Accretionary Wedge #50: Field Camp / Trip Moments

Some bewildered field camp students learning how to use Brunton compasses. Western USA, Fall 2005.

Ron Schott recently reminded me that I am hosting September’s Accretionary Wedge geoblog carnival. Sorry for the late posting, but quite honestly I forgot that I was hosting this month! Fortunately, I’ve thought of a fun topic, and the deadlines for the wedge are somewhat fluid. I’ll make entries due on October 10th.

Here’s the topic:

Share a fun moment from geology field camp or a geology field trip. You can share a story, a picture, a song, a slogan, a page from your field notebook– anything you like!

I think we all have many fun moments from geology field camp and trips. Feel free to share more than one, if you want! Here’s a few field camp and trip moments which I shared on Georneys in the past:
The Cow Game
Field Animal Favorites
Ternary Personalities
How Not to Lose Wireless GPS Receivers
Beware the Jungle Raccoon
Chondrite Town

Nome, Alaska in Pictures: Part I

Rust and paint on a gas tank in Nome.

I haven’t done an “…in Pictures” post for awhile, and I have many, many photographs from Nome, Alaska to share with you. I just spent 2 months living and working in Nome, which is an unusual town filled with gold miners in the summer and sled dog racers in the winter. About 3,000 people call Nome home year round. No roads lead to Nome, so everything (people, cars, mining equipment, etc.) is brought in either by airplane or by boat. Because of this, nothing ever leaves Nome. Well, people do, but things (aside from gold, of course) rarely do. The yards of many of the houses in Nome are filled with years of discarded cars, equipment, tools, and so on. Various fields at the edges of town are piled with mounds of junk. I guess it’s just too expensive to remove worn-out items. At first, I found Nome overwhelming and a little bit scary. After a few weeks, however, Nome– piles of rusted junk and all– began to grow on me. While I’m happy to be back at my home base in Cape Town now, I can truly say that I enjoyed my two months in Nome.

Today I’m going to share some pictures from Nome. I took all of the pictures in this post during a walk on a rare sunny (well, overcast… but the sun poked through the clouds sometimes) day back in August. In future posts I’ll share some additional pictures from Nome. Enjoy!

Nome #1. Those are little gold dredge boats on the horizon.
Nome #2. Again, those are little gold dredge boats on the horizon.
Nome #3. Some houses and a wood stockpile.
Nome #4. More houses.
Nome #5. Seagulls and a sign.
Nome #6. Another view of some little gold dredge boats.
Nome #7. A closer view of some gold dredge boats.
Nome #8. The nicest house in Nome?
Nome #9. A bush plane flying over some houses.
Nome #10. A closer view of the bush plane.
Nome #11. Interestingly, many of the locals are Green Bay Packers fans.
Nome #12. Bible & Bookstore.
Nome #13. Another house.
Nome #14. An interestingly shaped house.
Nome #15. A sidewalk mermaid.
Nome #16. Little gold dredge boats everywhere.
Nome #17. Another close-up view of some gold dredge boats.
Nome #18. Some of the little gold dredge boats seem to barely float!
Nome #19. A little gold dredge boat with another little boat in tow.
Nome #20. An ominous sky over the little gold dredge boats.
Nome #21. Looking back towards town from the beach.
Nome #22. The Nome Trading Company.
Nome #23. Well, I bet you won't see this creative home decoration in Martha Stewart's "Living."
Nome #24. A crazy caravan and an American flag.
Nome #25. Abandoned mining equipment from one of Nome's previous gold rushes.
Nome #26. Gears and tundra flowers.
Nome #28. An old cement mixer truck.
Nome #29. More old gold mining equipment.
Nome #30. Gold dredging equipment, old and new.
Nome #31. Addressed to Nome.
Nome #32. An old Ford.
Nome #33. A painted gas tank.
Nome #34. Truck trailers.
Nome #35. Big Jim's Auto Repair.
Nome #37. Junk everywhere!
Nome #37. Beaver digger.
Nome #38. Containers.
Nome #39. Subway... and Nome's movie theater!
Nome #40. Nome's best restaurant (in my opinion, anyway): The Bering Sea!

