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SEDIMENTOLOGY AND STRATIGRAPHY OUTLINE AND HANDOUTS Introduction I. Course Logistics II. Why study Sed./Strat? III. The sedimentary cycle A. Weathering;

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Presentation on theme: "SEDIMENTOLOGY AND STRATIGRAPHY OUTLINE AND HANDOUTS Introduction I. Course Logistics II. Why study Sed./Strat? III. The sedimentary cycle A. Weathering;"— Presentation transcript:

1 SEDIMENTOLOGY AND STRATIGRAPHY OUTLINE AND HANDOUTS Introduction I. Course Logistics II. Why study Sed./Strat? III. The sedimentary cycle A. Weathering; transportation; deposition; diagenesis; upheaval SECTION I: WEATHERING AND SILICICLASTIC ROCKS Weathering I. Mechanical weathering Processes A. Exfoliation B. Crystal, frost, and plant wedging C. Heat expansion II. Chemical weathering Processes A. Solution Enchanted Rock, Tx Lapworth Church, England (early teens)

2 B. Hydration C. Oxidation 1. Fe, Mn, Cu, Ti (Boggs, 1987) D. Hydrolysis 1. CO 2 + H 2 O = H 2 CO 3 = H + + (HCO 3 ) - = 2H + + (CO 3 ) -2

3 E. Chemistry and effected minerals in chemical weathering

4 III. Chemical weathering/early diagenesis in soil and sediment environments A. Early precipitation, solution, and replacement 1. Solubility diagrams Petrified wood (Blatt, et al., 1980)

5 2. Eh/PH diagrams a.Eh = E 0 + 2.303RT/nflog [Y] y [Z] z /[B] b [D] d b.Importance of Oxygen i. Photosynthesis / Respiration = CO 2 + H 2 O = CH 2 O + O 2

6 IV. Relative resistance to chemical weathering A. Mafic vs. felsic B. Soluble (e.g., gypsum) vs. insoluble (e.g., quartz) C. Residual vs. fresh

7 V. Conditions and locations which favor chemical weathering A. Rainfall B. Surface area C. Time and Stability D. Temperature E. Plant decay NE Australia Ivanpah Mts. southwestern U.S. Spheroidal weathering southern California

8 VI. Products of weathering A. Congruent vs. incongruent dissolution B. Mechanical vs. chemical weathering products

9 VII. Mineralogy of residuals A. Example phylosilicate mineral prior to weathering B. The illite step C. The smectite step D. The kaolinite step E. The gibbsite step

10 VIII. Relationship between residual mineralogy and chemical-weathering intensity

11 IX. Relationship between weathering processes and composition of average clastic rock (Boggs, 2006) X. Dating of weathering rates A. Dating weathering products Radiometric dates of weathering rinds

12 B. Dating denudation rates (Impact of relief, climate, bedrock ) C. Cosmogenic nuclides (Blatt, et al., 1980) (Longbein and Schumm, 1947) Radionuclides measured at PRIME Lab Radion uclide Half-life (years) Detection limit (10 -15 ) 10 Be1,500,0005 14 C5,7303 26 Al730,0005 36 Cl301,0001 41 Ca100,0005 129 I 16,000,00 0 20

13 -Weathering products -Detritus vs. Solutes -Siliciclastic sediments I.Grain size and grain-size distribution A. Wentworth scale B. Phi Scale Krumbein, 1934 1. Phi = -log 2 S i. S = grain diameter in millimeters Properties of Clastic Sediment

14 II. Measurement methods for clast size A. >Pebbles 1. The hard way B. Pebbles - sand 1. Sieving 2. Settling tube (principles discussed later) 3. Thin sections C. Silt and smaller 1. Pipette 2. Black-box approaches (e.g., laser diffraction, Coulter counter, etc.) 3. Microscopes, SEM, TEM 4. Good old sense of touch

