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!
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!
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.
Spider Savage

Mountain climber
The shaggy fringe of Los Angeles
Apr 26, 2012 - 11:48pm PT
Cool science project. I'd love to see a "Geologic Guide to the Walls of Yosemite Valley" guide. All the formations with their names and ages. Sweet!
zBrown

Ice climber
Chula Vista, CA
Apr 27, 2012 - 12:03am PT
This is very fascinating. I copied some photos off to hard disc so I can study 'em at will.

One question I have, though, couldn't you utilize one of those mini-helicopters to get all the photographs that you need?

Just randomly picked one:

mouse from merced

Trad climber
merced, california
Apr 27, 2012 - 12:07am PT
Tone it down, already.

I love it when a project starts and everyone says ooh cool

And then the project gets stalled out

And the money's gone the interest's waned.

Not to be a wet-blanket, I think it has a lot of potential.

But to what end? Where are the benefits, and to whom do they accrue?

I envision this as a practical benefit:

New rubber-to-rock coefficients of friction tables leading to

New free ascents.
How will you purchase your shoes in the year 2025?

Are you going to try that patch of oh-so-slippery pegmatite in your new pair of wing-tip Asolos that you got on sale at Mtn Sports?

Or would it go easier with the pair of Split Pinnacles made for liebacking on DeFucan diorite? You know, the pair with the red laces?

Have fun with this one!

I certainly plan on it.
bergbryce

Mountain climber
South Lake Tahoe, CA
Apr 27, 2012 - 12:31am PT
Really cool stuff.
To classify all of El Cap and put it into a map would be wild.
RP3

Big Wall climber
Temporarily Chapel Hill
Apr 27, 2012 - 08:41am PT
Early morning (for you west coasters) bump for geology!

This is Roger Putnam, the master’s student who is working with Minerals, Dr. Allen Glazner (UNC Chapel Hill) and Dr. Greg Stock (NPS). I just wanted to make a few contributions to Bryan’s spectacular post about the project.

With help from Bryan, Dr. Glazner and Dr. Stock, I have been working on synthesizing the high resolution photography of the SE face with Tom Evans photos and LiDAR data. We are beginning to get a rough map of the whole face that I have posted below. This map is VERY rough and includes many grey areas (places where we cannot see the contacts because of limitations in the quality of imagery available) and other errors. I am just posting it to give everyone an ROUGH idea of what the final product of this study will look like!




I will be in the valley from May 19th through July 8th to try to get this project done. During this time, I’m VERY excited to talk about this project with anyone who is interested and give scale bars to any climbers planning to climb routes for which we do not have any scale photographs yet. The routes that we already have are listed below:

Lurking Fear
Octopussy
Salathe
Shield
Triple Direct
Nose
Mescalito
NA Wall
PO Wall
Tangerine Trip
Zodiac
East Buttress


IF YOU ARE PLANNING ON CLIMBING ANYTHING NOT ON THIS LIST, PLEASE GET IN TOUCH WITH ME! Areas we are particularly interested include NA wall – Tangerine Trip and anything east of Zodiac.

We hope that YOU can help contribute to the understanding of the big stone that we love so much!

My e-mail is rputnam@live.unc.edu
My phone number is 508-776-7609

Thank you so much,
Roger Putnam
Peter Haan

Trad climber
San Francisco, CA
Apr 27, 2012 - 09:10am PT
This is such an excellent thread. It is actually so good it has to be somehow made a reference source on Supertopo, like a new tab created for "Geology" or similar. It is very very valuable and after half a century of modern climbing, elucidates what all the variety is about up on El Cap. Up till now we were just staring and enjoying what seemed random, as if it didn't have a story too and was just visual poetry. Amazing thread, thanks so much.
Prod

Trad climber
Apr 27, 2012 - 09:14am PT
Hi Roger,

We'll be there some time around Mat 8th. Not sure what route we are planning on though. Thinking Mescalito, which you have. But plabns do change... If on something else, I'd love to give a hand.

Prod.
Jaybro

Social climber
Wolf City, Wyoming
Apr 27, 2012 - 09:16am PT
What a cool project!

