Mudrocks. Introduction Mudrks mostly silt & clay Mudrks mostly silt & clay Sometimes called argillites Sometimes called argillites Make up 65% of sed.

MudrocksMudrocks

IntroductionIntroduction Mudrks mostly silt & clayMudrks mostly silt & clay Sometimes called argillitesSometimes called argillites Make up 65% of sed rksMake up 65% of sed rks Difficulties studying Difficulties studying

mudrocksmudrocks• RecessiveRecessive• F. grained F. grained • Clay alterationClay alteration• Hard to get to modern Hard to get to modern

analoganalog• Mineral i.d. difficult (qtz vs. Mineral i.d. difficult (qtz vs.

felds)felds)• Sed structure not common Sed structure not common

as in sandstoneas in sandstone• Thus problem w/ strat. Thus problem w/ strat.

columncolumn Organic rich mudrocks --Organic rich mudrocks --

economically imp. economically imp.

Thin section of mudrock. Hard to distinguish grains

Recessive MudstoneRecessive Mudstone

Overturned Overturned Mississippian Lisburne Mississippian Lisburne Formation (resistant Formation (resistant carbonate) in carbonate) in depositional contact depositional contact with overturned with overturned Permian Echooka Permian Echooka Formation (recessive Formation (recessive mudstone), on the mudstone), on the south face of Atigun south face of Atigun gorge, Alaska. (photo: gorge, Alaska. (photo: Alan Carroll)Alan Carroll)

More Recessive MudstoneMore Recessive Mudstone Contact between lower, light Contact between lower, light

brown sandstone and dark brown brown sandstone and dark brown silty mudstone within Imperial silty mudstone within Imperial Formation on a tributary to the Formation on a tributary to the Arctic Red River, Northwest Arctic Red River, Northwest Territories. Territories.

photo shows the character of bedding at a scale of a few meters. The thicker sand beds are typically a little coarser-grained and tend to be more resistant and stick out of the cliff. The finer-grained material is commonly in thinner beds and more recessive.

clasticdetritus.com/.../

www.nwtgeoscience.ca

Mudrock compositionsMudrock compositions Clays most abundantClays most abundant

• Kaolinites [AlKaolinites [Al22SiSi22OO55(OH)(OH)44]]   formed in warm moist climates where Ca, formed in warm moist climates where Ca,

Na, and K ions leached and removed by Na, and K ions leached and removed by weathering.  weathering. 

kaolinite clays indicates a source in a kaolinite clays indicates a source in a humid tropical climate.humid tropical climate.

• Smectites -Smectites - Are expanding clays. Are expanding clays.  Expand by taking in water between layers.Expand by taking in water between layers. Montmorillinite-Montmorillinite-

(½Ca,Na)(½Ca,Na)0.70.7(Al,Fe,Mg)(Al,Fe,Mg)44Si,Al)Si,Al)88OO2020(OH)(OH)44.nH.nH22O O is a good example. is a good example. 

Form from weathering of Fe -Mg rich ign & Form from weathering of Fe -Mg rich ign & meta rocks in temperate climates meta rocks in temperate climates

Most abundant clays in modern sediment.Most abundant clays in modern sediment.• Illites -  KIllites -  K1-1.51-1.5AlAl44SiSi7-6.57-6.5AlAl1-1.51-1.5OO2020(OH)(OH)44

Formed by weathering of feldspars in Formed by weathering of feldspars in temperate climates and by alteration of temperate climates and by alteration of smectite clays during diagenesis.smectite clays during diagenesis.

Have structure similar to muscovite.Have structure similar to muscovite.• Mixed layer clays Mixed layer clays

Interlayering between smectites like Interlayering between smectites like layers and illite like layers in same crystallayers and illite like layers in same crystal

Common in modern sediment.Common in modern sediment.• More illite w/timeMore illite w/time

i. 80% clay minerals in Paleozoic rks is i. 80% clay minerals in Paleozoic rks is illiteillite

ii. Reasons:ii. Reasons: increased volcanism; increased plant life,., increased volcanism; increased plant life,.,

climatic changes, diagenetic processesclimatic changes, diagenetic processes http://soils.missouri.edu/tutorial/page8.asphttp://soils.missouri.edu/tutorial/page8.asp

Mudstone Composition ContinuedMudstone Composition Continued

QtzQtz• Mostly silt-size, angularMostly silt-size, angular

FeldsparsFeldspars• Low concentrationsLow concentrations

Other Other • Muscovite, calcite (skeletal & Muscovite, calcite (skeletal &

diagenetic), pyrite, glauconite, diagenetic), pyrite, glauconite, hematite, etc.hematite, etc.

