Sedimentary Sedimentary RocksRocks

Sedimentary RocksSedimentary Rocks

Sediments = pieces of solid Sediments = pieces of solid material deposited on the material deposited on the Earth’s surface.Earth’s surface.

Sedimentary RockSedimentary Rock Rocks that are composed of the Rocks that are composed of the

weathered remains of preexisting weathered remains of preexisting rock, or plant and animal remains.rock, or plant and animal remains.

Sedimentary rocks commonly Sedimentary rocks commonly originate from sediments laid originate from sediments laid down in horizontal strata by water down in horizontal strata by water or wind.or wind.

Horizontal Beds of SedimentaryHorizontal Beds of Sedimentary RockRock

BedsBedding planes

Sedimentary RocksSedimentary Rocks

How is a sedimentary rock How is a sedimentary rock formed?formed?

Sediments get compacted and Sediments get compacted and cemented together.cemented together.

Deposition Compaction Cementation

Sedimentary RocksSedimentary Rocks Clastic – made from fragments of Clastic – made from fragments of

other rocks, that have been other rocks, that have been transported, deposited, then transported, deposited, then compacted and cemented together.compacted and cemented together.

Shale, sand, conglomerate, siltstone, Shale, sand, conglomerate, siltstone, brecciabreccia

Classified by the size of the fragments in Classified by the size of the fragments in the rocksthe rocks

Cemented RocksCemented Rocks Clastic sedimentary rockClastic sedimentary rock – rocks – rocks

composed of weathered composed of weathered sediments:sediments: Pebbles or gravel – usually quartzPebbles or gravel – usually quartz Sand – usually quartzSand – usually quartz Clay and silt – weathered feldspars Clay and silt – weathered feldspars

and mica :and mica : held together by a natural cementheld together by a natural cement

or by compaction of clay and silt.or by compaction of clay and silt.

ConglomerateConglomerate – – cemented sand, silt, and cemented sand, silt, and pebble sediments. If pebble sediments. If large fragments are large fragments are angular this rock is called angular this rock is called a breccia.a breccia.

SandstoneSandstone – – cemented cemented

quartz sand quartz sand grains. Feels grains. Feels

gritty. Unfilled gritty. Unfilled spaces between spaces between

grains make grains make most most

sandstones sandstones porous and porous and

permeable to permeable to water.water.

ShaleShale – clay and silt sized particles – clay and silt sized particles lithified by dehydration and lithified by dehydration and compaction. Note the cleavage at compaction. Note the cleavage at bedding planes. Thumps when you bedding planes. Thumps when you tap it with a nail and, moistened, it tap it with a nail and, moistened, it smells like damp earth.smells like damp earth.

Bedding planes

Sandstone in the Pinnacle Desert, Sandstone in the Pinnacle Desert, AustraliaAustralia

Photo used with permission from Mike Jarvis, Naperville Central HS, Naperville, IL

Sedimentary RocksSedimentary Rocks Chemical – formed when Chemical – formed when

minerals fall out of solution. minerals fall out of solution. From evaporation of salt water From evaporation of salt water or from chemical reactions.or from chemical reactions.

Rock salt, rock gypsum, some Rock salt, rock gypsum, some limestoneslimestones

Chemical Sedimentary RockChemical Sedimentary Rock Rocks formed either as Rocks formed either as

precipitates or as evaporites of precipitates or as evaporites of dissolved chemical sediments.dissolved chemical sediments.

Mineral salts that accumulate in Mineral salts that accumulate in water become concentrated by water become concentrated by evaporation until they precipitate evaporation until they precipitate from solution, orfrom solution, or

Rock saltRock salt, the , the mineral halite mineral halite (NaCl), left as an (NaCl), left as an evaporite as a evaporite as a shallow sea shallow sea evaporated.evaporated.

AlabasterAlabaster, the mineral , the mineral gypsum (CaSOgypsum (CaSO44), also ), also an evaporite.an evaporite.

Compact (or precipitate) limestoneCompact (or precipitate) limestone, the , the mineral calcite (CaCOmineral calcite (CaCO33), precipitated from ), precipitated from sea water as evaporation increased sea water as evaporation increased concentration. Many cavern systems are concentration. Many cavern systems are formed in this type of limestone.formed in this type of limestone.

Sedimentary RocksSedimentary Rocks Organic Rocks – formed from the Organic Rocks – formed from the

remains of plants and animals.remains of plants and animals.

Shells of marine animals pile up, Shells of marine animals pile up, compact and cement to create compact and cement to create fossiliferous limestone (coquina).fossiliferous limestone (coquina).

Sedimentary rocks are the only Sedimentary rocks are the only rocks that contain fossilsrocks that contain fossils

CoquinaCoquina – cemented – cemented aggregate of aggregate of geologicallygeologically modern modern shell fragments.shell fragments.

