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EOSC 326 > Stratigraphy/Correlation + Dating > Flashcards

Stratigraphy/Correlation + Dating Flashcards

1
Q

what are the 4 types of stratigraphy?

A
  1. lithostratigraphy: defined by what its made of (lithic charictaristics
  2. biostratigraphy: fossil content and what they contain
  3. sequence stratigraphy: organizing sediments into major packets, allostratigraphy,siesmic stratigraphy
    - under surface, good for oils
  4. chronostratigraphy: based on geological time, uses all methods of stratigraphy, define correlate, categorize
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2
Q

what are steno’s 3 principles?

A
  1. original horizontality (deposited horizontally)
  2. principle of superposition (young rocks on top)
  3. lateral continuity until i. it thins ii. edges of a depression/another sediment iii. edge of a basin is reached
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3
Q

what was neptunism?

A

werner: all rocks are igneous anf formed in sequence from a global ocean (noah’s ark) - supported by the church

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4
Q

what was catastrophism?

A

curvier: 6 catastrophies that wiped all of life out (i.e. 6 days of biblical creation - so the church agreed to it!!

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5
Q

what was uniformitarianism?

A 
Hutton!!
the other views lacked evidence, so it challenged them
- slow erosion process
-world must be old as heck
- "present is the key to the past"
- world is slow and cyclic
- igneous rocks came from MAGMA
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6
Q

what is actualism?

A

the modern version of uniformitarianism in which it allows for short changes

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7
Q

what is an unconformity and what are the 3 types?

A

gaps in the record of geology (hutton realized this)
period of nondeposition or active erosion
1. angular: tilted, eroded sediments on top, possibly tilted again!
2. non conformity: deposited onto something that wasn’t always sediments
3. disconformity: horizontal deposits (not tilted), but eroded randomly
*** see images of this on slides when this card arrives

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8
Q

whats cross cutting/fault?

A

cross cutting: invasion of sediment

fault: fracture in the rock that moves occasionally

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9
Q

what is the maximum missing time represented by an unconformity?

A

oldest possible rock - youngest possible rock!

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10
Q

whats a pluton?

A

magma cooled into granite/rock

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11
Q

who is james usher?

A

challenged the ‘young earth’ idea, that earth was 6000 years old, but uniformitariansts didn’t agree cause it wasn’t enough time

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12
Q

who was Charles lyell and what did he find out?

A

he liked the etna volcano, and discovered that etna must have formed AFTER all these little volcanos surrounding it. since it took thousands of years to come into existence (there are only records of one appearing), all the others must be even older!
-he found old fossils in limestone near etna, and the limestone went UNDER etna

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13
Q

whats a lithostratigraphic formation?

A

distinct rock with units above/below
must be able to move around and MAP it
dependant on rock type/fossils/structure of sediments

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14
Q

whats a formation and a group?

A

formation: one rock type or associations of rock types
group: association of formations
distinct but related

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15
Q

what is a facies?

A

sediments deposited that reflect the environment in which they were being deposited

  • sediment type, structure, fossil content all depend on whereabouts
    i. e. when talking about sea level, many facies depend on the depth of water, turbulence and size of sediments
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16
Q

whats the change of sediment deposition as you go DEEPER into the ocean?

A

starts with coarse material, then goes to finer material, then at the bottom you get carbonates (algae secreting skeletons that are dependent on biology and water temperature)

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17
Q

what are the 3 types of sea level change?

A
  1. no change, deposits stay in the same type of area
  2. Transgression (levels rise), using a core sample, the deep material would be at the top and the shallow at the bottom
    - facies boundaries tilted towards shore !!
  3. Regression (levels fall) using a core sample, the opposite would be true ^
    * **
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18
Q

what does diachronous mean?

A

time crossing

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19
Q

what is walthers law?

A

all facies are laterally adjacent but when sea levels change, they migrate over one another

EVIDENCE FOR THIS:

  1. facies are distrubuted due to changing conditions
  2. as conditions change, facies migrate to follow their patterns
  3. facies can be over top of each other
  4. verticle rock sucessions allows us to understand sea level change

Formally: facies of conformable verticle sucession of strata were once deposited laterally and adjacent to each other

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20
Q

what are local mechanisms of sea level change?

A

Crustal Deformation: mountains building due to subduction zone + continental collison
- sea level may fall locally depending on rate
Isosatatic redress: removing ice sheets causes earth to “bounce back” upwards again after being compressed.
- i.e. scotland (regression) and UK (transgression)

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21
Q

what is happening at England’s Temmes?

A

something to protect england from flooding, but now levels are getting too high to accomodate it, and the bridge can’t protect them much longer!

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22
Q

what is the michegan basin?

A

sediments deposited into a basin caused it to ‘sag’, which depresses the crust, making room for more sediments, which depress the crust POSTIVE FEEDBACK LOOP
(eventually the process was stopped by the north american plate slammin into european plate)

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23
Q

what are some methods of Global sea level change?

A

glaciation: ice on top of continents
spreading ridge activity: large ocean ridges displace water as they rise and push continents aside
- basically big long volcanos that cause transgression when they are very active,
- low activity = regression of sea levels
sea levels effect deposition over the entire planet !!

24
Q

what are ways that sea level can affect deposition over the planet?

A
  • distance travelled by sediments
  • areas of deposition
  • erosion
  • climate
  • sediments produced!! all change when sea level rises/falls
25
Q

what are the types of correlation and dating?

