GLG 101 - Physical GeologyGLG 101 - Physical Geology Bob LeightyBob Leighty

Sedimentary Rocks Sedimentary Rocks & Processes& Processes

These lecture notes are very similar to the ones I use in my traditional classes. You’ll find they are loaded with imagery and streamlined text that highlight the most essential terms and concepts. The notes provide a framework for learning and, by themselves, are not meant to be a comprehensive source of information.

To take advantage of the global knowledge base known as the Internet, I have included numerous hyperlinks to external web sites (like the Wikipedia, USGS, NASA, etc.). Follow the links and scan them for relevant info. The information from linked web sites is meant to supplement and reinforce the lecture notes – you won’t be responsible for knowing everything contained in them.

As a distance learning student, you need to explore and understand the content more independently than in a traditional class. As always, I will help guide you through this learning adventure. Remember, email Dr. Bob if you have any questions about today’s lecture (rleighty@mail.mc.maricopa.edu).Leave no questions behind!

Explore and have fun!Explore and have fun!

These notes and web links are your primary “lecture” content in this class. Additionally, various articles are assigned each week to supplement this “lecture” information. I believe you’ll have enough information to reference without having to purchase a costly textbook.

Sedimentary Sedimentary

RocksRocks

Features that form when sediment

is deposited

Can provide important clues in

sedimentary rocks

Sedimentary StructuresSedimentary StructuresSedimentary Sedimentary

RocksRocks

Water-laid sediments are originally deposited in

horizontal

layers (beds)

bedding forming today

Bedding = layering in sedimentary rocks

bedding in rocks

BeddingBedding

Sedimentary StructuresSedimentary StructuresSedimentary Sedimentary

RocksRocks

A bed with particles that decrease in size upwards

Sedimentary StructuresSedimentary StructuresSedimentary Sedimentary

RocksRocks

Graded BeddingGraded Bedding

> Represents waning flow after a flood event

How do graded beds form?How do graded beds form?

Sedimentary StructuresSedimentary StructuresSedimentary Sedimentary

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Graded BeddingGraded Bedding

ripple marks in sandstone(ancient currents)

currents forming ripple marks in sand today

Small ridges in sand/mud formed by currents (wind or

water)

Ripple MarksRipple Marks

Asymmetrical ripples are useful in

telling current direction

Sedimentary StructuresSedimentary StructuresSedimentary Sedimentary

RocksRocks

Tilted layers within a single bed

bed

Cross BeddingCross Bedding

Represent the cross section of ancient

sand dunes

Useful in telling current direction &

“up” direction

Sedimentary StructuresSedimentary StructuresSedimentary Sedimentary

RocksRocks

Sedimentary StructuresSedimentary StructuresSedimentary Sedimentary

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How do cross beds form?How do cross beds form?

Cross BeddingCross Bedding

cross bedding in sandstone(ancient sand dunes)

cross bedding forming in a sand dune today

Cross BeddingCross Bedding

Sedimentary StructuresSedimentary StructuresSedimentary Sedimentary

RocksRocks

desiccation cracks forming in mud today

desiccation cracks in mudstone(ancient mud cracks)

Wet, fine-grained sediment is exposed to air, dries, &

shrinks

Desiccation Cracks (Mud Cracks)Desiccation Cracks (Mud Cracks)

Sedimentary StructuresSedimentary StructuresSedimentary Sedimentary

RocksRocks

Trace FossilsTrace Fossils

Tracks, trails, burrows - Reworking of soft sediment by

organisms

Can describe critters & their movement and behavior

Sedimentary StructuresSedimentary StructuresSedimentary Sedimentary

RocksRocks

continental marinetransitional

Depositional EnvironmentsDepositional EnvironmentsSedimentary Sedimentary

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Depositional EnvironmentsDepositional EnvironmentsSedimentary Sedimentary

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sediment

Lithification – Compaction & cementation after

deposition

sedimentaryrock

Turning Sediment Into RockTurning Sediment Into RockSedimentary Sedimentary

RocksRocks

Clastic texture (made of

pieces)

Chemical texture (crystalline)

sed

imen

tary

rock

sed

imen

t

gravel

conglomerate

carbonatemud

limestone

Turning Sediment Into RockTurning Sediment Into RockSedimentary Sedimentary

RocksRocks

Sedimentary RocksSedimentary RocksSedimentary Sedimentary

RocksRocks

Sedimentary breccia

Clastic RocksClastic Rocks

Sedimentary RocksSedimentary RocksSedimentary Sedimentary

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Gravel-sized piecesGravel-sized pieces

Conglomerate

Quartz Sandstone

(“clean”)

