El Capitan Geologic Mapping Project

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Minerals

Social climber
The Deli
Topic Author's Original Post - Apr 26, 2012 - 05:12pm PT






Hey El Cap climbers!

Roger Putnam and Allen Glazner of the University of North Carolina at Chapel Hill, Greg Stock (YNP Geologist), and I are working on a project to geologically map the different plutonic rock types and their intrusive relations on the southeast face of El Capitan in great detail. Contrary to conventional geologic mapping techniques where one can walk across flat slabs and view outcrops in close proximity, the vertical face of El Cap poses a challenge in that it is impossible to view up close without climbing the wall or rappelling down from the summit. We are seeking help from climbers, to provide additional photographic data from routes on the southeast face, as well as the southwest face. So far, we have rock texture photos at belays from 11 different routes on the wall although some routes are incomplete with respect to belay photos. We are also interested in photos taken mid-pitch, and especially at contacts between different rock types.

If you are planning an ascent of any route on El Cap within the next year or two and would like to contribute to science and this exciting project, please contact Greg at greg_stock@nps.gov to obtain a photo scale board to include in your photos. If you have any questions and/or comments on this project, you can also contact Roger at rputnam@live.unc.edu or 508-776-7609, or you can contact me by email through this website (click on my username “Minerals” in the far upper left of this post). You can also just post questions and/or comments to this thread.

Please help to spread the word about this project to wall climbers who may not visit this website.

Thanks for taking a look at this thread and any interest in the geology of Yosemite that you may have!

 Bryan Law




Photo of the southeast face of El Cap, taken in 1930 by Frank Calkins of the USGS; note that the Footstool rock scar does not exist yet and El Cap Tree is healthy and full of life.



Here’s some basic background information on the geology of El Cap and some examples of the types of photos that we are looking for.


El Capitan Rock Types

From youngest to oldest:

 Aplite/pegmatite dikes (younger set and older set)
 North America Diorite
 Leaning Tower Granite/Granodiorite
 Tonalite/granodiorite
 Taft Granite (+ related mafic enclaves and pegmatite pods)
 El Capitan Granite (+ related mafic enclaves and pegmatite pods)






While doing fieldwork in the fall of 2010, I discovered Leaning Tower Granite on the southeast face of El Cap, which had not been mapped or noted in any of the El Cap literature in the past. Along with detailed field observations, this occurrence of Leaning Tower Granite has helped us to better understand the intrusive sequence of the different rock types on El Cap.


For specifics on granite and plutonic rock type classification, please refer to the following post:
http://www.supertopo.com/climbing/thread.php?topic_id=731799&msg=732325#msg732325



Gigapixel images of El Cap from the xRez panoramic photo project have proven to be quite helpful for mapping the different rock types on the southeast face.


Photoshop-enhanced xRez image of a section of the “Atlantic Ocean” area on the southeast face of El Cap showing complex intrusive relations between different rock types.

Yosemite Valley xRez website:
http://www.xrez.com/yose_proj/yose_deepzoom/



The following six images are from a poster that Greg presented at an American Geophysical Union meeting in December of 2010 (see listing in references section at the end of this post).




(A) Climber on “The Nipple Pitch” (pitch 10) in the Gray Circle on Zodiac.
(B) Geologic interpretation of rock units in the same photo showing El Capitan Granite, mafic intrusions, and aplite dikes.
Photo by Tom Evans.




An example of some of the detailed mapping of the southeast face that I have done from El Cap Meadow with a spotting scope; note El Cap Tree in the upper right of the images for photo location and scale.
(A) Small section of a gigapixel xRez image with contact lines drawn in between the different rock types.
(B) Geologic interpretation of rock types in the same photo showing (from oldest to youngest) El Capitan Granite, hybrid dikes (tonalite and granodiorite), North America Diorite, and at least two phases of aplite dikes, the older of which is offset by the younger.



Rock Texture Photos



Texture photos from belay stations on Mescalito showing compositional and grain size differences between El Capitan Granite (A) and Taft Granite (B). These are the kind of photos that we are looking for. The scale board lets us know where the photos were taken (belay #) and also acts as a reference tool in determining the grain sizes in the rock. Without some sort of a familiar object in a photo, it’s tough to determine the exact scale of the photo and the scale of the rock texture.



