How fast does limestone form?
I found a fossil dragonfly in a layer of limestone or sandstone in Big Bend National Park, and there was about 9 feet of limestone above it. So how long ago was that dragonfly fossilized? How long does it take to deposit 9 feet of limestone on a shallow seafloor?
- thegeologistLv 41 decade agoFavorite Answer
Since there's no telling where in the rock sequence that formation lies, its difficult to say anything precise about its age. However, its probably more than 65 million years old when some of the limestone deposits were still forming at that location. See the link below for more information about the geology of the park that may help you refine the age of the formation you were looking at.
Figuring out the rate of deposition is tricky without more information. Using the Redwall limestone formation in the Grand Canyon as an example, we could do some math and come up with a very rough estimate that it would take about half a million years to deposit 9 feet of limestone.
- 4 years ago
Limestone can form out of a dripping faucet in a mere 30 years or so. All fossils would require would be to be in a protected area and dripped on for awhile.
- Anonymous1 decade ago
Trouble is it doesn't come in exact layers. Some places might accumulate more sediment than others. So over 250,000 years one area might be covered by 800 meters of sediment while an area just 1.5 km away could be just 20 meters thick then a further 1.5km along another 800 meters could be accumulated.
- 1 decade ago
it takes a long time :]
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