This week’s Friday Field Foto is from the toe of the Athabasca Glacier in the Canadian Rockies. We were on our way to see these rocks and only had enough time to do the short walk to the front of the glacier from the parking lot.
sinuous channel in glacier ice, Athabasca Glacier in Jasper Nat'l Park, Canada (© 2009 clastic detritus)
I just thought it was cool how this small meltwater channels organized themselves into sinuous patterns.
Here’s a view zoomed out a bit. I don’t study glaciers … if you do, please feel free to comment below.
Athabasca Glacier in Jasper Nat'l Park, Canada (© 2009 clastic detritus)
Happy Friday!
If papers had a comments section
I’ve seen this in two separate places so far today, so I’m sure it’s making the rounds. Hilarious!
credit: PhD Comics (http://www.phdcomics.com/comics.php?f=1178)
Click on it to go to the source.
A paper on which I am second author is now out in the May 2009 issue of Journal of Sedimentary Research (you can find it here or here).
The paper summarizes a study of ancient submarine mass-wasting deposits and how their stratigraphic architecture influenced overlying sand-rich turbidite deposits.
The rocks are part of an Upper Cretaceous succession exposed in the mountains of the Patagonian Andes in southern Chile that I’ve posted about numerous times (see all posts tagged with ‘Patagonia’ here). The first author was a fellow student who also did part of his graduate research on these strata.
I will post about the paper in more detail when I can find some time … but in the meantime, here is a photograph of the outcrops (which isn’t in the paper) to whet your appetite. Click on it to see a slightly bigger version.
As you can see, the quality of the exposure is exceptional — it is quite rare to get such clean exposures over hundreds of meters of stratigraphic thickness.
The Sierra Contreras, Tres Pasos Formation, southern Chile (© 2009 clasticdetritus.com)
To give you a sense of scale — the uppermost sandstone package is approximately 25 m (80 ft) thick.
Sea-Floor Sunday #48: Waterways around New York City
This week’s Sea-Floor Sunday highlights an article I saw a couple weeks ago in New York magazine called Secrets of the Deep. It’s a great piece talking about what lies beneath one of the busiest harbors in the world.
The article mentions various human-made ‘artifacts’ found in the Hudson and East rivers. The image below is a map showing multibeam bathymetry (red colors shallower, blue colors deeper) and location of features discussed in article.
credit: New York magazine - http://nymag.com/news/features/56609/
It’s an interesting article … check it out.
Geopuzzle (updated with answer)
Haven’t done one of these in a while.
This could be easy, might be difficult … I’m not sure — simply comment below explaining this photograph.
(© 2009 clasticdetritus.com)
If you happened to be there with me you are not allowed to answer :)
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UPDATE: This was a tough one. I was on a field trip last weekend and as soon as I saw this feature I instantly knew I’d make it a great geopuzzle.
A few of the commenters speculated about this being some kind of collapse feature. That is exactly what it is — but the part of the story that you might not have guessed is that the collapse happened since the 1860s. This is from the Black Diamond coal mine (inactive since the early 1900s) near Antioch, California. The coal seam was removed and the overlying sedimentary rocks collapsed into the space. The dark material is bits of pieces of the lignite coal left.
Even though I knew what this was when we came across it (as our guide pointed it out), I was amazed how similar it looked to other soft-sediment or local-collapse deformation features I’ve seen from the geologic record.
To see more photos of this mine, check out my Flickr set here.
Thanks for playing!
Papers I’m Reading – May 2009
Instead of a ‘papers I’m reading’ list — this is more accurately a ‘papers to read’ list. The first one is a classic that I haven’t read in years … I came across a well-worn photocopy version in one of my binders while looking for something else and decided I needed to re-read it.
