Sedimentary Rocks

1. A. Sediment Source and History B. Formation of Sedimentary Rocks C. Types of Sedimentary Rocks D. Sedimentary Structures and Environments Sedimentary Rocks

2. These are composed of particles derived from pre-existing rocks or by the crystallization of minerals that were held in solutions. A general characteristic of this group is the layering or stratification. SEDIMENTARY ROCKS

3. Type of Sedimentary Rocks • Clastic Sedimentary are composed of particles of pre-existing rocks. These fragments show evidence of transport – rounding of the grains and size sorting. • Chemical sedimentary rocks are the result of either precipitation of solids from solutions (like salt from water) or by organic process, like shells from marine organisms.

4. Recipe forSedimentary Rocks • Sediment • Clasts: mineral particles from weathering of parent rock • Bioclasts: Shell and coral fragments (calcite or silica) • Chemical Precipitate: (calcite, silica, salts) • Accumulation and Preservation • Sedimentation > Erosion • Lithification • Compaction • Cementation A. After Deposition Overburden compacts and reduces pore space B. Compaction Cement from dissolved ions fills some pore space C. Cementation

5. Creation of Clastic Sedimentary Rocks

6. Sediment History Talus slopes Mtn. Streams Beaches Oceans Alluvial FansRivers Delta (Plains) • Effects: Rounding, Size, Sorting and Mineralalogy

8. Clastic Sedimentary Rock Classification (Indicates History and Environment) Increasing duration of weathering and winnowing out of silt and Clay sized particles (predominantly clay minerals) Immature Mature Gravel (and Sand), Poorly Sorted Sand and Silt, Poorly Sorted Sand, Well Sorted Clast Size and Sorting Angular Rounded Sub-Angular Clast Shape Rounded Rock Fragments Unstable Minerals More Stable Minerals Clast Composition Quartz Mountains Cliffs, Glaciers Mountain Streams Rivers, (Flood Plains) Depositional Environment Beaches and Dunes Quartz Sandstone Breccia Conglomerate Arkose Rock Type

9. Clastic Particle Sizes (Wentworth Scale) Gravel Kehew, Table 4-3 Example (mm) (Ø) Bowling Ball 256 -8 Pool Ball 64 -6 Buck Shot 2 -1 Powder /16 4 1/256 8 Boulder Cobble Pebble Sand Silt Clay* Sand Mud *very small particles are usually clay minerals

10. Talus Slopes • Gravel (boulders, cobbles etc.) • Poorly sorted • Angular • Fragments of rocks and minerals

11. Mountain Stream(Upstream) • Gravel (Cobbles, Pebbles etc.) • Poorly sorted • Sub-angular (Somewhat rounded) • Fragments of Rocks and minerals

12. Mountain Stream(Downstream) • Gravel (Cobbles, Pebbles etc.) • Poorly sorted • Rounded • Fragments of Rocks and minerals

13. Alluvial Fans • Sand • Poorly Sorted • Sub-angular • Many minerals

14. Sand Somewhat Sorted Sub-angular Many minerals Riverin the Plains

15. Quartz Sandstone: From Beaches and/or Dunes

16. Delta Silt and Clay i.e., Mud Deep Sea (Lakes, Oceans) Clay Fig. 10.30 Clay minerals and quartz

17. Breccia(#24) • is made of varying sizes of angular fragments cemented together. • Many form as the result of fault movement; others form as the result of rapid and short transportation, such as landslides.

18. Conglomerate (#17) • are very similar to breccias, but the fragments are rounded. • These rocks form in alluvial fans, stream beds and pebble beaches.

19. Sandstone (#16) • is made up of fine-grained particles (1/16 –2 mm). • The sand grains (often quartz) are commonly cemented by silica, carbonates, clay or iron oxides. • is identified by its sandy texture – which often translates into a gritty feel • Environments in which sandstones form include beaches, sand bars, deltas and dunes.

