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Questions tagged [precambrian]

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1answer
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Can we call the Precambrian eons (i.e. Archaic and Proterozoic) eras?

A diagram in a book I have places Archaic and Proterozoic under "eras". Is such naming correct? ICS says they are eons, so do most sources I could find, but a 1979 volume of "Treatise on ...
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0answers
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Precambrian shield and Don Valley Brickworks

living in Toronto, and interested in Geology, I am looking for some information on where the Precambrian shield rocks found in the Don Valley / Evergreen Brickworks originated. More specifically, can ...
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1answer
109 views

There is soil in Archean? [closed]

Following a mobilista approach over geological time, and considering the Earth's internal heat as responsible for tectonic regime, which was involved in the "Permobile type" during the early times of ...
11
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1answer
212 views

What caused a fall in atmospheric oxygen about 1.9 billion years ago?

Using chromium isotopes geochemistry, Frei et al. 2009, describe in the article Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes that after the Great Oxidation Event (...
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1answer
226 views

Could Earth have had a greater axial tilt?

In thinking about the question, Why is earth's axis tilted?, and reading articles about Earth's axial tilt, I came across the website Snowball Earth which describes an alternate theory for global ...
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3answers
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Why is Earth's age given by dating meteorites rather than its own rocks?

Reading a course on Precambrian, I read that: Earth Age (around 4.5 billion years) is dated thanks to the meteorites hitting Earth during its formation rather than the inner materials composing the ...
11
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1answer
168 views

Why would there be no hydrocarbons in the Sveconorwegian belt?

I've had an inconclusive chat about the Sveconorwegian belt of the Fennoscandian shield, the western parts in particular, and reasons as to why there would not be any deposits of hydrocarbons there. ...
10
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1answer
460 views

How was the Marinoan Glaciation triggered?

The Marinoan Glaciation (a.k.a. Elatina Glaciation) was a glaciation that is thought to have occurred towards the end of the aptly-named Cryogenian period at ca. 650Ma. It is particularly known as one ...
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How are the banded-iron-formation iron-ores formed?

Many of the richest and purest iron ores are found in so called banded iron formations, cm thick magnetite or hematite layers intermixed with iron poor rock layers. Since these are usually of pre-...