Sedimentary Rock Origins Classification · 2008-05-14 · The Simple Ideal Model for sedimentary...

Sedimentary Rock Origins

and Classification

Minerals and Rocks(and everything else)

Are StableOnly Under the Conditions

At Which They Form

Our Core Principle

Change the Conditions and They Must Change Also

http://www.homepage.montana.edu/~ueswl/images/theilinpike.gif

Selected Igneous Rock Locations of the United States

Our Core Principle

Our Core Principle

With weathering the two major sources of energy are:

Tectonic

Solar

Biological

Chemical

Initial molten state + Radioactive heat + its counter force, gravity

Heat causes things to expand which causes them to move

Heat from the sunHeat warms the air and water, setting up different pressures which causes them to move.

Inorganic reactions, of which there are many, many, many – some of which we need to understand

Organic chemistry, plus biological modifications of environments

The Simple Ideal Model of Sedimentary

Rock Evolution

Fractionation ProcessesAt the Earth’s Surface

P 128

The Simple Ideal Model for the Evolution of Sedimentary Rocks

Average ContinentalIgneous Rock

Granodiorite

Complete Weathering

3 Mixed WeatheringProducts

QtzSand

Quartz Sand

Clay

Kaolinite

Dissol.Calcite

Calcite

Separation DuringTransportation



http://www.nku.edu/~biosci/CostaRica2003/Punta%20Marenco/Day3/CR%20SanJose%20to%20PM.htm


http://www.nps.gov/olym/elwha/photos/elwhamouth.htm


http://www.serf.tamus.edu/ResearchProjects/TexasInletsOnline/BrazosRiverMouth/Brazos%20River%20Main.htm


QtzSand Clay Calcite


Beach

Near Shelf Far ShelfQtz. Sandstone

Shale Limestone


http://www.serf.tamus.edu/ResearchProjects/TexasInletsOnline/BrazosRiverMouth/Brazos%20River%20Main.htm

Tapeats Qtz ss

Bright Angle Shale

Muav Limestone

Middle Cambrian - 510

http://jan.ucc.nau.edu/~rcb7/nam.html

Begin first major sea level rise

Late Cambrian - 500


Early Ordovician - 485


Tran

scontine

ntal

ArchAnt

ietam

Weathering Processes

Mechanical Weathering• Making little pieces out of big ones.• Composition of original rocks does not

change.• Result: lithic fragments

Chemical Weathering• Original minerals chemically break down.• Result: formation of new minerals

stable at Earth-surface conditions.

http:��faculty.uaeu.ac.ae�~afarrag�physical%20geology�w

Mechanical WeatheringFrost Wedging via Freeze and Thaw

http://www.utexas.edu/depts/grg/hudson/grg301c/hudson_grg_301c/schedule/4_water_geomorph_images/10_weathering/2.htm


http://www.gly.fsu.edu/%7Esalters/GLY1000/10Weathering_Erosion/Slide27.jpg


http://www3.famille.ne.jp/~kazuo/SR-044.jpg

Mechanical WeatheringPlant Wedging

http://www.calstatela.edu/faculty/acolvil/weathering.html

Mechanical WeatheringExfoliation

http:��www.gly.fsu.edu�~salters�GLY1000�10Weathering_Erosio

Chemical Weathering• Original minerals chemically break down.• Result: formation of new minerals

stable at Earth-surface conditions.

Chemical WeatheringDissolution

CO2 + H2O H2CO3Carbonic Acid

H2CO3 H+ + HCO3

CaCO3 + H+ Ca++ + 2 HCO3-

DissolvedCalcium

BicarbonateIon

Calcite/Limestone

http:��edutel.musenet.org:8042�gravenet�images�close

Chemical WeatheringDissolution of Limestone

http:��web.mala.bc.ca�geoscape�Karst.htm


http:��www.the-spa.com�hanauer�gallery�Luray�c


http:��firupe.free.fr�Greece�Photo27g�27The_Kar


http:��www.people.auckland.ac.nz�Frances�Classical%20Art�Classical%20Architect.%20Sc


http:��www.people.auckland.ac.nz�Frances�Classical%20Art�Classical%20Architect.%20Sculpture�Erechtheion�Karyatids.JPGhttp:��www.calvin.edu�academic�clas�pathways�delphi�da


Chemical WeatheringOxidation

4 FeSiO3 + O2 + 8 H2O

4 FeO(OH).n H2O + 4 SiO4

Limonite Goethite

Pyroxene

Chemical WeatheringOxidation

Chemical WeatheringHydrolysis

KAlSi3O8 + H2CO3 + 12 H2OOrthoclase

2K+ + 2HCO3- + 5H4SiO4 +

Kaolinite Clay

Dissolved Silica

+ Al2Si2O5(OH)

KAl3Si3O10(OH)

http://faculty.uaeu.ac.ae/~afarrag/physical%20geology/physical5.htm


http://www.earthsci.gla.ac.uk/Holyrood7/Images/glacial/spweath.jpg

View of the Salisbury Crags sill from the Radical Road. Looking northeast. Spheroidal weathering is best seen in the centre of the image. The field of view is approximately 4 m.


http://epswww.unm.edu/facstaff/gmeyer/eps481/images/corestones.jpg


http://www.calstatela.edu/faculty/acolvil/weathering/spheroidal2.jpg


Mobility of Weathering ProductsVery

Mobile ImmobileCa > Na > Mg > K > Si > Fe > Al

Fast Weathering

SlowWeathering

NoWeathering

This provides the differences needed for fractionation and evolution to take place.

Mobility of Weathering Products

Very Mobile ImmobileCa > Na > Mg > K > Si > Fe > Al

LateriteSoil

Bauxite

A Chemical Fractionation Process

P 131

Basic Question: compared to the igneous rocks they started as, is the composition of a

clastic sedimentary rock higher on the reaction series, lower on the reaction series,

or at the same place?