Hope you enjoyed these pictures from Nome. I’ll share more soon.

Monday Geology Picture(s): Garnet Sands in Nome, Alaska

Gold-bearing garnet sands on Western Beach in Nome, Alaska, Summer 2012.
Gold-bearing garnet sands on Western Beach in Nome, Alaska, Summer 2012.

Above is a gorgeous beach sand picture for this week’s Monday Geology Picture. I took this picture a few weeks ago in Nome, Alaska after a summer storm. The beaches of Nome are rich in red garnet grains. The beaches of Nome are also very rich in grains of gold, and you can bet that if you pan some of the red garnet sand along the Nome beaches, you will find dozens of small flakes of gold. If you pan some of the more gravely beach material, you may even find yourself a gold nugget!

The beaches of Nome are always a rich red color, but after a storm the beaches look particularly red. This is because the storm waves remove some of the lighter beach sand grains (quartz and such) while leaving behind a lag of beautiful bright red garnet… and dark heavy minerals… and gold!

Here are two more pictures of the red garnet beach sands in Nome:

More red garnet sands along Western Beach in Nome, Alaska, Summer 2012. 
More red garnet sands– and beach cobbles– along Western Beach in Nome, Alaska, Summer 2012.

And here’s proof that if you pan some garnet sand from Nome, you will find gold:

Panned garnet sands from Western Beach in Nome, Alaska, Summer 2012. Note all the little gold glakes on the left side of the pan. Click to enlarge picture.

Gold panning is a gravity concentration process in which a large plastic pan and water are used to separate minerals according to their density. Gold is a very dense material (pure gold has a density of ~19.3 g / cm3), so gold will be sink to the bottom of the pan while much lighter sand grains are washed off during the panning process. Panning first removes the lightest sand grains such as quartz (density of ~2.7 g / cm3) and muscovite (density  of ~2.8 g / cm3) and leaves behind heavier grains such as garnet (density of ~3 to 4 g / cm3), magnetite (density of ~5.2 g / cm3), and ilmenite (density of ~4.7 g / cm3). Eventually, the panning process leaves behind a dark-colored, heavy mineral concentrate that is rich in gold!

Here I am with just such a concentrate from Western Beach in Nome:

Me, with a gold pan and a bag of gold-bearing heavy mineral concentrate in Nome, Alaska, Summer 2012. 

That’s an old gold dredge in the background of the above photo; I’ll write about the some of Nome’s old dredges in another post.

Plane Views: Anchorage to Nome

This is Part IV (the final part) of my series of “Plane View” pictures taken during my trip from Cape Town, South Africa to Nome, Alaska. Part I is here, and Part II is here, and Part III is here.

After we reached Anchorage, my husband and I had three nights to recover from jetlag (and do some work, kayaking, and shopping) before our flight up to Nome. Thus, we were rested and able to enjoy the views on the flight to Nome although cloud cover kept us from seeing the best views of Nome. Perhaps when we fly out next month the weather will be clearer, and we’ll be able to see more.

Enjoy the pictures! As usual, please feel free to comment on any interesting geological features which you observe.

Flying out of Anchorage:

To Nome #1.
To Nome #2.
To Nome #3.
To Nome #4.
To Nome #5.
To Nome #6.
To Nome #7.
To Nome #8.
To Nome #9.
To Nome #10.
To Nome #11.
To Nome #12.
To Nome #13.

Middle of Flight:

To Nome #14.
To Nome #15. A rainbow in the sky!

Flying into Nome:

To Nome #16.
To Nome #17.
To Nome #18.
To Nome #19. About to land!
To Nome #20. In Nome at last!!!

 

Plane Views: Minneapolis to Anchorage

This is Part III of my series of “Plane View” pictures taken during my trip from Cape Town, South Africa to Nome, Alaska. Part I is here, and Part II is here.

By this third flight, my husband and I were starting to become fairly tired. However, we managed to take some excellent pictures out the window anyway, particularly as we approached Anchorage. Enjoy! Feel free to comment on any interesting geology you see!

