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Minerals
Social climber
The Deli
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Topic Author's Reply - May 9, 2012 - 11:00pm PT
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Wow, super-cool post, “Stu”! Thanks. And you included metamorphic xenoliths with reaction rims and enclaves with chilled margins. Right on. Good ice cream analogy too. Have you seen any of the enclave swarm features in the Tuolumne Intrusive Suite, including ones that are cylindrical in shape, which we refer to as “enclave pipes”?
It is true that metamorphic xenoliths (chunks of the surrounding “host rock” or “country rock”) are quite rare in granites in the Sierra although interestingly, we have noticed that along with mafic and felsic enclaves, there is an abundance of xenoliths contained within ladder dikes in the Tuolumne Intrusive Suite. I attribute this abundance of inclusions to some sort of mechanical filtering during magma flow within the ladder dikes. But that is another whole story in itself.
Here’s a photo from the base of the Dawn Wall on El Cap, showing a dike of North America Diorite that has partially melted the surrounding El Capitan Granite, forming a sheath of leucogranite around the diorite. The mafic and felsic magmas then mingled, creating the felsic dikelets within the diorite.
JerryA, you asked about the different rock types on Yosemite Falls Wall. Although the area appears to be rather complex geologically in map view, there are only two different rock types exposed in the Yosemite Falls area – El Capitan Granite and younger Sentinel Granodiorite, plus minor aplite/pegmatite dikes that cut the two granitic rock types. Sentinel Granodiorite is thought to be a precursor unit of the Tuolumne Intrusive Suite.
Here’s the link to the Calkins Yosemite Valley Bedrock map again:
http://geomaps.geosci.unc.edu/parks/fulls/Yosemite%20-%20bedrock.jpg
What’s interesting is that it appears that these same aplite/pegmatite dikes that cut across Yosemite Falls Wall continue westward and are also exposed in the Three Brothers area as well as on El Cap. As you can see from the Calkins map, there are large dikes emanating from the western edge of the Half Dome pluton. Some of these dikes are more than 10 meters in thickness and can be seen in the area of the climb Bishop’s Terrace. I think the aplite/pegmatite dikes on the Falls Wall are coming off of the Half Dome pluton and extend at least as far west as El cap. This would indicate that there are rock types from three different intrusive suites exposed on the face of El Cap – the intrusive suite of Yosemite Valley, the intrusive suite of Buena Vista Crest, and the Tuolumne Intrusive Suite.
Here’s a section of the Calkins map, showing the Yosemite Falls area and the complex intrusive pattern formed by the intrusion of Sentinel Granodiorite into El Capitan Granite.
And here’s another Tom Evans photo, showing El Capitan Granite (lighter-colored rock) and Sentinel Granodiorite (darker-colored rock) on the lower section of the Falls Wall. Notice how the difference in color between the two rock types stands out more because the rock is wet.
Photo by Tom Evans.
Jerry, if you have any photos from the Lost Arrow that show field relations between the two rock types, I would be happy to see them.
Hey, anyone have any El Cap photos to post???
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stunewberry
Trad climber
Spokane, WA
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May 10, 2012 - 12:05am PT
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Minerals, your first picture (the diorite/aplite dikes) in your last post are extremely common in the Lamarck Granodiorite (it makes up all of Dusy Basin, and is the light colored stuff that lies at the base of the Palisades. It sends mucho dikes into the older, dark-colored Tinemaha granodiorite that makes up the Palisades). I called them composite dikes, and will post some pictures tomorrow along with what I thought they were. I won't include the geochemistry, which would bore most of the tacoans, but suffice it to say, "more work is indicated" to decipher their origin...
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hollyclimber
Big Wall climber
Yosemite, CA
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May 14, 2012 - 03:22am PT
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Minerals-
I will email Stock today. I have taken the whiteboard up several climbs and will be happy to take one up Magic Mushroom if Greg will give me a new one.
HBW
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wayne burleson
climber
Amherst, MA
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May 14, 2012 - 06:46pm PT
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Bump! Fun thread. I'm pretty illiterate on geology. Is the Valley unusual in its diversity of rock types? What about other climbing areas? Black Canyon comes to mind...