It's for science, Mouse.
Srbphoto

climber
Kennewick wa
Apr 27, 2012 - 09:22am PT
WOW do you geologist have too much time on your hands.
JohnnyG

climber
Apr 27, 2012 - 09:25am PT
NICE! Go for it guys. I'm a geology phd student who has done a few el cap routes -- so I'm totally stoked to see what you all find!
-John
Rhodo-Router

Gym climber
the secret topout on the Chockstone Chimney
Apr 27, 2012 - 09:55am PT
Nice work Roger! study hard.
JerryA

Mountain climber
Sacramento,CA
Apr 27, 2012 - 10:23am PT
What's the Lost Arrow made of ? Do you want pctures of it ?
martygarrison

Trad climber
Washington DC
Apr 27, 2012 - 10:32am PT
Geeze being a Geologist by education and a Valley climber by heart...This is the coolest post I have ever seen on ST!

Thanks a bunch,

Marty
Tobia

Social climber
Denial
Apr 27, 2012 - 10:34am PT
Have mercy.

WOW do you geologist have too much time on your hands.

What do you think geologists do?
RP3

Big Wall climber
Temporarily Chapel Hill
Apr 27, 2012 - 10:35am PT
JerryA,

Bryan can correct me if I am wrong (he has done a lot of climbing up there), but according to F. Calkins' 1985 geologic map of Yosemite Valley, Lost Arrow is made primarily of El Capitan granite with some possible Sentinel Granodiorite. However, given our general lack of understanding of what is exposed on the cliffs of Yosemite Valley, it probably is far more complex.

A map of that area is beyond the scope of this project (anyone else want a master's thesis??!). Thank you so much for your interest! PM me!
kaholatingtong

Trad climber
the green triangle, cali
Apr 27, 2012 - 11:24am PT
+4 bump. interesting, on topic, educational, +realmccoybonuspoint.
RP3

Big Wall climber
Temporarily Chapel Hill
Apr 27, 2012 - 11:58am PT
Bump... To give a real geology thread more posts than the pseudogeology "slot canyon" thread!!
ydpl8s

Trad climber
Santa Monica, California
Apr 27, 2012 - 01:20pm PT
This is one of the coolest threads in a long time! It's so gneiss, don't take it for granite! (I know, old bad jokes)
Jaybro

Social climber
Wolf City, Wyoming
Apr 27, 2012 - 01:50pm PT
Yeah this thread's the Schist!
Wade Icey

Trad climber
www.alohashirtrescue.com
Apr 27, 2012 - 01:52pm PT
that's some stony sh#t...
Mittens

climber
Apr 27, 2012 - 03:02pm PT
Roger,
This is one of the coolest things ever. Vertical jaking of El Cap!! Very near and dear, as I'm about to graduate with a degree in geology. Buried in schoolwork right now, but I'd love to help eventually!
Mark
Mittens

climber
Apr 27, 2012 - 03:04pm PT
...super psyched to see what kind of interpretations you guys will be able to make once complete...
Clint Cummins

Trad climber
SF Bay area, CA
Apr 27, 2012 - 03:59pm PT
Looks cool.

How about scanning your GSA photo scale to a PDF, so people can just print it out, then fill in the route / belay number for each photo?
Tom could even have a small stack for distribution....
gstock

climber
Yosemite Valley
Apr 27, 2012 - 04:02pm PT
Thanks for the positive feedback everyone. This is obviously a fun project for us to work on, but it may yield some real insights. It's not often that geologists get to examine a few square kilometers of perfectly clean granite in three dimensions, especially the vertical dimension.

Don't despair, DosXX, we are also mapping geologic structures, but not so much on the wall as by remote sensing techniques such as terrestrial laser scanning (lidar) data. There are several softwares available that allow us to map geologic structures in three dimensions with lidar data. However, it seems the lidar data can also help us map the geology - check out the obvious contacts in the image below, which are apparent due to the different reflectivities of the rock types.

Greg

(Roger, you can dispense with the "Dr." ;)

Dos XX

Trad climber
Los Angeles, CA
Apr 27, 2012 - 05:43pm PT
@greg & others involved in the study: I didn't mean to sound so in your face with my comments -- I got an early start on the Friday Night Posting While Drunk thread, I think ;-) The project sounds really cool. Maybe at some future date there could be a follow-up study that includes structural data collected on the rock itself, rather than remotely as will be done in the present study. You'd just need a few climbers who are handy with a Brunton.
Minerals

Social climber
The Deli
Topic Author's Reply - Apr 27, 2012 - 05:49pm PT
Thanks for all of your comments! Glad that this is of interest to climbers and geology students alike. Right on!

Thanks, Wade! Ah, the Alien Skull… But you know that’s megacrystic granodiorite from another intrusive suite…

Thanks again for the use of your photos, Tom! Way cool.

Spider, aside from the specific ages of the various rock types in the Valley, the geologic maps linked in the first post will answer your question on the rock types of each different formation. Have a look at the maps.

