Friday Field Foto #99: Angular unconformity in Darwin Canyon, California
This week’s Friday Field Foto is from an area just west of Death Valley called Darwin Canyon. As you can see, there is a sharp, angular contact between two sedimentary formations — an angular unconformity.
Angular unconformity in Darwin Canyon, California (© 2010 clasticdetritus.com)
Note person in lower right for scale.
When I took this photograph I didn’t have any specific knowledge of this geology because we were driving between stops. But 2 minutes on the google machine uncovered this fantastic web resource — Death Valley Geology: A Field Guide and Virtual Tour by Steven G. Spear from Palomar College.
The information for this angular unconformity is here and this is what they have to say about it:
The layers below the unconformity are the lower Permian Darwin Canyon formation seen at the folds up-canyon. The layers on top are Triassic marine deposits (and may correlate to similar age strata in Butte Valley). The angular discordance of the unconformity is about 20o. The age of this unconformity has been quite well dated. The youngest fossils in the beds from under the unconformity are Wolfcampian fusilinids of the Panamint Springs member of the Darwin Canyon formation. The oldest fossils from the layers above the unconformity are Guadelupian (Capitanian) brachiopods and mollusks.
Happy Friday!
The same end-of-year meme that went around last year is back — post the first sentence from the first post of each month — I wondered if doing the same thing as last year was uninteresting but then I couldn’t think of anything else to do, so here it goes:
January 2009: This week’s Friday Field Foto is from a short research cruise on went on a few years ago just off the coast of central California.
Push core samples of deep-marine mud, offshore central California (© 2009 clasticdetritus.com)
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February 2009: I was originally inspired to propose this theme after reading the book Year Million, which is a collection of essays from scientists, technologists, futurists, etc. speculating a million years into the future (most of the essays, not surprisingly, are about the fate of the human species and our civilization).
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March 2009: I am back in the States and very slowly reconnecting myself to the internet. The contrast from little to no connectivity while traveling and doing field work to full connectivity back at home is a bit overwhelming . It may take me a week or so to get back into the swing of things. To get things started, here are some photos from this recent trip. I’ve chosen photos that I think nicely portray what it is like to hike around some of these mountains.
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April 2009: This week’s Friday Field Foto is a close-up view of the Keystone Thrust in southern Nevada.
Keystone Thrust contact, near Valley of Fire, southern Nevada (© 2009 clasticdetritus.com)
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May 2009: This week’s Friday Field Foto is from Kilbourne Hole in southernmost New Mexico — very close to El Paso, Texas. This was my last field trip as a student back in 2007 — see more photos from that trip here.
Cross beds from pyroclastic density currents, Kilbourne Hole maar volcano, New Mexico (© 2009 clasticdetritus.com)
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June 2009: A special volume from GSA (Geological Society of America) titled Earth Science in the Urban Ocean is now available.
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July 2009: I just returned from a trip to Svalbard, which is an island group in the Arctic Ocean about 1000 km from the geographic North Pole.
Braid-delta from the air, Svalbard (© 2009 clastic detritus)
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August 2009: Most of my readers know that I have a passion for submarine geomorphology (e.g., the Sea-Floor Sunday series).
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September 2009: This week’s Friday Field Foto is from some Miocene sedimentary rocks exposed along the Atlantic coast of Tierra del Fuego.
Miocene sedimentary rocks, Tierra del Fuego (© 2009 clasticdetritus.com)
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October 2009: This week’s Friday Field Foto doesn’t highlight any specific sedimentary structure or relationship … I just think it’s pretty :)
Pine Spring Canyon, Guadalupe Mountains, west Texas (© 2009 clasticdetritus.com)
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November 2009: I was alerted to this image from a reader and also saw it linked to on geology.com/news and just had to share it.
zoomed-in view of mixing sediment plumes in Gulf of Mexico (image credit: NASA Earth Observatory - http://earthobservatory.nasa.gov)
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December 2009: Earlier this year a reader sent me a photograph of some rocks they had come across asking me what I thought they were or might represent.
Have a nice holiday break and a Happy New Year!
Note: This is a guest post from Steve Gough, the founder of Little Research & Design.
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Little River Research & Design is a small “semi-profit” organization I founded in 1991. For 16 years it was mostly just me doing consulting in applied river geomorphology. In 2007, I hired three people so we could shift more from consulting to river conservation science and education. We produce high quality educational video, some compiled on this DVD, and also movable bed river models (MBMs), including the big (4 m x 1.5 m) Emriver Em4 and the smaller, portable Em2. There are now fifty Em2s in use, about half of them are at university geoscience departments. We’re now working with museums, state and federal agencies, and other universities to develop MBM hardware (including open source designs) and curriculum. We’ve developed a unique color coded by size plastic modeling media that I think will revolutionize MBM use for research and teaching; short video here (.mov file) and are also working on cool new technologies like close range photogrammetry for use with MBMs.