15 III. Statistical textural descriptions A. Graphical 1. Histogram and frequency curve 2. Cumulative curve

16 B. Mathematical 1. Central tendencies i. Mode ii. Median iii. Mean iv. Standard deviation iv. Skewness

17 2. Calculation methods i. Graphical ii. Moment

18 IV. Grain shape A. Sphericity 1. General features 2. Significance B. Roundness 1. Powers scale 0 1 2 3 4 5 6

19 V. Application of textural data A. What can be told from texture 1. Travel history/travel distance i. Concept of textural maturity a. Sorting (well at 10 1 km in water and less in wind) b. Rounding (wind at 10 2 -10 3 shorter distance than water; water see Quartz pebbles rounded in km’s and quartz sand in 10 2 -10 3 kms)

20 2. Energy conditions during transport i. Coarse vs. fine grained ii. In detail in Section III 3. Rock physical strength and expansion characteristics B. Uses for textural data 1. Depositional conditions/environment i. Sediment transport thresholds and flux rates ii. Distance from source and level of reworking 2. Stratigraphic distinctions 3. Geoengineering i. Slope stability, sediment compressibility, soil expansion, etc. Interbedded mudstones and sandstones Sandstones with thin mudstone interbeds Energy Proximal Delta Front Distal Delta Front (USGS)

21 VI. Fabric A. Cubic vs. rhombohedral packing B. Imbrication C. Grain contacts D. Sedimentary structures 1. See Section III

22 B. What can be told from mineralogy? 1. Travel history/distance i. Concept of maturity a. Immature (<75%) submature (75-95%), mature (95-99%), supermature (99-100%) VII. Mineralogy A. Importance of durability 1. Order of resistance 2. Quartz, K-spar, secondary minerals vs. mafics and soluble

23 3. Provenance i. Source rocks ii Source weathering conditions 2. Diagenetic history i. See below

24 Diagenesis of Siliciclastic Sediment I. Introduction A. Eogenesis vs. mesogenesis vs. telogenesis B. Diagenetic vs. depositional environments II. The diagenetic environment A. Pressure 1. Lithostatic gradient 2. Hydrostatic gradient B. Temperature 1. Geothermal gradient i. Average 25 0 C/km ii. Sources of variability

25 C. Formation waters 1. Meteoric vs. connate vs. juvenile 2. Changes with depth i. Increases in salinity and pH ii. Decreases in pCO 2 and Eh III. Alteration and Authigenesis A. Alteration vs. Authigenesis (Blatt, et al., 1980)

26 B. Key framework minerals 1. Quartz 2. Feldspar 3. Lithic fragments 4. Clays

27 5. Other changes i. Thermal maturation Humble-Inc.com

28 ii. Compaction iii. Replacement A. The Calcite/Quartz example

29 V. Cementation A. Cementation and the range of cementing agents 1. Silica, calcite, Fe minerals. 2. Feldspar, pyrite, anhydrite, zeolite, clays, etc B. Silica 1. Role of in situ sources i. Pressure solution; dissolution of glass; hydrolysis 2. Problems 3. Role of external sources i. Circulation model C. Calcite 1. Role of sea water and >2x saturation D. Fe-oxides 1. Destruction of Detrital accessory minerals 2. Fe(OH) 3 conversion

30 Classification of Siliciclastic Rocks I. Features of a good classification scheme II. Mudstone A. Primarily silt and clay B. Approx. 50% of all sedimentary rocks

31 III. Sandstone A. The Turner/Gilbert, Folk, and McBride schemes (McBride, 1963) (Folk et al, 1970)

32 IV. Conglomerates A. >10-30% grains >2mm B. A classification scheme

33 Quartz and Quartz Arenites Milliken, Choh, and McBride, 2005 Sandstone Petrology: A Tutorial Petrographic Image Atlas Images in Siliciclastic Petrology

34 Angular Non-undulose Quartz Grain Colorado River Sand, TX

35 Quartz Grain with Undulose Extinction Colorado River Sand, TX

36 Highly Undulose Quartz and Chert Grain Colorado River Sand, TX Undulose Quartz Grain Chert Grain

37 Polycrystalline and Monocrystalline Quartz in Calcite Cement Cambrian Hickory Ss, TX Monocrystalline Quartz Grain Polycrystalline Quartz Grain Calcite Cement

