The Accretionary Wedge #4: Deskcrops

This month’s Accretionary Wedge is “My Pet Rock”. What samples do the geo-bloggers of the world treasure most?

This month’s Accretionary wedge is Deskcrops/My Pet Rock. A tour de force of rock collections, concentrating on the world’s geobloggers detailing their favourite samples. Why are they so interesting? What’s their history? Read on to find out.

First up is Andrew Alden from About:Geology who proudly display two of his favourites;
A Multiply Fractured Mudstone

A cherty mudstone was fractured and invaded several different times by mineral-depositing solutions, then nicely rounded in the Pacific surf.

and a Serpentinite Boulder

Photos can’t capture all the color and textural appeal of this serpentinite specimen, polished by deep movements in the California Coast Ranges.

Next up, Chris Rowan from Highly Allochthonous gives us a desktop full of Komatiite;

I’ve been meaning to discuss this one for a while: even though it’s not the prettiest in my collection, it tells a very interesting story about the early Earth.

Kim from All My Faults are Stress Related gives us a deskcrop with dizzy feldspars

If you want to know just how a rock changed shape, it helps to have a way to tell apart pure shear and simple shear. Generally, you need to find some kind of object that has tracked the movement – and this rock has one.

Brian over at Clastic Detritus gives us a trio of his favourites, a couple of which are from the Permian (!), which I’m chronologically jealous of;

Stopping along Highway 62/180 in between Guadalupe Mtns National Park and Carlsbad Caverns is a favorite for geology field trips of any kind. At this location, you are not in any national park and can smash and grab as much of this rock as you want.

A submission from Ron Schott gives us Bushels of Deskcrops;

See how many of the deskcrops you can identify on your own – when you recognize one you can “Take a Snapshot” and add a comment.

Jim Repka from Active Margin has a fulgurite sample to tell us about. And to be honest, fossil lightning sounds amazingly cool;

The subject of fulgurites, or fossil lightning, came up and I explained that quartz has a melting point of about 1600 degrees C, a temperature easily achieved in the near surface, though in very wet soils the charge can be dissipated pretty rapidly.

Lab Lemming gives us a rundown of their Trophy rocks;

My first trophy rock is a 4 kg boulder of the Lavras conglomerate from the Tombador formation of the mid-Proterozoic Espinhaço Supergroup.

And to round out the deskcrop theme, here’s all of the deskcrops described by thermochronic from Apparent Dip;

Thanks a lot to everyone who’s participated.

9 Responses to “The Accretionary Wedge #4: Deskcrops”

  1. A few of my favorite pet rocks « Clastic Detritus Says:
    December 16th, 2007 at 2:39 am

    [...] turbidites , west Texas For the 4th edition of The Accretionary Wedge blog carnival, which is hosted over at goodSchist, we are showing off our favorite pet rocks (or “deskcrops” as coined by [...]

  2. Ron Schott Says:
    December 16th, 2007 at 4:37 am

    Three more you might point to, Chris:

    James Repka made a pet rock post about some fulgurites.

    Lab Lemming has Trophy Rocks, though it appears to be lacking in visual evidence.

    And there are also Thermochronic’s original deskcrop posts.

    They may have neglected to notify you, but they certainly fit the theme.

  3. Chris Says:
    December 16th, 2007 at 7:58 am

    Thanks for the heads up Ron, I’ve added those links to the post.

  4. About Geology Says:
    December 16th, 2007 at 9:11 pm

    “In geology, we have The Accretionary Wedge, of which the fourth installment has just gone up. This time we’re all posting about our pet rocks or deskcrops…”

  5. BrianR Says:
    December 16th, 2007 at 9:23 pm

    thanks for hosting! This is a nice collection of posts.

  6. The Accretionary Wedge #3: My Pet Rock « The Accretionary Wedge Says:
    December 17th, 2007 at 12:32 am

    [...] #3: My Pet Rock The December 2007 edition of TAW is up at goodSchist.com — check it out here. Several geoscience bloggers are showing off their favorite “deskcrops” that [...]

  7. Sorting Out Science » Blog Archive » Carnivalia Says:
    December 19th, 2007 at 1:02 pm

    [...] The Accretionary Wedge #4 [...]

  8. Happy Solstice Says:
    December 22nd, 2007 at 6:58 pm

    [...] totally failed to participate in Accretionary Wedge #4, which is all about our favorite pet rocks. [...]

  9. Lab Lemming Says:
    December 22nd, 2007 at 11:01 pm

    I have pictures up now, for whomever is interested.

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