A new geopuzzle for you

Not only did everyone seemed to enjoy the big crater debate, but there were also suggestions in the comments that more conundrums of this ilk might be make a fun companion for What on Google Earth (which I never seem to actually see before someone’s solved it nowadays – darn time zones). It’s worth a go, anyway, although it might take a while to get the format and level of difficulty right…
This week, I’m asking: what is the origin of the structures in this photo (click for a larger version)?

gc2a.jpg

Let me know what you think in the comments.

Categories: geology

Comments (25)

  1. Bob O'H says:

    They evolved from apes.
    Bob

  2. Mike Dunford says:

    It’s really hard to tell without putting nose to outcrop, but at least superficially they look similar to some things I’ve seen in Maryland and West Virginia.
    It looks like the rocks were pretty clearly folded first, then faulted. My best guess would be that this is the result of the type of uplift that you get when two continents join.

  3. Tuff Cookie says:

    Huh. Cuspate folds…compressional stresses…
    Either that or these are the biggest freaking stromatolite fossils on the planet.

  4. Tegumai Bopsulai, FCD says:

    That has got to be a record size for sauropod vertebrae.

  5. Julian says:

    Another vote for compressional folds here.

  6. Greg Laden says:

    OK, I’m now thinking pillow lava or highly deformed greenstone.
    Karet trailers are common in South Africa and judging by a number of factors (mainly the hats) most of these people are students from South Africa, eastern region, like Transvaal or Mpumalanga.
    The funny thing is, I KNOW I’ve seen this outcrop before. I’ve been on about a third of the major roads in South Africa and I always watch the outcrops….

  7. Propter Doc says:

    Collapsed lava tubes? Infested by apes. Someone get the bug spray!

  8. Greg Laden says:

    OOO OOOO OOO Wait, wait, dont tell me!
    It’s Campbell Rand or Malmani stromatolitic dolomite. Somewhere on the N4. Yes? Yes?

  9. BrianR says:

    I think Tuff Cookie and Greg might be right with stromatolites … if not, then my second guess would be desiccation/cementation features that occur in mixed carbonate-evaporite systems (called “teepee structures”)

  10. Mel says:

    My vote is for carbonates as well. Is this something like a couple Waulsortion mounds or a variety of stromatolite? I’ve seen some weird ones in my day and I wouldn’t be surprised if there was another variety out there that made these dome structures. If you look towards the base of the outcrop, it looks more like domes and the weathering above has created nice cross sections of mounds.

  11. Mike Dunford says:

    After looking more closely at the picture, there is one feature that looks a little strange. Down toward the lower right of the photo, just above the roof of the car, there’s what appears to be a bed that appears to wrap up and around. That’s very dissimilar to the more obvious portion of the outcrop.
    Unless Chris wants to share more pictures of that area (hint, hint), though, it’s going to be really hard to figure things out from the one picture. The history of that outcrop is clearly complex, and I feel reasonably safe in saying that there was a lot of compression at one point, but there may well have been a lot more going on there.

  12. Karen says:

    Soft sediment deformation, perhaps followed much later by faulting to get the folds adjacent. Or maybe not. I think if the rock were well-lithified before folding, you’d see some variation in the competence of the layers.

  13. Tegumai Bopsulai, FCD says:

    Wherever it is, it’s way out in the boondocks. They’re parked right in the middle of the @$%@$% road.

  14. Ahcuah says:

    Fossils of Arrakian spice worms?

  15. Ron Schott says:

    First thing that came to my mind was stromatolites.

  16. flounder says:

    Two ideas.
    One is that these are lave tubes or pillows from a mafic/ultramafic flow, perhaps a komatiite.
    Another is that we are looking at a layered mafic intrusion such as Bushveld and we are seeing evidence of soft sediment deformation within the cumulate pile.
    The reason I think it is a similar situation as I describe is because you can see some dark minerals interlayer. I would think these are Fe-Ti oxides or chromite that would indicate a (ultra) mafic body.

  17. cope says:

    Drag folds along some small imbricate faults? What ever it is, I am in the pre-lithification camp.

  18. Mathias says:

    I think these are carbonates, too. The dark layers could respond to chert or maybe sedimentary manganese. To me this is the result of some major folding and faulting.
    Are these something like cap carbonates of the Transvaal?

  19. Karen says:

    Ahcuah,
    While I still vote for soft-sediment deformation, I wouldn’t rule out fossils of Arrakian spice worms. I would like to know how Chris is getting photos from Arrakis, though.

  20. dmonte says:

    I vote for carbonate and some form of stromatolite. Strange coincidence though as I was watching Dune just last night so I would like to see if there are excessively thick sand deposits surrounding these structures to be sand worms fossils

  21. divalent says:

    Okay, I’ll play.
    Not that anyone would every confuse me with a geologist, but it seems to me that these are way too large, and the layering much too regular and uniform, to be stromatolites.
    (Not that I’ve ever actually seen a stromatolite up close (but then again, it’s not as if I would ever recognise one if I ever did happen upon one))
    It’s interesting that the curvature seems to get tighter with depth, as if the axis of a fold (if it is a fold) was approximately right there where the people are standing on the road. The left-most structure is about 90 degrees of curvature, and the struture to its right is about 45 degrees. And the layers seem to be the same in both structures, as if it was orginally one folded structure (of at least 135 degrees, and then a faulting event caused the right most structure to detach and rotate up to the right.

  22. arby says:

    Do stromatolites get THAT big? I’d have to go with lava tubes too, but, given my ignorance, I’m almost certainly wrong. rb

  23. Lab Lemming says:

    exfoliation jointing in very small plutons.