Clastic RocksClastic Rocks

Sedimentary RocksSedimentary RocksSedimentary Sedimentary

RocksRocks

Arkose

(“dirty”)

Graywacke

Sand-sized piecesSand-sized pieces Sandstone

Mudstone (Siltstone, Shale)

Clastic RocksClastic Rocks

Sedimentary RocksSedimentary RocksSedimentary Sedimentary

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Mud-sized piecesMud-sized pieces

Carbonate rocks (CaCO (CaCO33))

Limestone, Dolomite

Chemical RocksChemical Rocks

Sedimentary RocksSedimentary RocksSedimentary Sedimentary

RocksRocks

Chert (SiO (SiO22))

Chemical RocksChemical Rocks

Sedimentary RocksSedimentary RocksSedimentary Sedimentary

RocksRocks

Evaporites

Chemical RocksChemical Rocks

Sedimentary RocksSedimentary RocksSedimentary Sedimentary

RocksRocks

Rock gypsum, Rock salt

Coal

Biochemical RocksBiochemical Rocks

Sedimentary RocksSedimentary RocksSedimentary Sedimentary

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Unoxidized, organic-rich (carbon) remains of plant

material

> Interpretation: low-energy deposition in shallow

water, floods,

exposed to the atmosphere

River Flood PlainRiver Flood Plain Common “flood plain” rocks = mudstone, sandstone

> Ripple marks, graded beds, mud cracks, abundant

land plant

& critter fossils

Interpreting Sedimentary RocksInterpreting Sedimentary RocksSedimentary Sedimentary

RocksRocks

River Flood PlainRiver Flood Plain

Permian Hermit Formation

(Grand Canyon)

Example of a “flood plain” rock formation:

Interpreting Sedimentary RocksInterpreting Sedimentary RocksSedimentary Sedimentary

RocksRocks

Sand DunesSand Dunes

> Interpretation: wind deposited dunes (desert or

beach)

> X-beds, ripple marks, sparse critter trace fossils

Common “sand dune” rocks = quartz sandstone

Interpreting Sedimentary RocksInterpreting Sedimentary RocksSedimentary Sedimentary

RocksRocks

Sand DuneSand Dune

Permian Coconino Sandstone

(Grand Canyon)

Example of a “sand dune” rock formation:

Interpreting Sedimentary RocksInterpreting Sedimentary RocksSedimentary Sedimentary

RocksRocks

Shallow MarineShallow Marine

> Interpretation: mostly low-energy deposition in a

shallow

(0-135 m) ocean

> X-beds, ripple marks, graded beds, marine fossils

Common “shallow marine” rocks = limestone,

sandstone, mudstone

Interpreting Sedimentary RocksInterpreting Sedimentary RocksSedimentary Sedimentary

RocksRocks

Shallow MarineShallow Marine

Example of “shallow marine” rock formations:

MississippianRedwall Limestone

PermianKaibab Limestone

Cambrian Muav Limestone

Interpreting Sedimentary RocksInterpreting Sedimentary RocksSedimentary Sedimentary

RocksRocks

WWW Links in this LectureWWW Links in this Lecture> Bedding - http://en.wikipedia.org/wiki/Bed_%28geology%29

> Graded bedding - http://en.wikipedia.org/wiki/Graded_bedding

> Ripple marks - http://en.wikipedia.org/wiki/Ripple_marks

> Cross-bedding - http://en.wikipedia.org/wiki/Cross-bedding

> Trace fossil - http://en.wikipedia.org/wiki/Trace_fossil

> Depositional environment -

http://en.wikipedia.org/wiki/Sedimentary_depositional_environment

> Lithification - http://en.wikipedia.org/wiki/Lithification

> Sedimentary breccia -

http://en.wikipedia.org/wiki/Clastic_rock#Sedimentary_breccias

> Conglomerate - http://en.wikipedia.org/wiki/Conglomerate_%28geology%29

> Sandstone - http://en.wikipedia.org/wiki/Sandstone

> Arkose - http://en.wikipedia.org/wiki/Arkose

> Graywacke - http://en.wikipedia.org/wiki/Greywacke

> Mudstone - http://en.wikipedia.org/wiki/Mudstone

> Carbonate rock - http://en.wikipedia.org/wiki/Carbonate_rock

> Limestone - http://en.wikipedia.org/wiki/Limestone

> Dolostone - http://en.wikipedia.org/wiki/Dolomite

> Chert - http://en.wikipedia.org/wiki/Chert

> Evaporite - http://en.wikipedia.org/wiki/Evaporite

> Coal - http://en.wikipedia.org/wiki/Coal

Sedimentary Sedimentary

RocksRocks