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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Here are some anticlinal structures from the Big Horn & Powder River Basins Wyoming
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jfailing
Trad climber
A trailer park in the Sierras
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Wow, you weren't kidding about the horror stories... you've got me stumped! I can imagine that a 12 pack might help in interpreting that sort of feature...
What kind of rock is it? The only thing that comes to mind would be some sort of compression cave-in or something close to its deposition or deformation - if it's related to a reservoir, this may be tangible?
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dipper
climber
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Topic Author's Reply - Jan 6, 2010 - 02:16am PT
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TT,
Very cool images.
Whenever I flew (not much any more) I always spent the bulk of my time with my nose pressed to the window to see just that sort of feature. I do believe I have flown over the images you posted, long ago.
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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BASE that structure in the image you posted looks like extensional faulting on the crest of a dome...a collapsed dome.
When we flew over the Powder River-Big Horn Basins I was stunned.
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BASE104
climber
An Oil Field
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My buddy shows me this map. We are all wicked drunk, but instead of chasing tail, the geologists pull maps out.
He asks us what we think it is (and this was a really subtle feature, but you could see it). We all strike out and he says, "Astrobleme." If only we knew the economic significance of this.
Nobody drilled into it because the deep zones in this place don't produce for fifty miles in any direction. It was known about for ages. It is near a tiny town in northern oklahoma, flat as a pancake wheat country, named Ames. It was dubbed the "Ames Hole" by geologists long ago.
Well, a deeper well was drilled to the cambro/ordovician on the rim, on a little structural closure, and found the rocks totally fractured..which they aren't anywhere else, and the zone covers three states, one being Texas. The rock was just a mess. It is pretty plain jane everywhere else.
Then it caught on, people drilled around the rim and made discoveries that were exciting, but not that remarkable. Then a company drilled into the rebound feature in the middle and found nothing but shocked Quartz in what should have been a granite basement. It looked like glass. Shocked Quartz was confirmed, a zillion articles were written about it, and the rebound feature made millions of barrels of oil. The impact feature was self-sourced, meaning that the organic source rock (normally the Woodford Shale in Oklahoma) was from Ordovician shale that filled the crater. You can type the hydrocarbons back to the source rock with a little geochemistry. I think that this one is about ten miles across. I can look it up, or you can google "Ames Hole" or "Ames Astrobleme."
There are some of these in sedimentary basins in western Canada that are huge producers as well.
Ya gotta wonder how many of these things are out there buried and/or deformed. Lots.
edit: All sedimentary limestones other than in the rebound feature, which supposedly was devoid of feldspars and other granitic jazz. Just quartz.
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BASE104
climber
An Oil Field
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And that Bighorn Basin stuff. Those are called Sheepherder Anticlines, because the sheepherders could see them they were so obvious.
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Jaybro
Social climber
Wolf City, Wyoming
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If you look in the farright corner of one of Tradster's photos, i believe you can see Frank waving from the top of the Second pitch of Mr Clean, on Deto!
Can a geomorphologist or a structural geologist ever be bored?
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BASE104
climber
An Oil Field
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Oh. I always yack too much. The feature is an Ordovician Astrobleme (impact crater). On the northern shelf of the Anadarko Basin. It hit a super thick limestone section. Covered with about 8000 feet of younger sediments. Read my long winded jazz above for details.
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jfailing
Trad climber
A trailer park in the Sierras
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BASE - that is WICKED! My first thought when I looked at that photo was "that looks like a crater, but... nawww" That's a pretty amazing feature... at 8000' too! Great story - blows my mind.
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BASE104
climber
An Oil Field
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Yeah, 450 million year old sucker. Punched through the seds into granite and the central rebound feature was nothing but quartz. The geologist who wrote this up said it looked exactly like broken glass. Which is not like normal quartz grains or crystals look like under a scope.
Whole thing was covered up and buried. I bet there are a zillion of these things if we could just peel off the surface and get a clean look at the stable craton surface.
You can't see it well in that image, but if you look straight down at the maps of the thing it is perfectly round.
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dipper
climber
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Topic Author's Reply - Jan 6, 2010 - 08:59pm PT
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Some more gravel to gander at
1
b (special Toulumne edition for Minerals)
gamma
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Jaybro: is this the photo you're referring to? This is a mega sink hole in Florida where phosphate mine tailings leached Uranium into the ground water. Local climbers took advantage of the steep wall and turned it into an outdoor climbing gym until Bechtel grouted it up.
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Jaybro
Social climber
Wolf City, Wyoming
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Nice!
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Fritz
Trad climber
Hagerman, ID
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Re. my Sawtooth story mentioned earlier. I am not a geologist, but this thread is fun to lurk on: since two of my old outdoor buddies were geologists. Geology is always of interest.
Plenty of Sawtooth crystals came out of pegmatites, but most of the crystals came out of miarolitic cavities(gas pockets) in pink leucoratic granite. In some areas these cavities are everywhere, but are very small (like pockets in rhyolite at Topez Mountain, Utah). Some are larger, a very few: much larger.
There are some huge Sawtooth smoky quartz crystals on display in the University of Idaho Geology Dept. building.
Certain areas of the range have spessartine garnet as well.
Cool stuff dudes!
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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cool sample Fritz...what's the mineral with the metallic luster?
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Fritz: just read your Sawtooth - Quartz crystal cave TR...great story. Thanks for posting it.
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BASE104
climber
An Oil Field
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I wish that all of you hard rock people had access to the toys of the oil business..mainly 3D seismic data. It can show incredible features now, and new attribute analysis is coming out every day. Downside is that it is uber pricey. You can now see things that are unreal.
Do you guys do any paleomag work? That is really cheap and interesting.
This site has a ton of publications.
You can see basement lineaments and make rose diagrams, see deeply buried incised valleys, all sorts of stuff. And it is all deep underground.
There is a paper in there on igneous intrusives in a sed basin in Mexico that most of you can enjoy.
Scroll down through the equations and gobbledy gook and look at the pretty pictures.
http://geology.ou.edu/aaspi/publications.php
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Minerals
Social climber
The Deli
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Will try to catch up on all of the cool new stuff that you guys have recently posted soon… This thread is way fun!
A few photos from today, in cold Northern Nevada:
Tertiary ash fall tuff (terminology???), containing pumice fragments (light-colored) and other volcanic fragments
Well-jointed Tertiary vesicular basalt and what looks to be a fault breccia to the left of the hammer
Closer view of breccia zone
Deformed Tertiary sedimentary rock
Geologic Time Scale:
http://www.geosociety.org/science/timescale/timescl.pdf
OK Jaybro… Here’s a photo that I’ve been meaning to post for ya for a while. Completely silicified bone fragments, found in loose float derived from Tertiary sedimentary rock. These are obviously mammal fossils, given that they are in Nevada. What’s up with them mammals from millions of years ago? Death by volcanic eruption (ash…)?
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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BASE: I did my MS Thesis in paleomag. Magnetostratigraphy of the Late Neogene Purisima Formation, Santa Cruz County, CA. Back in the days using a Schonstedt Spinner Magnetometer & AF demagnetization. Did all my number crunching on a main frame computer. I would carry a shoebox full of punch cards containing a Fortran program and my data that I would submit to be run overnight.
http://adsabs.harvard.edu/abs/1986E&PSL..79..431M
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