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