2. Geology 12: Sedimentary Facies and Structures

3. Facies: distinctive body of sediment Gravel On-shore fluvial Near-shore marine Off-shore marine Chert High Low Energy

5. Facies

6. Marine Environments –Changes in sea-level due to ice ages, warm oceans, or rising & sinking plates. –1. Marine Transgression “sea trespasses” Sea-level rises (buried by water and marine sediments) Buried docks, cities, beaches, trees Shoreline moves inland Marine facies moves inland Some facies deposited over very large areas

7. Drill hole Low E High E T = L / H Use note helper WS 6.2A

8. –2. Marine Regression “sea retreats” Sea-level falls exposed docks, beaches, marine fossil above sea- level Shoreline moves seaward Marine facies moves seaward Some facies deposited over very large areas

9. Drill hole Low E High E R = H / L Use note helper WS 6.2A

10. Transgression/Regression What happened here?

11.  Go to note helper WS 6.2 A and complete reverse side

12. a) H L L T Sea Land

13. b) L L H R Land Sea

14. c) L H L L L H R T R LandSea

15. Transgression/Regression H H L L L L T T R

17. Transgressional Seas

19. How man got to Australia

20. 140 m lower

21. 65 m higher

22.  Hand out note helper WS 6.2B  Remainder of Chp 6 notes to be completed on note helper.

23. Fluvial (river) Environments –Tend to be regressional (coastline moves seaward) as delta builds out –Cross-section of a river’s delta Meandering/wandering river beds

24. Fluvial Environments

26. Sedimentary Structures: features that form as a result of physical and biological processes. 1. Strata/Beds: distinct layers (mm to m thick) that vary in colour, grain size, or composition. sst sh 1 bed Sst from spring runoff or flood (Hi E) Sh from slow periods (low E)

27. Ex: Varves: 1 year Silt-clay: (spring-summer Clay (fall-winter) (used to determine age of glacial lake’s existence)

28. Strata/Beds

30. Varves

34. 2. Graded Bedding: grain size decreases upward in a single bed. Form a) at end of stream flood (where waters slow) b) from turbidity currents (underwater flows/landslide of sediments) 1 bed silt sand gravel

35. How it forms: –1. Large current moves materials of various sizes –2. current slows –3. large sediment drops out first, then progressively smaller and smaller material

36. Graded Beds

39. 3. Cross-bedding: inclined bedding within a thicker sedimentary layer (mainly sand). Direction of flow 1 bed Successive layers of sediments

40. Cross Bedding

41. What happened? Cross bedding is common in sand dunes, stream channels & shallow marine environments (shifting beach sand) Paleo-currents = ancient current directions

42. Cross Bedding

43. 4. Ripple Marks: ridges within a bed (fine to med’ sediments). 2 types a) current ripple marks = asymmetrical b) wave-formed ripple marks = symmetrical Current direction

44. Ripple Marks

47. 5. Mud Cracks: fine (clay) sediments that dry & shrink in the sun forming polygonal shapes Indicative of tidal flats and dried lake bottoms From in 3 steps: a) Mud deposited in low E environment

48. b) mud dries, shrinks & cracks c) Silt/sand is deposited on top & in the cracks preserving the structure. Side view Top view Side view

49. Mud Cracks

52. 6. Fossils: remains or traces of ancient organisms (or old teacher). 3 types: a)Body Fossil: i) Unaltered: original remains of organism Ex: Wooly Mammoth, Sabre-toothed Tiger ii) Altered: altered or replaced remains or organism Ex: wood replaced by silica = petrified wood Ex: leaves preserved as thin carbon film Ex: calcite shell replaced by iron sulfide

53. Fossils: Body Fossils

54. Fossils: Body Fossil

55. “Jaws” Woolly Mammoth

56. b) Trace Fossil: indication of past organic activity. Ex: tracks, trails, burrows, borings Ex: coprolites (fossilized feces = dino dung)

57. Fossils: Trace Fossil

58. Coprolites

59. c) Mold/cast: shape of organism. Mold Cast 1. Shell buried 2. Shell dissolved (void space) 3. Rock split to reveal mold mold 3. sediment/precipitate deposited in mold) 4. Rock split to reveal cast Lots more on fossils in chapter 8

60. Fossils: Cast & Mold

61. 7. Sole Marks: marks on which was originally the under surface of a bed Include various marks produced by animals and objects moving on the surface on which the sediment was deposited. Ex: a filled in scratch left by a moving boulder.

62. Sole Marks

64. 8. Flute Casts/Marks: elongated depressions that form at the base of a river channel Current direction

65. Flute Casts / Marks

68. Do WS 6.2