Fossiliferous Fossiliferous limestonelimestone – a – a

cemented aggregate cemented aggregate of original shell of original shell

fragments, molds, fragments, molds, and casts of ancient and casts of ancient marine organisms. marine organisms.

Note fossil mold of a Note fossil mold of a shell in this shell in this

specimen.specimen.

PeatPeat, a mass of , a mass of matted together matted together plant material plant material covered by Hcovered by H22O, O, which impedes which impedes decay. Hdecay. H22 and O and O22 are are lost, concentrating lost, concentrating carbon.carbon.

LigniteLignite, so called , so called “brown coal”, a soft “brown coal”, a soft

coal that forms coal that forms when peat is when peat is

compressed and compressed and aged, about 40% aged, about 40%

carbon.carbon.

Bituminous coalBituminous coal – soft coal formed when – soft coal formed when lignite is compacted and altered for lignite is compacted and altered for millions of years, about 85% carbon, millions of years, about 85% carbon, this coal is the most commonly mined this coal is the most commonly mined and used for a fuel.and used for a fuel.

Sedimentary Rock FeaturesSedimentary Rock Features

Features in sedimentary rock that Features in sedimentary rock that reflect the sedimentary environment.reflect the sedimentary environment.

Not found in other rock types.Not found in other rock types.

Features:Features: Stratification Stratification FossilsFossils Ripple marks & crossbedsRipple marks & crossbeds Mud cracksMud cracks Nodules, concretions & geodesNodules, concretions & geodes

Rock Stratification (layering) Bryce Rock Stratification (layering) Bryce Canyon, UTCanyon, UT

Photo used with permission from Mike Jarvis, Naperville Central HS, Naperville, IL

Ripple marksRipple marks caused caused by wave action on by wave action on the sandy bottom of the sandy bottom of a shallow baya shallow bay

Almost identical Almost identical ripple marks on ripple marks on the surface of a the surface of a

sandstone sandstone millions of years millions of years

old.old.

Mud cracksMud cracks in in drying muddrying mud

Mud cracks Mud cracks preserved on preserved on the bedding the bedding surface of a surface of a

shale.shale.

Groundwater dissolves hollow spaces in Groundwater dissolves hollow spaces in sedimentary rock, typically limestone, sedimentary rock, typically limestone, and mineral material is deposited inside and mineral material is deposited inside the hollow with crystal points growing the hollow with crystal points growing toward the center.toward the center.

Geode

Thunder Egg

Cross-bedding at Checkerboard Mesa Cross-bedding at Checkerboard Mesa Zion National Park, UT Zion National Park, UT

Photo used with permission from Mike Jarvis, Naperville Central HS, Naperville, IL

Dinosaur skeleton preserved in Dinosaur skeleton preserved in sedimentary rock - Chinasedimentary rock - China

Photo used with permission from Mike Jarvis, Naperville Central HS, Naperville, IL

Metamorphic rocksMetamorphic rocks

Metamorphic rocks are formed a few Metamorphic rocks are formed a few kilometers below the earth’s surface kilometers below the earth’s surface and extend into the upper mantleand extend into the upper mantle

2 types of metamorphism2 types of metamorphism ContactContact- when magma forces its way - when magma forces its way

into the rockinto the rock RegionalRegional-results in large scale -results in large scale

deformation of rock, usually takes place deformation of rock, usually takes place during mountain buildingduring mountain building

Agents of metamorphismAgents of metamorphism HeatHeat- the most important agent because - the most important agent because

it drives the energy needed for a it drives the energy needed for a chemical reactionchemical reaction

PressurePressure- results in a more compact - results in a more compact rockrock

Hydrothermal solution- Hydrothermal solution- very hot water very hot water based solution. When solution comes in based solution. When solution comes in contact with rock it will dissolve crystals contact with rock it will dissolve crystals and deposit new ones (only agent that and deposit new ones (only agent that changes the overall chemical changes the overall chemical composition of rock)composition of rock)

Metamorphic rocks are classified by Metamorphic rocks are classified by texturetexture 2 types2 types

Foliated-minerals recrystallize at right Foliated-minerals recrystallize at right angles to the direction of the force, angles to the direction of the force, rocks are said to be folded or have rocks are said to be folded or have bands that go around rocksbands that go around rocks

Example- Gneiss and SchistExample- Gneiss and Schist Nonfoliated-rocks that does not have Nonfoliated-rocks that does not have

banded texturebanded texture Examples- marble, quartzite, and Examples- marble, quartzite, and

anthraciteanthracite

Foliated Metamorphic RockFoliated Metamorphic Rock

Example- gneissExample- gneissNonfoliated Metamorphic rockNonfoliated Metamorphic rock

Example- marbleExample- marble