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GY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments Alluvial Fans, Braided Streams Instructor: Dr. Douglas W. Haywick UNIVERSITY OF SOUTH ALABAMA

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Page 1: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

GY 402: Sedimentary Petrology

Lecture 13: Immature Siliciclastic Sedimentary Environments

Alluvial Fans, Braided Streams

Instructor: Dr. Douglas W. Haywick

UNIVERSITY OF SOUTH ALABAMA

Page 2: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Last Time

1. Immature siliciclastic sediment

2. Immature siliciclastic sedimentary rocks

3. Point counting (for this or the next lab assignment)

Immature siliciclastic sediment and sedimentary rocks

Page 3: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Q

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

“Immature” rocks (mineralogically unstable)

Enriched in feldspars and unstable rock fragments

Siliciclastic Sedimentary Rocks

Page 4: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Important Grain Parameters

Grain Size (energy of deposition)

Rounding (degree of wear)

Sorting (energy of deposition)

Page 5: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Immature Siliciclastic Sediment

Is usually more diverse (mineralogy-wise) than mature sediment.

Grains include:

XN 250 μm

Plagioclase feldspar

Orthoclase

Microcline

Micas

Lithics

Quartz

Page 6: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Lithic Fragments

Page 7: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Lithic Fragments

Page 8: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

ppl xn 750 m

Arkose

plagioclase

Thin-section Photomicrographs

Page 9: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Today’s Agenda Immature siliciclastic sediment and sedimentary rocks

Pictorial overview

Alluvial fans

Braided rivers

Page 10: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

1 km

Page 11: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

1 km

Alluvial Fans

Page 12: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

Page 13: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

Page 14: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Fan head mid fan

Fan toe

Alluvial

plain

Alluvial Fans

Page 15: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

Page 16: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

Page 17: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

wind

Alluvial Fans

Page 18: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

Page 19: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

Page 20: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

Page 21: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

Page 22: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

Page 23: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans - view from the top

Page 24: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans

Fan-shaped deposits of siliciclastic sediment deposited at the base of mountains Gravel to clay sized

Angular to sub rounded

immature

Page 25: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Best developed in arid regions

Alluvial Fans

Page 26: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Best developed in arid regions

Best developed in tectonically active areas

From Walker, R.G. 1980. Facies Models. Geological Association of Canada

Alluvial Fans

Page 27: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Best developed in arid regions

Best developed in tectonically active areas

From Walker, R.G. 1980. Facies Models. Geological Association of Canada

Lateral fining

Alluvial Fans

Page 28: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Best developed in arid regions

Best developed in tectonically active areas

Formed primarily through the action of water flow, but there are also mass flow deposits

Alluvial Fans

Page 29: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Best developed in arid regions

Best developed in tectonically active areas

Formed primarily through the action of water flow, but there are also mass flow deposits

Debris flows, fluidized flow and “sieve” deposits

Alluvial Fans

Chalk Board

Page 30: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Wal

ker,

R.G

. and

Jam

es, N

.P.,

1992

. Fac

ies

Mod

els.

Res

pons

e to

Sea

Le

vel C

hang

e.G

eolo

gica

l Ass

ocia

tion

of C

anad

a, 4

09p.

Alluvial Fan Facies

Page 31: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

grav

el

Wal

ker,

R.G

. and

Jam

es, N

.P.,

1992

. Fac

ies

Mod

els.

Res

pons

e to

Sea

Le

vel C

hang

e.G

eolo

gica

l Ass

ocia

tion

of C

anad

a, 4

09p.

Alluvial Fan Facies

Page 32: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

sand

Wal

ker,

R.G

. and

Jam

es, N

.P.,

1992

. Fac

ies

Mod

els.

Res

pons

e to

Sea

Le

vel C

hang

e.G

eolo

gica

l Ass

ocia

tion

of C

anad

a, 4

09p.

Alluvial Fan Facies

Page 33: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

“mud

Wal

ker,

R.G

. and

Jam

es, N

.P.,

1992

. Fac

ies

Mod

els.

Res

pons

e to

Sea

Le

vel C

hang

e.G

eolo

gica

l Ass

ocia

tion

of C

anad

a, 4

09p.

