1. SEDIMENTARY ROCKS

2. TERMS Weathering: breakdown of pre-existing rock
Physical or chemical breakdown
Erosion: transport of sediment on Earth’s surface

3. SEDIMENTARY ROCKS Introduction Detrital Rocks
Chemical and Biochemical Rocks
Lithification

4. Sedimentary Rocks
Introduction

5. INTRODUCTION Origin Only form at Earth’s surface
PSCI 131: Sedimentary Rocks
INTRODUCTION
Origin
Only form at Earth’s surface
Weathering of pre-existing rock into soluble and insoluble sediments
Erosion of sediments
Deposition of solid sediment
Precipitation of dissolved sediment

6. INTRODUCTION Textures
PSCI 131: Sedimentary Rocks
INTRODUCTION
Textures
Clastic: made of grains held together by cement or compaction
Nonclastic: usually made of interlocking mineral crystals

7. Sedimentary Rocks
Detrital Rocks

8. Detrital Rocks “Detrital” from “detritus” - debris
PSCI 131: Sedimentary Rocks
Detrital Rocks
“Detrital” from “detritus” - debris
Composed of solid sediment grains; distinguished by size of grains
All detrital rocks have a clastic texture
Detrital rock with smaller grains
Detrital rock with large grains

9. Shale Most abundant sedimentary rock Made of clay grains
PSCI 131: Sedimentary Rocks - Detrital
Shale
Most abundant sedimentary rock
2/3 of all sedimentary rock is shale
Made of clay grains
Microscopic sheets
From chemical weathering of feldspar

10. Shale PSCI 131: Sedimentary Rocks - Detrital
Scanning electron microscope image of shale showing flat clay grains. Scale bar is cm.
From: claysandminerals.com

11. Sandstone Cemented sand-size grains Sand: 1/16mm – 2mm diameter
PSCI 131: Sedimentary Rocks - Detrital
Sandstone
Cemented sand-size grains
Sand: 1/16mm – 2mm diameter
Quartz is predominant mineral

12. CONGLOMERATE/BRECCIA
PSCI 131: Sedimentary Rocks - Detrital
CONGLOMERATE/BRECCIA
Cemented gravel-size grains
Gravel: greater than 2mm
CONGLOMERATE has rounded gravel
BRECCIA has angular gravel

13. Sedimentary Rocks
Chemical Rocks

14. Chemical and Biochemical Sedimentary Rocks
PSCI 131: Sedimentary Rocks
Chemical and Biochemical Sedimentary Rocks
Dissolved sediment precipitates out of solution as crystals
Chemical rocks: evaporation, chemical activity
Biochemical rocks: growth of shells

15. Chemical Rocks: Crystalline limestone
PSCI 131: Sedimentary Rocks – Chemical rocks
Chemical Rocks: Crystalline limestone
Nonclastic texture
Interlocking calcite crystals
Precipitated from seawater

16. Chemical Rocks: Microcrystalline limestone
PSCI 131: Sedimentary Rocks – Chemical rocks
Chemical Rocks: Microcrystalline limestone
Nonclastic texture
Interlocking microscopic calcite crystals
Precipitated from seawater

17. Chemical Rocks: Travertine
PSCI 131: Sedimentary Rocks – Chemical rocks
Chemical Rocks: Travertine
Nonclastic texture
Porous
Precipitated from groundwater in caves

18. Other chemical sedimentary rocks
PSCI 131: Sedimentary Rocks – Other chemical rocks
Other chemical sedimentary rocks
Rock gypsum and rock salt
Nonclastic texture
Interlocking mineral crystals
Evaporation of salt water
“Evaporites”
Bonneville Salt Flats, the ancient floor of Lake Bonneville, now mostly evaporated

19. Biochemical rocks: Coquina
PSCI 131: Sedimentary Rocks – Biochemical rocks
Biochemical rocks: Coquina
Clastic texture
Shell fragments & cement
Fragile
Shorelines

20. Biochemical rocks: Fossiliferous limestone
PSCI 131: Sedimentary Rocks – Biochemical rocks
Biochemical rocks: Fossiliferous limestone
Clastic texture
Shell fragments, whole shells, mud matrix, & cement
Hard
Shallow ocean

21. Biochemical rocks: Chalk
PSCI 131: Sedimentary Rocks – Biochemical rocks
Biochemical rocks: Chalk
Clastic texture
Microscopic shells (plankton)
Very soft
Deep ocean

22. Chert and flint Composed mainly of microcrystalline quartz
PSCI 131: Sedimentary Rocks-Other biochemical rocks
Chert and flint
Composed mainly of microcrystalline quartz
Nonclastic texture
Can be chemical or biochemical
Very hard
FLINT
CHERT

23. Sedimentary Rocks
Lithification

24. Lithification How sediment becomes rock “Lith” = stone
PSCI 131: Sedimentary Rocks - Lithification
Lithification
How sediment becomes rock
“Lith” = stone

25. Lithification Processes
PSCI 131: Sedimentary Rocks - Lithification
Lithification Processes
Compaction
Cementation

26. PSCI 131: Sedimentary Rocks - Lithification
Begins with deposition & burial of sediment under more sediment

27. Compaction Decreases porosity (empty space) Drives out water
PSCI 131: Sedimentary Rocks - Lithification
Compaction
Decreases porosity (empty space)
Drives out water
Can make flat grains stick together

28. Cementation New crystals form between grains
PSCI 131: Sedimentary Rocks - Lithification
Cementation
New crystals form between grains
Precipitation out of groundwater
Fills in remaining porosity
Original sand grain
Cement crystals
From: northstonematerials.com
From: unibe.ch

29. End of Sedimentary Rocks