Sunday Sed Structures - MONDAY EDITION

Might as well TRY to keep this arbitrary schedule o' mine, I guess! Anyway, briefly, here are some pictures I snapped down in the Guads. No carbonates (yet), but here are some nice pictures of some recent gravelly/cobbley cross-bedding in a modern stream cut. Flow is to the left!

Notice the direction of cross-bedding in ABOVE the fieldbook in the second photo? Kinda goin' the wrong-direction, ain't it? I reckon I'd call that backset cross-stratification, maybe do to the impingment of upper-flow regime conditions on the flow.

USGS Photo Library

Being out in the Southwest always makes me think about the O.G. (Original Geologists) who totally went out there Hammers-a-blazin', rockin' it Old School Style, nearly gettin' killed left and right, and all that sort of fun stuff. We can all agree that they were badass, but did you know they were also awfully photogenic? IT'S TRUE!

The USGS has a pretty slick on-line library of old photographs of ALL sorts of things, including some totally rad shots of famous geologists in the field. Now, most pictures of modern geologists look pretty silly; if you don't belive me, take a look at any Geology Dept's website. Profs, Grads, Undergrads...it's a well-known scientific fact that they all look pretty goofy! But man, look at ol' One-Armed Powell, there, looking rad and hanging out with a Paiute Cheif! How's that for a slick facebook picture!



Seriously, how's that for a slick picture?

Here he is again!


POWELL: "What's up, my Paiute Friend? I'm a kick-ass geologist! Wanna go cruise around the desert, get some brews, and pick up chicks?"
PAIUTE: "Awwwwww yeah!" *fist bump*
HORSE: "Neigh."



And look at this one! Powell in traditional Paiute gear! Dirty Hippie!

Sed Structure Sunday #2 - Saturday Edition!

Well, I'm fleeing to the Gaudaloupe Mountains for a carbonate field trip, sponsored by Exxon, so I'm posting my sed structure pictures ONE DAY EARLY!



The picture above (to embiggin it, click the picture) is of some Eocene stromatolite-like mounds from the Washakie Basin (Green River Fm) in SW Wyoming. These little guys formed along the edge of a big, fairly saline lake, and as such mark a discrete geographic boundary in these ancient lake settings.

I realize that I don't have many carbonate pics; maybe I'll have some to share when I get back in a week!

Dolphins: Nature's Fluid Hydrodynamicists

Jumpin' Cats! Have you guys seen this:



How awesome is that!?!

These dolphins blow a bubble into a turbulently roiling eddy, which causes it to become a bubble-ring (similar to a Gandalf-style smoke ring, actually) and then, being dolphins, decide to play with it in the most ridiculously cute fashion possible. Hydrodynamically, these rings are a kind of toroidal vortex, which in this case is made up of a combination of air and water moving as a kind of propagating vortex. Here are some pictures of human-made bubbles, with a discussion of the physics involved in these things.

EDIT: Turns out a geo-blogger had already talked about this: check out Riparian Rap!

Revenge of The Son of Meme!

Another hellish meme has been unleashed upon the unsuspecting geoweboblogonetosphere, bringing with it interminable link-backs and crushing despair. Oh well! This particular viral meme (classified as a Level VI List-Maker Meme on the Abradoff Scale by the CDC) is described (based on the experience of the first reported victim) as: “What are ten things that every geology major ought to know about? The only restriction is you're not allowed to list anything that has already been listed by a previous geoblogger. You don't have to list everything, just ten important things.”

Well, when in Kalaupapa, do as the lepers do, I guess! Here's my List of The Ten Things Every Major Should Know About Geology:

1. Hydraulic Geometry: this concept relates fluvial discharge to slope, channel width, channel depth, and velocity, and explicitly shows how delicate adjustments in one can result in changes in the others.

2. Paleocurrent indicators, and how to describe, interpret, and measure them (especially from trough axes)!

3. What are Froude and Reynold's Numbers, and what do they mean!?!

4. That a lithofacies is the sum of all textural, sedimentary structural, and lithological attributes that uniquely defines a given lithosome, and how THIS DIFFERS from a depositional environment model.

5. The basic sedimentary basin types (i.e., retroarc forelands, forearc, etc), and what subsidence patterns generally define them.

6. Why there are locks on the Panama Canal (the Geoid!)

7. The difference between lithostratigraphy and chronostratigraphy

8. How to draw a Wheeler Diagram

9. The timing and location of the major orogenies

10. Walther's Law

Whew! That was a hard one, since the early-birds already took all the EASY ones...I reckon that by the time this little contagion has passed on, we'll have some pretty esoteric lists of expectations for the next generation of geo-scientists, huh?

