Comments on: Friday Rock Blogging, Mailbag Edition

By: jim

jim — Wed, 29 Nov 2006 17:54:28 +0000

Looks like a feature found in proterozoic carbonates.

Google “molar-tooth” structure.

Or, as I would recommend, do a field run up to Glacier National Park and study the roadside rock walls.

By: Andrew Alden

Andrew Alden — Thu, 02 Nov 2006 19:43:04 +0000

It looks to me like a shale with soft-sediment deformation, mostly thin rip-up clasts. A laminated shale that was disturbed by slumping in a continental-slope setting. How’s that sound? But maybe if you look at the layers head-on, it’s really a trilobite orgy.

By: Melissa Barton

Melissa Barton — Sun, 01 Oct 2006 22:45:17 +0000

Seriously, though, it’s hard to tell without seeing the texture better, but I really want to think it’s sedimentary (and that the stripey bits are secondary).

By: sciencewoman

sciencewoman — Sun, 01 Oct 2006 22:10:03 +0000

Doesn’t look like any welded tuff I’ve every seen. My first thought was metamorphic something or other. But are there many metamoprhic rx in western UT?

By: Melissa Barton

Melissa Barton — Sat, 30 Sep 2006 08:56:41 +0000

Paleoworm tracks, duh.

/making stuff up

By: Lab Lemming

Lab Lemming — Fri, 29 Sep 2006 20:20:01 +0000

Could it be “structure” from a metamorphic core complex? The relief on the wavy things suffests that they are quartz (erosionally resistant) layers, possibly folded. So my first guess is a low grade metapelite with folded quartz veins.

My second guess is a welded tuff with quartz precipitated during devitrification.

Note that these two guesses require completely different geologic contexts.

so basically, I have no idea either. But I’d bet that the rock is seismically anisotropic.

By: Helen

Helen — Fri, 29 Sep 2006 15:49:45 +0000

Crayons! You know how you can draw on an Easter egg with white crayon, and the dye won’t stick there? Some little rock-gnome got artistic with the rock-gnome-crayon-equivalent and the erosion didn’t stick there. Or something. Maybe an ancient rock-gnome experiment in photolithography.

By: delagar

delagar — Fri, 29 Sep 2006 15:08:22 +0000

Yay! I have no idea what the stripey bits are. I’m just glad Friday rock blogging is back.