Tonalite at the base of the southeast face. Note the use of a photo scale card to determine grain sizes in the rock.



Leaning Tower Granite with characteristic “speckled” texture at the base of the southeast face.



Dark-colored North America Diorite at the base of the southeast face.



Another textural variety of North America Diorite at the base of the southeast face.



Close-up photo of the same rock in the above photo. It helps us to have a photo showing a larger section of the rock to get an overall view of the texture as well as a close-up photo to view details in the texture.



Sharp contacts between North America Diorite (left), tonalite (center), and El Capitan Granite (right). Photos that show the contacts between different rock types are helpful in that they tell us whether the contacts are sharp or gradational. Photos that show cross-cutting relations between different rock types can tell us which type is older and which is younger.



This photo is an example of what DOESN’T work. This rock is covered by a thin layer of mineral precipitates that formed from water seeping down the face and it’s impossible to decipher the rock type underneath. Lichen that covers the surface of the rock can also make it difficult to determine rock type. Try to find areas where the rock is clean and fresh and not obscured by surface material.



This gear placement is on pitch 5 of Virginia and by the speckled texture of the rock, we can tell that the rock is Leaning Tower Granite.
Photo by Holly Beck.


It’s best to take more than one photo at a given location so that you are sure that you have a photo that is in focus, as well as an overall view and a close-up view of the rock. For close-up photos, use the macro focus setting on your camera. Be sure to hold your camera parallel to the face of the rock, as opposed to at an angle; this prevents distortion and keeps most of the field of view of the photo sharp. Often times a photo taken in the shade will show the texture of the rock better than if the rock were in direct sunlight. Use your body to shade the rock if necessary and make sure that the white balance setting on your camera is set properly (i.e. auto, sunlight, or shade).

In some cases, there may be more than one rock type exposed at a belay station so you will need to take photos of all of the different rock types, including the contact(s) between them. For example, see the Tom Evans photo of Tangerine Trip below; there are two different rock types exposed at this belay.

It is very important to record the location of your photos – this is where the scale board comes in. Label the board with the appropriate belay number at each belay. If you are taking rock texture photos mid-pitch, use the scale board to record the pitch number and the approximate location on the pitch. If you don’t have the scale board handy mid-pitch, a carabiner or an index finger works for scale too. If possible, write down the locations of mid-pitch photos in a small notebook during your climb. If we have no idea where a photo was taken on a route, it’s difficult to use the photo for mapping purposes.

Gear placement photos are also great for determining rock type. If you have close-up photos of gear that show the texture of the surrounding rock and you know exactly where you took the photo (i.e. route name, pitch number, and location on pitch), please post up your photos here! Climbing photos or just ordinary wall photos sometimes show good examples of the different rock types and their intrusive relations, so feel free to post anything here that you think may be helpful.



Tom Evans Photos

Special thanks to Tom Evans for not only providing the climbing community with a great photo resource, but for providing geologists with valuable data as well.

You can find his photos on his website, El Cap Reports:
http://www.elcapreport.com/

The following photos were taken by Tom and show great examples of some of the intrusive relations of the rock types on El Cap. I have made some rough annotations on the photos to help show the different rock types and the differences in their appearance in color. Below is an explanation of the photo annotations.

p = pegmatite
a/p = aplite/pegmatite dikes
na = North America Diorite
lt = Leaning Tower Granite
tn = tonalite and granodiorite
ta = Taft Granite
ec = El Capitan Granite



The upper edge of the Gray Circle on Zenyatta Mondatta, belay 9.
Photo by Tom Evans.



Intrusive relations at belay 7 of Tangerine Trip; note the apparent right-lateral offset of the gray tonalite/granodiorite dike by the horizontal aplite/pegmatite dikes as shown by the red arrow.
Photo by Tom Evans.



North America Diorite magma intrudes Leaning Tower Granite magma, forming “pillows” or “mafic enclaves” (the dark-colored blobs), The Shortest Straw, belay 4.
Photo by Tom Evans.



Complex intrusive relations high on Zenyatta Mondatta, belay 11.
Photo by Tom Evans.



Sharp intrusive contact between Taft Granite (above) and tonalite (below) on The Shield headwall, below “The Groove Pitch”, belay 9.
Photo by Tom Evans.



