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Earth > Practical > Flashcards

Practical Flashcards

1
Q

Dip

A

Angle at which the plane is inclined from the horizontal
Calculate tanD= v(contour height)/h(distance between contours)

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2
Q

Dip direction

A

Direction in which the structure contour lines decrease in topographical height

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3
Q

Outlier

A

Younger rock surrounded by older
Mainly in ridges

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4
Q

Inlier

A

Older rock surrounded by younger
Mainly in valleys

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5
Q

What is a syncline fold?

A

When younger rocks are in the middle

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6
Q

What is an anticline fold?

A

When the older rocks are in the middle

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7
Q

Ecology, Taphonomy and Time scale of Stromatolites

A

Microbial mats
Deposition around and got preserved
Pre-cambrian to present

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8
Q

Ecology, Classification and Time scale of Trilobites

A

Burrowing, scavenger feeders
Moulting behaviour
Rapid burial perhaps
Phylum: Arthropoda
Cambrian- end Permian (251.9Ma)

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9
Q

Ecology, Classification and Time scale of Graptolites

A

Filter feeders, colonial
Phylum: Hemichordata
mid Cambrian (520Ma)- mid Carboniferous (320Ma)

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10
Q

Ecology, Classification and Time scale of Bivalves

A

Burrow (mya), Swimmers (Pecten), Cementers (Ostrea)
Benthic and epifaunal/infaunal
Phylum: Mollusca
Cambrian to present

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11
Q

Ecology, Classification and Time scale of Brachiopods

A

Filter feeders, pedicle attaches, toothed hinges (rarely found open)
Mollusca Brachiopoda
Cambrian to present

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12
Q

Ecology, Classification and Time scale of Echinoids

A

Filter feeder/ grazer dorsal at the top ventral underneath with teeth
Pentaradial symmetry
Phylum: Echinodermata
Cambrian to present

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13
Q

Ecology, Classification and Time scale of Crinoids

A

Suspension feeders, attach to logs and float
Ossicles often preserved
Phylum: Echinodermata, Class: Crinoidea
mid Cambrian to present

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14
Q

Ecology, Classification and Time scale of plants

A

Autotrophic, photosynthesise, respire, sessile
e.g. Genus Stigmaria, from Plantae kingdom
Cambrian to present

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15
Q

Ecology, Classification and Time scale of Bryozoan

A

Colonial, filter feeders, provide shelter
Phylum: Bryozoa, class of Gymnolaemata most successful
Ordovician (485Ma)

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16
Q

Ecology, Classification, Preservation and Time scale of ammonoids

A

Free swimmers, carnivorous
Aragonite shell, and moulds
Phylum: Mollusca, Class: Cephalopoda, Orders: Goniatitic, Ceratitic, Ammonitic
G=Dev (420-360Ma) -Permian (300Ma-251.9Ma)
C= Triassic (251.9Ma-200Ma)
A=Triassic- Cretaceous (66Ma)

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17
Q

Ecology, Classification, Preservation and Time scale of Nautiloids

A

Jet propulsion, Carnivores
Aragonite shell
Phylum: Mollusca, Class: Cephalopoda, Subclass: Nautiloid
Cambrian, then Triassic (251.9Ma-200Ma) coiled only

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18
Q

Ecology, Classification and Time scale of corals

A

Solitary/ Colonial
Phylum: Cnidaria, Subclasses: Scleractinia, Rugosa, Tabulata
T+ R= Ordovician (485Ma)- Permian (251.9Ma), in calcite
S= Triassic (250Ma) - present, in aragonite

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19
Q

Ecology, Classification, Presevation and Time scale of belemnites

A

Mesozoic squid, swimmers, carnivorous
Phylum: Mollusca, Class: Cephalopoda, Order: Belemnitida
Calcite guard
Jurassic (200Ma-145Ma) - Cretaceous (145Ma-66Ma)

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20
Q

How does a schist differ to a gneiss in thin section?

A

Schist- tiny crystals barely visible in clear lineation, muscovite, biotite
Gneiss- larger quartz crystals present, banding when looking with naked eye, quartz, feldspar

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21
Q

What are the optical differences between Clinopyroxene and Orthopyroxene?