To Anchorage #1. Somewhere in the Dakotas, we think.
To Anchorage #2. Golden stream.
To Anchorage #3. A meandering stream flanked by oxbow lakes, sparkling golden in the late afternoon light.
To Anchorage #4. Are those kettle holes dotting the landscape?
To Anchorage #5. Kettle holes?
To Anchorage #6. Interesting river features.
To Anchorage #7. Another view of the meandering stream.
To Anchorage #8. ALASKA at last!!! So beautiful!
To Anchorage #9.
To Anchorage #10. A mountain peeking through the clouds.
To Anchorage #11. Surreal scenery.
To Anchorage #12. Snow-covered mountaintops.
To Anchorage #13.
To Anchorage #14.
To Anchorage #15.
To Anchorage #16. Just gorgeous!
To Anchorage #17. A braided river in the valley.
To Anchorage #18. Another view of the valley with the braided river.
To Anchorage #19. More gorgeousness.
To Anchorage #20. Approaching the city.
To Anchorage #21. Almost ready to land!

I’ll try to post Part IV (the last part) sometime in the next several days, work schedule and internet connectivity permitting.

Plane Views: Amsterdam to Minneapolis

This is Part II of my series of “Plane View” pictures taken during my trip from Cape Town, South Africa to Nome, Alaska. Part I is here.

After traveling from Cape Town to Amsterdam, my husband Jackie and I boarded a flight from Amsterdam to Minneapolis. Below are some pictures taken out the airplane window. For this second flight, Jackie and I pulled out our nice camera, so the image quality is much better than the Blackberry pictures I shared in Part I. Feel free to point out any interesting geological features you see in the pictures… and enjoy!

Pictures of Iceland:

Iceland #1.
Iceland #2.
Iceland #3.
Iceland #4.
Iceland #5.
Iceland #6.
Iceland #7.
Iceland #8.

Pictures of Greenland:

Greenland #1, showing the location where the next several pictures were taken.
Greenland #2.
Greenland #3.
Greenland #4.
Greenland #5.
Greenland #6.
Greenland #7.
Greenland #8.
Greenland #9.
Greenland #10.
Greenland #11.
Greenland #12.
Greenland #13.
Greenland #14.
Greenland #15.
Greenland #16.
Greenland #17.
Greenland #18.
Greenland #19.
Greenland #20.

Pictures of Northern Canada:

Canada #1, showing the location where the next several pictures were taken.
Canada #2, showing glacial features such a kettle holes.
Canada #3, more kettle holes.
Canada #4.
Canada #5, more kettle holes.
Canada #6, lines of kettle holes.

That’s all for now. I’ll share some pictures from my second and third flights as time and internet connectivity permit.

The Geology of Star Trek: The Next Generation Episode “Chain of Command, Part I”

Spelunking Starfleet officers!

Like my fellow geoblogger Jessica Ball, I wish that I could be a geologist on Star Trek. I can think of no better, more exciting job than traveling the universe as a geological researcher for the United Federation of Planets. Sign me up, Starfleet!

Maybe one day in my life– or in my children’s or grandchildren’s lives– there will be opportunities for Earth geologists to travel to other planets and planetary bodies. Already, there are hundreds (thousands?) of geologists who work in the exciting field of Planetary Geology. However, today planetary geologists primarily rely upon remote sensing, rovers (on Mars and Earth’s moon), and little bits of space rock that fall to Earth to understand the geology of other planets and planetary bodies. While several humans have walked on the moon, only one geologist (Harrison Schmidt) has walked on the moon.

A few years ago I became interested in Star Trek after watching a few episodes of The Next Generation with some friends in graduate school. Now my husband and I are hooked on Star Trek. We’re currently watching Season 6 of The Next Generation, and I’m also watching Season 2 of Deep Space Nine (so that I have something to watch when my husband is away. He’s forbidden me from watching TNG without him). I’m contemplating buying a Star Trek uniform costume and visiting a Star Trek convention. Any suggestions, for either the uniform or a convention? Are there ever Star Trek conventions in Africa? Also, my husband and I (and also our friend Mo, a fellow Star Trek fan) have already penciled in a visit in 2014/2015 to the Star Trek theme park currently being built in Jordan.

