from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Plural form of sedimentary rock.
from the GNU version of the Collaborative International Dictionary of English
- adj. See Aqueous rocks, under Aqueous.
Sorry, no etymologies found.
Presumably the individual particles of silt or sand that go to make sedimentary rocks contain potassium-40 and other radioactive isotopes, and therefore could be said to contain radioactive clocks; but unfortunately these clocks are no use to us because they are not properly zeroed, or are zeroed at different times from each other.
At Dun-ross's blank look he added hastily, "Hydrocarbons are only found in porous sedimentary rocks of the Paleozoic era.