Little River Research & Design EM4 model (courtesy of Steve Gough)
As part of that work we’re collaborating with ten institutions, led by Southern Illinois University-Carbondale, on an NSF CCLI proposal due soon.
If you’ve ever used a stream table for research or education, you can help us by completing this survey. You can follow our work and developments in applied fluvial geomorphology on my blog Riparian Rap.
The last two years have been a struggle—almost all our clients are tax-supported, and the economic downturn hit us hard. Thanks to Brian for use of his excellent blog, and also to you for reading and forwarding this post to colleagues who might be interested in our work.
Little River Research & Design EM2 model (courtesy of Steve Gough)
Check out more photos of the models and of field work on LRRD’s Flickr page.
Today was the last day of the AGU meeting. Unlike some other meetings, the final day at AGU isn’t nearly as depressing. I’m not sure why — maybe because it’s a Friday and attendees are staying to hang out in the Bay Area for the weekend. It’s certainly not as happenin’ as the other days but it seems that the final day for conferences that end in the middle of the week are even worse.
Anyway, I spent the morning catching up with some friends and then we all headed to the “Interpreting Allogenic and Autogenic Processes in the Stratigraphic Record” session. What the heck does ‘allogenic’ and ‘autogenic’ mean? Maybe I’ll write a whole post about that someday, but the short answer is that allogenic forcings are those that are external to the system whereas autogenic refers to processes/dynamics that arise intrinsically. Examples of allogenic forcings on sedimentary systems include climatic fluctuations, tectonism, and sea level. Autogenic processes included the formation of channel-levee systems and the avulsion of delta or fan channels/lobes.
However, it’s not so simple … which was the point of the session. It was a great session, a nice mix of outcrop data, modern systems, and experimental systems. I gave a talk on some work I did during my Ph.D. on how various factors interacted and influenced deposition in a deep marine basin offshore southern California during the last 7,000 years. I felt I was going a bit fast — maybe was trying to squeeze too much info in — but I got some good feedback afterwards, so I think it was a success.
After that, I had a nice lunch with some friends and then we headed to the companion poster session that afternoon. The posters were very well attended and I had a bunch of follow-up discussions about my talk in addition to discussions about the posters.
Although I only went to two days of AGU this year and didn’t have time to branch out of my field of expertise, it was a great meeting as always!
I got off BART in San Francisco around 8:30 this morning, got a coffee, picked up my badge and headed right to the poster hall. Instead of diving immediately into the posters I had to find a relatively quiet corner to work on some finishing touches for my own talk. I spent about an hour getting it just how I wanted it and then spent a couple hours looking at the posters in the Deltas and Fans session. I ended up socializing with people I hadn’t seen in a while more than actually studying the posters … but, hey, that’s what conferences are all about. I caught up with friends and peers who are in both industry and in academia — and we all lamented 2009 for being a tough year in terms of convincing those who control $$$ to release some for research.
I then went and caught a couple of talks in a late morning session about computational modeling of sedimentary landscapes/seascapes. The two talks I saw were okay, but not great.
After that, lunch (pizza and beer) with a good friend of many years who I don’t get to see all that often.
I went to the entire early afternoon oral session on Deltas and Fans — the companion session to the posters in the morning. Pretty much all the talks were very good — pretty heavy on the experimental side, which isn’t really my expertise, but I always learn something and get ideas about what kinds of features to measure in natural systems and interesting patterns to keep an eye out for.
I headed back to poster hall to check out a particular poster about some modeling of hyperpycnal flows (i.e., river floods so chock full of sediment that they plunge under the water body they are entering into and create a sediment gravity flow). Very cool stuff.
Right before I headed home I uploaded my talk for tomorrow morning. I’m pretty happy with it, gave a sneak-preview to a friend and he liked it a lot. We’ll see how it goes tomorrow.
Great day!!
Although AGU 2009 is already half over I’m just getting ready for it! I’ve had an incredibly busy week with non-AGU obligations so tomorrow (Thursday) will be my first day at the conference. Unfortunately I missed a luncheon held for bloggers today, I’d be interested to hear how that was from others.
Several other geo-bloggers have been covering the conference (including AGU’s “official” blog, Dave’s Landslide Blog, Harmonic Tremors, Musings of a Life-Long Scholar, Active Margin, and Andrew at geology.about.com). See the blogroll for a bunch more. And the Twitter feed (using #AGU09 tag) is extremely active and highly recommended for keeping up with it all.
