1. Sedimentary RocksandSedimentary Environments

2. So, what do we get from weathering? • Big rocks break into smaller rocks and grains • Clast is a general term (fine material = sediment) • If still large enough, clasts may contain more than one mineral • Small clasts are generally only one mineral cobbles sand grains Size of clasts

3. Clast Size: terms • Clay (refers to a specific mineral that is often very fine grained, AND to any very fine grains) • Silt – almost all quartz • Sand – quartz with some other minerals • Pebbles – variable mineralogy • Cobbles – variable mineralogy • Boulders –variable mineralogy Size of clasts

4. So, what do we get from weathering? • Some minerals are not very stable • They may dissolve • Or break down to form other minerals • Oxidation => “rusty” red minerals • Hydrolysis => clay minerals oxidation clay Composition

5. Goldich’s weathering series Composition

6. Big picture

7. Stream load

8. Settling velocity low energy high energy

9. Big picture (continued) weathering and erosion clastic material dissolved material biological material transportation deposition gravity chem. precipitation lithification

10. The book sort of combines chemical and biological

11. The most common sedimentary minerals in clastic rocks Quartz Clay Why? Quartz grains in a sandstone 2 mm Shales are almost entirely made of Clay, but the grains are too small To see

12. Olivine beach - Hawaii

13. What kind of sediment collects . . . • On mountain sides • Near glaciers • In sand dunes • Along rivers • In lakes • At deltas • On beaches • In lagoons • In wetlands • Near reefs Oysters, Mancos Shale

14. Kinds of sedimentary rocks rock salt • Clastic • Chemical • Biological sandstone limestone

15. Kinds of sedimentary rocks rock salt • Clastic • Chemical • Biological sandstone limestone

16. Deposition in layers • Bed – relatively uniform layer E.g., “the limestone bed” • Strata – an identifiable layer May be smaller than a “bed” • Formation – a rock stratigraphic unit that has particular characteristics that allow it to be identified in different places. May not be completely homogeneous

17. Grand Canyon

18. Grand Canyon Rim

19. Supai Group

20. “Massive” layers

21. “Interbedded” layers

22. “Laminated” rocks

23. Examples of sedimentary rocks • Breccia • Conglomerate • Sandstone • Shale, etc • Carbonate • Evaporite Almost all clastic material Generally little clastic material

24. Carbonate rocks • Called limestone or dolostone • Or, generically, just limestone • Most form by precipitation of calcium carbonate from seawater • Generally in moderate to deep ocean basins • A few are freshwater • Some are reef deposits (organic) • Some contain clastic components

25. Evaporite rocks • From by evaporation of ocean waters • Gypsum => gyp rock • Halite => rock salt

26. Examples of sedimentary rocks • Clastic Sedimentary Rocks • Breccia • Conglomerate • Sandstone • Shale, etc • Chemical Sedimentary Rocks • Carbonate • Evaporite

27. Kinds of Sedimentary Rocks • Clastic • Chemical • Biological coal coquina

28. Kinds of Sedimentary Rocks • 1. Clastic rocks shale conglomerate sandstone

29. Kinds of Sedimentary Rocks • 1. Clastic rocks • 2. Chemical sedimentary rocks Limestone with fossils evaporite evaporite Rock salt Gyp rock

30. Salt flats Halite deposits

31. Gypsum precipitates Gypsum in red soil

32. Kinds of Sedimentary Rocks lignite (coal) • 1. Clastic rocks • 2. Chemical sedimentary rocks • 3. Biological sedimentary rocks anthracite (coal) Coquina = “beach rock” Limestone (petrified reef)

33. Examples of sedimentary rocks • Clastic Sedimentary Rocks • Breccia • Conglomerate • Sandstone • Shale, etc • Chemical Sedimentary Rocks • Carbonate • Evaporite • Biological Sedimentary Rocks • Coal • Coquina Named according to grain size and shape Named according to composition

34. Why do we have different kinds of sedimentary rocks on top of each other? • Change in the environment of deposition • = a facies change

35. Transgression and regression • Transgression = increase in ocean depth • Regression = decrease in ocean depth

36. (relative) sea level changes • Due to climate change • Uplift of continents • Downdropping of continents • Depth of water may change • Areas may become dry land • Dry land may flood

37. Sedimentary facies • Facies = environment of deposition • Different kinds of sediment deposited in different places at the same time

38. Characteristics of different facies