Alluvial Fan Facies

Page 34: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Wal

ker,

R.G

. and

Jam

es, N

.P.,

1992

. Fac

ies

Mod

els.

Res

pons

e to

Sea

Le

vel C

hang

e.G

eolo

gica

l Ass

ocia

tion

of C

anad

a, 4

09p.

Alluvial Fan Facies

Page 35: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Debris flows

Wal

ker,

R.G

. and

Jam

es, N

.P.,

1992

. Fac

ies

Mod

els.

Res

pons

e to

Sea

Le

vel C

hang

e.G

eolo

gica

l Ass

ocia

tion

of C

anad

a, 4

09p.

Alluvial Fan Facies

Page 36: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Channel deposits

Wal

ker,

R.G

. and

Jam

es, N

.P.,

1992

. Fac

ies

Mod

els.

Res

pons

e to

Sea

Le

vel C

hang

e.G

eolo

gica

l Ass

ocia

tion

of C

anad

a, 4

09p.

Alluvial Fan Facies

Page 37: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Alluvial Fans - sed. sections

Nemec, W. and Steel, R.J., 1984. Alluvial and coastal conglomerates: their significant features and some comments on gravelly mass-flow deposits. In Koster, E.H. and Steel, R. eds), Sedimentology of Gravels and Conglomerates. Canadian Society of Petroleum Geologists Mem. 10, 1-31.

Page 38: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Nemec, W. and Steel, R.J., 1984. Alluvial and coastal conglomerates: their significant features and some comments on gravelly mass-flow deposits. In Koster, E.H. and Steel, R. eds), Sedimentology of Gravels and Conglomerates. Canadian Society of Petroleum Geologists Mem. 10, 1-31.

Alluvial Fans - sed. sections

Page 39: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Nemec, W. and Steel, R.J., 1984. Alluvial and coastal conglomerates: their significant features and some comments on gravelly mass-flow deposits. In Koster, E.H. and Steel, R. eds), Sedimentology of Gravels and Conglomerates. Canadian Society of Petroleum Geologists Mem. 10, 1-31.

Interbedded gravel/ sand

beds

Alluvial Fans - sed. sections

Page 40: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Lenticular, scoured sediment bodies

Alluvial Fans - sed. sections

Page 41: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Braided Streams

Page 42: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Braided Streams

Meandering

Braided

Page 43: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Braided Streams Best developed in alluvial plains with “steep gradients” (1 to 3

degrees of slope); frequently in mountainous areas

http://www.ak.nrcs.usda.gov/technical/images/Braided%20River.jpg

Page 44: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Stream morphology

Walker, R.G. and James, N.P., 1992. Facies Models. Response to Sea Level Change.Geological Association of Canada, 409p.

Braided Anastomosing Meandering

Page 45: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Braided Streams Facies

Walker, R.G. and James, N.P., 1992. Facies Models. Response to Sea Level Change. Geological Association of Canada, 409p.

Page 46: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Walker, R.G. and James, N.P., 1992. Facies Models. Response to Sea Level Change. Geological Association of Canada, 409p.

Gravel beds comprise the majority of channel and bar facies, but sand and mud are also common (flood plain facies)

Braided Streams Facies

Page 47: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Hei

n, F

.J. 1

984.

Dee

p-se

a an

d flu

vial

bra

ided

cha

nnel

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es: a

com

paris

on o

f tw

o ca

se st

udie

s. In

Kos

ter,

E.H

. and

Ste

el, R

. eds

), Se

dim

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of G

rave

ls a

nd

Con

glom

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es. C

anad

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ety

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.

Braided Streams Facies

Page 48: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

Braided Stream –sed sections

Walker, R.G. and James, N.P., 1992. Facies Models. Response to Sea Level Change. Geological Association of Canada, 409p.

Page 49: GY 402: Sedimentary Petrology - University of South AlabamaGY 402: Sedimentary Petrology Lecture 13: Immature Siliciclastic Sedimentary Environments . Alluvial Fans, Braided Streams

GY 402: Sedimentary Petrology

Lecture 13: Alluvial Fans

Instructor: Dr. Doug Haywick [email protected]

This is a free open access lecture, but not for commercial purposes. For personal use only.