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Classroom presentations to accompany Understanding Earth, 3rd edition prepared by Peter Copeland and William Dupré University of Houston Chapter 7 Sediments.

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Presentation on theme: "Classroom presentations to accompany Understanding Earth, 3rd edition prepared by Peter Copeland and William Dupré University of Houston Chapter 7 Sediments."— Presentation transcript:

1 Classroom presentations to accompany Understanding Earth, 3rd edition prepared by Peter Copeland and William Dupré University of Houston Chapter 7 Sediments and Sedimentary Rocks

2 Tom Bean/DRK

3 Processes of the rock cycle Weathering Erosion Transportation Deposition (sedimentation) Burial Diagenesis

4 Sedimentary Stages in the Rock Cycle Fig. 7.1


6 Sedimentary rock (a) Rock resulting from the consolidation of loose sediment that has been derived from previously existing rocks and accumulated in layers (detrital or clastic) (b) Rock formed by the precipitation of minerals from solution by either organic or inorganic processes (chemical)

7 Sedimentary rocks 5 % by volume of the upper crust 75% by area of continental areas Often the only record of geologic events: e.g. The Himalayas will someday be sandstone

8 Transport and deposition of clastic sediments Movement of sediment by wind, ice or water. Mode of transport produces distinctive deposits.

9 Transport affects the sediment in several ways Sorting Sorting : measure of the variation in the range of grain sizes in a clastic rock or sediment Well-sorted sediments indicate that they have been subjected to prolonged water or wind action. Poorly-sorted sediments are either not far-removed from their source or deposited by glaciers.

10 Sorting Well-sortedPoorly-sorted

11 Transport affects the sediment in several ways Roundness Roundness : measure of how rounded the corners are Sphericity Sphericity : measure of how much it is like a sphere Sorting, roundness, and sphericity all increase with amount of transport.

12 Rex Elliott Fig. 7.2 Well-sorted Sand

13 Poorly-sorted Sand Rex Elliott Fig. 7.2

14 Roundness and sphericity Fig. 7.3

15 Types of detrital rocks Largely based on the size of the particles, which may be anything. Conglomerate Breccia Sandstone (quartzite, arkose, greywacke) Shale Mudstone Siltstone

16 Sedimentary structures stratification = bedding = layering Produced due to differences in 1. size of particles 2. kinds of particles

17 Clues to interpreting sedimentary environment Sedimentary structures Sorting, roundness, sphericity Sequence of beds

18 Types of chemical sedimentary rocks LimestoneCaCO 3 ChertSiO 2 SaltNaCl, KCl, K 2 SO 4 GypsumCaSO 4 2H 2 O Coalaltered organic debris

19 Chemical environments: Carbonates Clear water — away from big rivers (or volcanoes) Warm water — subtropical to tropical shallow water, two reasons: Organic:sunlight only penetrates to about 100 m Inorganic: CCD (dissolution CaCO 3 dependant on P)

20 Chemical environments: Evaporites Restricted environments (Mediterranean Sea, Texas coast) Minerals precipitate according to solubility. Gypsum Halite 50%90% CaSO 4 2H 2 O NaCl

21 Sedimentary structures Particular structural features can give information about the environment of deposition. Structures also help determine if a bed is right-side-up. — this is important in deformed rocks

22 Graded bedding Scale may be mm to m

23 Turbidity currents Suspension of water, sand, and mud that moves downslope (often very rapidly) due to its greater density than that of the surrounding water (often triggered by earthquakes) Speed of turbidity currents first appreciated in 1920 — breaking of phone lines in the Atlantic; also gave indication of distance traveled by a single deposit

24 Other up indicators Cross-bedding Ripple marks Mudcracks Raindrop impressions Fossils (some may have been preserved in growth position)

25 From sediment to sedimentary rock (lithification) Compaction: reduces pore space Clays and muds are up to 60% water; 10% water after compaction. Cementation: chemical precipitation of mineral material between grains (SiO 2, CaCO 3, Fe 2 O 3 ) binds sediment into hard rock Recrystallization: P and T increase with burial 30°C/km or 1°C/33 m 2

26 Unconformity Buried surface of erosion

27 Fig. 7.4 Characteristics of a Sedimentary Environment

28 Fig. 7.5 Common Sedimentary Environments



31 Peter Kresan Fig. 7.6 Cross-bedded Sandstone

32 Formation of Cross-beds Fig. 7.7

33 Raymond Seiver Fig. 7.8 Modern Rippled Sand

34 Reg Morrison/Auscape Fig. 7.8 Ancient Ripple-marked Sandstone


36 Fig. 7.9

37 Chip Clark Bioturbation Tracks and Tunnels

38 Typical Alluvial Cycle Deposited by a Migrating River Fig. 7.11

39 Fletcher & Baylis/Photo Reseaerchers Fig. 7.11 Partial Alluvial Cycles in China

40 Products of lithification

41 Fig. 7.12 Compaction (Primarily of Muds) Precipitation of new minerals or additions to existing ones

42 Fig. 7.12 Dissolution of More Soluble Minerals Recrystallization of Unstable Minerals

43 Fig. 7.13 Quartz grain Calcite cement Peter Kresan


45 Fig. 7.14 Relative Abundance of Sedimentary Rock Types Relative Abundance of Sedimentary Rock Types

46 Fig. 7.15a Conglomerate Breck Kent

47 Fig. 7.15bFig. 7.15a Sandstone Breck Kent

48 Fig. 7.15c Shale D. Cavagnaro/Visuals Unlimited

49 Four Major Groups of Sandstones Fig. 7.16

50 Fig. 7.16a Quartz Arenite: Pure Quartz

51 Fig. 7.16b Arkose: Feldspar-rich

52 Fig. 7.16c Lithic Sandstone: Rock Fragment-rich

53 Fig. 7.16d Graywacke: Matrix-rich


55 Foraminifer in the Eye of a Needle Fig. 7.17 Chevron Corporation

56 Coral Reef Surrounding Volcanic Island Fig. 7.18 Jean-Marc Truchet/Tony Stone Worldwide

57 Breck Kent Fig. 7.19a Limestone

58 Breck Kent Fig. 7.19b Gypsum

59 Breck Kent Fig. 7.19c Halite

60 Breck Kent Fig. 7.19d Chert

61 Fossiliferous Limestone Peter Kresan

62 One Model for the Formation of Evaporites

63 Rifting can create a sedimentary basin

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