There were many, many examples of this, my photo simply shows a situation where I had even light and time to take a photo without making anyone wait for me.

The basic rock is obviously sandstone. While it is basically horizontal in this photo other locations were far from horizontal.

There are these intrusions of some other material into the rocks, always occurring as very thin layers, always sticking up a bit so it must be more erosion resistant than the sandstone.

I could understand one intrusion but they were all over the place, generally quite parallel although I saw deviations of up to about 20 degrees in small areas and generally about perpendicular to the layers of the sandstone. Most of the rocks show far less variation between the two sides of the intrusion, at least in sunlight. (This shot was in the shade so there would be no shadows messing it up.)

This was taken in Valley of Fire state park, Nevada, USA. The environment was far wetter than normal and this was taken not far from a deep puddle that forced a detour on us.

What's this rock?

  • $\begingroup$ Without more information I would suggest that the lines of more resistant rock that resist weathering more are related to narrow fractures in the rock which have been subjected to aqueous solutions containing either carbonates or silcas which have been deposited within the cracks where they cement the sand grains together more tightly than the majority of the sandstone matrix. Close up of the material in the raised areas might be helpful as would an acid test between the raised and more eroded areas. $\endgroup$ – Friddy Feb 11 at 23:45
  • $\begingroup$ @Friddy Aha, I was trying to picture how something forced itself in, but if it's deposits in fractures it's nowhere near as strange. As much of it is nothing like horizontal it's clearly been very stressed at some point in the past, I could see fractures forming. $\endgroup$ – Loren Pechtel Feb 12 at 5:18

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