The sea is salty

Soluble

Soluble

The sea is salty

Clastic Rocks Carbonate Rocks

Soluble

Basic Question: compared to the igneous rocks they started as, is the composition of a clastic sedimentary rocks higher on the reaction series, lower on the reaction series, or at the same place?

Clastic sedimentary rocks (sandstones and shales) evolve.

Fates of Weathering

Products


Average ContinentalIgneous Rock

Granodiorite

Complete Weathering

Mixed WeatheringProducts

QtzSand

Quartz Sand

Clay

Clay

Calcite

Calcite


Beach

Near Shelf Far Shelf

SandstoneShale Limestone

Rock Mineral CationWeathering

ProduceSedimentaryOutcome

Gabbro

Diroite

Alkaligranite

Olivine

Pyroxene

Ca plagioclase

Amphibole

Na plagioclase

Orthoclase

Quartz

FeMg

Ca

FeMg

Na

K

Quartz

Hematite/Limonite

CaCO3calcite

CaSO4gypsum

Hematite/Limonite

NAClhalite

Kaolinite

Quartz

Stains(yellow, brown, red)

Stains(yellow, brown, red)

Limestone

Gypsum

Rock Salt

Clay/Shale

Sand grains

Weathering of Igneous Rocks

Classifying Sedimentary Rocks with Ternary

Diagrams

The Simple Ideal Model for sedimentary rocks results in three end members: quartz sand, clay, and calcite in solution.

Things show up in threes a lot when we look at the Earth, and many classifications are based on threes – that is a triangular (or ternary) diagram.

Reading Ternary Diagrams

Base line= 0%

Scale lineAdds to 100%

10%

20%

30%

40%

50%

60%

70%

80%

90%


10%

20%

30%

40%

50%

60%

70%

80%

90%

100%


10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Reading Ternary Diagrams P 131


A

ASSSHLS

50%20%30%


B

BSSSHLS

10%70%20%

C

CSSSHLS

80%20%00%

D

DSSSHLS

20%40%40%

ASSSHLS

50%20%30%

A

Naming Sedimentary Rocks

BSSSHLS

10%70%20%

CSSSHLS

80%20%00%

DSSSHLS

20%40%40%

ASSSHLS

50%20%30%

SandstoneShaley-limey Sandstone

Sandy-limey Shale

Shaley Sandstone

Sandy-shaley Limestone38%42%

Sedimentary Rock Classification

Carbonates

Clas

tics

Evolution of Clastic Sediments

on a Ternary Diagram

Sediment Evolution on a Ternary Diagram1 1Quartz

Feldspar

Ca Plagioclase

Na Plagioclase

Orthoclase

Lithics

Clay (matrix)(shale)

The Q, FL, and M Axes


Feldspar/

Granite

Lithics

Plagiogranite

Gabbro Syenite

Gabbro &Syenite

Q = 30%F = 65%L = 05%

Q = 00%F = 45%L = 55%

Q = 00%F = 80%L = 20%

Igneous Rock Composition



Feldspar/

Granite

Lithics

weathering30% Q70% F & L Feldspar/lithics to clay

30% Q70% clay

Weathering

Igne

ous

Rock

s Sedimentary Rocks



Feldspar/

Granite

Lithics

30% Q70% F & L

30% Q70% clay

sorting

Sand goes to top

Clay goes to bottomNear shore shelf

Stays on beach

Sorting



Feldspar/

Granite

Lithics

30% Q70% F & L

10 clay60 FL

2050

3040

4030

5020

6010 30% Q

70% Clay

30% Q70% F & L CLAY

Step by Step Weathering

Completed Weathering



Feldspar/

Granite

Lithics

10 clay60 FL

2050

3040

4030

5020

6010 30% Q

70% Clay

Step by Step Weathering

Completed Weathering

10 clay30 FL

2020

3010

4030

60 Q40 FL

25 % line for F & L

10 % line for F & L



Feldspar/Lithics

Naming the Rocks

This triangle has greater than 25% F & L, either solely, or mixed with quartz + varying amounts of clay.

Feldspathic(arkosic)

or, Lithic

This area is approaching the end of weathering; F & L are down to between 10 and 25%.

Sub-feldspathicor sub-lithice.g. a lithic sandstone

Shale

Quartz wacke

25% line

10% line

The last sliver has mostly quartz, or clay, or mixed quartz and clay.

Quartz ss

Sub-feldspathicwacke

Feldspathicwacke



Feldspar/Lithics

Clastics and Carbonates

or a lithic wacke Shale

Quartz wacke

Quartz ss

Sub-feldspathicwacke

Feldspathicwacke



Feldspar/Lithics

Carbonates and Evaporates

Ca Plagioclase

Na Plagioclase

Ca/Naleaves the diagram

LimestoneGypsumRock Salt



Feldspar/Lithics

Clastics and Carbonates

Ca/Naleaves the diagram

LimestoneGypsumRock Salt

Clastic R

ocksCarbonate/

Evaporate


Dead Sea

http://www.galilcol.ac.il/ecards.asp

Dead SeaSalt concentrations are so high that people

can float in the water without effort.

Salt crusts on the edge of the Dead Sea

http://www.galilcol.ac.il/ecards.asp

http://www.trekearth.com/gallery/Africa/Tunisia/South/photo78623.htm

http://members.tripod.com/bradleyvw/

Great Salt Lake, Utah

http://www.life.umd.edu/emeritus/reveal/pbio/biome/lec35f1.html

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Sedimentary Rock Origins Classification · 2008-05-14 · The Simple Ideal Model for sedimentary...

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