Interesting idea on the use of a remote-control helicopter for taking photos. Thanks. I don’t know if it would be possible to get close enough to the wall to get rock texture photos and it would be tough to see the thing if it were too high up the wall. We might end up picking up a bunch of pieces at the base… Would you want to be stuck at a belay or on lead if I were at the controls…?!? : )

Prod, I think it would be helpful to get more photos from routes where we already have belay photos. If you end up climbing Mescalito, it would be great to get more photos, including mid-pitch and at contacts between different rock types.


There certainly are many structural features on El Cap, and joint systems that repeat in a pattern across the wall; the many dihedrals on the southwest face are a great example. One of the things that has struck me over the years is how the major dihedrals/corner systems on the upper portion of the Muir Wall, The Nose, The Real Nose, the Wall of Early Morning Light, Space, and Mescalito have formed in Taft Granite, yet these major features end roughly at the lower contact of Taft Granite and the band of tonalite below. This must be due to differences in competence and structural behavior of the different rock types.



Another good example of the differences in structural behavior of different rock types can be seen to the left of belay 6 on Tangerine Trip. Notice the series of joints in the tonalite/granodiorite dike on the left side of the photo; this series of joints appears to be oriented roughly perpendicular to the dike and they terminate just past the dike margins.
Photo by Tom Evans.


The red arrow in this photo points to the rightmost joint in a series of at least 7 left-leaning joints, some of which form ramps. Several different climbing routes take advantage of these joints, from Zodiac to Bad to the Bone. Also notice the repetition of right-leaning ramps in the lower portion of the photo, on pitch 5 of The Shortest Straw, the left side of the Black Tower (Zodiac), and the left side of The Devil’s Tower (Born Under a Bad Sign).



How about magmatic faults?


Apparent right-lateral offset of a dike hosted within Taft Granite, with a climber on the first pitch of Zenyatta Mondatta.
Photo by Tom Evans.


Apparent right-lateral offset of a magmatic feature in El Capitan Granite at the base of the southeast face, below Iron Hawk.


Apparent right-lateral (dextral) offset of a tonalite/granodiorite dike by magmatic faults and apparent left-lateral (sinistral) offset by the intrusion of a younger aplite/pegmatite dike on Mescalito (I annotated this photo a while ago). The question is, what has caused the change in direction of apparent offset over time? Is this a function of a change in regional or localized stress fields? There are two separate sets of aplite/pegmatite dikes exposed on El Cap; please refer to the 7th and 8th images in the first post of this thread. The older set appears to offset plutonic features in a left-lateral sense while the younger set appears to offset plutonic features in a right-lateral sense.
Photo by Tom Evans.


View looking up the wall from the base of The Footstool. Notice the large concave depression where the main portion of North America Diorite is exposed on the face. This is due to rock type – the diorite is much more susceptible to fracturing than the granites, which has caused the diorite to fall apart at an accelerated rate. I think the presence of North America Diorite is the main cause for the overall concave shape of the southeast face of the wall. If North America Diorite were not present, I am guessing that the southeast face would be more planar or convex, rather than concave.


Thanksgiving Ledge seems like it would be related more to the Salathe Roof and Chickenhead Ledge if one were to try to connect these sub-horizontal structural features, don’t you think?

Are the major joint systems seen on El Cap and the rest of the Valley regional tectonic and/or uplift features, or are some of these joints older cooling features of the plutons?



Roger and Greg, thanks for your posts! Great stuff!!!


Don’t knock it Jeremy; you are in one of the photos… ; )

stunewberry

Trad climber
Spokane, WA
Apr 27, 2012 - 06:05pm PT
Two pix up, the late aplite has matching walls, and 2m left of the old magic dike, the zig zags appear to match-- which, unless it's a 3D viewing effect, indicates only extension on the late aplite opening, no horizontal translation.

Be careful about right and left lateral when in fact the horizontal surfaces should be called east or west vergent (depending of course which way the wall faces)

Bravo to this effort! More later

"Stu"

Edit --the iPad knows more about what I wanted to say than I did "magic" should be "mafic"

Also -- being asked to participate in "bedrock" ( sorry) science like this is unique. The climbing community is generally intelligent, curious, and observant, as well as skilled in techniques no one else can do. It's like, if they'd existed at the time, the Galapagos Island Chapter of the Audubon Society had been asked by Charles Darwin to measure the sizes and shapes of the finch's beaks on the islands. everyone knows what.a waste of time that data and understanding it allowed turned out to be!

