sedimentology and stratigraphy outline and handouts introduction i. course logistics ii. why study...
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SEDIMENTOLOGY AND STRATIGRAPHYOUTLINE AND HANDOUTS
Introduction
I. Course Logistics
II. Why study Sed./Strat?
III. The sedimentary cycleA. 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)
B. Hydration C. Oxidation
1. Fe, Mn, Cu, Ti
(Boggs, 1987)
D. Hydrolysis
1. CO2 + H2O = H2CO3 = H+ + (HCO3)- = 2H+ + (CO3)-2
E. Chemistry and effected minerals in chemical weathering
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)
2. Eh/PH diagrams
a. Eh = E0 + 2.303RT/nflog [Y]y[Z]z/[B]b[D]d
b. Importance of Oxygen
i. Photosynthesis / Respiration = CO2 + H2O = CH2O + O2
IV. Relative resistance to chemical weathering
A. Mafic vs. felsic
B. Soluble (e.g., gypsum) vs. insoluble (e.g., quartz)
C. Residual vs. fresh
V. Conditions and locations which favor chemical weathering
A. Rainfall
B. Surface area
C. Time and Stability
D. Temperature
E. Plant decay
NE AustraliaIvanpah Mts. southwestern U.S.
Spheroidal weathering southern California
VI. Products of weathering
A. Congruent vs. incongruent dissolution
B. Mechanical vs. chemical weathering products
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
VIII. Relationship between residual mineralogy and chemical-weathering intensity
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
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
Radionuclide
Half-life (years)
Detection limit (10-15)
10Be 1,500,000 5
14C 5,730 3
26Al 730,000 5
36Cl 301,000 1
41Ca 100,000 5
129I16,000,00
020
-Weathering products
-Detritus vs. Solutes
-Siliciclastic sediments
I. Grain size and grain-size distribution
A. Wentworth scale
B. Phi Scale Krumbein, 1934
1. Phi = -log2S
i. S = grain diameter in millimeters
Properties of Clastic Sediment
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
III. Statistical textural descriptions
A. Graphical
1. Histogram and frequency curve
2. Cumulative curve
B. Mathematical
1. Central tendencies
i. Mode
ii. Median
iii. Mean
iv. Standard deviation
iv. Skewness
2. Calculation methods
i. Graphical
ii. Moment
IV. Grain shape
A. Sphericity
1. General features
2. Significance
B. Roundness
1. Powers scale
0 1 2 3 4 5 6
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)
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 Interbedded mudstones mudstones and and sandstonessandstones
Sandstones Sandstones with thin with thin mudstone mudstone interbedsinterbeds
En
erg
y
Proximal Delta Front
Distal Delta Front
(USGS)
VI. Fabric
A. Cubic vs. rhombohedral packing
B. Imbrication
C. Grain contacts
D. Sedimentary structures
1. See Section III
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
3. Provenance
i. Source rocks
ii Source weathering conditions
2. Diagenetic history
i. See below
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
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)
(Blatt, et al., 1980)
B. Key framework minerals
1. Quartz
2. Feldspar
3. Lithic fragments
4. Clays
5. Other changes
i. Thermal maturation
Humble-Inc.com
ii. Compaction
iii. Replacement
A. The Calcite/Quartz example
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
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
III. Sandstone
A. The Turner/Gilbert, Folk, and McBride schemes
(McBride, 1963)
(Folk et al, 1970)
IV. Conglomerates
A. >10-30% grains >2mm
B. A classification scheme
Quartz and Quartz Arenites