- Parker, R.B., 1985, Buffers, energy storage, and the mode and tempo of geologic events: Geology, 13, 440-442. [link]
- Carter, R.M., 1988, The nature and evolution of deep-sea channel systems: Basin Research, 1, 41-54. [link]
- Metivier & Gauderner, 1999, Stability of output fluxes of large rivers in South and East Asia during last 2 million years: implications on floodplain processes: Basin Research, 11, 293-303. [link]
- Elliott, T., 2000, Megaflute erosion surfaces and the initiation of turbidite channels: Geology, 28, 119-122. [link]
- Mohrig et al., 2000, Interpreting avulsion process from ancient alluvial sequences: Guadalope-Matarranya system (northern Spain) and Wasatch Formation (western Colorado): GSA Bulletin, 112, 1787-1803. [link]
- Jerolmack & Mohrig, 2007, Conditions for branching in depositional rivers: Geology, 35, 463-466. doi: 10.1130/G23308A.1 [link]
- DeCelles et al., 2009, Cyclicity in Cordilleran orogenic systems: Nature Geoscience, 2, 251-257. doi: 10.1038/NGEO469 [link]
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See all the Papers-I’m-Reading lists here.
Note: The links above will likely take you to a subscription site; as a policy, I don’t e-mail PDF copies of papers to people (sorry).
RSS feeds for geoscience journals
Several months back, there were some posts going around summarizing RSS feed information for various geoscience journals (see Mel’s list from Ripples in Sand here; and see a post from Chris at Highly Allochthonous here). If you aren’t familiar with what an RSS feed is and why you should use them, check out this page.
Building on their information, I compiled the list below. Firstly, I wanted to find feeds to individual journals (not the topical feeds some publishers offer). I started with the list from my recent post about impact factors for sedimentary geology journals and added a few more as well. Secondly, please note that this list is not comprehensive — I am not including journals focused on petrology/mineralogy, volcanology, paleontology/paleobiology, geochemistry, and so on. I encourage others to compile RSS feed info for other Earth science journals (provide a link in the comment thread if you do so).
In the list below, the link goes to additional journal information (for reference) and the RSS feed address is written out fully next to it (so you can copy/paste it wherever you want). Journals are ordered alphabetically within each category.
General science:
- Nature — http://www.nature.com/nature/current_issue/rss/
- Science — http://www.sciencemag.org/rss/current.xml
General geology (journals that include multiple sub-disciplines):
- Earth-Science Reviews — http://rss.sciencedirect.com/publication/science/5802
- Earth & Science Planetary Letters (EPSL) — http://rss.sciencedirect.com/getMessage?/registrationId=GEBDGFBDHKBEOECFIEBKGJDDHIBIKIGEPWDLJKFEJB
- Geological Journal — http://www3.interscience.wiley.com/rss/journal/1903
- Geological Society of America (GSA) Bulletin –http://gsabulletin.gsapubs.org/rss/current.xml
- Geology — http://geology.gsapubs.org/rss/current.xml
- Geophysical Research Letters (GRL)^ — http://www.agu.org/pubs/rss/gl_rss.xml
- Journal of the Geological Society (Geological Society of London) — no RSS feed available*
- Journal of Geophysical Research (JGR) – Solid Earth^ — http://www.agu.org/pubs/rss/jb_rss.xml
- Nature Geoscience — http://www.nature.com/ngeo/current_issue/rss/
- Terra Nova –http://www3.interscience.wiley.com/rss/journal/118535585
- The Journal of Geology –http://www.journals.uchicago.edu/action/showFeed?ui=0&mi=0&ai=t4&jc=jg&type=etoc&feed=rss
Tectonics
- Tectonics^ — http://www.agu.org/pubs/rss/tc_rss.xml
- Tectonophysics — http://rss.sciencedirect.com/publication/science/5830
Sedimentary and marine geology:
- Basin Research –http://www3.interscience.wiley.com/rss/journal/118541711
- Facies — http://www.springerlink.com/content/110833/?sortorder=asc&export=rss
- Journal of Sedimentary Research (JSR) — no RSS feed available*
- Journal of Geophysical Research (JGR) – Earth Surface^ — http://www.agu.org/pubs/rss/gl_rss.xml
- Marine and Petroleum Geology — http://rss.sciencedirect.com/publication/science/5911
- Marine Geology — http://rss.sciencedirect.com/publication/science/5818
- Palaios — no RSS feed available*
- Palaeogeography, Palaeoclimatology, Palaeoecology — http://rss.sciencedirect.com/publication/science/5821
- Sedimentary Geology — http://rss.sciencedirect.com/getMessage?registrationId=IGDAIHDAJMDBQGEBKGDHILEJIPFHJKFJNYFILOJDIE
- Sedimentology — http://www3.interscience.wiley.com/rss/journal/118503415
Petroleum geology:
- American Association of Petroleum Geologists (AAPG) Bulletin — http://rss.aapg.org/bulletin.xml
- Journal of Petroleum Geology — http://www3.interscience.wiley.com/rss/journal/117977017
- Petroleum Geoscience — http://api.ingentaconnect.com/content/geol/pg/latest?format=rss
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UPDATE (5/20/09): I’ve updated the list above with feed info thanks to fellow blogger — see this post from The Lost Geologist with even more geoscience journal RSS feed information.
