1. Geology 12 Presents

2. Sedimentary Rocks 95% of the Earth’s volume is igneous and metamorphic rocks but 75% of the Earth’s surface is covered by sediments or sedimentary rocks. Derived from pre-existing rocks: –1. detrital/clastic rocks: mineral grains or rock fragments (mechanical or biological weathering) –2. chemical: dissolved & precipitated minerals (chemical weathering).

3. Ex: granite: Quartz + Fs + Biotite Weathering: Mech/bio quartz sand clays Transport – River, wind, ice Deposition – Beach delta ocean lithification – Cemented Rocksandstone shale

4. Sedimentary Rocks

5. Ex: granite: Qtz + Ca plag’ Fs + Biotite Weathering: Chem’ calcium Transport – solution in river Deposition – ocean lithification – precipitation Rock limestone

7. Terminology Precipitation: opposite of dissolve: aqueous to solid lithification: materials are compacted and/or cemented together to form rock. Rounded: angular fragments become rounded (& smaller) through abrasion as they are transported

8. Rounding

9. Deposition: ice, wind, or water deposit/drop sediment in river bed, moraine, lake, beach, ocean, etc. Facies: a distinct sediment or rock type Sorting: process by which particles are separated according to size (& density) –Clay with clay –Sand with sand –Gravel with gravel Water & wind are excellent sorters, ice is poor

10. Sorting

11. Gravel SandSiltClay faciesfaciesfacies facies highlow river Energy gravel lake/ocean delta beach sand silt clay sorted

14. Pore space = porosity = voids between particles Clay 80% sand 20% mixture 5% Well sorted

15. Porosity

16. Compaction: weight of overlying sediment compresses sediments, forces water out and “glues”/lithifies mud siltstone & shale Cementation: weathered silica, calcite and iron oxides dissolved in water precipitate in pore spaces to cement/lithify particles together. Friable: rock is easily crumbled (like dry cake)

17. Fissile: rock breaks easily along closely spaced parallel lines –Like cleavage in rock

18. Fissile

19. Sedimentary Rocks 1. Detrital/Clastic 2. Chemical 3. Biochemical

20. 1. Detrital/Clastic –Detritus = solid particles or pre-existing rocks –Clastic = composed of rock fragments

21. Sediment size description rock name Gravel >2mmrounded conglomerate gravel angular breccia gravel Sand 1 / 16 – 2mm (mostly Qtz) sandstone Mud < 1 / 16 mm silt siltstone silt & clay mudstone < 1 / 256 mm clay claystone shale

22. Sandstone = Sst: sandy –Red sandstone: with lots of K Fs (pink Fs) = arkose sst Siltstone: gritty with wet mud smell Shale: greasy with wet mud smell

33. Siltstone

37. 2. Chemical: originate from substances taken from solution from chemical weathering These chemicals are extracted from lake or ocean water via: –i) precipitation (Ex; drying lake bed) –Ii) organisms (coral reef) BUT this is a biochemical rock!

38. Death Valley Salt Flats

39. Dead Sea

41. Texture Composition Rock Name Varies calcite CaCO 3 limestone/Lst Varies dolomite CaMgCO 3 dolostone Crystalline gypsum CaSO 4 rock gypsum Crystalline halite NaCl rock salt carbonate

42. Travertine: Lst that precipitates out of hotsprings but is rare Lst: most is biochemical Dolostone: forms from Lst that is altered in: i) very saline lagoons –ii) where Lst has been uplifted above the water table and fresh water with Mg leeches through replacing the Ca Lst Dolostone CaCO 3 CaMgCO 3 HCl Test!Barely fizzesFizz!!!

49. Travertine Terraces in Turkey

50. Evaporites: (rock gypsum and rock salt) precipitate from land-locked lakes and seas where the evaporation raises the salinity to the saturation point. Very salty water evaporation Gypsum & halite crystals

51. Rock gypsum: white-pink-grey, massive or tabular crystals, H =2, white streak Rock salt = halite: colourless, cubic crystals, salty taste, H = 2-3 Silvite = KCl = potash: a fertilizer formed from evaporation on vast, shallow seas in Saskatchewan

52. Gypsum

53. Gypsum Thin section

57. 3. Biochemical Texture Composition Rock Name Clastic - calcite CaCO 3 limestone/Lst crystalline chalk: microscopic coquina: shells Fine quartz chert Fine- carbon C coal crumbly

58. Limestone: accumulation of billions of skeletons of corals,shellfi`sh,algae, etc. Originally as aragonite which alters to calcite. Forms: –Massive: shells broken and ground into powder before lithification –Sugary = crystalline –Coquina (KD)= cemented broken shells –Chalk = soft, microscopic fossils HCl test!

65. Chert: forms 2 ways: i) silica rich waters percolate up through earth replacing the Lst in the form of nodules, a bulbous mass of chalcedony (“elephant man”) ii) organisms (sponges, diatoms) that use silica for skeletons die; the silica accumulates on the ocean floor to form bedded chert (usually grey). Flint = black chert Jasper = red chert

69. Chert thin section

70. Radiolarians

72. Coal: form in the process i) land plants accumulate in swamps, bogs low in pH and low in O 2 to prevent bacterial decay of organic matter (OM). ii) The OM accumulates to form peat. iii) heat + time drives off the volatiles (H 2, N 2 & O 2 ) leaving C to form coal Black, H = 1 – 3, SG = 1 (light)

75.  Do Lab 6.1  Do WS 6.1 Go to Lab 6.1 Go to 6.2 Notes