ClassificationClassificationGrain Size Grain Size Description Description Fissile Fissile

Rock Rock Nonfissile Nonfissile Rock Rock

>2/3 silt >2/3 silt Abundant silt sized grains Abundant silt sized grains visible with a hand lens visible with a hand lens

Silt-shale Silt-shale Siltstone Siltstone

>1/3, <2/3 silt >1/3, <2/3 silt Feels gritty when chewed Feels gritty when chewed Mud-Mud-shale shale

Mudstone Mudstone

>2/3 clay >2/3 clay Feels smooth when Feels smooth when chewed chewed

Clay-Clay-shale shale

Claystone Claystone

Depends on grain size & if rk fissile or notDepends on grain size & if rk fissile or not Fissile rock tends to break along sheet-like planes Fissile rock tends to break along sheet-like planes

nearly parallel to bedding planes nearly parallel to bedding planes Fissility caused by clay minerals deposited with Fissility caused by clay minerals deposited with

sheet structures parallel to depositional surface.  sheet structures parallel to depositional surface. 

TextureTexture

Grain ShapeGrain Shape• Clays and quartz Clays and quartz

usually angularusually angular Not much Not much

rounding rounding because grains because grains small & carried small & carried in suspensionin suspension

Thin section; cross polarized. Thin section; cross polarized.

Scale: each tick mark = 1 mmScale: each tick mark = 1 mm geohistory.valdosta.edu

Texture ContinuedTexture Continued Fissility—Depends onFissility—Depends on

• Abundance of clay-more Abundance of clay-more clay more fissileclay more fissile

• Orientation of claysOrientation of clays Clay grains adhere to Clay grains adhere to

one anotherone another Adhesion of grains Adhesion of grains

called flocculationcalled flocculation• Also depends on Also depends on

salinity & organic salinity & organic matter=more = matter=more = more flocculationmore flocculation

BioturbationBioturbation• Destroys orientation Destroys orientation

of claysof clays DiagenesisDiagenesis

• Aligns grains Aligns grains perpendicular to perpendicular to max stress directionmax stress direction

Get slaty Get slaty cleavage and cleavage and foliation in foliation in metamorphic metamorphic rocksrocks

geology.uprm.edu

Structureless Mudstone geology.about.com

Describing MudrocksDescribing Mudrocks

Fissility--part parallel to Fissility--part parallel to beddingbedding

Bioturbation--Bioturbation--massiveness?massiveness?

Flocculation inhibits fissilityFlocculation inhibits fissility Laminations Laminations

Lamination vs bed?Lamination vs bed?• 1 cm1 cm

Origin of laminaOrigin of lamina• a. productivity variationa. productivity variation• b. grain sizeb. grain size• c.compositionc.composition• d. biochemicald. biochemical

No laminations = massive No laminations = massive (bioturbation/redeposition)(bioturbation/redeposition)

Laminations due to textural differences Sand-Laminations due to textural differences Sand-laminated dark grey mudstone from unit laminated dark grey mudstone from unit MMa, Tom ore deposit, Paleozoic, Northern MMa, Tom ore deposit, Paleozoic, Northern Canada Canada gsc.nrcan.gc.ca/.../ sedex/tom/index_e.php

Laminated Phospatic Mudstone, Laminated Phospatic Mudstone, Monterey Fm, Mussel RocMonterey Fm, Mussel Roc

Cross laminated mudrock, Cross laminated mudrock, BrazilBrazil

Describing Describing MudrocksMudrocks

ConcretionsConcretions• Nodular or Nodular or

stratiformstratiform• Some Form Some Form

immediately after immediately after deposition; deposition; Evidence?Evidence?