Milliken, Choh, and McBride, 2005
Sandstone Petrology: A Tutorial Petrographic Image Atlas
Images in Siliciclastic Petrology
Angular Non-undulose Quartz GrainColorado River Sand, TX
Quartz Grain with Undulose ExtinctionColorado River Sand, TX
Highly Undulose Quartz and Chert GrainColorado River Sand, TX
Undulose Quartz Grain
ChertGrain
Polycrystalline and Monocrystalline Quartz in Calcite CementCambrian Hickory Ss, TX
Monocrystalline Quartz Grain
Polycrystalline Quartz Grain
Calcite Cement
Quartz Grain with Inclusions showing PseudotwinningJurassic Norphlet Fm, AL
Transported and Rounded Quartz OvergrowthsSouth Padre Island Beach Sand, TX
Overgrowth
Grain Boundary
Well-rounded Quartz Grains in Quartz Overgrowth CementQuartz Arenite, Permian Lyons Ss, CO
Quartz Arenite with Chalcedony CementCretaceous Cox Ss, TX
ChalcedonyCement
Non-unduloseQuartz Grain
QuartzOvergrowth
Quartz Arenite with Microquartz CementCretaceous Cox Ss, TX
Undulose Quartz Grains
Non-unduloseQuartz Grains
Included Quartz Grains
Microquartz Cement
Quartz Arenite with Concavo-Convex and Longitudinal Grain ContactsLocation Unknown
Concavo-Convex Contact
Longitudinal Contact
Quartz Cement
Feldspars and Arkoses
Milliken, Choh, and McBride, 2005
Sandstone Petrology: A Tutorial Petrographic Image Atlas
Images in Siliciclastic Petrology
Twinned Plagioclase and Quartz GrainsColorado River Sand, TX
Plagioclase Grain with Albite Twinning Quartz
Grain
Zoned Un-twinned Plagioclase in Calcite CementMiocene Zia Fm, NM
Zoned Plagioclase(Similar Appearance to Zoned Quartz)
Calcite Cement
Un-twinned PlagioclaseEocene Jackson Group, TX
(Similar appearance to some K-spar)
Stained K-sparRiver Sand, Alberta
Microcline GrainColorado River Sand, TX
Perthite GrainPlio-Pleistocene, Offshore, LA
Cleavage Plains
Albite
Stained K-Spar
Feldspar Grain Dissolving at CleavagesTrinity River Sand, TX
Tangential Contacts
Sericite Conversion of Plagioclase GrainColorado River Sand, TX
Sericite
Albite Twins
Complete Sericite Conversion of Plagioclase to PseudomatrixPennsylvanian Breathitt Fm, Eastern KY
Quartz Grain
Quartz Grain
K-spar Overgrowth on Leached PlagioclaseOligocene Frio Fm, TX
Leached Plagioclase
Stained K-sparOvergrowth
Albitized Feldspar GrainOligocene Frio Fm, TX
Albite
K-spar
Lithic Fragments and Litharenites
Milliken, Choh, and McBride, 2005
Sandstone Petrology: A Tutorial Petrographic Image Atlas
Images in Siliciclastic Petrology
Limestone Clast with Intraclasts Cemented by Sparry CalciteLocation Unknown
Intraclasts
Volcanic Glass ClastRiver Sand, New Zealand
Volcanic Rock Fragment
Compacted Shale Clast among Fractured K-spar GrainsCretaceous, WY
Shale Clast
FracturedK-spar
FracturedK-spar
Compaction-Deformed Shale ClastCretaceous, WY
Compacted Pelidic (mostly Phillite or Slate) FragmentsOrdovician Martinsburg Fm, VA
Quartz grains
Pelite Pelite
Litharenite with Kaolinized Muscovite within in Pelitic FragmentsTertiary, North Sea
Kaolinized Pelidic Fragments
Quartz Grains
K-spar with Carlsbad Twinning
Plagioclase
Pelidic (Schist)Fragment Quartzite or Siltstone Grain
Siltstone Grain
Pelidic MetamorphicGrains
Pseudomatrix
Pseudomatrix
Litharenite with Mix of Grains in Pseudomatrix
Martinsburg Fm, VA
Phillite
Slate
Sutured Quartz Grains in Mica PseudomartixPennsylvanian Breathitt Fm, Eastern KY
Quartz Grain with Inclusions
Quartz Grain with Inclusions
Mica Pseudomartix
Sutured Contact
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