Dos XX

Trad climber
Los Angeles, CA
Apr 27, 2012 - 06:15pm PT
Regarding the accelerated wasting of the black diorite on El Cap's southeast face, here's something that my Geomorphology professor (Larry Lattman, who was taught by Hans Einstein) mentioned regarding dark rock in a lighter coloured matrix: the dark rock would be more susceptible to thermal weathering than the lighter coloured rock and thus waste at a greater rate, leaving localized concavities. Intuitively, that makes sense, but I remember when I heard Prof. Lattman say that, I immediately thought of one of my favourite climbing crags that had countless, black diorite chickenheads protruding from a sea of white monzonite -- just the opposite of what my professor indicated should happen. Geology: it's a wonderful art ;-)
Minerals

Social climber
The Deli
Topic Author's Reply - Apr 27, 2012 - 08:48pm PT
Thanks, “Stu.”

“… the late aplite has matching walls, and 2m left of the old mafic dike, the zig zags appear to match…”

I’m not sure I understand what you mean by this. I used the word “apparent” to indicate that overall offset direction may not be what we see in the rock in two dimensions because we don’t know exactly how the dikes are oriented in three dimensions. In the Zenyatta photo (4 photos up), the arrows are to show that the dike is offset; movement towards or away from the observer could also create this apparent offset, depending on how the dike is oriented in the third dimension. Am I making any sense?


Dos XX, as far as thermal effect of weathering of rock, I asked some questions about that in this thread:
http://www.supertopo.com/climbing/thread.php?topic_id=1784752&msg=1789192#msg1789192

Mafic minerals are less resistant to chemical weathering so we would expect mafic enclaves to weather out faster than surrounding granite, rather than slower, such as is indicated by the “chickenheads” found in the western part of Yosemite Valley and other granite areas. I think this is a function of grain-size, where the finer-grained mafic enclaves (usually diorite) weather slower than the coarse-grained granite host, leaving really cool holds for climbing. In some cases I have seen the opposite, where fine-grained mafic enclaves have weathered out faster than the surrounding granite, leaving a cavity in the rock. I’m not sure why the weathering rates are inconsistent.

gstock

climber
Yosemite Valley
Apr 30, 2012 - 06:34pm PT
I'm not sure either why mafic enclaves sometimes stick out as chickenheads and sometimes erode back as jugs. The most interesting boulder I've seen this play out on is at Turtleback Dome. It's a sloping boulder with parallel sides (the top side is a slab and the underside is an overhang). The mafics on the top stick out, and the ones on the bottom are eroded back. Check it out next time you're there - it's a mind-bender.
PSP also PP

Trad climber
Berkeley
Apr 30, 2012 - 08:13pm PT
Mapping the different types of granite on El Cap sounds like fun especially the climbing and the rapping. Other than that it sounds extremely tedious and just maybe a bit boring. Kind of like identifying all the differnet kinds of oatmeal in the world; which could be fun if it was all on a vertical face.
213

climber
Where the Froude number often >> 1
Apr 30, 2012 - 08:33pm PT
Killer maps Roger! Really pumped for the 'fieldwork' and knowledge enhancement that will go down as a result of your work. Here's my one comment: The maps need a scale bar!!!! (I know you are gonna go 'DOH!' at that one :) hehe).
Send my regards to miz robin and the dawg!
-ben

Edit to add: Those joints on Tangerine Trip belay 6 look a lot like boudins, could they be?
Bob Harrington

climber
Bishop, California
Apr 30, 2012 - 08:34pm PT
Here's my theory on mafic enclave innies and outies: when the rock surface has been exposed for a long time (whatever that is...), the grain size effect that Minerals mentioned is the principal factor in the weathering rate, resulting in chickenheads that stick out from the rock surface. In subsurface weathering in fractures where the soil water has lower pH than precip (from soil gas CO2 and organic acids), chemical effects dominate and the mafics weather faster than the granite. The road cut at Donner has a lot of innies.

I'd like to see that boulder on Turtleback.

