin
Small and round
Sediment close to source
Larger and angular

7. Lithification Sediment is deposited in low spots
Transportation continues—new sediment buries older sediment
Buried sediment is compacted (loss of empty space)
Cementation—filling in spaces

8. Compaction VS. Cementation

9. Types of Sed. Rocks Clastic Organic Chemical Bioclastic
formed from compacted sediment
Organic
formed from lithified plant/animal remains
Chemical
formed from direct precipitation of ions from solution
Bioclastic
formed from broken shell fragments

10. Clastic Sed. Rocks →Increasing Grain Size → Shale siltstone
conglomerate
sandstone

11. Organic Sed. Rocks Coal Buried and compressed dead things From this
To this
…in a matter of eons

12. Chemical Sed. Rocks
Water evaporates leaving behind mineral deposits (evaporite deposits)
Death Valley, CA
Great Salt Lake, UT

13. Bioclastic Sed. Rocks Seawater contains dissolved ions
Critters use these ions to make their shells
When they die, their shells fall to the ocean floor where lithification can take place
coquina

14. Sedimentary Structures
Features that develop in sediment during or shortly after deposition
Most common types
Bedding
Cross-bedding
Ripple marks
Mud cracks

15. Bedding Layering in sedimentary rocks
Sediment accumulates layer by layer

16. Cross-Bedding
Basically, lithified sand dunes

17. Ripple Marks Small, parallel ridges and troughs
Created by wave and wind action
Modern ripples on a sand dune
Ancient ripples preserved in sandstone→

18. Mud Cracks Polygonal cracks formed as mud dries and shrinks
Modern mud cracks→
Ancient mud cracks in mudstone→