Geology > Pre-Cambrian > Flashcards

Pre-Cambrian Flashcards

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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
What was the first form of life?
Photosynthetic Cyanobacteria
26
What were formed by Cyanobacteria?
Stromatolites
27
Microbes incorporates sediment into the stromatolite through what processes?
Trapping and binding
28
What are stromatolites made of?
Limestone (calcite)
29
What was the result of Cyanobacteria emergence?
Oxygen level increases
30
What is a wrinkle structure?
Wrinkle structures are the preserved remnant of microbial mat in a sandy beach environment. Wrinkle structure are a sedimentary structure.
31
The Proterozoic occurs between what two factors?
The start of oxygenated atmosphere and the first animals
32
what is the evidence of oxygen rich atmosphere during Proterozoic?
Proterozoic rocks consist of banded iron
33
what is the modern mountain building event called? And definition?
Orogeny, an orogeny forms a mountain belt.
34
During the Archean, plates were __, but were still very __, and ______.
solid, hot, easily deformed
35
What are three type of stresses operate on Earth?
Tension (divergent), compression (convergent), shear (transform)
36
What are the three types of faults
Normal, reverse, strike-slip
37
Where preserves the one of the earliest orogenic events recorded on earth?
The slave province of Canada
38
What are remnants of orogenies consist of?
Igneous rock, metamorphic rock, faults
39
Before Pangea, what was the Proterozoic age supercontinent?
Rodinia
40
When did rodinia split?
800 million years ago
41
Death Valley record sites
Kingston peak, noonday, johnnie, stirling, wood canyon
42
When was the most severe ice age began?
720 million years ago
43
When glaciers were present on every continent on earth, how do scientists call this time?
Snowball earth
44
What are the large boulders in mudstone in Death Valley called?
Dropstones, they were carried by glaciers and dropped when ice melt
45
What happened when ocean were ice sealed?
Iron build up below and oxygen couldn’t react with iron
46
In the end of the ice age, what emerged?
Diverse multicellular life
47
What are some of the earliest evidence for multicellular life?
Ediacaran organisms
48
When did ediacaran organisms appear?
Near the end of Proterozoic
49
What are some features of ediacaran organisms?
Soft bodied, had no mouth, lived a stationary lifestyle
50
How did ediacaran organisms getting food?
Diffusion
51
How did these soft bodied organisms preserved?
The presence of microbial mats aided preservation
52
All ediacaran organisms preserved as ______
Sandstone casts formed with microbial mats enhanced molds
53
the emergence of ediacaran organisms coincides with what result?
The rise of atmosphere oxygen
54
Sponges consists of simple cells held together by a common animal protein called ___
Collagen
55
Paleozoic is the first era of ___
Phanerozoic
56
The late Proterozoic ____ preserves small impression of a tub-shaped animal
Stirling quartzite
57
What was the first shelled animal ever?
Cloudina
58
Drill holes are an indicator of what feeding strategy?
Predation
59
Cloudina is considered to be a _____
Sediment sticker
60
What is another animal that lives as a sediment sticker?
Ediacaran organism
61
What is the sign of Precambrian-Cambrian boundary?
The first occurrence of treptichnus pedum
62
What is treptichnus pedum?
A specific trace fossil to incorporate a significant vertical component
63
The Cambrian marks the first occurrence of _____ and ______
Vertical burrowing, complex behaviors
64
When was early Cambrian?
542-509 million years ago
65
What is bioturbation?
Bioturbation refers to the mixing of sediment through the burrowing activity of animals
66
What is the result of bioturbation?
Bioturbation destroy sedimentary structure
67
How was bioturbation measured?
Using a semi-quantitative scale called ichnofabric index (ii)
68
When did bioturbation starts to occur?
Cambrian
69
What causes microbial mats disappear?
Bioturbation and grazing from animal
70
What is the other result of microbial mats disappearance?
Decease stromatolites diversity
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