EOS 201 MT
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What is sedimentology vs sedimentary petrology
sedimentology: processes that erode, transport, and deposit sediments
petrology: charectoristics and origins of sed rocks
what is a facies
facies refers to spefic charectoristics of a rock as a product of its depositional enviornment
which dep enviorn has the best preservation, Why?
Deep ocean basins, due to the low oxygen content and low energy.
anything above sea level is being eroded and moved to below sea level.
what is the principle of Uniformitarianism?
that the processes that have shaped earth in th epast will exist in the future thus we can use events in the past to predict the future.
Physical weathering products & effects & name (4) types
effect of amalgamated physical weathering is that it increases the surface area of existing rock.
Products: clasts and matrix material
- +freeze thaw (water vol inc/dec)
- +insolation (thermal exp/dec)
- +orogenic or glacial rebound
- +organic activity (roots/burrows)
from organisms, works as both chemical and physical weathering
Chemical weathering products, effects and (4) types
- effect: breakdown into alteration materials
- product: cements
- Dissolution (cal, hal)
- oxidation (olv, pyx)
- hydrolosis (silicates)
- hydration/dehydration (anhydrite, gyp)
What does the following describe
CaCO3 + H2CO3--->Ca2++ 2H2O
A dissolution reaction (new ions in solution in products)
this particular rxn is the dissolution of calcium carbonate with carbonic acid to produce calcium ions in solution
what does the following describe?
(Fe2+)2SiO6 + O2 + H2O -> 4Fe3+(OH)3 + H4SiO4
A oxidation or redux reaction (notice how the oxydation number of Fe has changed)
specifically this reaction is the oxidation of pyroxene to limonite
what does the following describe?
CaSO4·2H2O <-->CaSO4(s) + H2O(l)
This is a hydration/dehydration (the forward is dehydration) Note the solid product with water a s a by product
this specific rxn is that of anyhrite dehydration to gypsum
what does the following describe
KAlSi3O8 + H+-->Al2Si2O5(OH)4 + K+ +H4SiO4
This is a hydrolysis reaxtion not the H+ in the reactants side of the rxn
this specific rxn is feldspare to kaolinite with k ions in sol and silic acid as by product
generally rock fragments (clasts) such as qtz & musk are products of
generally clay minerals such as illite, kaolinite are products of
they are hydrous aluminum phyllosillicates which are the proucts of
evaporites such as gypsum, halite, calcite, carbonate anre products of?
these are all products of precipitations from dissolution rxns
why is there a salinity difference between fresh and marine water?
because of the transport in fresh and the holding tank that is marine. all due to residency times and and solubility
what is the corelation between solubility and evaporation
High solubility=low evaportaion
calcium precips before gypsum then halite
∴halite is at the center of a closed basin and the landward edge of a restricted basin
which chemical weathering depends on rain? which doesent?
oxidation does not dpepend on rain, in diffrent ways you could argue the others, hydration, dissolution hydrolosis
what type of soil will limestone make?
trick question, it will make ions in solution not soil
describe weathering in the artic
mostly physical (although lichens do play a bio and chem role)
primarily freeze thaw lithic frags
describe desert weathering
primarily physical due to insolation flds may be present as lithics as no water for ions in sol.
oxidation makes iron oxides
fine sediment may bel blow all the way around the world
describe temperate weathering
includes all types and proccesses, typically a lot of lithics, larger grain saize a younger soil
describe tropical weathring
includes all types but chemical weathering is highest due to high Temp making rxns faster/easier.
lots of thick clays (think jungle quicksand) lots of hematite and kaolinite
extrabasinal or siliclastic rock types
- clast framework differs from matrix
- clast and 2ndry provenace is outside of depositionl basin
seds typ: qtz,flds,msk,clays, Fe3+
- sandstones 2-1/16thmm
- mudstone < 1/16thmm
- * claystone=smoth
Intrabasinal rock types
originate within the depositional basin from dissolved constituients
chemical-evaporites and Iron formations
biochem/biogen/organic- carbonates, cherts, phosphates, carbonacious
refers to the the grains size of a sample
- unimodal-one size typical of delta or deep sea
- bimodal- 2 sizes- typical of river
- polymodal- several sizes typical of glacier
what are allochems (2 specific names)
carbonate (limestone) grains that form intrabasinally
- peloids- poop
- ooids- coated grains (skelatal or lithic)
what is spar
coarse crystaline cement that fills the pore spaces of carbonate rocks
what is micrite?
carbonate mud acts as a cement in carbonate rocks
can begin to crystalize at which point it is called micro-spar
(spar is the crystal)
black shales are typical of what type of sed rock
black shales are often common of phospherites
the black coming from the high amount of organic rich undecayed carbon material they posses
whare are humic materials what is significant about them?
