Thursday, January 24, 2008

Rock of the (not quite mid) week: disharmonic folds

Folds are complicated structures. These are in marble just below the Snake Range Decollement. The quartzites below them are mylonitic, stretched to flat slabs. But the marbles have folds like these:

"Disharmonic" folds have different wavelengths, different hinge locations, and so forth in different layers. The marble looks for all the world like it's a pot of paint that has been stirred. And yet it hasn't been a liquid. It was calcium carbonate - easy to dissolve in water, and easier to deform by intracrystalline deformation than many other minerals, but still solid.

Why does it look like this? Heck if I know. But it looks cool.

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