This is a follow on from the
Global Flood Evidence: A Place For Faith to Present Some thread.
Limestone is composed of the skeletons of microorganisms which live in the top 10 meters or so of shallow seas. When these tiny creatures die their calcium rich skeletons sink to the sea floor, and over long periods of time the depths of limestone accumulation can become substantial. The limestone layers of the White Cliffs of Dover are 200 to 300 meters thick and are thought to have accumulated over a period of around 10 million years.
A flood scenario that would have laid down the limestone layers in less than a single year just a few thousand years ago presents several problems.
First, the radiometric age of all limestone layers is much older than a few thousand years. For example, the limestone layers of the White Cliffs of Dover are thought to range from 84 to 94 million years old.
Second, limestone layers can only be deposited in quiet seas. Turbulent seas would keep the microscopic skeletons suspended in the water.
Third, there is far more limestone on the earth than could have been deposited in a single year. Limestone in modern oceans accumulates at the rate of about 5 inches per thousand years. It would have taken at least a million times more microscopic life to deposit the limestone layers of the White Cliffs of Dover in only a single year. Naturally, this much more life would have required a million times the amount of food, generated a million times more waste and heat, and required a millions times more volume. In effect, the entire solid 200 meters of the White Cliffs of Dover would have had to have been alive at roughly the same time. Even aside from these problems, with the organisms packed so tightly together only the top millimeter could have received any light at all (these organisms live by photosynthesis), so only a tiny fraction could live under such circumstances.
It should be added that modern sea floors represent a record of continual very slow deposition over very long time periods, a couple hundred million years in some places. For example, the depth of sediment at the mid-oceanic ridge of the Atlantic Ocean is almost non-existent, while furthest away from the ridge near the continental coasts (but not too near because the sedimentation there is largely affected by continental runoff and river deltas) it is at its deepest. At no point in this hundred million year record is there a sudden discontinuity with hundreds of extra meters of sediment.
And this isn't the end of the problems. As if accounting for limestone layers weren't difficult enough, in many parts of the world beneath the limestone layers lies, not bedrock, but more sedimentary layers!!! Creationists have to figure out how that got there, too, but that's another thread.
Creationists who believe in a global flood have to overcome all these problems and show that a global flood creating deep limestone layers in short periods of time is a real possibility.
--Percy
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