Sedimentary Rxpages 548-557 Sedimentary Rxpages 548-557 For thousands, even millions

of years, little pieces of our earth have been eroded--broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.

http://www.fi.edu/fellows/payton/rocks/create/sediment.htm

Sedimentary rock isSedimentary rock is

Most common rock at Earth's surface

Thin blanket over 2/3 of the surface covering igneous and metamorphic rocks

Fossils are often found in sedimentary rock.Fossils are often found in sedimentary rock.

Ammonite Fossil fish

SedimentationSedimentation

Volcanism builds new rocksWeathering breaks them down

into sediments

Two types of weathering:Two types of weathering:

Mechanical and Chemical

Mechanical weathering breaks rock into smaller pieces

Mechanical weathering breaks rock into smaller pieces

Three ways Frost wedging

Root wedging

Gravity

Mechanical weathering increases the surface area of the rock exposed to chemical weathering

Mechanical weathering increases the surface area of the rock exposed to chemical weathering

2. Chemical Weathering2. Chemical Weathering

Chemical Reactions with water dissolve rock

H2O + CO2 H2CO3

Water and carbon dioxide yields carbonic acid

This is what dissolves limestone and makes caves

ErosionErosionErosion--movement of seds What can move it?

(Agents of erosion)WindWaterIce

The larger the sediment the harder it is to move

Deposition—seds are depositedDeposition—seds are depositedWhen deposited sediment

accumulates, it begins to transform into

sedimentary rock

Two typesof sedimentary rocksTwo typesof sedimentary rocks

ClasticMade of bits and pieces of recycled rock

Chemical

Form by precipitation or evaporization

Called Precipitates and evaporites

Transformation of Clastic rocksoccurs in two ways:

Transformation of Clastic rocksoccurs in two ways: Compaction

seds are pressed together

– grains interconnect

CementationSeds are cemented together like glue

– Calcite, – silica, and – iron oxide are the

most common cements.

Clastic sedimentsbits and pieces of old rock/plants/animals

Clastic sedimentsbits and pieces of old rock/plants/animals

Clastic sedimentary rocks are classified by

their sediment size and shapeMost common is shale--very fine particles

Sandstone—sand sized particles

Siltstone—silt size

Rounder seds mean longer transportRounder seds mean longer transport

And by shape of sedsAnd by shape of seds

Conglomerate-rounded seds

Breccia—angular sedsBreccia—angular seds

Egyptian statue made from breccia

Chemical Sediments Chemical Sediments

Chemical sediments precipitate from water

Two types–Carbonates–Evaporites

CarbonatesCarbonates

Made of mostly calcite CaCO3or CaMgCO3

Limestone is CaCO3

Very common here

Dolomite is CaMgCO3

Some of the carbonate is replaced by magnesium

EvaporitesEvaporites

Evaporites evaporate from water when a basin dries up

Gypsum CaSO4. H2O

Halite (Rock Salt) NaCl

Halite--—a salt playaHalite--—a salt playa

Sedimentary Rock LabSedimentary Rock Lab

Name the rocks you find in your sample bag.

ChoicesSandstoneCoalConglomerateCoquinaGypsumRock saltOolitic limestone

Sed rock reviewSed rock review A sed rock quiz

Sedimentary environmentsSedimentary environments

Sedimentary rocks provide information about events that occurred on Earth's surface

Their color, grain size, and composition give us information about what was happening when they formed

Sedimentary rock environments

Crossbedding and Ripple MarksCrossbedding and Ripple Marks Crossbedding gives us

an indication of wind or water direction

Ripple marks may beSymmetrical-oscillating Asymmetrical- current ripple marks

Caves form in sedimentary rockCaves form in sedimentary rock

Depositional EnvironmentsDepositional Environments

Delta-a fan-shaped body formed when water flows from a stream into a standing body of water

Example the Mississippi River DeltaThe Nile River Delta

EnvironmentsEnvironments River—Alluvial

Desert--aeolian

Delta

Shoreline

Alluvial--River ChannelAlluvial--River ChannelUnconsolidated

gravels, sand, and clay

Alluvial FanAlluvial Fan Forms when sediment

flows from a steep incline onto a flat floored valley and looses velocity rapidly

Seds are laid down the largest first, followed by progressively smaller and smaller as the velocity slows

Oxbow lake formationOxbow lake formation

An oxbow lake occurs between here and Oxford

Conglomerate-rounded sedsConglomerate-rounded seds

Rounded seds indicate a longer distance of transport

Evaporites---Gypsum Ca SO4.

H2OHalite (Rock Salt) NaCl

Evaporites---Gypsum Ca SO4.

H2OHalite (Rock Salt) NaCl

GypsumGypsum

Sandstone would indicate a beach or desert was once there

Sandstone would indicate a beach or desert was once there

Limestone

Sedimentary environmentSedimentary environment

What ancient environment would produce the following:

What ancient environment would produce the following:

A REEF A REEF

a. A linear outcrop of fossiliferous limestone, massive bedding, many corals and algal structures

SAND DUNESSAND DUNES

b: cross-bedded, well-sorted sandstone, with frosted quartz grains

c: Unsorted, unstratified, the angular boulders have scratches

c: Unsorted, unstratified, the angular boulders have scratches

GLACIAL

A Glacial MoraineA Glacial Moraine

d. Unsorted, unstratified, the the angular boulders don't have scratches.

d. Unsorted, unstratified, the the angular boulders don't have scratches.

ALLUVIAL FAN

Name this structureName this structure

e: poorly sorted, but somewhat stratified sandstone and conglomerate with cut and fill structures.

e: poorly sorted, but somewhat stratified sandstone and conglomerate with cut and fill structures.

RIVER

f: very fine parallel bedding, diatoms, red clay, some thin graded bedding.

f: very fine parallel bedding, diatoms, red clay, some thin graded bedding.

DEEP OCEAN

g. Thick deposits rock salt and gypsum. g. Thick deposits rock salt and gypsum.

RESTRICTED CONTINENTAL SEAS

Jurassic Seaway-example of a continental seaJurassic Seaway-example of a continental sea

h. Fine-grained sand (made of shell fragments) with ripple marks and worm burrows.

h. Fine-grained sand (made of shell fragments) with ripple marks and worm burrows.

LAGOON BEHIND REEF