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Geology/Formation can be sedimentary only ?



Dear Sir, I was wondering and often get confused that why is it that we always hear of sedimentary formations and not of igneous and metamorphic ones.
1. Can igneous and metamorphic be the formations?
2. If yes, then why don't we hear of them that often?

Best Regards,

Dear Taseer Ahmad, Fraternal Greetings!

Sorry for the delay in answering your question as I was out of country for sometime.

Regarding your question, it is highly confusing and there is no clarity till date why the Geologists call formation only for Sedimentary rocks and not for igneous and metamorphic.

in fact it is general connotation rather than any indication. Any material with particular length and breadth with minimum thickness prevails then it is called Formation. Generally all these qualities may be seen in Sedimentary rocks predominantly.

Sometimes it is called Dharwar formations which include even igneous and metamorphic rocks also.Hence the term formation can also be used for igneous and metamorphic rocks.

Hence to the best of my knowledge we can call the Formation for igneous and metamorphic also but the usage of this term is rare for unknown reasons.  


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Dr D S Subrahmanyam


All questions related to Geology, Geotechnical Engineering (especially in-situ stress, in-situ Deformability and Shear investigations) required for underground tunnels and excavations, Dimensional Stone Mining. Can't answer Soil dynamics related to Geotechnical Engineering


Geology and Geotechnical Engineering and Dimensional Stone Mining

National Institute of Rock Mechanics (Govt of India)

International Journal of Mining Engineering and some other Indian journals

Doctorate in Geology

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