Cannonball Concretions, New ZealandCannonball Concretions, New Zealand

More Concretions, North DakotaMore Concretions, North Dakota

Describing MudrocksDescribing Mudrocks ColorsColors

• Gray to black, generally > 1% o.m.Gray to black, generally > 1% o.m.• Conditions favorable for o.m. preservationConditions favorable for o.m. preservation

Little oxygenLittle oxygen Rapid sedimentationRapid sedimentation Low temperatures of waterLow temperatures of water Low permeabilityLow permeability Oxygen present, o.m. goes to water & carbon dioxideOxygen present, o.m. goes to water & carbon dioxide

• 3. Red, brown, yellow, green--iron present3. Red, brown, yellow, green--iron present Reflect oxidation state of FeReflect oxidation state of Fe Oxidizing conditions the most Fe = FeOxidizing conditions the most Fe = Fe+3+3

• Give rock red, brown, orange colorsGive rock red, brown, orange colors• Hematite (Fe2O3) = red colorHematite (Fe2O3) = red color• Iron hydroxide [FeO(OH)] (geothite) = brown color Iron hydroxide [FeO(OH)] (geothite) = brown color • Limonite gives sediment yellow color Limonite gives sediment yellow color • Lack of iron then green (illite, chlorite, & biotite)Lack of iron then green (illite, chlorite, & biotite)• Use color for descriptive purposes Use color for descriptive purposes

Color of Mudrocks:Color of Mudrocks:Green-oygenated environmentGreen-oygenated environmentBlack-Organic-rich, low oxygenBlack-Organic-rich, low oxygen

Depositional Depositional EnvironmentsEnvironments

A. Major mudrock typesA. Major mudrock types• Residual--weathering & soil Residual--weathering & soil

formation on pre-existing rockformation on pre-existing rock i. Preservation potential?i. Preservation potential?

• Detrital--erosion, transportation Detrital--erosion, transportation & deposition& deposition

• Weathering & alteration of Weathering & alteration of volcanic depositesvolcanic deposites

B. ResidualB. Residual• Calcretes (caliche)--common Calcretes (caliche)--common

where evap>precipwhere evap>precip C. DetritalC. Detrital

• Marine/non-marineMarine/non-marine• Distinguishing features:Distinguishing features:

Fossils, bioturbation to Fossils, bioturbation to laminatedlaminated

Deposition below active wave Deposition below active wave basebase

May pass shoreward to May pass shoreward to sandstonessandstones

May be organic richMay be organic rich Local example is Monterey Local example is Monterey

Fm.Fm.

Residual Soil http://blass.com.au/definitions/residual%20soil

Raymond Wiggers

Dropstone in laminated mudstone, Dropstone in laminated mudstone, BrazilBrazil

Mudcracks in red-brown mudstone, Watahomigi Formation. Mudcracks in red-brown mudstone, Watahomigi Formation. Red from hematite. Courtesy USGSRed from hematite. Courtesy USGS

Depositional Environments Depositional Environments ContinuedContinued

Non-marineNon-marine• Common in river floodplains, assoc. w/s.s.Common in river floodplains, assoc. w/s.s.• Lacustrine environments--varvedLacustrine environments--varved

Glacial lakes = coarse = spring melting, winter= Glacial lakes = coarse = spring melting, winter= finesfines

Non-glacial lakes--opposite- why?Non-glacial lakes--opposite- why?

Volcaniclastic derived mudrocksVolcaniclastic derived mudrocks• Volcanic material alters to clayVolcanic material alters to clay• If alteration is to montmorillonite then mudrock If alteration is to montmorillonite then mudrock

known as bentoniteknown as bentonite• How identify volcaniclastic origin of mudrock?How identify volcaniclastic origin of mudrock?