I like Star Trek for many reasons, one of which is the favorable light in which science is portrayed on the show and also the rational way in which science (even if it’s fake “Star Trek science”) is used an explanation for mysterious phenomena which occur on the show. However, the science on Star Trek is often not real science. That is, the scientific explanations on the show are sometimes inaccurate– or at least apply a bit of poetic license to a scientific fact or theory. Also, much of the show’s technology, such as teleportation and warp drive, is not currently scientifically feasible. I recently learned about a book written by Lawrence Krauss called The Physics of Star Trek (next in the queue on my Kindle reading list!) that goes into some of the physics shown on the show.

After I heard about Krauss’s book, I thought to myself: why not write about the geology of Star Trek? This is the first post in what may become a series of posts about the geology of Star Trek. In this post I am going to point out some of the geological inaccuracies of a particular episode, but I hope that these posts will not always be about nit-picking the scientific details. I hope that the geology of Star Trek, even if sometimes scientifically inaccurate, can inspire some young people (myself included, perhaps?) to learn more about planetary geology and geology in general.

I can imagine several topics of interest regarding the geology of Star Trek:

-Types of planets encountered on Star Trek

-Geology of non-Earth-like planets

-Terraforming planets for settlement

-Geoengineering of environment (atmosphere, climate, weather, soil, etc.) and of plate tectonics

-Diversion of meteoroids / comets / asteroids from impact with inhabited planets and planetary bodies

-Volcanic activity of Star Trek planets

-Best geologic lairs for Vulcans, Klingons, Romulans, Cardassians, and other Star Trek species

-Building stones seen/used on Star Trek

-Magnetic fields of Star Trek planets

-Atmospheres of Star Trek planets

-Geochemistry of Star Trek. If it hasn’t been done already, someone should really come up with a Star Trek periodic table. Which element names mentioned on the show are real and which are made up?

-Tools of Star Trek geologists (Do they just need tricorders? What geologic measurements can be made with a tricorder? Why didn’t I have a tricorder for my PhD thesis research?)

-Various mining operations shown in Star Trek

-What are those dilithium crystals made of, anyway?

Perhaps my blog readers can suggest additional topics?

Now that I’ve introduced “The Geology of Star Trek” series, let me move on to my first topic of discussion. In this post, I’d like to talk a little about the geology of a cave shown in the Star Trek: The Next Generation episode “Chain of Command, Part I.” In this episode, Captain Jean-Luc Picard,  Chief Medical Officer Beverly Crusher, and Lieutenant Worf are sent on a covert mission to the Cardassian planet Celtris III to destroy a biological weapons facility. The facility is supposedly located in a deep underground cave.  Decked out in black with various spy gear, Picard, Crusher, and Worf make their way through the cave to the supposed location of the weapons facility. When they arrive, they discover that there is no biological weapons facility. Rather, the intelligence about the supposed facility was leaked by the Cardassians as a trap to capture Picard. The episode ends with Picard being taken away by the Cardassians as Crusher and Worf escape.

Sneaking through the cave on Celtris III.

The overall plot of this particular Star Trek episode is excellent, but the geology of the cave on Celtris III is somewhat implausible. I suspect that many of the walls of the “cave” are artificial and part of a Hollywood sound stage set-up. Some views of the cave interior also seem to feature painted backgrounds or special effects. Fake and painted rocks aside, however, there are still some fundamental problems and inconsistences with the geology of the cave.

For example, after reaching a steep drop in the cave, Picard says, “We’ll have to rappel from here. This is sheer granite. We’ll have to use fusing pitons.”

"This is sheer granite. We'll have to use fusing pitons."