Sed Structure Sunday #1 - Interference Ripples

Well, the ol' Blog turned 100 today (with this very post). To mark such an exciting, arbitrary milestone, I reckon i'll introduce a new feature for the Dynamic Earth: Sed Structure Sunday! Each sunday, I'll post a picture of some sedimentary structure, ancient or modern, cross-stratification or form-set, for the internets to enjoy.

Today's structure comes from the Wilkins Peak Member of the Eocene Green River Fm, in SW Wyoming (click on the picture and it will get larger!):



Interference Ripple Formsets! These little bastards form where there are two dominant paleoflow directions, and reflect the complexity that many flows exhibit as they move sediment around. It also serves as a good example as to why ripples are, for the most part, the most useless of the sed structures; they are commonly subject to extremely local whims of turbulent flow. Oh well!

Oil Shale Will Set Us Free! (right?)

Recently, NPR had a story about the role of oil shale in the American petro-economy complex (I made that phrase up, but I think it sounds kind of neat), likening the Pieance Basin to an "American Saudi Arabia" rich in oil shale. It was an interesting story, particularly in the context of the recent reversal of an old Bush policy that made it easier for Companies to lease and explore oil shale production schemes. Now, I work in rocks of similar age to the Pieance (specifically, the clastic phase of the Wilkins Peak Member of the Green River Fm, famous for it's own oil shale), so I was a little familar with the crazy development schemes some folks have come up for these oil shale deposits. One of the things that always strikes me is the fact that very few discussions about oil shale actually tell you what the stuff is, which is kind of important, as prospecting and (potentially) developing oil shale economically is pretty different from the more traditional hydrocarbon methods. The picture below is a bit of organic-rich oil shale in Outcrop from the Laney Member of the Green River Fm. The richest oil shales are always that blueish-purple in outcrop.



So, what exactly is "Oil Shale"? Well, to paraphrase a geologist who has worked extensively in these deposits, oil shales are neither Oil nor Shale. Actually, they are organic rich micrites, relatively common in some lacustrine deposits (such as those formed by Eocene Lake Gosiute in SW Wyoming). The organic matter is mostly derived from algae living in the lake, and total organic content can range considerably; in the Mahogany Zone, one of the major oil shale intervals of the Uinta Fm in the Pieance Basin, total organic carbon is 40%!



The picture above shows just how rich these rocks are in organics; pretty black stuff, huh? This picture is from oil shales in the Tipton Member of the Green River Fm, SW Wyoming.



This picture above is an interval of Oil Shale from the Wilkins Peak Mbr in core. Again, organic rich, huh?



YET ANOTHER picture, also from the Tipton; these rocks actually smell like petroleum, and sure enough you can set them on fire and they'll burn. Of course, they smell like a tire fire, but that's the price of Energy Independence, I guess.



And there are a LOT of these THICK intervals in the Green River Fm, too; the picture above is from the Tipton, again, showing a thick (whitish) interval of rich oil shale. Start thinking about this in 3-D, and you quickly realize that there is a considerable volume of these oil shales throughout SW Wyoming (in the Green River) and down into the Uinta Fm in the Pieance Basin, in Colorado.

Now, some folks start thinking about all that hydrocarbon, and can't help but get droolin' a little. But how would you get these at these hydrocarbons? Well, as you can see in the Green River (and the Uinta Fm), these intervals are fairly shallowly buried (if not directly exposed). You could mine them directly, and then cook the oil out in some sort of processing, I reckon. Of course, then you're left with a huge, ugly-as-hell open pit hole sitting there.

Other schemes are plentiful, of course, and include in situ heating, hyrdo-fracing, and all sorts of Strangelovian schemes that generally require a substantial input of energy, which changes the ol' equation a bit, you know? I sort of wonder what kind of efficiency you could hope to get out of subsurface extraction?

Oh, and remember how I said that these things smell terrible when burned? Well, turns out there are probably several good reasons for this; oil shales are dirty. Like, filthy. Like, Larry Flynt filthy, man. This study, done on an Estonian power plant that burns Oil Shale for energy, shows that these things have ridiculously high concentrations of heavy metals in them, much higher than even low-grade coals. Kinda grim, really.

All in all, I think I have to applaude Obama's "Hold-on-a-minute-there-pardner!" policy reversal in regards to Oil Shale development. It's fine to push technical and geological innovation, and I certainly think oil shales warrant further study. I can tell you, there are some VERY interesting stratigraphic relationships between these organic rich intervals, clastic phases, and evaporite phases in the Green River Basin (check HERE if you don't believe me!), and careful study of the stratigraphy and depositional processes associated will probably help us understand all sorts of source-rock issues (at least). BUT, I think that there are substantial economic, social, and environmental issues at stake here that really do need careful, considered, and multidisciplinary study before we dig up all of SW Wyoming in some mad bid to become "Energy Independent".