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* Or, maybe I couldn’t find it – if you know the feed address for these specific journals, comment below. If feeds don’t exist, then GeoScienceWorld (JSR, Journal of the Geological Society, Palaios), needs to get with the program and offer RSS feeds for the free content (titles and abstracts). E-mail alerts were fine a decade ago and may still work for some people, but I get far too many e-mails already — feeds clean all that up.
^ Go here to see a list of feeds for all AGU (American Geophysical Union) journals.
This week’s Friday Field Foto is from the foothills of the French Alps (not far from Nice).
As you all know I’m a turbidite connoisseur — today’s photo is from a rather famous turbidite formation called the Annot Sandstone (Eocene-Oligocene, or ~40-30 million yrs old). It is ‘famous’ because this is the locale where Arnold Bouma did his dissertation research in the late 1950s. The story is that while trying to correlate across covered/eroded sections of outcrop he started using the sedimentary structures in the beds themselves, which led to the recognition of a general repeating pattern. This pattern of vertical stacking of types of sedimentary structures became known as the Bouma Sequence.
plane-laminated and ripple-laminated sandstone, Eocene Annot Formation, France (© 2009 clasticdetritus.com)
The photo above is from the same section of rocks and nicely shows the plane-laminated (or Tb) part of the sequence in the lower part with the wavy- to cross-laminated (or Tc) division in the middle part of the photo. The boundary between Tb and Tc is very commonly gradational and, in some cases, alternates. At the top of the photo, the structureless sandstone is very likely the basal division (or Ta) of the next turbidite bed. The Ta division typically shows normal grading — I’ll refer you to a recent post over at Hindered Settling that nicely discusses the concept of normal grading.
It is important to note that the ideal Bouma sequence is just that — ideal. In many turbiditic sequences it can be difficult to find beds with the perfect stacking of these divisions. Over the decades, sedimentologists have come to appreciate many variations on the Bouma sequence as well as deposits that represent wholly different processes but are still lumped into what we call ‘turbidites’. In many guidebooks or papers, you might see well-developed Bouma sequences referred to as ‘classical’ turbidites.
If you are doing field work and come across sandstone beds with these sedimentary structures, make sure to describe them as objectively as you can (e.g., plane-laminations, ripple-laminations, normal grading, etc.). Then, make the interpretation that they are turbidites.
Happy Friday!
This week’s Sea-Floor Sunday should look familiar to those who get the journal Geology.
credit: Geological Society of America; Image created by: Alastair Graham, using ArcScene (click on image to go to source)
This is the cover for the May 2009 issue — and this image corresponds to this paper.
Here is the short blurb about what it is you are looking at:
Perspective view of multibeam swath bathymetry data from the Amundsen Sea embayment, showing streamlined landforms, scours, and channels generated at the bed of converging paleo-ice streams. The view is looking northeast from above Wright Island. See “Subglacial bedforms reveal complex basal regime in a zone of paleo-ice stream convergence, Amundsen Sea embayment, West Antarctica” by Larter et al., p. 411-414. (Bathymetry in this image also includes multibeam data obtained on the R/V Nathaniel B. Palmer during cruises supported NSF.
Very cool!
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Clastic Detritus 