The Shield headwall, with red arrows pointing to the sharp contact shown in the above photo.
Photo by Tom Evans.



Links to Geologic Maps

Yosemite Quad map
http://geomaps.geosci.unc.edu/quads/fulls/Yosemite.jpg

Yosemite Valley Bedrock map
http://geomaps.geosci.unc.edu/parks/fulls/Yosemite%20-%20bedrock.jpg

Yosemite National Park map
http://geomaps.geosci.unc.edu/parks/fulls/Yosemite%20National%20Park.jpg



References

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., 1999, Mesozoic convergent margin of central California: Geological Society of America Special Publication 119, p. 118 – 135.

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

Stock, G. M., Glazner, A. F., Ratajeski, K. and Law, B., 2010, Geological mapping of the vertical southeast face of El Capitan, Yosemite Valley, California: American Geophysical Union, Fall Meeting Abstracts, abstract #V11C-2304.
http://adsabs.harvard.edu//abs/2010AGUFM.V11C2304S

Stock, G. M., Uhrhammer, R. A., 2010, Catastrophic rock avalanche 3600 years BP from El Capitan, Yosemite Valley, California: Earth Surface Processes and Landforms, v. 35, p. 941 – 951.
http://www.nps.gov/yose/naturescience/loader.cfm?csModule=security/getfile&PageID=350428


Gene

climber
Apr 26, 2012 - 05:20pm PT
Love it!
Ron Anderson

Trad climber
USA Moundhouse Nev.
Apr 26, 2012 - 05:21pm PT
WOW! Nice info!!!!!!!!!
micronut

Trad climber
Apr 26, 2012 - 05:24pm PT
Awesome work. Super cool.
Mike.

climber
Apr 26, 2012 - 05:25pm PT
This is very cool. Way to get into it, B!
eKat

Trad climber
BITD3
Apr 26, 2012 - 05:27pm PT
This is absolutely fantastic.

FANTASTIC!

TFPU. . .
QITNL

climber
Apr 26, 2012 - 05:29pm PT
Excellent!
Grampa

Trad climber
OC in So Cal
Apr 26, 2012 - 05:31pm PT
Very interesting. Thanks.
Mark Hudon

Trad climber
Hood River, OR
Apr 26, 2012 - 05:42pm PT
Email sent!
Grippa

Trad climber
Salt Lake City, UT
Apr 26, 2012 - 06:15pm PT
I'd love to climb a route on the SE face now so I can not only send a great aid line, but also receive credit in a major piece of geologic research. As a budding geology student I can honestly say this is the coolest piece of work I've seen in progress recently!
spenchur

climber
Flagstaff/Thousand Oaks
Apr 26, 2012 - 06:18pm PT
this is probably the coolest thread of the last few months...especially for a geology student such as myself!
Wade Icey

Trad climber
www.alohashirtrescue.com
Apr 26, 2012 - 06:25pm PT
Nice work Minerals

survival

Big Wall climber
Terrapin Station
Apr 26, 2012 - 06:38pm PT
THAT is freekin' awesome!

Beautiful to the max!
elcap-pics

Big Wall climber
Crestline CA
Apr 26, 2012 - 07:25pm PT
Very interesting... I have always wondered about the various rock types I see and shoot on ElCap.
Thanks for your work Brian, Greg, and Roger. Keep it going!
Prod

Trad climber
Apr 26, 2012 - 07:29pm PT
CFS.

(Cool F*#king Shit)

Prod.
Hardly Visible

Social climber
Llatikcuf WA
Apr 26, 2012 - 11:33pm PT
great stuff Bryan thanks for sharing
Dos XX

Trad climber
Los Angeles, CA
Apr 26, 2012 - 11:37pm PT
Only petrology, no structure??? It's like bread without butter ;-(
Dos XX

Trad climber
Los Angeles, CA
Apr 26, 2012 - 11:44pm PT
Thanksgiving Ledge: an expression of a very pervasive structure.
Chaz

Trad climber
greater Boss Angeles area
Apr 26, 2012 - 11:44pm PT
Just totally fascinating!

I learned more about El Cap in five minutes than I ever knew before.
Dos XX

Trad climber
Los Angeles, CA
Apr 26, 2012 - 11:48pm PT
Thanksgiving Ledge, the Shield Roof --- all the same structure!

EDIT: Maybe.
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