A

Clinopyroxene- Inclined extinction, Colourless/ greyish, Pink to orange with CP
Orthopyroxene- Straight extinction, Colourless/ reddish/ green, Grey to purple with CP

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22
Q

Describe the optical properties of magnetite

A

Black in Plane and cross polars
Small
Can be found as intrusion

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23
Q

What are the optical properties of Olivine?

A

Curving cracks
Bright second order colours CP
Pale yellow PP
High relief
Quite euhedral usually

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24
Q

What are the optical properties of plagioclase feldspar?

A

Lamellar twinning CP
Low relief
Distinct cleavage
Inclined extinction

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25
Q

What are the optical properties of Amphibole/ Hornblende?

A

Pleochroic green to brown
Clear cleavage 56 and 124 degrees
Shows twinning
High second order interference

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26
Q

What are the optical properties of quartz?

A

Low relief
No cleavage
Low 1st order colours

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27
Q

What are the optical properties of garnet?

A

Colourless
Isotropic
High relief

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28
Q

What are the optical properties of biotite/ mica?

A

Speckled extinction
Straight extinction
May contain zircons
Low relief
Pleochroic

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29
Q

What are the optical properties of orthoclase/ K+ feldspar?

A

Straw colour
Lack of striations
Low birefringence
Pleochroic
Cleavage
No barcode extinction

30
Q

What are the optical properties of microcline feldspar?

A

Cross hatch extinction
Low relief
Colourless
Inclined extinction

31
Q

What are the optical properties of muscovite/ mica?

A

Rainbow coloured CP
Moulted appearance
Green tint in PP
Straight speckled extinction

32
Q

What are the optical properties of chlorite?

A

Some pleochroism
Some twinning
Green tint PP
Brown/ Dark green/ blue CP (not on chart)

33
Q

What are the optical properties of epidote?

A

Yellow- green pleochroic
High relief
purple w/orange outline in CP
Some lamellar twinning
Inclined extinction

34
Q

What does a red colour in a rock suggest? What type of magma/ minerals are likely to be present?

A

Red suggests oxidised iron
Minerals: Quartz, feldspar
Magma: Rhyolitic

35
Q

What are the 3 low density igneous rocks and their differences?

A

Pumice- light coloured
Scoria- dark coloured
Tuff- orange, brown, more sediment like

36
Q

What are the features of a QFP and Quartz porphyry?

A

Large crystals of quartz and feldspar, in a fine ground mass
May have some iron staining
Rhyolitic magma origins, high Si content

37
Q

What are the features of a breccia?

A

Large angular clasts
In a fine ground matrix
Large variety of minerals
Poorly sorted

38
Q

What are the features of eclogite and its original environment?

A

Green - pyroxene
Pink- garnet
Basaltic origins, undergone metamorphism
Some quartz, amphibole

39
Q

What are the features of amphibolite and its origins?

A

Black- hornblende, slightly shiny
White- K+ feldspar
Regional metamorphism, from basaltic origins

40
Q

What are the features of quartzites?

A

Sandpaper glassy texture
Pink and white crystals (Q and K feldspar)

41
Q

What are the features of pelites and its origin?

A

Fine grained
Dark coloured
Originally mudstone/ siltstone

42
Q

What are the features in ooids and their origins?

A

Small spherical spheres
Dark brown radial rings
Made of calcite
Formed in shallow tropical waters

43
Q

What are the features of conglomerates and their origins?

A

Rounded clasts in a fine grained matrix
From floods
Matrix may be sand (quartz)

44
Q

What are the properties of a limestone and its origin?

A

Easily scratched
Light coloured
Reasonably small grain size
Formed from precipitation out of water due to biological and non-biological processes

45
Q

What are the properties and origin of chalk?

A

Low density
White
Formed from remain of marine organisms

46
Q

What are the properties and origins of dolomite?

A

Slight red colour Ca:Mg 1:1
May have cavities due to alteration shrinkage
Formed in high intertidal and sabkhas (coastal mudflat)

47
Q

What are the properties and origins of chert/ flint?