Marine SedimentsMarine Sediments

Most ocean floor covered by marine sedimentsMost ocean floor covered by marine sediments• Sediment thickness is thinnest at mid-ocean ridge and Sediment thickness is thinnest at mid-ocean ridge and

thickest at continental marginsthickest at continental margins

Sediment Accumulation Rates Cm/1000yrsSediment Accumulation Rates Cm/1000yrs

Continental MarginContinental Margin• Shelf-Shelf- 15-4015-40• SlopeSlope 2020• Fraser River DeltaFraser River Delta 700,000700,000

Deep SeaDeep Sea• Coccolith OozeCoccolith Ooze 0.2-3.00.2-3.0• ClaysClays 0.03-0.80.03-0.8

Types of Ocean SedimentsTypes of Ocean Sediments

• Terrigenous – “rock-derivedTerrigenous – “rock-derived

•Biogenous – “life-derived”Biogenous – “life-derived”

• Cosmogenous – “cosmic-derived”Cosmogenous – “cosmic-derived”

• Hydrogenous – “water-derivedHydrogenous – “water-derived””

Lithogenous SedimentsLithogenous Sediments

Composed mostly of quartz sand and clayComposed mostly of quartz sand and clay

• Derived from the weathering of rocks – continents or Derived from the weathering of rocks – continents or volcanic islandsvolcanic islands

• Most deposited on continental marginsMost deposited on continental margins• Transported by rivers, glaciers or windTransported by rivers, glaciers or wind

• Covers about 45% of ocean floorCovers about 45% of ocean floor

Lithogenous Sediments - DeltasLithogenous Sediments - Deltas

Lithogenous Lithogenous sediments added sediments added to marine to marine environment by environment by deltasdeltas

Delta common Delta common featuresfeatures

Pelagic and Neritic DefinedPelagic and Neritic Defined Pelagic sediments deposited in deep ocean away Pelagic sediments deposited in deep ocean away

from shelf processes influencesfrom shelf processes influences• Usually clays, unless turbidites – other gravity Usually clays, unless turbidites – other gravity

flows, ice raftingflows, ice rafting Neritic sediments deposited in shallow water over Neritic sediments deposited in shallow water over

shelves.shelves. Pelagic sediments in abyssal plains most red Pelagic sediments in abyssal plains most red

claysclays Growing anthropogenic contribution –factory Growing anthropogenic contribution –factory

dust, plastic (PCBs), time markersdust, plastic (PCBs), time markers

Lithogenous Sediment - Lithogenous Sediment - ExamplesExamples

Red ClaysRed Clays– Terrigenous from rivers, dust, and Terrigenous from rivers, dust, and volcanic ashvolcanic ash

– Transported to deep ocean by winds Transported to deep ocean by winds and surface currentsand surface currents

– Common in deep oceans, clays most Common in deep oceans, clays most commoncommon

– Accumulates 2 mm (1/8”) every 1,000 yearsAccumulates 2 mm (1/8”) every 1,000 years

Mt. Pinatubo Mississippi River Sahara Desert

Red Clays--PacificRed Clays--Pacific

Lacks calcium Lacks calcium carbonate carbonate materialmaterial

Note siliceous Note siliceous materials—materials—Diatoms & Diatoms & sponge spiculessponge spicules

Paula Worstell

Sediment DistributionSediment Distribution

• Calcareous and Siliceous OozesCalcareous and Siliceous Oozes

Biogenous SedimentBiogenous Sediment Biogenic ooze – greater than 30% biogenous sedimentBiogenic ooze – greater than 30% biogenous sediment

• Composed mostly of hard skeletal parts of once-living Composed mostly of hard skeletal parts of once-living organismsorganisms

• Two main compositions of hard parts:Two main compositions of hard parts:

1.1. Calcium Carbonate (CaCOCalcium Carbonate (CaCO33))a)a)Coccolithophore (phytoplankton)Coccolithophore (phytoplankton)b)b)Foraminifera (zooplankton)Foraminifera (zooplankton)c)c)Pteropod--molluscsPteropod--molluscs

2. 2. Silica (SiOSilica (SiO22) ) a) Diatoms (phytoplankton)a) Diatoms (phytoplankton) b) Radiolarian (zooplanktonb) Radiolarian (zooplankton))

• Distribution depends on chemistry, ocean productivityDistribution depends on chemistry, ocean productivity

