petropetrolologigi2 SKS teori2 SKS teori1 SKS praktikum1 SKS praktikum

by:by:hill. gendoet hartonohill. gendoet hartono

Semester 2, 2008-2009Semester 2, 2008-2009

Senin, jam 09.50 – 10.40Senin, jam 09.50 – 10.40 jam 10.45 – 11.35jam 10.45 – 11.35

Clastic Rocks - Hand SpecimensClastic Rocks - Hand Specimens

BrecciasBreccias: angular particles: angular particles ConglomeratesConglomerates: rounded particles: rounded particles SandstonesSandstones

Quartz sandstoneQuartz sandstone: dominated by quartz grains: dominated by quartz grains Arkose sandstoneArkose sandstone: composed of qtz & fsp : composed of qtz & fsp

grainsgrains GraywackeGraywacke: dominated by lithic (rock) : dominated by lithic (rock)

fragmentsfragments ShalesShales: mud and silt particles: mud and silt particles

Sedimentary RocksSedimentary Rocks

Detrital/Siliciclastic Sedimentary RocksDetrital/Siliciclastic Sedimentary Rocks conglomerates & brecciasconglomerates & breccias sandstonessandstones mudstonesmudstones

Carbonate Sedimentary RocksCarbonate Sedimentary Rocks limestoneslimestones dolostonesdolostones

Other Sedimentary RocksOther Sedimentary Rocks evaporitesevaporites phosphatesphosphates organic-rich sedimentary rocksorganic-rich sedimentary rocks chertscherts volcaniclastic rocksvolcaniclastic rocks

Detrital Sediments & Sedimentary Detrital Sediments & Sedimentary RocksRocks

gravelgravel& &

conglomerateconglomerate

sandsand& &

sandstonesandstone

clay, siltclay, silt&&

mudstonemudstone

Types of sedimentary rocksTypes of sedimentary rocks

Chemical rocksChemical rocks – sediment – sediment from ions that were once in from ions that were once in solutionsolution

Detrital rocksDetrital rocks –sediment –sediment transported as solid particlestransported as solid particles

Detrital sedimentary rocksDetrital sedimentary rocks Constituents of detrital rocks can includeConstituents of detrital rocks can include

Clay mineralsClay mineralsQuartzQuartzFeldsparsFeldsparsMicasMicas

Particle size is used to distinguish among Particle size is used to distinguish among the various types of detrital rocksthe various types of detrital rocks

Detrital sedimentary rocksDetrital sedimentary rocks

MudrocksMudrocks: grains less than .06 mm: grains less than .06 mm1. Mud1. Mud: small particles easily kept in suspension: small particles easily kept in suspension Settles only in quiet waterSettles only in quiet water Rock types include Rock types include ShaleShale: m: mud-sized particles ud-sized particles

<.004 mm deposited in thin bedding layers called <.004 mm deposited in thin bedding layers called laminaelaminae

The most common sedimentary rockThe most common sedimentary rock

2. 2. Larger mudrock grains called Larger mudrock grains called siltssiltssilt-sized particles .004-.06 mmsilt-sized particles .004-.06 mm

Gritty grains can be feltGritty grains can be felt

Mudrock (Shale) containing Mudrock (Shale) containing plant fossilsplant fossils

lamellae

Fossil Leaves Wilkes Barre, PAFossil Leaves Wilkes Barre, PA

Detrital sedimentary rocksDetrital sedimentary rocks

SandstonesSandstonesMade of sand-sized particles .064 – 2 mm … Sand is Made of sand-sized particles .064 – 2 mm … Sand is

a size!a size!Forms in a variety of environmentsForms in a variety of environmentsSorting, angularity and composition of grains can Sorting, angularity and composition of grains can

be used to interpret the rock’s historybe used to interpret the rock’s historyQuartz is the predominant mineral (due to its Quartz is the predominant mineral (due to its

durable nature)durable nature)

Sandstone (note large number of quartz grains)Sandstone (note large number of quartz grains)

Photomicrograph of quartz rich sandstone (Arenite)Grains subangular to subrounded, sandstone is poorly sorted

Plagioclase grainPlagioclase grain

Classifying SandstonesClassifying Sandstones

Making thin sectionsMaking thin sections

Types of SandstoneTypes of Sandstone

Quartz Arenite >90% quartz grainsQuartz Arenite >90% quartz grains Beach and dune depositsBeach and dune deposits

Arkoses >25% feldspar, angular, poor sort.Arkoses >25% feldspar, angular, poor sort. Transform boundaries; exposed granitesTransform boundaries; exposed granites Any felsic rock eroded, not transported farAny felsic rock eroded, not transported far