Great thread, thanks you guys.
213

climber
Where the Froude number often >> 1
Apr 30, 2012 - 09:11pm PT
the finer-grained mafic enclaves (usually diorite) weather slower than the coarse-grained granite host

That seems a bit counter-intuitive (lol, like many physical processes), finer grains mean greater surface area, so would that point more towards porosity and permeability as driving the rates?
hairyapeman

Trad climber
Fres-yes
Apr 30, 2012 - 09:41pm PT
Very cool! I have always wondered about tangerine and NAW. Interesting! I will be following this!!!
eeyonkee

Trad climber
Golden, CO
Apr 30, 2012 - 09:45pm PT
Big thumbs up!
Captain...or Skully

climber
Apr 30, 2012 - 09:52pm PT
Dig it, Jeremy. Most things are a waste of Time. Some folk even think Wall Climbin' is a waste of Time(Jinkies! Say it ain't so!)
At least it's cool.Even I managed to learn a little Geology while climbin' with the Mineral Boy. The focus is astounding.

Right on, Bryan & co.....I can dig it.
eeyonkee

Trad climber
Golden, CO
Apr 30, 2012 - 09:58pm PT
Is there a route where you stay on the same rock type all of the way up? Seems unlikely...but it would be nice to describe the route as start here and stay on the tonalite. It might look easy, but if its diorite, you're OFF ROUTE!
RP3

Big Wall climber
Temporarily Chapel Hill
Apr 30, 2012 - 10:08pm PT
eeyonkee,

The closest I believe you could come to a route of that nature on the SE face would be the Pacific Ocean Wall. As you climb it, you are basically in El Capitan granite the whole way up. The last couple of pitches appear to run through a tonalite band. However, I believe it is as close as you can come.

Many of the routes on the SW face remain in El Cap granite the whole way (of the routes we have surveyed so far, Lurking Fear, the Aquarian Wall, and the Salathe are all entirely within El Capitan granite.

Good question!

-Roger Putnam
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
May 1, 2012 - 12:30am PT
Bryan: TFPU. What an exciting project. Any thoughts of using 3D visualization software (EarthVision, 3D voxler, Gocad, etc) to generate a 3D model of the intrusive units?
DonC

climber
CA
May 1, 2012 - 12:44am PT
related to tuolumne_tradster's post - in general what technology are you using? How are you processing the lidar and what mapping/display packages are you using?

I'm interested in both the geology problem as well as the technology you are using.

RP3

Big Wall climber
Temporarily Chapel Hill
May 1, 2012 - 08:30am PT
Regarding the previous two posts:

We are using I-Site Studio software developed by Maptek to process the LiDAR data. I have been digitizing contact lines within ArcGis and will georeference it to the LiDAR data once I am finished with the digitizing the contacts between intrusive units.

tuolumne_tradster: I have not personally used any of those programs. However, what you are talking about is the end goal of all of this. Dr. Allen Glazner and Dr. Kent Ratajeski mapped the summit in great detail about a decade ago, and we plan on combining that data with the results of this project to do exactly the modeling you speak of. It is pretty exciting because, as far as we know, a three-dimensional map of a portion of a batholith has never been made.

Thanks for the interest!
stunewberry

Trad climber
Spokane, WA
May 3, 2012 - 08:57pm PT
I was going to start a new thread about chickenheads, but the El Cap mapping thread makes a perfect place to introduce this stuff and at the same time bump the thread back to the top of the list. A lot of the pictures Minerals posted in his two main posts in this thread show some of the kinds of relationships I want to talk about.

Most of the darker-colored, fine-grained goobers in granites that climbers call “chicken heads” are called by geologists “mafic inclusions.” There are a lot of ways for errant chunks to end up in a granitic magma as it forms through melting, makes its way upwards, mixes with what it meets along the way, and crystallizes to form what we finally see exposed at the surface. The first is through an unmelted bit of the source area being carried along with the magma as it rises. Inclusions of this sort aren’t common in the high Sierra granites, or if they are they are present they haven’t been recognized.

The second is as chunks of the wall rocks that a magma passes through are ripped from the walls of the conduit and incorporated in the rising magma. These are recognized as being quite different from the host granitic rock, often being angular in outline and being metamorphosed sedimentary or other igneous rocks. Sometimes they are chemically and mineralogically unstable in the granite magma and react to form new metamorphic minerals, like the oblong chunk of green skarn with a coarse grained rim (metamorphosed dirty limestone, note the very coarse grained reaction rim. The brown patches are just dirt on the rock). The second picture is a biotite hornfels (metamorphosed shale) inclusion from the other side of the same block. Both inclusions are in a swarm of mafic inclusions, which are the next type to discuss. When a magma intrudes a solid host, the process may be arrested, with abundant dikes of the invading magma breaking the host up into a “magmatic breccia” along dikes where the angular pieces of the host can still be matched up across the dikes.


