Tuesday, May 21, 2013

Fault Breccia on Slickenside Ridge

Up above our last hiking stop on Slickenside Ridge, MOH and I came across this wonderful exposure of a breccia (hiking stick for scale).
Here's a closer view, showing massive and drusy quartz cementing  the breccia and filling vugs left in the rock.
This is a type of fault breccia — though I was so into my admiration of the breccia that didn't think to look for the fault  — and you can see hints of slightly oblique slickenlines on the smooth upper surface in the first photo.

In fact, it just occurred to me to show you what I mean, so here are two photos of that upper surface, one without drawings, one with.
Planar fault surface from the 1st photo, enlarged.
Same photo with some lines drawn in.
The possible slickenlines in the upper left are the ones I noticed first; the second possible slickenline direction shown in the lower right is vaguer, might be my imagination. More field work required!
A zoomed view of the "best" part of the breccia.
Looking northwest toward Winnemucca Mountain (hidden from view by my choice of framing).
Now I've walked back over to the spot where I left you in the last post, looking down Water Canyon toward the northwest. Just above the bright reddish orange dike rock on the right side of the photo, on the hill across the canyon, you can see the lower part of a rock wall first mentioned in this early post about the dikes.
Looking back down the hill and across the canyon.
And so now, as we turn to head back down the hill, we might think about investigating the rock wall on the far hill, the one we sometimes call "Dike Hill."


Hollis said...

ooohhh! I'm so envious ... gorgeous scenery and rocks. Doesn't look like I'll get to the Great Basin until fall this year.

Silver Fox said...

Let me know if you do, maybe we'll have time to meet -- time has been seeming in short supply so far this year, though.

Hollis said...

ok, that would be great ...