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SEDIMENTOLOGY AND STRATIGRAPHY OUTLINE AND HANDOUTS Introduction I. Course Logistics

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

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SEDIMENTOLOGY AND STRATIGRAPHY OUTLINE AND HANDOUTS Introduction I. Course Logistics

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  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. CO2 + H2O = H2CO3 = H+ + (HCO3)- = 2H+ + (CO3)-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 • Eh = E0 + 2.303RT/nflog [Y]y[Z]z/[B]b[D]d • Importance of Oxygen • i. Photosynthesis / Respiration = CO2 + H2O = CH2O + O2

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

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

  12. (Blatt, et al., 1980) (Longbein and Schumm, 1947) • B. Dating denudation rates (Impact of relief, • climate, bedrock ) • C. Cosmogenic nuclides Radionuclides measured at PRIME Lab

  13. Properties of Clastic Sediment • -Weathering products • -Detritus vs. Solutes • -Siliciclastic sediments • Grain size and grain-size distribution • A. Wentworth scale • B. Phi Scale Krumbein, 1934 • 1. Phi = -log2S • i. S = grain diameter in millimeters

  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 101 km in water and less in wind) • b. Rounding (wind at 102 -103 shorter distance than water; water see Quartz pebbles rounded in km’s and quartz sand in 102-103 kms)

  20. Proximal Delta Front Energy Sandstones with thin mudstone interbeds Distal Delta Front Interbedded mudstones and sandstones • 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. (USGS)

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

  22. VII. Mineralogy • A. Importance of durability • 1. Order of resistance • 2. Quartz, K-spar, secondary minerals vs. mafics and soluble • 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%)

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

  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 250C/km • ii. Sources of variability

  25. (Blatt, et al., 1980) • C. Formation waters • 1. Meteoric vs. connate vs. juvenile • 2. Changes with depth • i. Increases in salinity and pH • ii. Decreases in pCO2 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. Images in Siliciclastic Petrology Quartz and Quartz Arenites Milliken, Choh, and McBride, 2005 Sandstone Petrology: A Tutorial Petrographic Image Atlas

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

  35. Quartz Grain with Undulose Extinction Colorado River Sand, TX

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

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

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

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

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

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

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

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

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

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

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

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

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