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Mighty Hiker
climber
Vancouver, B.C.
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May 14, 2012 - 06:51pm PT
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OK, I get the part about the vanilla ice cream and the hot fudge sauce, but where do bananas and maraschino cherries fit in the mix?
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Blakey
Trad climber
Newcastle UK
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May 15, 2012 - 04:09pm PT
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I am nothing less than humbled by how clever some folks are....
This is amazing stuff, how folks figure it all out is way beyond me.....
Steve
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BASE104
Social climber
An Oil Field
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May 15, 2012 - 09:15pm PT
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Are you guys going to put this into a 3-D model?
It would be really sweet if you could correlate these rocks across the valley. We do that all of the time in Petroleum geology. I have software that might be adaptable to it, but it won't be easy.
And for all ye nay-sayers: Get over it. Pure research is fundamental in geology. And yep, you don't have to look further than five feet around you to find something found by geologists.
At this company I am working for now, we have this 3D vis room. It is a big conference room where everyone power points their progress each week, but you can also put on a virtual reality helmet and walk around inside of the 3D models.
They never let me do that. Bummer. It looks kind of like the war room in Dr. Strangelove.
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'Pass the Pitons' Pete
Big Wall climber
like Ontario, Canada, eh?
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May 19, 2012 - 02:19pm PT
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Bump for cool rocks. Will try to remember for Bryan this spring.
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Minerals
Social climber
The Deli
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Topic Author's Reply - May 22, 2012 - 01:11am PT
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Thanks, Holly! And thanks for your help with contributing photos in the past!
Thanks, Pete! It would be great if you can take some photos for us during your climbs this year. I will be around later this week and can give you a scale board and some geology beta, if you would like.
As far as the diversity of plutonic rock types in Yosemite Valley, I wouldn’t say that it’s very unusual with respect to the rest of the Sierra Nevada Batholith, but there are a lot of different granitic rock types exposed. These rock types span an age range of roughly 30 million years, from approximately 90 Ma (million years ago) at the far eastern end of the Valley (Half Dome Granodiorite) to approximately 120 Ma at the far western end of the Valley (Bass Lake Tonalite/tonalite of the Gateway). The various rock types in Yosemite Valley belong to four different intrusive suites: the Tuolumne Intrusive Suite, the intrusive suite of Buena Vista Crest, the intrusive suite of Yosemite Valley, and the Fine Gold Intrusive Suite (from youngest to oldest). Please refer to the geologic map links in the first post of this thread, and lower down in this post for more details on rock types and intrusive suites.
What’s interesting about the face of El Cap is that there are several different rock types that are clearly exposed in one area, which gives us the opportunity to study the field relations between the different rocks and how magmas interacted, the timing of the formation of the rocks, and the mechanisms by which magmas were emplaced. We are lucky to have such a great “window” to the inner workings of a magmatic arc, such as the face of El Cap.
I don’t know much about the Black Canyon of the Gunnison, but the canyon walls appear to be composed of metamorphic rock that is crisscrossed by large pegmatite dikes, both of which are much, much older than the granitic rocks of the Sierra Nevada Batholith.
Yes, we are working towards a 3D geologic map of El Cap, by combining detailed maps from the SW and SE faces, as well as from the summit.
Here’re a few images that Allen put together about 10 years ago, showing a rough 3D view of the geology of the Valley, based on the USGS geologic map of the park:
http://www.geosci.unc.edu/page/draped-and-shaded-geologic-maps
Many of the granitic rock types do correlate from one side of the Valley to the other, as can be seen in the geologic maps. El Capitan Granite covers a large area of the central and western portions of the Valley and younger Taft Granite forms smaller masses within El Capitan Granite, as does the Diorite of the Rockslides. The eastern end of the park is composed of rocks of the Tuolumne Intrusive Suite, from Sentinel Granodiorite, to the tonalite of Glacier Point, to Half Dome Granodiorite. Rocks of the Fine Gold Intrusive Suite, such as the granodiorite of Arch Rock and Bass Lake Tonalite (tonalite of the Gateway), are exposed at the far western end of the Valley, in Lower Merced Canyon.
