UNIVERSITY OF SOUTH ALABAMA
Lecture 4:
Sedimentary Rock Classification
Instructor: Dr. Douglas W. Haywick

Last Time
(in class)
1.
Six modes of sediment movement
2.
Real simple fluid dynamics (ideal conditions)
3.
Initiation of sediment movement
4.
Nasty mathematical relationships (Shield’s Diagram)
5.
Useful empirical relationships (Hjulstrom’s Diagram)

Sediment Motion
• Rest (no movement)
• Roll
• Slide
• Saltation (“bouncing”)
• Suspension
• Mass flow ( viscous flow )

Modes of Viscous Flow
(from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p)

Ideal Fluid Flow
(from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p)

Ideal Fluid Flow
This cartoon is critical and is the basis for grain size analysis!

Vg = gd 2 (

-

)
18
 g = gravitational constant (9.8 m/s 2 ) d = particle size diameter (mm)

= grain density (g/cm 3 )

= fluid density

= dynamic fluid viscosity
Vg = settling velocity

Vg

kd 2
Vg is proportional to grain size

Composite curves (Stoke’s + Impact)
10 3
10 2
10 1
10 0
10 -1
10 -2
Laminar flow
Turbulent flow
10 -4 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 log d (mm)

Grain Size Analysis

Grain Size Analysis
Sand and gravel are determined via sieving sand fractions: vc, c, m, f, vf, gravel fractions: not routinely done
Analysis done using simple excel spread sheet
(will be available on departmental computers and/or e-mailed to you)

Fluid Flow &
“entrainment”
Entrainment is synonomous with:
“initiation of grain movement”
(from Blatt, H, Middleton, G. and Murray, R., 1980. Origin of Sedimentary Rocks. Prentice Hill, 782 p)

Sediment Entrainment
Shear Velocity
(from Blatt, H, Middleton, G. and Murray, R., 1980. Origin of Sedimentary Rocks. Prentice Hill, 782 p)

Sediment Entrainment (Shield’s Diagram)
(from Blatt, H, Middleton, G. and Murray, R., 1980. Origin of Sedimentary Rocks. Prentice Hill, 782 p)

Sediment Entrainment (Hjulstom’s Diagram)
(from Blatt, H, Middleton, G. and Murray, R., 1980. Origin of Sedimentary Rocks. Prentice Hill, 782 p)

Sediment Entrainment
(Hjulstom-Sundborg Diagram)
(from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p)

Sediment Entrainment
(Hjulstom-Sundborg Diagram)
(from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p)

Today’s Agenda
1.
Why bother with sedimentary classification?
2.
Siliciclastic sedimentary rock schemes
3.
Volcaniclastic sedimentary rock schemes
4.
Carbonate rock schemes

Siliciclastic Rock Classification
1.5 mm FOV, PPL

Siliciclastic Rock Classification
Particle size classification
= energy of deposition
1.5 mm FOV, PPL

Siliciclastic Rock Classification
Orthoclase
Porosity
Particle size classification
= energy of deposition
Grain type classification
= origin of sediment
Quartz
Lithic
1.5 mm FOV, PPL

Siliciclastic Rock Classification
1.5 mm FOV, PPL
Particle size classification
= energy of deposition
Grain type classification
= origin of sediment
The Problem:
Sedimentary rocks come in more “flavors” than any other type of rock.
How do you classify all of them?

Sedimentary Rock Classification

Grain size specific and/or…

Sedimentary Rock Classification

Grain size specific and/or…

Particle type specific
(e.g. need specific schemes for major sedimentary rocks classes)

Sedimentary Rock Classification

Particle type specific
1.
Siliciclastic sedimentary rocks
(Quartz, Feldspars, Clays,
Lithic Fragments, Micas, etc.)
2.
Shales and Mudstones
(grain to “matrix” content)
3.
Volcaniclastic sedimentary rocks
(vitric fragments and ash, phenocrysts, lithics )
4.
Carbonate sedimentary rocks
(skeletal grains, non-skeletal grains and matrix)
5.
Organic sedimentary rocks
(kerogen content, coal grade etc.)