A

lithostratigraphy (mappable rock type) { issue! facies migrate over time }
biostratigraphy (fossils)
chronostratigraphy (time of strata, radioactive decay etc)
a formation: traceable unit across a country

26
Q

who was a big dude in the world of biostratigraphy?

A

william smith, who mapped britians strata and got credit stolen from him! his colours were ages of rocks NOT composition.
PRINCIPLE OF FAUNAL SUCCESSION: groups of fossils are found together (describing evolution, fossils succeed one another through time)

27
Q

who is younger, dinos or triobites?

A

DINOSAURS ARE YOUNGER!! triobites are OLDER

28
Q

whats a fossil range?

A

time a species is found in a section (package of time)

29
Q

whats seration?

A

ordering taxa by age of appearance in time!

30
Q

whats a zone/biozone?

A

time interval defined by fossils , 1st appearance used as a baseline, and the occurance of other fossils
LAD: last appearance datum
FAD: first appearance datum

31
Q

who was oppell?

A

described the world as having 30 zones (there are 66 today)

darwin came out with his theory of evolution 1 year later, which led to a global biozonaion

32
Q

why would there be a gap in certain biozone maps?

A

because there are no overlapping/useful sole fossils!

33
Q

what makes a good zone fossil?

A
  1. rapid evolution
  2. widespread (facies independent)
  3. common
  4. easy to identify
34
Q

whats a graptolite?

A

floats in the water, preserved wherever they fall, ratehr than ‘burrowing’ or anything,
HOWEVER when they get too close to shore, turbulence breaks them, so they need to be cross references with baciopods/trilobites
PLANKTONIC

35
Q

what’s a gastropod/bivalve?

A

organisms (snails/clams) that live in specific sediments and facies
BENTHIC
***

36
Q

which fossils are important for global correlation in each period? (periods upcoming flashcards)

A

keep ur eye out!

37
Q

cenozoic

A

foraminifera, bivalves, gastropods

38
Q

cretaceous

A

forminifera, ammonoids, crinoids

39
Q

jurrasic

A

ammonoids

40
Q

triassic

A

ammonoids

41
Q

permian

A

foraminifera, ammonoids

42
Q

devonian

A

ammonoids

43
Q

silurian

A

graptolites

44
Q

ordovician

A

nautioids, trilobites, graptolites

45
Q

cambrian

A

trilobites

46
Q

what are the two main eons and their sub eons/eras

A 
Phanerzoic eon (541 MA)
       Cenozoic Era(66 Ma)
       Mesozoic Era(252 Ma)
       Paleozoic Era(541 Ma)
Percambian Super Eon (4.5 Ga)
       Proterozoic Eon (2.5 Ga)
       Archaeon Eon (3..8 Ga)
       Hadean Eon (4.5 Ga)
47
Q

what are the periods of the phanerzoic from oldest to newest?

A 
(541 Ma)
cambrian
ordivician
silurian
devonian
carboniferous
permian
(252 Ma)
triassic
Jurrasic
Certaceous
(66 Ma)
Paleogene
Neogene
48
Q

what are the different geochronical time periods matched to their time stratigraphic rock equivalents?

A 
super eon - nothing
eon - eonothom
era - erathem
period- system
epoch - series
age - stage
chron - zone (chronozone)
49
Q

what is a type section?

A

areas defined by IUGS as “reference sections” for the base of a geological time period
(golden spikes define them)
i.e. the silurian period is at Scotland Dobs Linn

50
Q

what is a golden spike?

A

1st occurence of a distinctinve fossil (i.e. the graptolite in the silurian system)

51
Q

what are the 4 sections/biozones of the silurian period?

A
  1. pridoli (latest - in czech)
  2. ludlow
  3. wenlock
  4. Llandovery (earliest 435 Ma) - first epoch
52
Q

what is the criteria for a type section?

A
  1. continuous sediment
  2. few unconformities
  3. little disturbance/metamorphic
  4. rich in fossils
53
Q

what is radiometric absolute dating

A

an atom of a parent radioactive isotope decays into a stable daughter isotope with the release of radiation
- isolated (closed) system required!
Decay = half life is like a clock.
i.e. decay in crystals of igneous rock!

54
Q

what is fission track dating method?

A

small tunnels produced when high energy particles are thrown off during spontaneous fission

  • particles go thru crystal, tearing away e- and leaving them positive, so they repel each other making a track
  • slow uniform decay = tracks can determine number of years elapsed since it solidified

you use microscope to count the tracks and items that are disintegrated
bombard with neutrons so the remaining items have a signal
find decay rate by couting tracks in sample of synthetic glass

can find few hundred to few million years old!

CLOSES THE GAP BETWEEN 100,000 AD 1 MILLION YEARS OLD! when using potassium argon (oldest) and carbon 14 (newest)

however if rocks have been heated, the tracks can ‘melt’ away

55
Q

what are the limits to dating?

A

weathering and erosion of sample crystals
metamorphism: resets the clock and makes readings inaccurate by melting evidence/fossils/chemical reset
measuring new rock formation NOT the original

majority of surface rock is sedimentary and can’t be dated because you’d be measuring the parent rock from which it was deposited from

56
Q

how do we date sedimentary rock?

A

volcanos! ash that is spread all over during an eruption has little crystals of fragmented magma that hold info!
bracket in between eruptions is used for relative dating

EOSC 326 (11 decks)

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