A third way, and the one that probably creates most of the chicken heads in Yosemite and elsewhere, is when two different composition magmas physically interact along some kind of interface, they will have different compositions, heat contents, degrees of and kinds of initial crystallinity and mineralogy, viscosity, and other parameters. Different mixing scenarios can be envisioned in which initially small amounts, or globs, of hot, mafic (diorite) magma mix with large volumes of another, usually cooler, felsic (granitic) magma. When this happens the higher temperature mafic magma loses heat quickly to the enveloping granite, and the minerals that form (hornblende, biotite, plagioclase feldspar as the main ones) are usually fine grained. As the degree of crystallinity of the mafic glob increases, its viscosity increases, and the mafic glob becomes partially solid as the growing crystals interfere with one another. At the same time, the heat lost from the mafic magma heats up the cooler granite magma, and may reduce its viscosity and even partially melt some of the crystals it may contain. If enough mafic magma is introduced, eventually the system gets heated up by the earlier batches, and the viscosity of the newly introduced magma may remain low enough that it does not form an effective solid, but instead can mix with the host granitic magma (which by now has heated up and may be partially remelted).

The analogy that I like to draw, and something you can try at home, is to take pre-stirred but still cold vanilla ice cream (the granite magma), into which you introduce increasing amounts of hot fudge sauce (the diorite magma). You have to use real hot fudge sauce, chocolate syrup doesn’t have the appropriate viscosity characteristics. Mix in just a bit of HFS and you get globs of chilled chocolate. Mix in more and eventually the ice cream begins to melt while the HFS doesn’t chill to globs, leading to true mixing between the chocolate and the vanilla, creating a hybrid. Some of the initial globs may remain as globs in the hybrid. All kinds of interesting mish-mashes can result, including multiple-generation mixtures, just like in the real world, as the next pictures show.


Large inclusions may quench such that the rims are fine-grained, while the cores retain their heat longer and thus crystallize more slowly, forming larger crystals in the core. Here is a picture of two adjacent mafic inclusions with fine-grained margins and coarser-grained (and visually lighter-colored) cores, the one on the left later cracked as a brittle solid. Following the cracking, the still-fluid ‘granite’ intruded into the crack (the pen points to the granite-filled crack).



When a lot of inclusions are present, they can travel with the host magma as it moves, or they may gravitationally settle through the host to accumulate as layers of inclusions at the bottom of whatever volume the magma occupies. The first picture in this post shows skarn and hornfels chunks along with some more typical mafic inclusions; the entire pile could only form through some physical (flow or gravity) accumulation of the chunks and globs.

I don’t think anyone has looked systematically at the weathering characteristics of inclusions and their hosts to see what the “inny-outy” controls of weathering of mafic inclusions are. The chicken head (outy) weathering may be related to the tightly-interlocking nature of the fine grained crystals of the inclusions, and/or there may be more microcracks in the host granite which promotes introduction of water and weathering, but those are just speculations.

"Stu"
Dos XX

Trad climber
Los Angeles, CA
May 4, 2012 - 08:28am PT
Excellent material, Stu. Hooray for chickenheads!
Minerals

Social climber
The Deli
Topic Author's Reply - May 9, 2012 - 11:00pm PT
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???

stunewberry

Trad climber
Spokane, WA
May 10, 2012 - 12:05am PT
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...
hollyclimber

Big Wall climber
Yosemite, CA
May 14, 2012 - 03:22am PT
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
wayne burleson

climber
Amherst, MA
May 14, 2012 - 06:46pm PT
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...
Mighty Hiker

climber
Vancouver, B.C.
May 14, 2012 - 06:51pm PT
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?
Blakey

Trad climber
Newcastle UK
May 15, 2012 - 04:09pm PT
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
BASE104

Social climber
An Oil Field
May 15, 2012 - 09:15pm PT
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.
'Pass the Pitons' Pete

Big Wall climber
like Ontario, Canada, eh?
May 19, 2012 - 02:19pm PT
Bump for cool rocks. Will try to remember for Bryan this spring.
Minerals

Social climber
The Deli
Topic Author's Reply - May 22, 2012 - 01:11am PT
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

Mighty Hiker

climber
Vancouver, B.C.
May 22, 2012 - 01:15am PT
OK, so the garnets are the oldest rocks of all in the Valley? And they're somehow inserted into the intrusions?

Heh heh.
Minerals

Social climber
The Deli
Topic Author's Reply - May 23, 2012 - 03:13pm PT
Quite the opposite…

Now go back to eating your dessert!

