Thursday, November 11, 2010

Help us identify these features in the Navajo Sandstone

Readers, we need your help. Some time ago, we received these photos of unusual features in what appears to be the Betatakin section of the Navajo Sandstone, asking if we could identify their origin.

The features are not on bedding planes. One suggestion is that they could be skolithus-like burrows that created bioturbation. Another proposal is that they are the result of some early but undefined diagenesis of the rocks.

Does anyone have an explanation for these features?


  1. Anonymous4:23 PM

    Ya'at'eeh, I am from the Navajo Land. These photo's to me look like work of humans and it might be to make a tunnel or even to level out the area for some odd reasons. It is hard to determine the reason by the limited info on the pic's. I hope that it answers your curiousity.
    K. Bye

  2. I'm guessing bioturbation. I wish I were there in person, to eyeball the features (though I might be just as baffled). I can see why Anonymous mentions the activity of people -- I've seen a lot of pillaging over the years from people who spot (or think they've spotted) fossils. I'm astounded at the number of folks who will commit this kind of vandalism. The area in the upper left of the top photo looks like it might be evidence of that kind of activity -- though it may have chipped away for another reason.

  3. Definitely look like burrows that were dug into a surface that is at an angle to the bedding planes. This means they were possibly formed in sandstone after sediment had been deposited, buried, lithified, then uplifted and exposed at the surface by erosion.

    Skolithos is a worm-type organism. Could it burrow into solid rock? I don't know. Several types of mollusks and crustaceans can. Maybe these are burrows from some kind of clam- limpet-, or crustacean-type creature.

  4. Anonymous7:10 AM

    The photos upper right and immediately below that remind me of ungulate prints. Could these be animal prints, from herding, with the ringed longitudinal marks being evidence of a tail swinging low(some marks appear angular to a possible direction of travel),occasionally brushing against the ground?

  5. I believe they are the "fossil" evidence of burrowing and crawling creatures, possibly when the sand was covered in water.

  6. I agree with the bioturbation comment. I really don't believe that these are anthropogenic and I'm not convinced about skolithos. It would be nice to have an image that shows how this surface related to festooning (if any) in the bedding. From what I see, it looks like it may be near the base of the dune where bioturbation would be most likely, especially if this was part of an interdunal pond.

  7. Anonymous9:51 AM

    It looks more like burrowing associated with feeding behaviour (in soft wet sand) to me. ...something digging for food, either in one place and then moving to another place, in some instances, or moving along and leaving a line in others. On the linear progressions, the continuing foraging softens the lines of the previous activity, but leaves a deeper, more crisp impression at the end of the line in the last spot dug before the creature moved on.

  8. Anonymous11:39 AM

    I have seen crab burrows that look a lot like that in intertidal areas of South Africa.

  9. chris gr7:03 AM

    Maybe is something like flutes.... or scallops. we can't be sure ....

  10. Anonymous7:16 AM

    Creatures dit it. I agree with Get.

  11. U Utah Ichnology Student8:57 AM

    It's really tough to tell with low resolution pictures, but I think these could potentially be a trace fossil called Taeniduim. The shapes that go across the Trace fossil look like meniscate backfill. One key diagnostic feature that is missing is a vertical cross section view of one. Other possibilities include Psammichnites or maybe some odd preservation of Ophiomorpha.

  12. Anonymous3:24 PM

    I am really surprise by this diagnose challenge. My first remark will be the lack of scale on the different picture provided. Then a map or log to locate the outcrop geographically or geologically could be useful (even if it crosses bedding). Is it a highly restricted event or is it extended?
    Can we see other fossil to built an ichnofacies?
    Finally could one find only prints or some organic matter could still be found?
    Remember analysing an outcrop is not only looking at it but also thinking about its context.
    I agree with Icnology Student a section could be useful.
    As a first hit I would have thought about (skolitus-like) bioturbation too. I am not a specialist but what about Diplocraterion or Trypanites.

  13. U Utah Ichnology Student4:18 PM

    I agree with the most recent Anon. Scales are critical here - as well as way up! I think these are almost certainly burrows though. It is not necessary to see more trace fossils because generating a comprehensive ichnofacies isn't necessarily required. What would be most useful would be some frame of reference with bedding orientation. Skolithos tend to be normal to bedding planes, so if this is subhorizontal (like it looks like to me in these 4 images) then it is probably not skolithos. Additionally, before I would identify this as Diplocraterion or an Arenicolites I would want to see some clear U shapes in the burrow tubes.

    I think that my final guess based on these images would probably be Ophiomorpha Annulata ( or or Taenidium (but I would need to see a section view).

  14. Ichnofossils, i think it is a ichnofossils. But, and about the sedimentary environment of deposition?


  16. Anonymous11:01 PM

    Because of the sedimentary environment and the look of the bed which looks like upper high tide line,I think too that probably are some kind of arenicolas marine tubes.

  17. Anonymous5:20 PM

    To looks as though many people from years and years ago...late 1800's to 1910 maybe were practicing their skills

    the long tube/pipe like lines, in the image, that has the broken up sandstone looks to me to be jackhammer lines, each at different depths and some showing the jackhammers being turned sideways.

    (see the lines in the image above)

    some of the images show what looks to be jackhammer 'points' while others were chiseled points.

    this area could have been a place for the men to 'practice' their jackhammer skills before they actual used them on the project itself. (yes, there were jackhammers back in the late 1800's)

    not sure where these image were taken (mystery images) but if they were close or near area that had/created tunnels for roads, etc (late 1800's to 1910) then this could explain the marks, so in my opinion these look like jackhammer lines.

  18. Anonymous3:18 PM

    They look very much like shrimp burrows, from a time when the ocean covered North America.

  19. Margaret M. Maher9:10 PM

    The Navajo Sandstone is a marine formation, so a biogenic source is probable. What's the angle of the formation here? The holes appear to be burrows made by some kind of animal, but does the angle at which they currently appear reflect the original position? Does anyone know where these holes are located? If they are burrows, a thin section under polarized light might show a change in composition of the rock around the hole to indicate some secreted substance from the animals that stabilized the sand and preserving the configuration. A thin section would also show impact fractures in the surrounding crystals re: comment about holes drilled by jackhammers. Or are these evidence of deposition of some odd water soluble mineral concentrated in this area? Unlikely, but again a thin section might provide evidence.