Biogenous – Calcareous ExamplesBiogenous – Calcareous Examples

Composed of CaCOComposed of CaCO33

• Widespread in Widespread in relatively shallow relatively shallow areasareas

Coccolithophore

Foraminifera

Foraminifera

www.noc.soton.ac.uk

Biogenous – Biogenous – Siliceous ExamplesSiliceous Examples

Diatoms

Radiolarians

• Composed of SiOComposed of SiO22

• Base of food chainBase of food chain• Like forams Benthic ones Like forams Benthic ones better survivebetter survive

Sediment DistributionSediment Distribution – – Calcareous/SiliceousCalcareous/Siliceous

Biogenous – Siliceous OozeBiogenous – Siliceous Ooze

Covers 15% of ocean floorCovers 15% of ocean floor

• Diatoms common at higher latitudesDiatoms common at higher latitudes• Radiolarians common at equatorial regionsRadiolarians common at equatorial regions

• Distribution - areas of high productivity (zones of upwelling)Distribution - areas of high productivity (zones of upwelling)

• Dissolve more slowly than calcareous particlesDissolve more slowly than calcareous particles•Seawater undersaturated wrt silica, siliceous particles should dissolveSeawater undersaturated wrt silica, siliceous particles should dissolve•Surface waters more depletedSurface waters more depleted•Bottom waters colder, most dissolution on seafloorBottom waters colder, most dissolution on seafloor

Siliceous OozesSiliceous Oozes How do planktonic organisms How do planktonic organisms

get to bottom?get to bottom? Lightweight, driftLightweight, drift Biopackaging—marine snow, Biopackaging—marine snow,

feacal pelletsfeacal pellets

Biogenous – Biogenous – Calcareous oozesCalcareous oozes Cover greater than 50% of ocean floorCover greater than 50% of ocean floor

• Distribution controlled by dissolution processesDistribution controlled by dissolution processes

• Cold bottom waters undersaturated with respect to CaCOCold bottom waters undersaturated with respect to CaCO33

– slightly acidic ( COslightly acidic ( CO22))– readily dissolves CaCOreadily dissolves CaCO33

• Calcium Carbonate Compensation Depth (CCD)Calcium Carbonate Compensation Depth (CCD) – the depth at – the depth at which the rate of accumulation of calcareous sediments which the rate of accumulation of calcareous sediments equals the rate of dissolutionequals the rate of dissolution

Lysocline = depth at which Lysocline = depth at which dissolution of carbonate dissolution of carbonate material beginsmaterial begins

Most dissolution takes Most dissolution takes place on seafloor, only place on seafloor, only pass short distance pass short distance through corrosive zonethrough corrosive zone

Depth of CCD depends on Depth of CCD depends on degree of undersaturation, degree of undersaturation, productiviy, & fluxproductiviy, & flux

faculty.uaeu.ac.ae/

Paleoclimatology/ProductivityPaleoclimatology/Productivity• A. Diatomaceous RocksA. Diatomaceous Rocks

1. Monterey, Sisquoc Fm1. Monterey, Sisquoc Fm 2. Increased Miocene Oceanic Productivity2. Increased Miocene Oceanic Productivity 3. Miocene sealevel changes3. Miocene sealevel changes

• B. Phosphatic RocksB. Phosphatic Rocks 1. o.m. content 4-301. o.m. content 4-30 2. high productivity2. high productivity 3. low oxygen levels in oceans3. low oxygen levels in oceans

• C Oxygen Isotopes & MudrocksC Oxygen Isotopes & Mudrocks 1.O2 isotopes in shells in deep marine rocks1.O2 isotopes in shells in deep marine rocks 2. Construct isotope curves2. Construct isotope curves 3. Show changes in ocean temp.3. Show changes in ocean temp. 4. Tie to sea level curve4. Tie to sea level curve

• D. Carbon Isotopes & MudrocksD. Carbon Isotopes & Mudrocks 1. Reflect changes in productivity, continental runoff, ocean 1. Reflect changes in productivity, continental runoff, ocean

circulation, atmospheric circulation, atmospheric

gsc.nrcan.gc.ca/.../ sedex/tom/index_e.php

Laminated Monterey FormationLaminated Monterey Formation