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GLGY 301 > 7 Precambrian History > Flashcards

7 Precambrian History Flashcards

1
Q

Define stratigraphic subdivision

A

A stage is a crucial subdivision of strata, each minutely following each other while bearing a unique, distinctive assemblage of fossils. Thus, stages can be described as a group of strata consisting of the same major fossil assemblages.

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2
Q

What happens when the sea level fall (shoreline regression)

A

Tectonic Uplift

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3
Q

What happens when sea levels rise (shoreline transgression)

A

Tectonic collapse

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4
Q

Define stratigraphic sequences

A

Packages of rocks bounded by unconformities

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5
Q

What are the two ways stratigraphic subdivisions can be separated?

A
  1. Sequences by time
  2. Sequences by depth
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6
Q

Where is another name for the Laurentia?

A

North American Craton

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7
Q

What time frame was the crystalline basement?

A

Archean to Paleoproterozoic (1.8-2.8 Ba)

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8
Q

How many parts are there to the crystalline basement?

A

Many different parts and is complex

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9
Q

Where is Canada is the crystalline basement exposed?

A

The Canadian Shield

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10
Q

What’s the main difference between a failed and successful rift?

A

A successful rift differs from a failed rift in that the asthenosphere makes it all the way to the surface and is able to form new crust

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11
Q

Define a rift

A

A rift is one or more depressions (GRABENS) resulting from tectonic extension that caused faulting, stretching and thinning of the asthenosphere

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12
Q

What’s an example of a failed (abortive) rift?

A

Sea between the UK and Europe

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13
Q

What time frame was the Wernecke Supergroup?

A

Paleoproterozoic to Mesoproterozoic (1.8- ~1.3 Ba)

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14
Q

What belt is the Wernecke supergroup in and what is special about it?

A

Has the oldest rocks and is in the foreland belt

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15
Q

What fossils do we see in Wernecke Group and what do these fossils look like?

A

Stromatolites can be small or large and are the result of microbial life

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16
Q

What conditions need to exist for stromatolites to form?

A

There has to be very contact with other organisms hence why they grew so large when it was only microbial life

17
Q

What is an important fossil fact about stromatolites?

A

They are the oldest formation to exist

18
Q

What time frame was the Purcell/ Belt Supergroup?

A

Mesoproterozoic

19
Q

What kind of rock is in the Purcell/ Belt Supergroup?

A

Platform/ shelf basin carbonates

20
Q

Where does most of the Purcell/ Belt Supergroup exist? (2)

A
  1. Glacier National Park, Montana
  2. Waterton Lakes National Park, SW AB
21
Q

Why does the Purcell-Belt Supergroup have two names?

A

Because its in both Canada and the US that named them differently (Purcell-Canada, and Belt-USA)

21
Q

What conditions were the Purcell-Belt Supergroup formed?

A

Deposited in deltaic to deep marine enviorments

22
Q

What time frame was the Mackenzie Mountains Supergroup formed?

A

Mesoproterozoic to Neoproterozoic (~1.3-0.8 Ba)

23
Q

What kind of fossils would you see in the Mackenzie Mountains Supergroup?

A

Stromatolite reefs

24
Q

See slide 73-75

A

Info of stromatolite reefs

25
Q

What time frame was the Windermere Supergroup?

A

Neoproterozoic (0.8-0.57 Ba)

25
Q

What kind of rock is in the Windermere Supergroup?

A

Coarse clastics

26
Q

What are the characteristics of the rock in the Windermere Supergroup?

A

Highly faulted and metamorphosed (in the omenica)

27
Q

What fossils are in the Windermere Supergroup?

A

Stromatolites

28
Q

How were most of the Windermere rocks deposited?

A

As deep-water turbidite flows, along continental margins or in an active volcanic rift basin

29
Q

What weather events occurred during the formation of the Windermere Supergroup?

A

Glaciation occurred during this time, as evidenced by diamictite

30
Q

Define diamictite

A
  • The clasts floating in fine grain matrix
  • is a type of sedimentary rock that consists of non-sorted terrigenous sediment containing particles that range in size from clay to boulders, floating in a matrix of mudstone or sandstone.
31
Q

See slide 90-95

A

Snowball earth

32
Q

What is Ediacarian Fauna and what’s important about it?

A

It is the earliest shelly animal and first showing of multicellular life, found in the Neoproterozoic ~585 Ma

GLGY 301 (14 decks)

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