17 June 2011

Friday fold: a granite dike

Posted by Callan Bentley

This Friday, I give you a fold from the shores of the Rockfish River, south of Charlottesville, in Virginia’s Blue Ridge basement complex, and just down the road from the Lawhorne Mill High Strain Zone. The fold distorts (and improves) a felsic dike cutting the darker granite of the basement. You can make this (stitched composite) picture bigger by clicking it:

Here’s the texture of the dike granite:

Here’s the texture of the host rock granite:

And here’s another look at the host granite, in the hinge area of an antiform in the folded dike. Notice how much more foliated it is in this high-strain area:

This outcrop also featured a series of small fractures arranged in sets:

Some of these fractures showed a small amount of offset where good marker units were present:

Folds and faults! …It must be your lucky day…