Siliciclastic Sedimentary Rocks
(Arenites)
Source: Blatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p.

Siliciclastic Sedimentary Rocks
(Arenites)
Source: Blatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p.

Siliciclastic Sedimentary Rocks
(Arenites)
Source: Blatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p.
GY 402 seal of approval

Siliciclastic Sedimentary Rocks
Source: Blatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p.

Siliciclastic Sedimentary Rocks
Mudstone
>75% mud matrix
Source: Blatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p.

Siliciclastic Sedimentary Rocks
Wackes
15 to 75% mud matrix
Source: Blatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p.

Siliciclastic Sedimentary Rocks
Arenites
<15% mud matrix
Source: Blatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p.

Siliciclastic Sedimentary Rocks
Q = Quartz
F = Feldspars (orthoclase + plagioclase)
R/L = Lithic Fragments

Siliciclastic Sedimentary Rocks
Q = Quartz + chert (sometimes)
F = Feldspars (orthoclase + plagioclase)
R/L = Lithic Fragments

Siliciclastic Sedimentary Rocks
Q = Quartz
F = Feldspars (orthoclase + plagioclase)
R/L = Lithic Fragments + chert (usually)

Siliciclastic Sedimentary Rocks
Q = Quartz
F = Feldspars (orthoclase + plagioclase)
R/L = Lithic Fragments
Granite mountain

Siliciclastic Sedimentary Rocks
Q = Quartz
F = Feldspars (orthoclase + plagioclase)
R/L = Lithic Fragments
Sediment apron
Granite mountain

Siliciclastic Sedimentary Rocks
Q = Quartz
F = Feldspars (orthoclase + plagioclase)
R/L = Lithic Fragments
2 cm
Granite mountain

Siliciclastic Sedimentary Rocks
Q = Quartz
F = Feldspars (orthoclase + plagioclase)
R/L = Lithic Fragments
2 cm an “ F ” grain
(microcline)
Granite mountain

Siliciclastic Sedimentary Rocks
Q = Quartz
F = Feldspars (orthoclase + plagioclase)
R/L = Lithic Fragments an “ F ” grain
(albite)
2 cm
Granite mountain

Siliciclastic Sedimentary Rocks
Q = Quartz
F = Feldspars (orthoclase + plagioclase)
R/L = Lithic Fragments a “ Q ” grain
2 cm
Granite mountain

Siliciclastic Sedimentary Rocks
Q = Quartz
F = Feldspars (orthoclase + plagioclase)
R/L = Lithic Fragments an “ R ” grain
2 cm
Granite mountain

Volcaniclastic Sedimentary Rocks

Carbonate Sedimentary Rocks
Folk Classification Scheme
Source: Blatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p.

Carbonate Sedimentary Rocks
Source: Prothero, D.R. and Schwab, F., 1996. Sedimentary Geology. W.H. Freeman, 575 p.
GY 402 seal of approval

Carbonate Sedimentary Rocks
Source: Prothero, D.R. and Schwab, F., 1996. Sedimentary Geology. W.H. Freeman, 575 p.
Equivalent to sandstone/mudstone in siliciclastic rock schemes

Carbonate Sedimentary Rocks
Source: Prothero, D.R. and Schwab, F., 1996. Sedimentary Geology. W.H. Freeman, 575 p.
Equivalent to conglomerates in siliciclastic rock schemes

Carbonate Sedimentary Rocks
Source: Prothero, D.R. and Schwab, F., 1996. Sedimentary Geology. W.H. Freeman, 575 p.
No equivalents in siliciclastic rock schemes

Upcoming Stuff
Homework
1) Write 2 Ass. (Abstract write up) Due NOW
2) Write 1 Assignment redo (Paper Structure) Due NOW
3) Peer 1 Assignment Due Tomorrow
Today’s Lab
Grain Size Analysis (First column run starts at 12:30: BE THERE!
)
Next Lecture:
Bed form Development (5)

Lecture 4: Classification of Sedimentary
Rocks
Instructor: Dr. Doug Haywick dhaywick@southalabama.edu
This is a free open access lecture, but not for commercial purposed.
For personal use only.