6
votes
Why is coal classified as a sedimentary rock?
I'm not sure why you are including shale in your question, unless you are referring to carbonaceous shale, which in not coal, but shale with carbon throughout the matrix of the shale.
Shale is an ...
- 24.1k
3
votes
Accepted
Is this a fossil or something anorganic?
It is a chemical concretion. the shape and structure are a common form of concretion. there may be a tiny flake of fossil that acted as a seed for chemical deposition but this could be microscopic or ...
- 6,803
3
votes
What makes pollen varieties useful index fossils?
Depends upon the species. If the pollen spores are large enough, and of wide spatial distribution, and easily recognizable, and preserves well in sediments, and of distinctive age range (geologically),...
- 14.2k
2
votes
What makes pollen varieties useful index fossils?
In addition to what @GordonStanger said, there are a few other points to consider.
Pollens and spores are made out of sporopollenin which preserves way better than what one would expect.
Although ...
- 5,338
2
votes
Why is coal classified as a sedimentary rock?
Rocks are not necessarily made out of minerals. Yes, most of them are but it's not a requirement. Also, not every collection of minerals is a rock. For instance, sand is not a rock.
This is not ...
- 23k
1
vote
Where did all the CO₂ come from that was deposited as coal during the Carboniferous?
Prior to the carboniferous period, and until the human industrial era, the majority of carbon dioxide in the atmosphere was due to volcanoes.
For billions of years, geological processes like ...
- 24.1k
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