from sea water.
Why are they separate, instead of in a mixture
>such as we find in the ocean today?
They were mixed in the water but they deposit out in slightly different
solubilities leaving a partially graded deposit. But there are mixtures
like the varved, Castile/Bell Canyon formation of West Texas which has
calcite/salt etc
To make the great gypsum deposits, or
>trona layers, you would have to have very large lakes of very saline water
>evaporating largely undisturbed for many centuries. Is this realistic?
Yes if the earth is old.
glenn
Adam, Apes and Anthropology
Foundation, Fall and Flood
& lots of creation/evolution information
http://www.isource.net/~grmorton/dmd.htm