Sedimentary Rocks

1. Sedimentary rocks are products of mechanical and chemical weathering of preexisting rocks They account for about 5% (by volume) of Earth’s outer 15 kilometers The account for 90% of the upper ½ kilometer Contain evidence of past environments Provide information about sediment transport by one of the geologic fluids Often contain fossils Sedimentary Rocks

2. Sedimentary rocks are important for economic considerations because they may contain • Coal • Petroleum and natural gas • Sources of iron, aluminum, and manganese • Natural fertilizers • Materials for concrete and bitumen

3. Types of sedimentary rocks • Sediment originates from mechanical and/or chemical weathering • Rock types are based on the source of the material • Detrital or clastic rocks – transported sediment as solid particles • Chemical rocks – sediment that was once in solution

4. What is a sediment? • A material deposited by one of the geologic fluids (wind, water, ice) at the earth’s surface.

5. Types of Sediments • Clastics • Materials transported and deposited by wind, water, or ice • Chemical • Materials deposited by chemical precipitation • Biologic •  Parts of living organisms

6. Clastic or Detridal • Pieces of solid stuff transported ad deposited by a geologic fluid • Size and amount is controlled by • Fluid • Density, viscosity • Velocity

8. Generalized Geologic Map

9. Evaporites • Reduce the volume by  44%    (CaMg)CO3   (Limestone - Dolomite)  2.2 g/cm3 81%    (CaMg)SO4    (Gypsum)   2.6 g/cm3 91%    (Na,K)Cl         (Rock Salt)  1.8  g/cm3  

11. Sedimentary Sequence in the Mediterranean Basin •                         ClasticsCycle 3            Salt                        Gypsum                        Limestone •                         ClasticsCycle 2            Salt                        Gypsum                        Limestone                        ClasticsCycle 1            Salt                        Gypsum                        Limestone

12. Clastics         2.0 g/cm3Limestone     2.2 g/cm3Gypsum        2.6 g/cm3Salt                1.8  g/cm3

14.    Biologic • Parts of living organism • Rock Forming organisms • (coral, algae)     limestones • Organic Rocks from dead organisms • Plants (coal) • Fragments of organisms • (oozes, muds, fossils)  limestones

15. Rock forming Organisms • Coral • Blue-Green algee

16. Dead Coral

17. Distribution of reefs • Clear warm water • Normal salinity

18. Dead organisms • Plants • Swamps (anoxic) • Peat • lignite • subbituminous • bituminous • superbituminous • Shells • Fragments

19. Shells

20. Burpee Museum, Rockford, Illinois Coal Swamp

21. Major Coal U.S. Basins

22. Sedimentary environments • A geographic setting where sediment is accumulating • The environment determines the nature of the sediments that accumulate (grain size, grain shape, etc.)

23. Types of sedimentary environments • Continental • Dominated by stream erosion and deposition • Glacial • Wind (eolian) • Marine • Shallow (to about 200 meters) • Deep (seaward of continental shelves)

24. Types of sedimentary environments • Transitional (shoreline) • Tidal flats • Lagoons • Deltas

25. Sedimentary Environments • ..\POG Lect\sed environments.jpg

26. Sedimentary Facies • Different sediments often accumulate adjacent to one another at the same time • Each unit (called a facies) possesses a distinctive set of characteristics reflecting the conditions of a particular environment • The merging of adjacent facies is a gradual transition

27. Sedimentary Facies

28. Big Bend, Texas

29. Sedimentary structures • Strata, or beds (most characteristic of sedimentary rocks) • Bedding planes that separate strata

30. Sedimentary structures • Cross-bedding • Graded beds • Ripple marks • Mud cracks • Fossils