A

Conchoidal fracture
Dark brown/ grey colour
Non-clastic formed from microcrystalline quartz
Form as nodules

48
Q

Give a technical description of a brachiopod

A
  • Contains a pedicle which it uses to attach - filter feeder
  • Pedicle is at the posterior end
  • Diductor muscles for opening
  • Adductor muscles for closing
  • Leaves less muscle scars and has less muscle mass
  • Has tooth and socket system
49
Q

Give a technical description of a bivalve

A

-Only has adductor muscles
- Open when adductor muscles relax
- Beak is called the umbo, and points towards anterior
- Has pallial line inside- marks where muscles attached
- Very clear muscle scars
- Contain ligament near tooth
- Has tooth and socket system

50
Q

Why does calcium carbonate sometimes biomineralize in calcite and sometimes aragonite?

A

Depends on the minerals present in the water
If no Mg present then will biomineralize in stable calcite, if Mg present will form metastable aragonite

51
Q

Original composition of skeletal material of trilobites

A

Calcium carbonate- specifically calcite

52
Q

Original composition of skeletal material of echinoids

A

Calcium carbonate- specifically calcite
Ossicles formed of small calcite crystals

53
Q

Original composition of the skeletal material of bivalves

A

Calcium carbonate

54
Q

How do muscovite and biotite differ?

A

Hand specimen
Biotite- black, dark
Muscovite- light, w/green tinge
PP
Biotite- Brown/ green
Muscovite- colourless
CP
Both show straight speckled extinction

55
Q

What are the optical properties of augite?

A

Clear cleavage, many parallel to each other
Second order blue, orange CP
Pale colourless in PP
Moderate relief
Clinopyroxene so inclined extinction

56
Q

What are examples of black minerals in hand specimen?

A

Magnetite
Biotite mica
Augite pyroxene (dark green)
Hornblende/Amphibole

57
Q

What are the properties of Diorite?

A

White- plagioclase
Black- biotite
Present are also pyroxene and amphibole
Intrusive rock (large crystals), acidic origins

58
Q

What are the properties of gabbro?

A

Coarse grained intrusive mafic rock
Dark minerals- Pyroxene
Lighter minerals- feldpspars

59
Q

What are the properties and the environment formation of blueschists ?

A

Blue colour
Blue- glaucophane
Green- epidote, jadeite
Pink- garnet
Metamorphism at subduction plate
Originally basaltic (oceanic plates)

60
Q

What are the properties and environments of formation for marble?

A

White, pink
Granular texture
Metamorphosed limestone

61
Q

What are the differences between nautiloids and ammonoids?

A

Nautiloids thicker shell
Nautiloids simpler suture lines
Ammonoids septa curve inwards into body
Nautiloid siphuncle central, ammonoid is lateral

62
Q

How can tectonic setting be inferred from thin sections?

A

Large crystals- intrusive vice versa
Quartz- rhyolitic magma, olivine/ pyroxene- basalt
Presence of muscovite, chlorite, glaucophane, epidote- suggest metamorphism

63
Q

What are the optical properties of glaucophane?

A

Blue
Good cleavage
Twinning
Accompanied with epidote and jadeite

64
Q

What are the optical properties of spinel?

A

Isotropic
No cleavage
High relief
Brown in PPL
In mafic igneous rocks

65
Q

What are the optical properties of serpentine?

A

Green in PPL
Low relief
1st order birefringence
‘skin of a serpent’

66
Q

What part of a belemnite is commonly preserved?

A

(Rostrum)
Calcitic guard

67
Q

What are the key features on an echinoid?

A

Periproct (anus)
Peristome (mouth)
ambulacra (where spines attach 5 radial things)
Interambulacra (inbetween the above)
Spine attachement
Ventral and dorsal

68
Q

How to calculate stratigraphic thickness?

A

Cos(Dip) x vertical thickness (calculate by the contour structure difference between top and bottom of boundary)

69
Q

How to estimate dip direction?

A

If valley, then direction of veeing
If ridge then opposite direction to veeing

70
Q

What 4 labels should be added to graptolites?

A

Nema
Sicula
Thecae
Stipe

Earth (4 decks)

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