38 Quartz Grain with Inclusions showing Pseudotwinning Jurassic Norphlet Fm, AL

39 Transported and Rounded Quartz Overgrowths South Padre Island Beach Sand, TX Overgrowth Grain Boundary

40 Well-rounded Quartz Grains in Quartz Overgrowth Cement Quartz Arenite, Permian Lyons Ss, CO

41 Quartz Arenite with Chalcedony Cement Cretaceous Cox Ss, TX Chalcedony Cement Non-undulose Quartz Grain Quartz Overgrowth

42 Quartz Arenite with Microquartz Cement Cretaceous Cox Ss, TX Undulose Quartz Grains Non-undulose Quartz Grains Included Quartz Grains Microquartz Cement

43 Quartz Arenite with Concavo-Convex and Longitudinal Grain Contacts Location Unknown Concavo-Convex Contact Longitudinal Contact Quartz Cement

44 Feldspars and Arkoses Milliken, Choh, and McBride, 2005 Sandstone Petrology: A Tutorial Petrographic Image Atlas Images in Siliciclastic Petrology

45 Twinned Plagioclase and Quartz Grains Colorado River Sand, TX Plagioclase Grain with Albite Twinning Quartz Grain

46 Zoned Un-twinned Plagioclase in Calcite Cement Miocene Zia Fm, NM Zoned Plagioclase (Similar Appearance to Zoned Quartz) Calcite Cement

47 Un-twinned Plagioclase Eocene Jackson Group, TX (Similar appearance to some K-spar)

48 Stained K-spar River Sand, Alberta

49 Microcline Grain Colorado River Sand, TX

50 Perthite Grain Plio-Pleistocene, Offshore, LA Cleavage Plains Albite Stained K-Spar

51 Feldspar Grain Dissolving at Cleavages Trinity River Sand, TX Tangential Contacts

52 Sericite Conversion of Plagioclase Grain Colorado River Sand, TX Sericite Albite Twins

53 Complete Sericite Conversion of Plagioclase to Pseudomatrix Pennsylvanian Breathitt Fm, Eastern KY Quartz Grain

54 K-spar Overgrowth on Leached Plagioclase Oligocene Frio Fm, TX Leached Plagioclase Stained K-spar Overgrowth

55 Albitized Feldspar Grain Oligocene Frio Fm, TX Albite K-spar

56 Lithic Fragments and Litharenites Milliken, Choh, and McBride, 2005 Sandstone Petrology: A Tutorial Petrographic Image Atlas Images in Siliciclastic Petrology

57 Limestone Clast with Intraclasts Cemented by Sparry Calcite Location Unknown Intraclasts

58 Volcanic Glass Clast River Sand, New Zealand Volcanic Rock Fragment

59 Compacted Shale Clast among Fractured K-spar Grains Cretaceous, WY Shale Clast Fractured K-spar Fractured K-spar

60 Compaction-Deformed Shale Clast Cretaceous, WY

61 Compacted Pelidic (mostly Phillite or Slate) Fragments Ordovician Martinsburg Fm, VA Quartz grains Pelite

62 Litharenite with Kaolinized Muscovite within in Pelitic Fragments Tertiary, North Sea Kaolinized Pelidic Fragments Quartz Grains K-spar with Carlsbad Twinning Plagioclase Pelidic (Schist) Fragment Quartzite or Siltstone Grain

63 Siltstone Grain Pelidic Metamorphic Grains Pseudomatrix Litharenite with Mix of Grains in Pseudomatrix Martinsburg Fm, VA Phillite Slate

64 Sutured Quartz Grains in Mica Pseudomartix Pennsylvanian Breathitt Fm, Eastern KY Quartz Grain with Inclusions Mica Pseudomartix Sutured Contact

65 Chlorite Pore Filling and Chlorite Replacement of Glass and Volcanic Rock Fragments Cretaceous Woodbine Fm, TX Chlorite-Replaced Volcanic Grains Chlorite (Altered or Authogenic?) Matrix


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