Most of the rocks belonging to the intrusive suite of Buena Vista Crest are exposed on the south side of the Valley in the Cathedral Rocks area, and south of the Valley itself, although there are a few outcrops of Leaning Tower Granite shown on the maps on the north side of the Valley, to the west of El Cap. I discovered that there is Leaning Tower Granite/Granodiorite exposed on the SE face of El Cap, which, in addition to other field observations, has led me to interpret some things a little bit differently than some geologists have previously concluded.
Reid et al. (1983) divided the mafic (dark-colored) dikes on the face of El Cap into two sets – an older, moderately dipping set, composed of tonalite to granodiorite, and a younger, steeply dipping set, composed of North America Diorite. The authors hypothesized that the rocks of the older set of dikes formed by mixing of felsic magmas (such as those that formed the granites of the intrusive suite of Yosemite Valley) and coeval mafic magmas, resulting in a byproduct of a “hybrid” magma composition.
Ratajeski et al., (2001) largely supported the interpretations of Reid et al., (1983) and referred to the older set of mafic dikes as “pre-North America dikes” and included these dikes as part of the intrusive suite of Yosemite Valley. The authors also included North America Diorite in the suite and interpreted the diorite as coeval with Taft Granite, contradictory to the previous work of Calkins et al. (1985) and Bateman (1992).
Here’s the geologic map of the summit of El Cap that Roger mentioned earlier in the thread. The map shows the basic geology of the summit, including the different rock types that are exposed, although the map doesn’t show a lot of detail. I hope to spend some time on the summit this year, in order to map the area in greater detail to combine with our detailed mapping of the face of El Cap.
From Ratajeski et al., 2001
As denoted by the dotted pattern on the summit map, the authors interpreted the band of tonalite that separates Taft Granite from El Capitan Granite (just north of the summit of The Nose) to be a mafic facies of Taft Granite, exposed at the margins of a “Taft Granite magma chamber.” This band of tonalite is also exposed on the upper SW and SE faces of the wall, as shown in the last two Tom Evans photos in the first post of this thread.
Here’s the second of those two photos; the red arrows point to the sharp contact between Taft Granite (above) and tonalite/granodiorite (below).
Photo by Tom Evans.
And once again:
p = pegmatite
a/p = aplite/pegmatite dikes
na = North America Diorite
lt = Leaning Tower Granite/Granodiorite
tn = tonalite and granodiorite (pre-North America dikes)
ta = Taft Granite
ec = El Capitan Granite
Based on my field observations, I interpret this band of tonalite to belong to the set of pre-North America dikes, which I believe is not related to Taft Granite and is younger than the granite. Some of the pre-North America dikes are composed of Leaning Tower Granite/Granodiorite, indicating that the pre-North America dikes are composed of at least two different rock types. I disagree with the interpretation that North America Diorite and Taft Granite are coeval and I interpret North America Diorite as belonging to the intrusive suite of Buena Vista Crest and not the intrusive suite of Yosemite Valley. This interpretation is in agreement with Bateman (1992) and Peck (2002) and is supported by field evidence that indicates that Leaning Tower Granite/Granodiorite magma has mingled with North America Diorite magma, suggesting that the two are coeval.
Here’s a repost of a photo from the beginning of this thread:
North America Diorite magma (na) intrudes Leaning Tower Granite/Granodiorite magma (lt), forming “pillows” or “mafic enclaves” (the dark-colored blobs), The Shortest Straw, belay 4.
Photo by Tom Evans.
Pre-North America dikes sharply cut Taft Granite, as well as El Capitan Granite, indicating that both of the granites must have been completely or near completely solidified at the time of pre-North America dike emplacement and therefor must be older. In some cases, North America Diorite intrudes coeval pre-North America dikes, which act as structural and thermal weaknesses through the surrounding granites. If the pre-North America dikes are younger than Taft Granite and are coeval with North America Diorite, then Taft Granite and North America Diorite must not be coeval.