British Library of Online Theses

Hey! Do you guys know about EThOS? That akward looking acronym stands for Electronic Theses Online Service, and it does pretty much what it sounds like: it lets you search for British theses and download pdfs...FOR FREE! It's pretty handy, actually. I recently had a doozy of a time trying to get some unpublished PhD dissertations out of Aberdeen, for instance. With this, though, it seems to be pretty easy to quickly search out and download documents.

You have to register, but it's free, and it seems to have a lot of geo-science related theses up and available...AND if they don't have a particular one, you can put in a request and they'll get it scanned for you (probably by some Cockney street-urchin wearing a lot of Houndstooth, I reckon). Pretty handy, actually.

Tiny Debris Flow...

...or a really big hammer?

An example of a tiny, cohesive debris flow from SW Wyoming; erosion of muddy materials on the hillslopes provides a lot of cohesive sediment which, combined with a little water and the relarively high slopes, makes for some nifty little debris flows.

Look at the cohesive levees on the side of that sucker!

History of Science Podcasts!

It's probably a safe bet to assume that most of us in the geoblogosphere really like science. However, as we all know, the accumulation of workers, knowledge, practices, and communication-networks that makes up big-S "Science" is a complicated web that sometimes leaves folks...confused. In particular, fundamental misunderstandings of WHAT science is and HOW science is done continue to plague our society; I'm thinking of creationists, or those Earth Expanders that we've all run into recently.

Obviously, these poor, misguided, salt-of-the-earth types (you know, morons) just don't understand what science is. How do we get non-scientists to understand science? Well, how about through the rigorous, academic field of the History of Science?

I recently came across a set of really awesome podcasts from the CBC called Ideas: How To Think About Science. These 24 episodes, ~1 hour long apiece, interview people who, broadly, undertake the academic study of Science and Scientists, and offers a fundamental "crash course" in the modern field of Science Studies. They're fun to listen to, and would make a great resource for students too!

Earthworms: Nature's Mineralogists

Everybody knows earthworms are cool; from playing a role in many soil forming processes to serving as excellent fishin' bait, earthworms are some of nature's hardest working critters. Heck, Darwin himself wrote a hefty tome on the subject of the Humble Earthworm, showing in his own imitable style how absolutely amazing and utterly vital to the development of our life-sustaining soils these little fellows are.


Look! A cartoon from Punch about Darwin! What are the odds!?!

One of Darwin's observations in his 1881 volume "The formation of vegetable mould, through the action of worms, with observations on their habits" was that earthworms excreted little calcite balls, up to a millimeter in size, which actually made up an appreciable amount of mass in any given soil volume. Subsequent work has shown that your average worm (Lumbricus terrestris) can produce up to 2.2 mg of Calcite per day, and that this wormogenic calcite is indeed a commonplace feature in soils today.

Recognizing the ubiquity of worm-poop calcite in soils, a recent paper by Lee et al. (2008) in Geology interrogated the shit out of these little limestone pellets (get it!?!). Anyway, apparently no one had really taken the time to do a detailed bit o' mineralogy/petrology on these calcite granules. Lee et al. (2008) used a variety of analysis and imaging techniques, including backscatter electron diffraction, to really get into the nitty-gritty detail of these pellets (ha! another one!).

To get to the point, Lee et al. (2008) found that the calcite was initially precipitated as amorphous calcium carbonate in the guts of the worm (by the appropriately named calcifierous gland). This amorphous calcium carbonate phase gloms onto a quartz grain in the gut of the worm, where it undergoes eventual crystallization into calcite BEFORE being excreted. This crystallization process is mediated by a migrating fluid film, resulting in a stromatolite-esque coated grain (see below for a figure taken from the paper):

Apparently, the fine-scaled zonation of these calcite crystal is unique for biominerals; the authors point out that, given calcite growth rates inside the worm, the properties of the mediating fluid film must have fluctuated on the scale of tens of minutes in order to produce such zoning.

Why go through all that trouble? The authors suggest that crystallization may be a way the worm avoids remobilization and absorption of calcium carbonate. The solubility of the these different phases is dramatically different, and by forcing the amorphous stuff to crystallize into more stable calcite, the worm can ensure the stuff stays put. As for the larger question of "Why do worms secrete this stuff anyway?" is one that the authors can't answer. Apparently, no one knows why worms do this!

Of course, this probably isn't idle musing for cloistered academics. Lee et al. (2008) close their paper by pointing out that the amount of calcite produced by these worms is in such quantities that it probably plays a major role in the soil carbon cycle. As such, a clearer understanding of this process might have an impact on our understanding of and ability to model biogeochemical cycles.

I think Darwin would be pleased that the Noble Earthworm still has some important stories to tell us.

WORKS CITED:

Lee, M.R., Hodson, M.E., and Langworthy, G., 2008, Earthworms produce granules of intricatley zoned calcite: Geology, v. 36, n. 12, p. 943-946.