; p
Dos XX

Trad climber
Los Angeles, CA
May 23, 2012 - 03:23pm PT
Fascinating. The bedrock maps help me understand why the Cathedral rocks look so different from everything else in the Valley.
kev

climber
A pile of dirt.
May 23, 2012 - 03:32pm PT
Kickass Bryan!

Since were getting all scientific....

lt + na = bomber knob bands ==> happy FA's
Hoots

climber
Toyota Tacoma
May 24, 2012 - 02:33pm PT
Geology is a blast! Unless you have to help haul rocks to the top of El Cap!
Here are some photos from the first of the mapping missions, a trip up the Muir to catalog the upper corners.

http://ryanhuetter.blogspot.com/2012/05/climbing-muir-wall-for-science-el-cap.html

Climbing for science! Woot!
skywalker

climber
May 25, 2012 - 10:51am PT
Bump! Super cool! Thanks!

S...
RP3

Big Wall climber
Temporarily Chapel Hill
May 30, 2012 - 09:53am PT
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
RP3

Big Wall climber
El Portal/Chapel Hill
Jun 23, 2012 - 09:21pm PT
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
Michelle

Social climber
SH60091
Jun 24, 2012 - 12:24am PT
ha! the most awesome troll EVER!





jk. stay busy and Ill call you soon.
Minerals

Social climber
The Deli
Topic Author's Reply - Sep 9, 2012 - 10:05pm PT
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!
Mark Hudon

Trad climber
Hood River, OR
Sep 9, 2012 - 10:09pm PT
Max and I are going up on Lost in America in early October, we'll gladly take photos!
Minerals

Social climber
The Deli
Topic Author's Reply - Sep 9, 2012 - 10:17pm PT
Thanks, Mark!
RP3

Big Wall climber
El Portal/Chapel Hill
Sep 26, 2012 - 07:30pm PT
The first draft is done!

If it INTRIGUES you, go to Greg Stock's presentation at Facelift tomorrow night to find out more.

If it INSPIRES you to help out (there is A LOT of fine tuning left to do) send me a message! rputnam@live.unc.edu

RP3

Big Wall climber
El Portal/Chapel Hill
Sep 26, 2012 - 07:46pm PT
The map is VERY detailed:


klk

Trad climber
cali
Sep 26, 2012 - 08:58pm PT
awesome.

Jingy

climber
Somewhere out there
Sep 26, 2012 - 09:26pm PT
Wow!!

That is incredibly detailed work you got goin' there..

Hoping for the best, and wish I had the equipment and could assist in this endeavor.


krahmes

Social climber
Stumptown
Jun 12, 2013 - 01:49pm PT
Well done. Not quite a tale of ten plutons but great work.

http://news.nationalgeographic.com/news/2013/06/130612-yosemite-el-capitan-rock-mapped/
Peter Haan

Trad climber
Santa Cruz, CA
Jun 12, 2013 - 10:33pm PT
Superb.
deuce4

climber
Hobart, Australia
Jun 13, 2013 - 04:04pm PT
Amazing work. Incredible combination of climbing talent, photography talent, and programming talent from various sources to make it all possible. Well done!
Dr. Christ

Mountain climber
State of Mine
Jun 13, 2013 - 04:40pm PT
EXCELLENT!
gstock

climber
Yosemite Valley
Jun 13, 2013 - 05:48pm PT
I've posted this before, but here is a quick video showing the resolution of the terrestrial LiDAR (laser scanning) data for El Capitan. The different rock types (granite, diorite, aplite dikes) are clearly visible due to their differing reflectivities.

[Click to View YouTube Video]
MisterE

Social climber
Jun 14, 2013 - 01:29am PT
Bump for a great project!
RP3

Big Wall climber
El Portal/Chapel Hill
Jun 14, 2013 - 01:33am PT
Love that video!
RP3

Big Wall climber
Twain Harte
Aug 6, 2014 - 10:25pm PT
Time to reactivate this beautiful thread.

After many years of work by myself, Bryan Law (Minerals), Greg Stock (gstock) and Allen Glazner (no avatar on ST, but an occasional lurker), the geologic map of El Capitan is finally completed! It made it through peer review and has been published by the Geological Society of America's Maps and Charts Series. Check out the first high-resolution map ever made of a km deep section of a pluton.

Below is a low-rez image of the map (which, in reality, is a 38"x34" poster.) Unfortunately, it is somewhat expensive for non-GSA members, so get in touch with your geologist friends, and have them pick you up a truly one-of-a-kind map at a member discount!

