Q:

How long has sedimentary rock been around?

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Quick Answer

As of August 2014, the oldest sedimentary rocks known are banded iron formations from Greenland and Quebec that have been dated to 3.8 or 3.9 billion years old. The material composing these rocks may have been extracted from the Earth's mantle as much as 4.28 billion years ago.

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Full Answer

Researchers from the University of Chicago and the University of Colorado state that these rocks probably precipitated from seawater under oxygen-starved conditions and that the iron came from hydrothermal vents along mid-ocean ridges. Banded iron formations are not being formed in modern times because seawater now contains a much higher proportion of dissolved oxygen that would cause iron to precipitate rapidly near the vents.

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Related Questions

  • Q:

    What is the sedimentary rock formed from sand deposits called?

    A:

    The sedimentary rock formed from sand deposits is referred to as "sandstone." This type of rock accounts for about one-quarter of all sedimentary rock on the planet, second only to mudstone.

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  • Q:

    What are sedimentary facies?

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    Sedimentary facies are the characteristics of a given layer of sedimentary rock, including organic and inorganic deposits. The facies of sedimentary rocks help date layers, and they are also important in describing the environment in which those rocks were formed.

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  • Q:

    Where do sedimentary rocks come from?

    A:

    Sedimentary rocks come from the fragments of pre-existing rocks called sediments. There are three types of sedimentary rocks, each coming from different kinds of sediments. Clastic sedimentary rocks are created from the broken pieces of other rocks, while chemical sedimentary rocks form from mineral crystals like halite and gypsum.

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  • Q:

    What are organic sedimentary rocks?

    A:

    Organic sedimentary rocks are sedimentary rocks formed from the remains of organisms. The three types of organic sedimentary rock are limestone, chert and coal. Both limestone and chert are formed largely from the hard structures of organisms, while coal is formed from dead plants after a long period of exposure to the correct environmental conditions.

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