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Geology > Pre-Cambrian > Flashcards

Pre-Cambrian Flashcards

1
Q

The Precambrian refers to the time before what factor?

A

The emergence of large and visible animal fossils

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2
Q

The Precambrian refers to how many years ago?

A

542 million years ago

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3
Q

What’s the order of Earth EON

A

Hadean, Archean, Proterozoic, Phanerozoic

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4
Q

When did Hadean start and end?

A

Started at 4560 m.y. ago and ends at 4000 m.y. ago

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5
Q

When did Archean start and end?

A

Started 4000 m.y. and ended at 2500 m.y

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6
Q

When did Proterozoic started and end?

A

2500 to 542 m.y.

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7
Q

What era was in Phanerozoic? In what order?

A

Paleozoic, Mesozoic, Cenozoic

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8
Q

What periods were in Paleozoic? In what order?

A

Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian

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9
Q

What period were in Mesozoic?

A

Triassic, Jurassic, Cretaceous

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10
Q

What period were in Cenozoic

A

Tertiary, Quaternary

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11
Q

What is the key aspect of Cambrian?

A

Appearance of animals

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12
Q

Times before Cambrian refers to?

A

Precambrian

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13
Q

Why there is no history before 4.5 to 4.0 billion years ago?

A

No rocks were preserved

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14
Q

What eon were included in Precambrian

A

Hadean, Archean, Proterozoic

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15
Q

Modern continents are built around what?

A

Stable cores of Archean-Proterozoic rock called cratons

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16
Q

What make the ancient continent of laurentina?

A

Greenland and North America

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17
Q

What makes cratons?

A

Very old metamorphic rocks and intruded by igneous rocks, most are folded gneiss with some granite

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18
Q

Continents grow around cratons through what?

A

Accretion

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19
Q

What does accretion refers to?

A

The addition of continental landmass due to continental collisions

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20
Q

Accretion occurs at what geological event?

A

Convergence boundaries

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21
Q

When did North America was accreted to the N.A. craton?

A

During the last 600 million years

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22
Q

A craton can be divided into distinct terranes, what is terrane?

A

A terrane is a geologically distinct region of earth’s crust that behaves as a coherent crustal block

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23
Q

What can be found in river deposits from Archean time?

A

Pyrite

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24
Q

What are the oldest fossils?

A

Archean age bacteria

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25
Q

What was the first form of life?

A

Photosynthetic Cyanobacteria

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26
Q

What were formed by Cyanobacteria?

A

Stromatolites

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27
Q

Microbes incorporates sediment into the stromatolite through what processes?

A

Trapping and binding

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28
Q

What are stromatolites made of?

A

Limestone (calcite)

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29
Q

What was the result of Cyanobacteria emergence?

A

Oxygen level increases

30
Q

What is a wrinkle structure?

A

Wrinkle structures are the preserved remnant of microbial mat in a sandy beach environment. Wrinkle structure are a sedimentary structure.

31
Q

The Proterozoic occurs between what two factors?

A

The start of oxygenated atmosphere and the first animals

32
Q

what is the evidence of oxygen rich atmosphere during Proterozoic?

A

Proterozoic rocks consist of banded iron

33
Q

what is the modern mountain building event called? And definition?

A

Orogeny, an orogeny forms a mountain belt.

34
Q

During the Archean, plates were __, but were still very __, and ______.

A

solid, hot, easily deformed

35
Q

What are three type of stresses operate on Earth?

A

Tension (divergent), compression (convergent), shear (transform)

36
Q

What are the three types of faults

A

Normal, reverse, strike-slip

37
Q

Where preserves the one of the earliest orogenic events recorded on earth?

A

The slave province of Canada

38
Q

What are remnants of orogenies consist of?

A

Igneous rock, metamorphic rock, faults

39
Q

Before Pangea, what was the Proterozoic age supercontinent?

A

Rodinia

40
Q

When did rodinia split?

A

800 million years ago

41
Q

Death Valley record sites

A

Kingston peak, noonday, johnnie, stirling, wood canyon

42
Q

When was the most severe ice age began?

A

720 million years ago

43
Q

When glaciers were present on every continent on earth, how do scientists call this time?

A

Snowball earth

44
Q

What are the large boulders in mudstone in Death Valley called?

A

Dropstones, they were carried by glaciers and dropped when ice melt

45
Q

What happened when ocean were ice sealed?

A

Iron build up below and oxygen couldn’t react with iron

46
Q

In the end of the ice age, what emerged?

A

Diverse multicellular life

47
Q

What are some of the earliest evidence for multicellular life?

A

Ediacaran organisms

48
Q

When did ediacaran organisms appear?

A

Near the end of Proterozoic

49
Q

What are some features of ediacaran organisms?

A

Soft bodied, had no mouth, lived a stationary lifestyle

50
Q

How did ediacaran organisms getting food?

A

Diffusion

51
Q

How did these soft bodied organisms preserved?

A

The presence of microbial mats aided preservation

52
Q

All ediacaran organisms preserved as ______

A

Sandstone casts formed with microbial mats enhanced molds

53
Q

the emergence of ediacaran organisms coincides with what result?

A

The rise of atmosphere oxygen

54
Q

Sponges consists of simple cells held together by a common animal protein called ___

A

Collagen

55
Q

Paleozoic is the first era of ___

A

Phanerozoic

56
Q

The late Proterozoic ____ preserves small impression of a tub-shaped animal

A

Stirling quartzite

57
Q

What was the first shelled animal ever?

A

Cloudina

58
Q

Drill holes are an indicator of what feeding strategy?

A

Predation

59
Q

Cloudina is considered to be a _____

A

Sediment sticker

60
Q

What is another animal that lives as a sediment sticker?

A

Ediacaran organism

61
Q

What is the sign of Precambrian-Cambrian boundary?

A

The first occurrence of treptichnus pedum

62
Q

What is treptichnus pedum?

A

A specific trace fossil to incorporate a significant vertical component

63
Q

The Cambrian marks the first occurrence of _____ and ______

A

Vertical burrowing, complex behaviors

64
Q

When was early Cambrian?

A

542-509 million years ago

65
Q

What is bioturbation?

A

Bioturbation refers to the mixing of sediment through the burrowing activity of animals

66
Q

What is the result of bioturbation?

A

Bioturbation destroy sedimentary structure

67
Q

How was bioturbation measured?

A

Using a semi-quantitative scale called ichnofabric index (ii)

68
Q

When did bioturbation starts to occur?

A

Cambrian

69
Q

What causes microbial mats disappear?

A

Bioturbation and grazing from animal

70
Q

What is the other result of microbial mats disappearance?

A

Decease stromatolites diversity

Geology (3 decks)

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