All hail El Capitan geology:


Thanks to the many organizations (National Geographic Waitt Society, GSA, AAC, NPS, UNC-Chapel Hill, Patagonia, Metolius, Bluewater, Maptek, xRez Studios) and climbers who have helped with this effort over the years.
Captain...or Skully

climber
in the oil patch...Fricken Bakken, that's where
Aug 7, 2014 - 04:28am PT
That is BADASS.
clinker

Trad climber
Santa Cruz, California
Aug 7, 2014 - 05:22am PT
The rockhounds rule. Crazy map of the vertical.
JohnnyG

climber
Aug 7, 2014 - 05:29am PT
Nice work!
TwistedCrank

climber
Released into general population, Idaho
Aug 7, 2014 - 06:42am PT
For the win! It's a climbing geologists dream come true. Proud.
Hudhopper

climber
Jan 15, 2015 - 11:37am PT
Not sure how many remember this, but the publisher is offering $15 off in honor of Caldwell and Jorgeson's climb. The map is now only $19. From their Facebook page:

GSA would like to honor Tommy Caldwell and Kevin Jorgeson's incredible ascent of El Capitan's Dawn Wall by offering $15 off our map, Geologic Map of the Southeast Face of El Capitan. This unique, vertically oriented, decimeter-resolution geologic map was accomplished by remote sensing using terrestrial LiDAR and gigapixel photography and was ground-truthed by climbing and rappelling. Visit the GSA Store (http://bit.ly/1u9H0Mr); and enter coupon code PITCH15 at checkout. ‪#‎DawnWall‬
oldgeologist

Mountain climber
Elyria, Ohio
Jul 21, 2015 - 09:18am PT
Wonderful project.

Sometime around 1956 Art Smith hiked around the rim of Yosemite and collected samples, which he sliced up and put under the petrographic microscope. They were classified, and the project was turned in to Howell Williams (petrographers will know who he was) at the University of California as a master's thesis in geology. He didn't pursue it any more, as he worked for the Bureau of Land Management, retiring out of Kingman, Arizona. I wonder if he caught any of these different formations.

By the way, my favorite portrait is me standing next to El Cap Tree. I still don't know how they got the first bolts into the overhanging wall on the rappel.
Wade Icey

Trad climber
www.alohashirtrescue.com
Jul 21, 2015 - 10:18am PT
this is a great reminder to me that Minerals is one of the most incredible humans I've been privileged to know, and what an honor it has been to to spend time in the mountains and elsewhere in his presence. I can't count the times I've jugged up to a belay raving about the 'beautiful granite.' only to have Bryan, in his quiet way, say "uh, actually......"
I could probably go for a geology degree if I could remember even 10% of the knowledge he has shared over the years.

Right on.


RP3

Big Wall climber
Twain Harte
Jul 21, 2015 - 05:08pm PT
It is funny this thread just got bumped because our paper about the petrology of El Capitan was just published. We used El Cap's ~1 km tall exposure to test hypotheses regarding the emplacement and evolution of plutons.

Thanks to the MANY people on this site who contributed to this project over the years.

-Roger Putnam

Check it out here.

Here is the abstract:
Detailed geologic mapping on the ∼1-km-tall, vertical southeast face of El Capitan was completed to determine the chronology and geometry of emplacement. Field relations reveal a complex intrusive history at the boundary between two intrusive suites involving interaction between several granitic units. No resolvable faulting or other postemplacement deformation was observed. New U-Pb zircon geochronologic data (laser ablation and isotope dilution) demonstrate assembly of the El Capitan Granite and diorites of the Rockslides and North America between ca. 106 and 103 Ma. New ages for the Taft (106.6 ± 0.7 Ma), Leaning Tower (104.1 ± 0.10 Ma), and Bridalveil (103.4 ± 0.4 Ma) plutons reveal that they intruded over the same interval as the other plutonic rocks exposed on the face of El Capitan, although field relations and geochronology suggest a distinct order of emplacement.

Two sets of aplite dikes are also exposed. Their whole-rock compositions suggest segregation at depths of 5–6 km and derivation from the intrusive suites of Yosemite Valley or Buena Vista Crest. Chemical analysis of samples collected along ∼1-km-tall vertical transects through the El Capitan and Taft Granites reveals no systematic variations in major or trace elements. Analysis of 78 photographs within the El Capitan Granite also shows no systematic variations in texture or mineralogy with elevation. Lack of resolvable vertical variations in both field and petrologic observations is consistent with incremental assembly, and is hard to reconcile with models that envision magma chambers as large fractionating bodies.
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