Graywackes Quartz, feldspar, volcanicsGraywackes Quartz, feldspar, volcanics Port sorted, angularPort sorted, angular Erosion of Island ArcsErosion of Island Arcs Rift Valley Sediments Rift Valley Sediments

Detrital sedimentary rocksDetrital sedimentary rocks

Conglomerate and brecciaConglomerate and brecciaBoth composed of particles > 2mm in Both composed of particles > 2mm in

diameterdiameterConglomerateConglomerate consists largely of consists largely of

rounded clastsrounded clastsBreccia is composed of large angular Breccia is composed of large angular

particlesparticles

ConglomerateConglomerate

Breccia Breccia (shattered rock accumulates at the base of a cliff)(shattered rock accumulates at the base of a cliff)

Note sharp angular clastsNote sharp angular clasts

EnergyEnergy

Coarse sediments are deposited in high Coarse sediments are deposited in high energy (fast water) environments such as energy (fast water) environments such as under breaking waves at the beach, or in under breaking waves at the beach, or in the beds of fast streams.the beds of fast streams.

Fine sediments are deposited in low Fine sediments are deposited in low energy environments, e.g. the slow water energy environments, e.g. the slow water of deep lagoons, the abyssal plain, etc.of deep lagoons, the abyssal plain, etc.

Outcrop of conglomerateOutcrop of conglomeratewith cobble-sized clasts with cobble-sized clasts interbedded with sandstoneinterbedded with sandstone

Conglomerates are fast-water sediments“High Energy”K.E. = 1/2mv2

In fast water, smaller sizes In fast water, smaller sizes swept awayswept away

ChemicalChemical sedimentary rocks sedimentary rocks

Precipitated material once in solutionPrecipitated material once in solution Precipitation of material occurs two Precipitation of material occurs two

ways:ways:Inorganic processes: the minerals Inorganic processes: the minerals

precipitate out of waterprecipitate out of waterOrganic processes: animals and plants Organic processes: animals and plants

precipitate the minerals to use as shells precipitate the minerals to use as shells or skeletonsor skeletons

http://www.ucmp.berkeley.edu/collections/micro.html

A foraminiferan,a type of microfossil

Common chemical sedimentary rocksCommon chemical sedimentary rocksLimestoneLimestone

Most abundant chemical rockMost abundant chemical rockMade of the mineral calcite CaCOMade of the mineral calcite CaCO33

Marine biochemical limestones form Marine biochemical limestones form as coral reefs,as coral reefs, coquinacoquina (broken (broken shells), and shells), and chalk chalk (microscopic (microscopic organisms)organisms)

Inorganic limestones include Inorganic limestones include travertinetravertine (caves) and (caves) and oolitic oolitic limestonelimestone ( (BahamasBahamas))

Coquina Coquina

Fossiliferous limestoneFossiliferous limestoneNote shells and lime matrix

Chalk Outcrops in SE USA

Chalk Hand Specimen

Oolitic Limestone - Bahama Shoals

Oolitic Limestone - Hand Specimen

Ooids under microscopeInorganic Chemical SedimentsInorganic Chemical Sediments

Other chemical sedimentary rocksOther chemical sedimentary rocksChertChert

Made of microcrystalline quartzMade of microcrystalline quartz Usually deposited as siliceous ooze in deep Usually deposited as siliceous ooze in deep

oceans (can be diatomaceous)oceans (can be diatomaceous)

chertDiatomaceous chert

Other chemical sedimentary rocksOther chemical sedimentary rocks Dolostone (made of mineral Dolomite)Dolostone (made of mineral Dolomite) Like Calcite, but some Ca is replaced by MgLike Calcite, but some Ca is replaced by Mg

The Dolomites, sediments thrust up when the Alps formedThe Dolomites, sediments thrust up when the Alps formed

6_196_19

Evaporation

Seawater enriched in Mg2

Limestone

DolostoneDolostone

Mg2 replaces some of theCa2 in limestone

Mg2 -rich seawater circulatesthrough porous limestone

How to make Dolomite

Common chemical sedimentary rocksCommon chemical sedimentary rocks

EvaporitesEvaporitesEvaporation triggers deposition Evaporation triggers deposition of chemical precipitatesof chemical precipitates

Examples include Examples include rock saltrock salt and and gypsumgypsum

http://www.ndsu.nodak.edu/instruct/ashworth/coursework/g410/evaporites/saltbeds.jpg

Chemical sedimentary rocksChemical sedimentary rocks

Common chemical sedimentary rocksCommon chemical sedimentary rocksCoalCoal

Different from other rocks because it Different from other rocks because it is composed of organic material is composed of organic material

Stages in coal formation (in order)Stages in coal formation (in order)1. Plant material1. Plant material2. Peat2. Peat3. Lignite3. Lignite4. Bituminous4. Bituminous

Stages in coal formationStages in coal formation

Sedimentary EnvironmentSedimentary Environment

Is the geographic setting where Is the geographic setting where sediment accumulatessediment accumulates

Determines nature of sediment that Determines nature of sediment that accumulates (grain size, shape, etc.)accumulates (grain size, shape, etc.)

