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
Enchanted Rock, Tx
II. Chemical weathering Processes
A. Solution
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
Petrified wood
1. Solubility diagrams
(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
Spheroidal weathering southern California
E. Plant decay
Ivanpah Mts. southwestern U.S.
NE Australia
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
X. Dating of weathering rates
A. Dating weathering products
Radiometric dates of weathering rinds
(Boggs, 2006)
B. Dating denudation rates (Impact of relief,
climate, bedrock )
(Blatt, et al., 1980)
(Longbein and Schumm, 1947)
C. Cosmogenic nuclides
Radionuclides measured at PRIME Lab
Radion
uclide
10Be
Half-life
(years)
Detection
limit (10-15)
1,500,000
5
14C
5,730
3
26Al
730,000
5
36Cl
301,000
1
41Ca
100,000
5
16,000,00
0
20
129I
Properties of Clastic Sediment
-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
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
Proximal
Delta Front
Sandstones
with thin
mudstone
interbeds
B. Uses for textural data
1. Depositional conditions/environment
i. Sediment transport thresholds and flux rates
Distal
Delta Front
Interbedded
mudstones
and
sandstones
ii. Distance from source and level of reworking
2. Stratigraphic distinctions
3. Geoengineering
i. Slope stability, sediment compressibility, soil expansion, etc.
(USGS)
VI. Fabric
A. Cubic vs. rhombohedral packing
B. Imbrication
C. Grain contacts
D. Sedimentary structures
1. See Section III
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%)
2. Diagenetic history
i. See below
3. Provenance
i. Source rocks
ii Source weathering conditions
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
Images in Siliciclastic Petrology
Quartz and Quartz Arenites
Milliken, Choh, and McBride, 2005
Sandstone Petrology: A Tutorial
Petrographic Image Atlas
Angular Non-undulose Quartz Grain
Colorado River Sand, TX
Quartz Grain with Undulose Extinction
Colorado River Sand, TX
Undulose
Quartz
Grain
Chert
Grain
Highly Undulose Quartz and Chert Grain
Colorado River Sand, TX
Monocrystalline Quartz Grain
Calcite Cement
Polycrystalline Quartz Grain
Polycrystalline and Monocrystalline Quartz in Calcite Cement
Cambrian Hickory Ss, TX
Quartz Grain with Inclusions showing Pseudotwinning
Jurassic Norphlet Fm, AL
Overgrowth
Grain Boundary
Transported and Rounded Quartz Overgrowths
South Padre Island Beach Sand, TX
Well-rounded Quartz Grains in Quartz Overgrowth Cement
Quartz Arenite, Permian Lyons Ss, CO
Quartz
Overgrowth
Non-undulose
Quartz Grain
Chalcedony
Cement
Quartz Arenite with Chalcedony Cement
Cretaceous Cox Ss, TX
Microquartz
Cement
Included
Quartz Grains
Undulose
Quartz Grains
Non-undulose
Quartz Grains
Quartz Arenite with Microquartz Cement
Cretaceous Cox Ss, TX
Quartz Cement
Longitudinal Contact
Concavo-Convex Contact
Quartz Arenite with Concavo-Convex and Longitudinal Grain Contacts
Location Unknown
Images in Siliciclastic Petrology
Feldspars and Arkoses
Milliken, Choh, and McBride, 2005
Sandstone Petrology: A Tutorial
Petrographic Image Atlas
Plagioclase
Grain with
Albite Twinning
Quartz
Grain
Twinned Plagioclase and Quartz Grains
Colorado River Sand, TX
Calcite Cement
Zoned Plagioclase
(Similar Appearance
to Zoned Quartz)
Zoned Un-twinned Plagioclase in Calcite Cement
Miocene Zia Fm, NM
Un-twinned Plagioclase
Eocene Jackson Group, TX
(Similar appearance to some K-spar)
Stained K-spar
River Sand, Alberta
Microcline Grain
Colorado River Sand, TX
Albite
Stained K-Spar
Cleavage Plains
Perthite Grain
Plio-Pleistocene, Offshore, LA
Tangential
Contacts
Feldspar Grain Dissolving at Cleavages
Trinity River Sand, TX
Sericite
Albite Twins
Sericite Conversion of Plagioclase Grain
Colorado River Sand, TX
Quartz Grain
Quartz Grain
Complete Sericite Conversion of Plagioclase to Pseudomatrix
Pennsylvanian Breathitt Fm, Eastern KY
Stained K-spar
Overgrowth
Leached Plagioclase
K-spar Overgrowth on Leached Plagioclase
Oligocene Frio Fm, TX
K-spar
Albite
Albitized Feldspar Grain
Oligocene Frio Fm, TX
Images in Siliciclastic Petrology
Lithic Fragments and
Litharenites
Milliken, Choh, and McBride, 2005
Sandstone Petrology: A Tutorial
Petrographic Image Atlas
Intraclasts
Limestone Clast with Intraclasts Cemented by Sparry Calcite
Location Unknown
Volcanic Rock
Fragment
Volcanic Glass Clast
River Sand, New Zealand
Fractured
K-spar
Shale Clast
Fractured
K-spar
Compacted Shale Clast among Fractured K-spar Grains
Cretaceous, WY
Compaction-Deformed Shale Clast
Cretaceous, WY
Pelite
Pelite
Quartz grains
Compacted Pelidic (mostly Phillite or Slate) Fragments
Ordovician Martinsburg Fm, VA
Plagioclase
Kaolinized Pelidic
Fragments
K-spar with Carlsbad Twinning
Quartz Grains
Pelidic (Schist)
Fragment
Quartzite or Siltstone Grain
Litharenite with Kaolinized Muscovite within in Pelitic Fragments
Tertiary, North Sea
Phillite
Pseudomatrix
Siltstone Grain
Pelidic
Metamorphic
Grains
Slate
Pseudomatrix
Litharenite with Mix of Grains in
Pseudomatrix
Martinsburg Fm, VA
Mica
Pseudomartix
Quartz Grain with Inclusions
Sutured Contact
Quartz Grain with Inclusions
Sutured Quartz Grains in Mica Pseudomartix
Pennsylvanian Breathitt Fm, Eastern KY
Chlorite (Altered or Authogenic?) Matrix
Chlorite-Replaced
Volcanic Grains
Chlorite Pore Filling and Chlorite Replacement of Glass and
Volcanic Rock Fragments
Cretaceous Woodbine Fm, TX