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/Organic Rocks Classification Lithification

4. Sedimentary Rocks Introduction

5. 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 GEOL 131: Sedimentary Rocks

6. Sedimentary Rocks Detrital Rocks

7. “Detrital” from “detritus” - debris Composed of solid sediment grains Distinguished by size of grains GEOL 131: Sedimentary Rocks Detrital rock with large grains Detrital rock with smaller grains

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

9. Shale GEOL 131: Sedimentary Rocks - Detrital From: From: claysandminerals.com Scanning electron microscope image of shale showing flat clay grains. Scale bar is 0.005 cm.

10. Shale Formation Quiet environment Burial and compaction of clay grains Not cemented Weak GEOL 131: Sedimentary Rocks - Detrital From: From: geoexpro.com

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

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

13. Sedimentary Rocks Chemical Rocks

14. Dissolved sediment precipitates out of solution as crystals “Inorganic” processes: e.g. evaporation, chemical activity “Biochemical” processes, e.g. growth of shells GEOL 131: Sedimentary Rocks From: rogerdhansen.wordpress.com Bonneville Salt Flats, Utah

15. Chemical Rocks: Limestones Composed mainly of calcite (CaCO 3 ) Several kinds – Some biochemical and some inorganic Most form in marine environments GEOL 131: Sedimentary Rocks - Chemical

16. Biochemical Limestones GEOL 131: Sedimentary Rocks - Chemical From: www.pitt.edu From: seashellsbymillhill.com From: proprofs.com Fossil limestone -Shells + matrix -Hard Coquina -Shells only -Fragile Chalk -Microscopic plankton shells -Very soft

17. Biochemical Limestones GEOL 131: Sedimentary Rocks - Chemical Chalk under a scanning electron microscope, showing shells (round) and calcite crystals. Scale bar is 0.002 cm. From: From: greenelectron-images.co.uk

18. Inorganic Limestones GEOL 131: Sedimentary Rocks - Chemical Micrite -Microscopic calcite crystals -Precipitated from oversaturated seawater Travertine -“Cave rock” -Porous From: www4.uwm.edu From: russianriverschoolhouse.com

19. Chemical Rocks: Chert Biochemical Composed mainly of microcrystalline quartz Very hard; sharp edges Made from compacted microscopic plankton shells GEOL 131: Sedimentary Rocks - Chemical

20. Chemical Rocks: Evaporites Inorganic Evaporation of water (usually salt water) Rock salt, rock gypsum GEOL 131: Sedimentary Rocks - Chemical Bonneville Salt Flats, the ancient floor of Lake Bonneville, a salty lake now mostly evaporated

21. Chemical Rocks: Coal Organic, no minerals Chemically altered dead plant matter Need oxygen- poor water GEOL 131: Sedimentary Rocks - Chemical From: eis.uow.edu.au

22. Sedimentary Rocks Classification

23. Classification: Detrital GEOL 131: Sedimentary Rocks

24. Classification: Chemical GEOL 131: Sedimentary Rocks

25. Sedimentary Rocks Lithification

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

27. Lithification Processes Compaction Cementation GEOL 131: Sedimentary Rocks - Lithification

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

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

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

31. End of Sedimentary Rocks