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Re: Terra Nova: thoughts

 I know that limestone didn't originate in teh Cretaceous, unless you
 happen to live where it did. I don't think it's all that old
 everywhere on Earth. Certainly not in Texas. Evidently all
 pre-Cretaceous rock here is sandstone and shale. And occasional
 granite. Also chert, but in isolated small rocks, and probably from
 the same source as the limestone.

 Back in the Adirondacks, most rock was granite, gneiss, quartz, and a
 much older and harder sort of limestone, but you had to look for the
 limestone, it was hardly 95% of the rock.

Over here, almost all limestone -- and there's lots of it -- is Triassic, and most of the rest is Permian. However, it was mostly still underwater in the Cretaceous.

Stromatolites are limestone, and in some places they're common enough to form entire formations. In short, there's billion-year-old limestone out there.