20. Shale (#14) • It is the most common type of sedimentary rock. • It is made of silt and clay sized particles. • It is generally very thin-bedded and splits along the bedding planes. • Normally gray to black, shale may be brown to dark red, depending on the amount of included iron oxide. • form in quiet environments, such as lakes, swamps, deltas and offshore marine. Black shale, deposited in a offshore basin in a Middle Cambrian sea. Wheeler Shale with trilobite fossil (Elrathiakingii) Fish scales

22. Chemical Sediments

23. Weathering &Sediments Sediments Weathering Biotite Quartz Na Feldspar

24. Quartz1 Feldspar1 Clay2 Hematite3 Ions4 • Chemical Weathering • 2.Converts silicates* to clay • 3.Oxidizes iron in minerals • (i.e., ferromagnesian minerals) • 4.Dissolves some ions • (e.g, Ca, Na, K, Mg) • *except quartz Sediments of: Weathering of Granite 1.Mechanical Weathering formsrock and mineral fragments of parent rock Biotite Quartz Na Feldspar

25. Weathering and Erosion of Hawaii Haleakala Past and Present 1.3mya • What are the products of the weathering of Hawaii? • Hint: Think of the black sands of Hawaii

26. Sediments from Weathering • Black sands of basalt and dark minerals • Pyroxene and • Ca-feldspar • Chemically weathered to • Dissolved ions • Iron oxides, and • Clay (Washed away and deposited in deep sea) Maui, Hawaii, 1.3 my old

27. Chemical Weathering Dissolving  ions Oxidation  iron oxides Clay minerals Erosion carries sediments to ocean Chemical Weathering and Erosion Ocean Water Deep Ocean Sediments Kauai: An ancient volcanic island, 4.7 my old

28. Chemical and Biochemical Sedimentary Rocks Fore Reef Back Reef Reef Sandstone (sand) Shale (clay) Limestone (Shell frag. & lime mud)

29. Limestone (CaCO3) (#18) • Generally it is dense, fine-grained, and usually white to dark gray. • Its most distinguishing feature is its solubility in weak hydrochloric or acetic acid accompanied by brisk effervescence. • The environment of deposition if generally warm, shallow seas. • Limestone can be made two ways: • Bioclastic: Fragments of Coral, Algea and Shells • Inorganic: precipitated directly from water • It comes in many different formats

30. Limestone – Travertine (#22) • Looks sugary with bands of different colours • Created when hot, carbon dioxide rich water dissolve limestone and then cools off to deposit the dissolved calcium carbonate.

31. Limestone - Fossiliferous • Made primarily of seashells and other aquatic organisms.

32. Limestone - Chalk • White, soft, and powdery • You could break it part with you hands.

33. Limestone – Coquina (#19) • Contains nothing but seashells. • Made from old coral refs and shallow seas.

34. CHERT (#13) • It is made from quartz or silica crystals • It is made by replacing the calcium carbonate in limestone with silica. • It is often the result of the dissolution of volcanic ash and is sometimes found in extensive beds. • It has waxy luster, is translucent, looks glassy and can be any color, but extensive beds are generally white to gray. • It is also used to make blades.

35. GYPSUM (#21) Satin Spar Alabaster • It is made of calcium sulfate • It is found in geographically wide-spread deposits resulting from the evaporation of a body of water, such as ocean basin or playa lake. • It is soft. • Gypsum is mined for use in wallboard and plasters, as an agricultural amendment and to control the set/cure time of Portland cement. Selenite Gypsum & Anhydrite (water-less calcium sulfate), Carlsbad, NM

36. ROCK SALT • Is knownsodium chloride • It is a deposit resulting from evaporation of a marine basin or lake. • It is used as a source of chlorine and sodium, as a food supplement, in water softeners and as a road de-icer. Halite Trona, CA

37. COAL (#20) • Coal is considered a rock, although it is not composed of minerals, but rather the decomposed remains of large volumes of vegetation that accumulated in a wet, low oxygen environment, such as a swamp or marsh. • Peat, Lignite and Sub-Bituminous & Bituminous are sedimentary varieties of coal and are used as fuels. Coal (sub-bituminous) out of the Cretaceous Dakota Formation of north-eastern Arizona.

38. DIATOMITE • is composed of the siliceous shells of microscopic alga called diatoms. • It is light weight and is generally white. • It is used as an abrasive, insecticide, filtering medium, and paint “flattener”. San Manuel, AZ

39. Dolomite (#23) • Composed of calcium magnesium carbonate • The rock has over 90% carbonate and fossils are rare in these rocks • Does not react with acid.

41. Sedimentary Structures Bedding: Sediments are deposited in • Horizontal layers (original horizontality) • Deeper rocks are older (superposition)

42. La Castilla, Peru Tilted Sedimentary Rock Layers

43. Sedimentary Structures Other information preserved in sedimentary rocks • Cross Bedding (Dunes) • Graded Bedding (Turbidity Currents) • Ripple marks (water or wind) • Mud Cracks (dried lake) • Fossils (many sediments)

44. Indicates current and direction Wind Water Cross Bedding

47. Homework • P. 132 #1,2,3 • P. 127 #1- 4