Tonalite/granodiorite dikes (tn) of the pre-North America dike set intrude both El Capitan Granite (ec) and Taft Granite (ta) at the base of the SE face, just left of the Footstool, displaying sharp intrusive contacts. North America Diorite (na) is present in the upper left of the photo and typical aplite/pegmatite dikes (a/p) cut all other rock types.
North America Diorite (na) intrudes a coeval dike of Leaning Tower Granite/Granodiorite (lt) that is hosted in El Capitan Granite (ec) at the base of the SE face, approximately 50 meters west of the start of Tangerine Trip. Leaning Tower Granite/Granodiorite (lt) contains genetically related mafic enclaves, as well as mafic enclaves of North America Diorite (na).
I also believe that the pre-North America dikes on El Cap may belong to the intrusive suite of Buena Vista Crest. Thus, the face of El Cap exemplifies the plutonic relations between the older granites of the intrusive suite of Yosemite Valley and the northern extent of the oldest rock units of the intrusive suite of Buena Vista Crest, and the initiation of the emplacement of this younger intrusive suite. Future field observations and detailed lab analyses will help to solidify these interpretations or disprove them, or add a new twist to the story.
Side note: Geologic maps list the rock type “Leaning Tower Granite” but this rock looks more like granodiorite to me, hence my use of “Granite/Granodiorite” in this thread.
Here are a few images of geologic maps draped over Google Earth terrain images, showing the geology of Yosemite Valley in three dimensions. The maps don’t line up exactly with the Google Earth images, so some things don’t look quite right. Also keep in mind that Calkins didn’t recognize the difference between Sentinel Granodiorite and the tonalite of Glacier Point, so the two are shown as Sentinel Granodiorite on his map. Peck’s map does include the tonalite of Glacier Point although the map shows less overall detail than Calkins’ map.
Yosemite Valley geologic bedrock map – USGS/Calkins et al., 1985; view looking approximately northeast.
Yosemite Valley geologic bedrock map – USGS/Calkins et al., 1985; view looking approximately southwest.
Yosemite Valley geologic quadrangle map – USGS/Peck, 2002; view looking approximately southwest. Note the rock units of the intrusive suite of Buena Vista Crest to the south of the Valley, as shown in different shades of blue and purple.
The full versions of these maps can be found here, with explanations of the various rock types (posted again):
Yosemite Valley Bedrock map – Calkins et al., 1985
http://geomaps.geosci.unc.edu/parks/fulls/Yosemite%20-%20bedrock.jpg
Yosemite Quad map – Peck, 2002
http://geomaps.geosci.unc.edu/quads/fulls/Yosemite.jpg
Here’s a short video that I put together, showing an animated view of the Yosemite Valley geologic bedrock map (Calkins et al., 1985) draped over Google Earth terrain images. The quality of the video could certainly be better and I’ve found that QuickTime doesn’t do the greatest job with video screen captures, but I didn’t spend enough time searching for free software online that may do a better job. This video does give you a good idea of the bedrock geology of the Valley in three dimensions.
[Click to View YouTube Video]
References (again):
Bateman, P. C., 1992, Plutonism in the central part of the Sierra Nevada batholith, California: U. S. Geological Survey Professional Paper 1483, 185 p.
Calkins, F. C., Huber, N. K., and Roller, J. A., 1985, Geologic bedrock map of Yosemite Valley, Yosemite National Park, California: U. S. Geological Survey Map I-1639, 1 sheet, scale 1:24,000.
(See map link above)
Peck, D. L., 2002, Geologic map of the Yosemite quadrangle, central Sierra Nevada, California: U. S. Geological Survey, Geologic investigations series, report I-2751, 1 sheet, scale 1:62,500.
