Sedimentary Rocks and Sedimentary Rocks and Depositional Depositional

EnvironmentsEnvironmentsLab 1Lab 1

Rock Types - BackgroundRock Types - Background

Igneous Igneous Metamorphic Metamorphic SedimentarySedimentary

Broken down to form sedimentsBroken down to form sediments– SedimentsSediments – fragments of rock, individual – fragments of rock, individual

mineral grains (quartz), parts of plants or mineral grains (quartz), parts of plants or animals, clay minerals, and other animals, clay minerals, and other mineralsminerals

Minerals - BackgroundMinerals - Background

Igneous, metamorphic, and sedimentary Igneous, metamorphic, and sedimentary rocks are made of mineralsrocks are made of minerals

MineralsMinerals – substances that make up – substances that make up rock; the building blocks of rocksrock; the building blocks of rocks

Example minerals – quartz, potassium Example minerals – quartz, potassium feldspar, biotite mica, muscovite mica, feldspar, biotite mica, muscovite mica, calcitecalcite

Sedimentary Rock Sedimentary Rock CharacteristicsCharacteristics

Grain sizeGrain size RoundingRounding MineralsMinerals MatrixMatrix ColorColor

Grain SizeGrain Size The average diameter of the particlesThe average diameter of the particles

GravelGravel > 2 mm> 2 mm Visible to the unaided eyeVisible to the unaided eye

SandSand < 2mm,< 2mm,

>1/8 mm>1/8 mmVisible to the unaided eye, feels Visible to the unaided eye, feels very grittyvery gritty

SiltSilt

(mud)(mud)<1/8 mm,<1/8 mm,

> 1/256 mm> 1/256 mmInvisible to the unaided eye, can Invisible to the unaided eye, can see with a hand lens, feels grittysee with a hand lens, feels gritty

ClayClay

(mud)(mud)< 1/256 mm< 1/256 mm Cannot be seen without a Cannot be seen without a

microscope, feels smooth, dull microscope, feels smooth, dull lusterluster

** Ruler in Back of AGI Manual **** Ruler in Back of AGI Manual **Pg. 1-2 of lab manual

MineralsMinerals Building blocks of rocksBuilding blocks of rocks

MineralMineral HardnesHardnesss

CleavagCleavagee

ColorColor Distinguishing Distinguishing

FeatureFeature

QuartzQuartz 77 NoneNone

(fracture(fractures)s)

Milky toMilky to

ColorlessColorlessHardness and Hardness and

lookslooks

glassyglassy

PotassiuPotassium m

feldsparfeldspar

66 2 to 3 2 to 3 planesplanes

Salmon to Salmon to RedRed

ColorColor

Biotite Biotite micamica

2.52.5 1 plane1 plane Black to Black to dark dark

brownbrown

Black flakesBlack flakes

Muscovite Muscovite micamica

33 1 plane1 plane Colorless Colorless to light to light brownbrown

Light colored Light colored flakes; shinyflakes; shiny

CalciteCalcite 33 3 planes, 3 planes, rhombrhomb

White to White to GrayGray

Reacts with acid Reacts with acid (HCL)(HCL)

Pg. 1-3 of lab manual

MatrixMatrix

Sedimentary rocks are composed of large Sedimentary rocks are composed of large particles (grains) surrounded by smaller particles (grains) surrounded by smaller particlesparticles

The smaller particles are the The smaller particles are the matrixmatrix The fill in between larger grainsThe fill in between larger grains

Much

None—there are almost no open spaces

All

Some

Sedimentary EnvironmentsSedimentary Environments

A rock will display certain characteristics A rock will display certain characteristics depending on the environment in which it depending on the environment in which it was formedwas formed

The study of the composition and other The study of the composition and other characteristics of the sed. rocks can characteristics of the sed. rocks can reveal info. about the conditions reveal info. about the conditions occurring during deposition (helps occurring during deposition (helps determine environment) determine environment)

Sedimentary EnvironmentsSedimentary Environments

Alluvial FansAlluvial Fans River ChannelsRiver Channels GlaciersGlaciers SwampsSwamps DeltasDeltas Beaches and Beaches and

Barrier Barrier

IslandsIslands DunesDunes

LagoonsLagoons Tidal FlatsTidal Flats ReefsReefs Continental Shelf, Continental Shelf,

Slope, and RiseSlope, and Rise Deep marine Deep marine

environmentsenvironments

Refer to Figure 1.1 pg. 1-2

Alluvial FanAlluvial Fan

Rivers in mountainous Rivers in mountainous areas erode and areas erode and transport sedimenttransport sediment

