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