I hope you’ve paced yourself and are still hungry for what I think are some great sessions. This is how I will be spending my time at the meeting:
Thursday AM
EP41A (Moscone South) — Dynamics and Processes of Deltas, Fans, and Their Distributary Channels I (Posters)
EP42A (2008 Moscone West) — Computational Modeling of Landscape and Seascapes: Models, Data Sets, and Applications I (Oral) — specifically, I’m going to try and check out the following in this session:
- EP42A-01: Modeling the complex dynamic interactions between surface processes, crustal deformation, and climate change (Braun et al.)
- EP42A-05: Reconstructing the Waipaoa sedimentary systems at the LGM (Upton et al.)
- EP42A-06: Community sediment-transport modeling system (CSTMS) (Sherwood et al.)
- EP42A-08: Computational investigation of turbidity currents and river outflows (Meiburg et al.)
Thursday PM
EP43D (Moscone South) — Computational Modeling of Landscape and Seascapes: Models, Data Sets, and Applications II (Posters) — I will check out all, but hope to get some good discussions going about this one:
- EP43D-0672: Flow dynamics and sediment entrainment in natural turbidity currents inferred from numerical modeling (Traer et al.)
EP43F (2008 Moscone West) — Dynamics and Processes of Deltas, Fans, and Their Distributary Channels I (Oral) — this whole session looks fantastic
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Friday AM
EP52A (2002 Moscone West) — Interpreting Allogenic and Autogenic Processes in the Stratigraphic Record I (Oral) — this session explores the interactions of external (or allogenic) forcings and intrinsic dynamics (or autogenic processes) on what is preserved in the stratigraphic record. I am giving a talk in this session that starts at 11:35am titled:
- EP52A-06: High-frequency allogenic forcings on the Holocene stratigraphy of Santa Monica Basin, California
Friday PM
EP53A (Moscone South) — Interpreting Allogenic and Autogenic Processes in the Stratigraphic Record II (Posters) — this is the companion poster session to the morning oral session and has a bunch of awesome stuff. I really hope people stick around until Friday afternoon to argue about discuss what is actually being recorded in the stratigraphic record.
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I’m excited … now I need to finish preparing my talk.
One of my more popular posts, based on site stats, is this one highlighting a nice image of the seafloor in the region of the Puerto Rico trench. This week’s Sea-Floor Sunday image shows a new bathymetric image of this region that I found on the USGS Woods Hole Science Center website.
Shaded relief and colored bathymetry of the Puerto Rico Trench (credit: http://woodshole.er.usgs.gov/project-pages/caribbean/seafloor.html)
Click on the image above (or here) to read the description from the researchers who acquired the data.
Below is another image from this dataset — this one is zoomed in a bit and also reoriented (north is to the lower right).
Perspective view of part of Puerto Rico Trench (credit: http://woodshole.er.usgs.gov/project-pages/caribbean/tsunamiFig.html)
Click on the image to go to the page that describes the features shown here and a key to the annotation. The ‘amphitheaters’ refer to areas of geologically recent submarine landslides (note the possible debris fans at the base of slope; one of them outlined with a black dashed line).
This week’s Friday Field Foto is from along the west coast of the U.S. just south of the town of Eureka, California.
I especially like the margin of this sedimentary system, which includes intricate and beautiful mini-canyons eroding and contributing sediment. The photo below zooms in on these features.
I know I’ve seen others show their photographs of features like this (e.g., Through the Sandglass blog) so feel free to include links in the comments below.
Happy Friday!
Earlier this year a reader sent me a photograph of some rocks they had come across asking me what I thought they were or might represent. I ended up posting the photograph here as a ‘geopuzzle’ and asked all of you to comment on it with your thoughts (see that post here). It was pretty fun and worked so well that I thought I’d do it again.
A few weeks ago a reader sent me a couple photos of some interesting features in some fine-grained sedimentary rocks near her home in northeastern Oregon Washington. I replied with my own educated guess but would like to see what you all think.
The features of interest in these rocks are the numerous saucer-shaped rocks eroding out of the outcrop.
photograph from reader
In the photo above you can see these ’saucers’ in lower right of photo as float.
photograph from a reader
Again, look at the lower right of the photo above for another view.
zoomed-in part of previous photo showing disc-shaped features eroding out of the outcrop (photograph from a reader)
So, add your two cents below and I’ll summarize the consensus on this geopuzzle tonight or tomorrow with an update.
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UPDATE (12/8/2009): Well thanks to everybody for ‘playing’. Here is my initial response to the reader regarding these saucer-shaped features:
It’s difficult to tell for sure w/ that photo … but my gut instinct is that the saucer-shaped stones are “concretions”, which are features that form after deposition (sometimes millions yrs after) from differential chemical cementation. The wikipedia page is actually pretty good for this: http://en.wikipedia.org/wiki/ConcretionThat’s just my best guess from that photo and your description … I could be wrong.