When meets flat plain When meets flat plain deposits sediment in deposits sediment in fan-like shapefan-like shape

Common rocks: Common rocks: sandstone, sandstone, conglomerate, conglomerate, breccia, diamictonbreccia, diamicton

River ChannelsRiver Channels

Rivers vary in size and Rivers vary in size and energy levelenergy level

Contain various Contain various sediment types sediment types (gravel, sand)(gravel, sand)

Feldspar less commonFeldspar less common Common rocks: Common rocks:

sandstone, sandstone, conglomerateconglomerate

GlaciersGlaciers

Not able to sort Not able to sort sediment sizesediment size

Glacial sediments (till) Glacial sediments (till) are mixtures of gravel, are mixtures of gravel, sand, silt, and claysand, silt, and clay

Rock types: diamictonRock types: diamicton

SwampsSwamps

Lots of organic matterLots of organic matter Slow decompositionSlow decomposition Buried and compacted Buried and compacted

organic matter organic matter hardens to form coalhardens to form coal

Common rocks: coal, Common rocks: coal, shaleshale

DeltasDeltas

Rivers flow into lakes or Rivers flow into lakes or oceansoceans

Deposit sediment in a Deposit sediment in a fan-like shapefan-like shape

Mississippi River Delta, Mississippi River Delta, Nile DeltaNile Delta

Large areas composed of Large areas composed of various environments various environments (channels, swamps, (channels, swamps, bays)bays)

Common rocks: shale, Common rocks: shale, siltstone, sandstone, coalsiltstone, sandstone, coal

Beaches and Barrier IslandsBeaches and Barrier Islands

Barrier island is like a beach separated from the Barrier island is like a beach separated from the mainland by a lagoon mainland by a lagoon

Constant wave action separates sand sized grains from Constant wave action separates sand sized grains from othersothers

Sediment has traveled far from source, so well roundedSediment has traveled far from source, so well rounded Common rocks: sandstoneCommon rocks: sandstone

DunesDunes

Form adjacent to beaches and barrier islandsForm adjacent to beaches and barrier islands Contain non-marine fossilsContain non-marine fossils Common rocks: sandstoneCommon rocks: sandstone

LagoonsLagoons

Behind a barrier Behind a barrier island or reefisland or reef

Barrier island/reef act Barrier island/reef act as breakwaters as breakwaters protecting the lagoon protecting the lagoon from wave actionfrom wave action

Low-energy environmentLow-energy environment Fine grain sizes settle and Fine grain sizes settle and

accumulate (silt, mud)accumulate (silt, mud) Common rocks: shale, Common rocks: shale,

siltstonesiltstone

Tidal FlatsTidal Flats

Broad, flat areas that are periodically covered in Broad, flat areas that are periodically covered in water when tide rises and dry when tide is lowwater when tide rises and dry when tide is low

Variable energy levelsVariable energy levels Alternating layers of coarse and fine sedimentAlternating layers of coarse and fine sediment Common rocks: siltstone, shale, limestoneCommon rocks: siltstone, shale, limestone

ReefsReefs

Organisms build large, rocky accumulations by Organisms build large, rocky accumulations by cementing their shells or other structurescementing their shells or other structures

Common in tropical regions (warm water)Common in tropical regions (warm water) Calcite precipitatesCalcite precipitates Common rocks: limestoneCommon rocks: limestone

Continental shelf, slope, and Continental shelf, slope, and riserise

Shallow marineShallow marine: extend from beach to water : extend from beach to water depths of 100 m; low energy; fine grains settle; depths of 100 m; low energy; fine grains settle; common rocks are sandstone, siltstone, shalecommon rocks are sandstone, siltstone, shale

Deep marineDeep marine: extend down to thousands of : extend down to thousands of meters; low energy; fine grains settle; fossils are meters; low energy; fine grains settle; fossils are rare; common rocks are shale, sandstonerare; common rocks are shale, sandstone

Today’s Lab!!Today’s Lab!!

List properties of unknown List properties of unknown sedimentary rockssedimentary rocks

Identify the unknown rock specimens Identify the unknown rock specimens (rock name)(rock name)

Determine possible depositional Determine possible depositional environment(s) where the rock formedenvironment(s) where the rock formed

Rock NamesRock Names

ShaleShale SiltstoneSiltstone

SandstoneSandstone ConglomerateConglomerate

BrecciaBreccia DiamictonDiamicton LimestoneLimestone

CoalCoal