6_56_5

Particles are large andirregular, and consist ofa variety of lithologies,including the leastresistant.

Particles are mid-sizedand of intermediatesphericity, and includeresistant and nonresistantlithologies.

Particles are small andnearly spherical, andconsist mainly of themost resistant lithologies,such as quartz.

Character of detrital sediments depends on time, distance, Character of detrital sediments depends on time, distance, and energy. For example, in streams:and energy. For example, in streams:

HIGHLANDSHIGHLANDS LOWLANDSLOWLANDS NEAR-COASTALNEAR-COASTAL

Clastic wedgesClastic wedges

Sediment MaturitySediment MaturitySediment Maturity is

indicated by decreasingclay content, increasingdegree of size sorting,and increasing roundingof grains within the deposit

Sorting refers to the range of particle sizes in the sediment

Well-sorted - uniform grain sizePoorly-sorted - mixture of grain sizes

Poorly sorted Well sorted

immature mature

Texas A&M UniversityTexas A&M University

OceanographyOceanographyOCNG 251OCNG 251

6_66_6Fine-grained sediment

on floodplain

Flood water

Erosion of uppermostfine-grained sediment

Older sediment

1 Pre-floodPre-flood

Flood stageFlood stage2

Post-floodPost-flood3

Fining-upward flood deposit

Bedding plane is anerosional surface

Floods change the local Floods change the local conditionsconditions

We can recognize past floodsWe can recognize past floods

Bounders on bottom, sands and muds suspended

Flood: One source of Graded Bedding

Types of sedimentary environmentsTypes of sedimentary environmentsContinentalContinental

Streams Streams cross beds from ripples, fine mud w/ cracks cross beds from ripples, fine mud w/ cracks

on floodplainon floodplain Lakes – Fine parallel lamellae - Varves Lakes – Fine parallel lamellae - Varves Wind (dunes) well sorted, frosted grainsWind (dunes) well sorted, frosted grains Glacial Ice: Poorly sorted, unstratifiedGlacial Ice: Poorly sorted, unstratified

MarineMarine Shallow (< 200 meters deep) carbonate-rich Shallow (< 200 meters deep) carbonate-rich

sands, mudssands, muds Deep (seaward of continental shelves)Deep (seaward of continental shelves)

microfossils, volcanic ash, turbiditesmicrofossils, volcanic ash, turbidites

Types of sedimentary environmentsTypes of sedimentary environmentsTransitional (shoreline)Transitional (shoreline)

Tidal flat Sands w/ symmetrical ripplesTidal flat Sands w/ symmetrical ripplesLenses of tidal creek mudsLenses of tidal creek muds

Lagoons – including Bays behind Barrier Lagoons – including Bays behind Barrier Islands.Islands.Organic rich black muds and sandsOrganic rich black muds and sands

DeltasDeltasComplex, e.g. Sandstones w/ large Complex, e.g. Sandstones w/ large

foresets at seaward faceforesets at seaward face

A picture glossary of sedimentary environmentsTurbidite: underwater landslide = graded bedding

Sedimentary Sedimentary FaciesFaciesDifferent sediments accumulate Different sediments accumulate next to each other at same timenext to each other at same time

Each unit (called a Each unit (called a faciesfacies) possesses ) possesses a distinctive characteristics a distinctive characteristics reflecting the conditions in a reflecting the conditions in a particular environmentparticular environment

The merging of adjacent facies The merging of adjacent facies tends to be a gradual transitiontends to be a gradual transition

Nearshore sandsStillwater mudsAbyssal Ooze

Some facies in an oversimplified drawing

Sedimentary structuresSedimentary structuresTell us something about past Tell us something about past

environmentsenvironmentsTypes of sedimentary structuresTypes of sedimentary structures

Strata, or beds (most Strata, or beds (most characteristic of sedimentary characteristic of sedimentary rocks)rocks)-bedding planes that separate -bedding planes that separate strata caused by variation in strata caused by variation in depositiondeposition

Strata- Bedding PlanesStrata- Bedding Planes

Fine Scale Bedding- LamellaeFine Scale Bedding- Lamellae

Recognizable Sedimentary StructuresRecognizable Sedimentary Structures Types of sedimentary structures 1Types of sedimentary structures 1

Graded beds: waning flow Graded beds: waning flow (flood, turbidite)(flood, turbidite)

Sediments become coarser upwardSediments become coarser upward

Determines “Right side up”Determines “Right side up”

Graded Beds – grains fine upward

Note: Beds were tilted from horizontal after deposition

Recognizable Sedimentary StructuresRecognizable Sedimentary Structures RipplesRipples

Irregularities in bottom sediment lead to Irregularities in bottom sediment lead to ripplesripples

Asymmetric types indicate flow Asymmetric types indicate flow direction.direction.