Humic materials are those derived from plants, they are a major source of carbon in sed rocks
primarily humic materials are responsible for coal deposits
what are sapropelic materials
when where/are they most common?
sapropelic materials are decomposed marine organisms (phyto/zoo plankton) they are major contributors to oil resivors anre are what commonloy give phospherites their dark-black color
most common during anoxic (without oxygen) periods in earth history due to high levels of CO2
what are the 4 types of coal from least to most Carbon content
- bitumasious coal
what is karogen?
another name for oil shale. kerogen bearing mudstones have ~25% carbon matter.
kerogen is microbially altered plant and animal mater
what is the relationship between kerogen and petroleum?
petroleum is the end product that is derived through the maturation of kerogen to hydrocarbon polymers
the older of the two iron rich ssed rocks
laminations a/o beeding of iron rich material (hematite magnetite) between marine muds/shales/cherts
phanerozoic iron stones newer then bifs
not laminated/intrabedded the way BiFS are
from errosion of latericit (fe or al rich) soil
two main ways rocks are transported
1- intrabasinally as ions in solution producing crystaline chem or biochem rock
2- extrabasinaly as clasts produce clastic sed rocks
what are the three forces related to sediment transport and how do they effect transport
- FG-gravity- holds grain to btm
- FD-drag force or shear force
- FL-Lift force- Bernoulli effect
- FG>FD+FL sed remains on bed or settles out
- FG<FD+FL sed will be entrained in current
what is the bernoulli effect?
basically as current velocity changes above and below a sediment an area of low pressure above and downstream of a sediment which helps it to become entrained in the current flow
what is a hjulstrom cruve
a graph showing the relationship between stream velocity and the ability to entrain varrying sized sediments
what are the two chars of fluid transport
- 1- reynolds number
- 2- froudes number
what is Reynolds number
ratio of inertia to viscosity
determines whether a flow is laminated or turbulent
- reynolds low= laminar
- reynolds high= turbulent
laminar flow vs turbulent flow
laminar is smooth, sub parellel sheets flowing slowly, mostly viscous fluids
turbulent is rough, irregular flow, eddies, lower viscosity fluids
what is froudes number
what are the difrences in structure created by the high or low number
ratio of inertia to gravity
fr<1=tranquil flow, small quantity sediment transport. ripples, sandwaves and dunes
fr>1= rapid flow, large quantity sediment transported, plane beds, antidunes, chutes and pools
what is bedload transport
sediment moves along bedding surfaces through
traction- rolling sliding creeping
slatation- intermittent contact with the bed due to eddies...think of it bouncing down the bed form
what is suspended load transport
when sediment is entrianed in the current flow
usually smaller grains
turbulence is needed to keep grains entrained
unidirectional flow FR<1 means what?
water surface?quantity of sed transported?
- Fr<1= lower flow regime
- irregular water surface
- small sed transport
creates ripples sandwaves and dunes
unidirectional flow FR>1 means what?bedforms?water surface?quantity of sed transported?
Fr>1= upper flow regime
- glassy streaked out water
- large quantity of sed transport
creates plane beds, antidunes, chutes and pools
more simply put what is the diffrence between reynold and fruede number telling us
reynolds number tells us the type of flow laminar or turbulent
frueds tells us bedforms (low fr= ripples, dunes, sandwaves...hig= planebeds, antidunes chutes and poools
what is the angle of cross bedding in air compared to water
cross bedding refers to what side of a dune/ripple
water tends to have a much shalllower x-beeding in the area of 15°
air tends to be steepper around 30°
x bedding will be indicitive of the lee (steeper)side ∴ the cross bedding tends to dip in the dirrection of flow
how can we tell orientation from cross bedding?
cross bedding is indicitive of the lee (stepper side) of the dune/ripple there for it basicly will appear to dip down stream
cross beding will have a ntangential base which tells us which is the top/btm side of the bed
how is hearing bone cross startification diffrent then cross stratification
cross stratification is created by asymetrical ripples showing unidirectional motion, thus the lee side of the ripples is presserved in a parrellel planar fashion
hearing bone is from bi directional symetrical ripples/dunes
typicaly marine is a bidircetional flow which creates symetric features.
