Folded and refolded rhyolite, Chiricahua Mountains, Arizona

&lt;p&gt;We know that rhyolitic flows are much stiffer than basaltic flows, and this is evident in the flow structure displayed by this rock. &amp;nbsp;The clarity of the delicate flow laminae is quite nice, and it is obvious that the fricitional flow of the stiff lava locally created tight folding. &amp;nbsp;A particularly striking example in this rock is the tight isoclinal fold residing between flow layers. &amp;nbsp;Moreover, because of progressive deformation during flow, early formed patterns can be refolded, and this rock contains a perfect example of this: &amp;nbsp;the obvious broad fold has refolded the earlier formed isoclinal fold.&lt;/p&gt;

Whereabouts

I collected this rock in 1973 just outside of Chiricahua National Monument in southeastern Arizona, at a time in which I was directing geology field camp at The University of Arizona. I like this specimen for it underscores the stiff nature of rhyolitic lava, and it is my very best example of refolded folds.

Age & Formation

Miocene rhyodacitic volcanic rock, ~27 Ma.