Symmetric types formed in tidal areasSymmetric types formed in tidal areas

Cross Beds – Cross Beds – ripples in cross sectionripples in cross section

In cross section these look like lines In cross section these look like lines at an angle to the horizontal – “cross at an angle to the horizontal – “cross beds”beds”

Form determined by velocity and size Form determined by velocity and size of particles.of particles.

Slabs of eroding sandstone with ripple marks

Cross bedding in Sand Dune deposits

Sandstone deposited Sandstone deposited in ancient sand dunes in ancient sand dunes

Sand Dune? Look for Frosted GrainsNavaho Sandstone

Shoreline of Shoreline of an interior an interior

seawayseaway

Frosted Grains

Recognizable Sedimentary StructuresRecognizable Sedimentary Structures

Types of sedimentary structures 3Types of sedimentary structures 3

Non-marineNon-marine

Mud Cracks – floodplains, playasMud Cracks – floodplains, playas

Also good for right side upAlso good for right side up

Mud Cracks: clay layer shrinks during drying, curls upward; cracks fill next flood

Mudcracks indicate drying events. Geologists can determine if rocks overturned.

Sedimentary EnvironmentsSedimentary Environments

Sediments are formed in many different Sediments are formed in many different environmentsenvironments

Each have characteristic appearance Each have characteristic appearance today, features that allow them to be today, features that allow them to be recognized in the geologic recordrecognized in the geologic record

• Streams (includes big Rivers), with floodplains and levees, called fluviatile. The Point Bar Sequence is typical for meandering streams. Cutoffs generate Oxbow deposits.

High gradient streams with high sediment load are Braided.

• Lake deposits called lacustrine, generally still waters, often varved deposits if winters cold

Fresh Water Facies

http://hays.outcrop.org/gallery/rivers/arid_meander?full=1

FloodplainFloodplain

MeanderingMeanderingStreamStream

OxBowOxBow

http://hays.outcrop.org/gallery/rivers/arid_meander?full=1

Deposits Associated with Meandering Streams

Point-bar Sequence:

Point Bar SequencePoint Bar Sequence

Erosion

Gravel of bed

Crossbeds of Bar

Fines of Floodplain

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Continentalshelf

Continentalslope

Shallowmarine

Deep marine

Submarinevolcanoes

Terms for Marine (i.e. Ocean) Environmentsand some characteristic sediment facies

AbyssalPlain

6_296_29River Direction of migration

of shoreline, and landwardshift of sedimentary facies

Shoreline attime B

Shoreline attime A

Time B

Time ASea levelrising

Depositedat time A

Depositedat time B

Shallowmarine

BeachRiver

Deepmarine

Deepmarine

Shallowmarine

Beach

Shallowmarine

Comparison of sediments deposited

Facies changes due to rising sea level - water getting deeper everywhere

REMEMBER: the facies follow the shoreline

Fossils: Evidence of past lifeFossils: Evidence of past life

By definition, fossils are the traces or By definition, fossils are the traces or remains of prehistoric life now preserved in remains of prehistoric life now preserved in rockrock

Fossils are generally found in sediment or Fossils are generally found in sediment or sedimentary rock (very rarely in sedimentary rock (very rarely in metamorphic or igneous rocks)metamorphic or igneous rocks)

Fossils: Evidence of past lifeFossils: Evidence of past life

Geologically fossils are important for Geologically fossils are important for several reasonsseveral reasons

Aid in interpretation of the geologic pastAid in interpretation of the geologic pastServe as important time and environment Serve as important time and environment

indicatorsindicatorsAllow for correlation of rocks from different Allow for correlation of rocks from different

placesplaces

3 Billion Year Old Algal Mounds (Stromatolites) Australia

CO2 inO2 out

Natural casts of Natural casts of shelled invertebrates in limestoneshelled invertebrates in limestone

Dinosaur footprint in mudstoneDinosaur footprint in mudstone

Dilophosaurus Jurassic Park Dennis Neary and Peter Dodson