(See map link above)
Ratajeski, K., Glazner, A. F., and Miller, B. V., 2001, Geology and geochemistry of mafic to felsic plutonic rocks in the Cretaceous intrusive suite of Yosemite Valley, California: Geological Society of America Bulletin, v. 113, p. 1486 – 1582.
http://gsabulletin.gsapubs.org/content/113/11/1486.abstract
Reid, J. B., Evans, O. C., and Fates, D. G., 1983, Magma mixing in granitic rocks of the central Sierra Nevada, California: Earth and Planetary Science Letters, v. 66, p. 243 – 261.
http://www.sciencedirect.com/science/article/pii/0012821X83901395
Anders…! Figures you would come up with such a question… : )
The bananas represent the aplite dikes that “split” the wall – they are both rich in potassium. The cherries represent small red garnets, which can be seen in some of the aplite dikes. Throw a little whipped cream on top and you’ve got some pegmatite blobs too… like “The Brain” on The Shortest Straw and “The Cauliflower” on Ned’s Excellent Adventure. Just add a few pieces of black licorice as well, so that the late-stage mineral Tourmaline doesn’t feel left out. Now you are ready to eat dessert!
I apologize for the temporary disappearance of the photos that I posted earlier – between this thread, the Porcelain thread, and the Tomahawk thread, the monthly bandwidth allotment of 10GB for my Photobucket account was reached. The photos are back now. Except for large photos (greater than 800 pixels max dimension), I use Photobucket for hosting because there is too much photo compression when uploading to SuperTopo and the uploaded photos do not appear as the originals do – there is a loss in quality. We discussed this a few months ago in another thread.
 Bryan
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Mighty Hiker
climber
Vancouver, B.C.
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May 22, 2012 - 01:15am PT
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OK, so the garnets are the oldest rocks of all in the Valley? And they're somehow inserted into the intrusions?
Heh heh.
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Minerals
Social climber
The Deli
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Topic Author's Reply - May 23, 2012 - 03:13pm PT
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Quite the opposite…
Now go back to eating your dessert!
; p
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Dos XX
Trad climber
Los Angeles, CA
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May 23, 2012 - 03:23pm PT
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Fascinating. The bedrock maps help me understand why the Cathedral rocks look so different from everything else in the Valley.
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kev
climber
A pile of dirt.
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May 23, 2012 - 03:32pm PT
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Kickass Bryan!
Since were getting all scientific....
lt + na = bomber knob bands ==> happy FA's
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skywalker
climber
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May 25, 2012 - 10:51am PT
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Bump! Super cool! Thanks!
S...
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RP3
Big Wall climber
Temporarily Chapel Hill
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May 30, 2012 - 09:53am PT
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Bump for more mapping help!
Right now, we have 3 scale bars moving up El Cap and we need more! If you are planning an El Cap climb, please get in touch with me before you go! I will carry a load for you in exchange for your services!
Right now, we have scale bars moving up Iron Hawk, Grape Race, and the Salathe. I surveyed the Muir a week ago (see Hoots' post above this one!). That means there is A LOT of the big stone we still need to look at!
Get in touch if you want to contribute to understanding the big stone we all love so much!
Roger Putnam
rputnam@live.unc.edu
508-776-7609
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RP3
Big Wall climber
El Portal/Chapel Hill
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Jun 23, 2012 - 09:21pm PT
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BUMP!
Thanks to all who have helped already! Because of climber help we have been able to survey The Prophet, The Shortest Straw, NA Wall (1st half), Tempest (in progress), New Dawn, Tribal Rite (in progress), the Muir Wall and the Salathe.
That leaves approximately 70 El Cap routes in need of scale photography!
I am still around the Valley and excited to hump loads for your help!
-Roger
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Michelle
Social climber
SH60091
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Jun 24, 2012 - 12:24am PT
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ha! the most awesome troll EVER!
jk. stay busy and Ill call you soon.
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Minerals
Social climber
The Deli
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Topic Author's Reply - Sep 9, 2012 - 10:05pm PT
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BUMP for fall wall season.
We are still looking for more rock texture photos from El Cap, so please help if you can!
Check out the beginning of the first post on this thread for info.
Thanks!
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Mark Hudon
Trad climber
Hood River, OR
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Max and I are going up on Lost in America in early October, we'll gladly take photos!
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SuperTopo on the Web
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Let us know!