What are the asymetiric marine features
lenticular, wavy and flaser beding strucutres
appear as wavy lines of mud inbetween beeding lenticular is thickes flaser thinest
created from tidal currents where there is more force in one direction
what is hummoky cross stratafication
it is a product of ocean storm systmes
hummocks are the high swales are the low
what are the 3 dry components of gravity driven transport
- 1- rockfall (rock must go through the air)
these have little internal deformation of the material
what are the 4 wet types of gravity driven transport
- 1- grain flow
- 2- debris flow
- 3-turbidity current
- 4- fluidised flow
key points of grain flows
- slope > 30°
- support by grain interactions= dispersive pressure
- typical of aeolian sand slidding down face of dune
key points of a fluidised flow
- same thing as liquifaction
- support by rising fluid through medium
- can flow on slope of 3°
key points of debris flow
- support by cohesive mud matrix
- slope ~10°
- huge variation in grain size
think of lahahrs volcanic mudflow
key points of turbidity currents
turbulence is the grain support mechanism
like an underwater debris flow but more fluid = higher reynolds number
what is the bouma series
its a series of layers a-e (e on top) as the result of a turbidy current loosing its velocity
- low velocity
- E- fine mud with possible bioturbation (often not preserved)
- D- suspension settling of fine material may display lenticular to flaser laminations
- C- low flow regime seetling indicated by ripples a/o climbing ripples
- B- high flow regime planar beddng of coarser material
- A- more massive bed of coarsest sediments
- highest velocity
what is a flame structure
a feature on the btm side of bedding where a more dense material has overrode a lighter matierial. the lighter material is pulled up into the upper layer
what is a load cast
when a suspended sediment is pulled downward by gravity into the underlying still soft bed.
ball and pillow structures
liquifaction of a less dense layer below a more dense layer allows the more dense amterial to be completyl pulled into it or something like that
what is an ichnofacies
what are the 4 types
trace fossils...fossils of marine organism tracks that help to determine things like water temp, depth salinity etc.
- 1-skolith-vertical tubes burrows
- 2-cruziana- horizontal u shaped troughs
- 3-zoophycos-arcuarate(bow shaped) feeding traces
- 4-nereites-meandering feading trials
what is diagenisis?
al lthe changes that occur after deposition that turn it into a sed rock
maybe biological, physical or chemical
creates tighter grain packing thus a reduction in porosity
mud compacts the most 70% porosity to 20%
deals with the bioturbation and microbal activity. typically effeyts sediment size and chemistry of pore fluids.
helps to create kerogen and thus HC resivoirs
what are the 5 components of chemical diagenisis
- 5- dissoulution
what is a stylotite
serrated surfaces where mineral material has been removed by pressure dissolution
name/describe 4 diagenitic structures
- 1-liesegangen bands (rings of alterations material)
- 2-concretions or nodules (hard percipates of mineral cement)
- 3- sand xstals (large diagenitc calcite xstals)
- 4-geodes- void in rock with diagentic minerals growing in it
what is the typical vertical profile of an alluvial fan?
It coarsens upwards
After biological and physical diagfenisis do you have lithification?
no you still need something to bind the rock we need chemical diagenisis
2 points about diagenic cementation
turns the sediments into rock by binding the partilcles i.e. LITHIFASACTION
cement fills almost all reming pore space significantly reducing porosity
common cements in sandstone are?
calcite and qtz, and iron oxide (1-2% will make it red)
common carbonate cements?
calcite, aragonite and dolomite
cement textures for sandstones
- mosiac- between clasts
- overgrowths- around clasts
what is authigenis and examples of three commons
authigenisis is the creations of new minerals in-situ
- 1- clay minerals kaolonite to illite or chlorite
- 2-feldspar-->clay--> sericite
- 3- hematite and pyrite from fe bearing
what is replacement diagenisis
- chemical diagenisis refering to the replacement of one mineral to another
- for example petrifid wood all organic carbon is replaced by chert
what is recrystalization diagenisis
existing clasts retain their chemistry but grain size gets larger
such as micrite turing in into spar
what is dissolution in diagenisis?
important process tha tincrease 2nd degree porosity in rocks by removing solubale minerals
difference between bars in braided and meandering systmes
- braided have tranverse and longitudal bars
- tranverse-sndier cross bedded
- longitudal- massive planar bed forms, imbricated pebbles x bedding at down stream side
meandering have point bars- epsilon cross bedding from the lateral movement of the point bar and cut bank
6 points to recognizing fluvial deposits in the stratigraphic record
- 1- total lack of absence of MARINE fosils
- 2-relitivly poor sorting
- 3- red color common of oxidation
- 4- unidirectional patterns
- 5- downstream decrease in grain size
- 6- fining upwards
easy to mistake with glacial outwash and delta plain deposits
where is an envoirnment where you would expect to see fining up ward and coarsening upward
finning upward at a point bar or delta
coarsening upward in aluvial fans and progradtions
would an aeolian enviornment be compositionaly mature or imature?
imature, compositionaly mature is an extremly high level of only qtz. in aeolian there is still abundant feld and others that have not been removed due to the lack of water
aeolian deposit charectoeristics
- high angle 30deg (compared to 10-15 in water)
- thick tabular cross bedding
- no typical vertical sequencing
- rare fossils
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