Granite caves are not unheard of, but they are somewhat unusual. Caves are most commonly formed as solutional caves in soft, easily dissolved and re-precipitated rocks such as limestone, dolomite, and halite. The re-precipitation of minerals such calcite forms speleothems, including stalagtites and stalagmites, that are commonly found in solutional caves. Granite is a very hard rock that is not easily dissolved and re-precipitated. Therefore, solutional caves are not going to form in granite, and granite caves are not going to contain significant speleothem precipitates. The most common type of cave that forms in granite is an erosional cave, a type of cave that forms when flowing water (a stream or possible seawater) erodes rock to form a cave.  Some granite caves also may form by seismic activity.

So far, I’m willing to buy that Picard, Crusher, and Worf are in a granite cave. A close-up shot of a fusing piton being inserted even makes the rock (or fake rock) look pretty similar to granite:

The rock looks granite-ish to me. Or maybe rhyolite-ish with phenocrysts.

However, the next few shots show that the “granite” cave has abundant speleothems, which would rarely (never?) occur in a granite cave! The big speleothems look much more similar to what would be seen in a classic limestone solutional cave:

Picard contemplates the cave, which now looks like a limestone cave!
Rapelling down a wall in the granite/limestone cave.

After Picard, Crusher, and Worf repel (500 meters, according to the dialogue) down the wall of the “granite” cave and continue walking along, they reach a solid wall and cannot progress any farther. Fortunately, Picard is able to tell with his tricorder that,  “There’s a lava tube beyond here [the wall] that runs for 75 meters, and it connects with another chamber. We need to get through here.”

Investigating the rock wall with tricorders.

Hang on a minute! Aren’t Picard, Crusher, and Worf supposed to be in a granite cave (that strangely resembles a limestone cave in some shots)? Lava tubes are a common type of cave, but they aren’t going to be found in a granite cave, and they are very unlikely to be found at 700 meters depth (in one of the early cave scenes Picard notes that the supposed weapons facility is located ~700 meters depth, and the lava tube seems to connect very close to the supposed weapons facility cavern).

For those of you who are not familair, let me explain a little bit about igneous rocks. Igneous rocks are rocks which form from molten material, which is called magma in the subsurface and lava on the Earth’s surface. There are two types of igneous rocks: plutonic rocks (which form in the subsurface from magma) and volcanic rocks (which form on Earth’s surface from lava). Granite is one type of plutonic igneous rock. A common volcanic rock is basalt.

Lava tubes are common primary caves, but they are found close to Earth’s surface, not at 700 meters depth! Furthermore, lava tubes may sometimes be connected to other lava tubes or types of volcanic primary caves, but they are rarely connected to extensive networks of caverns. Since granite is a plutonic rock and not a volcanic rock, it is impossible for a lava tube to form in granite.

To sum up, there are three geological issues with the cave featured in this Star Trek episode:

1. Granite caves are uncommon.

2. Granite caves do not generally contain speleothems such as stalagtites and stalagmites. These are generally a feature of solutional caves in rocks such as limestone.

3. Lave tubes are not found in granite caves and not found in caves at depth. This is because (a.) granite does not form from lava, and (b.) lava flows on Earth’s surface.

Bad geology aside, I do think that it’s pretty cool that Picard, Crusher, and Worf can map out the cave with their tricorders and that Worf can conveniently cut through a rock wall to the hidden lava (err… granite? limestone?) tube by using his phaser. Just check this out:

Phaser versus cave wall #1.
Phaser versus rock wall #2.
The "lava tube" revealed!
Crawling through the "lava tube."

If anyone has an extra tricorder and phaser lying around, could you please send them to me for my upcoming geologic fieldwork in Alaska? Thanks!

Monday Geology Picture(s): Duiker Footprints at Gnoem Gnoemskloof

Teeny tiny footprints, with hammer for scale.
Little duiker footprint!

When my husband and I visited Gnoem Gnoemskloof in the Robertson area of South Africa a little over a week ago, we noticed some teeny tiny footprints, shown above with a rock hammer for scale. We’re not animal footprint experts, but we suspect that these tiny footprints belong to the duiker, a little antelope which is found throughout sub-saharan Africa. Most likely, these are footprints of the common duiker.

I have yet to take a good picture of a duiker in the wild (these little antelope move quickly!), but here are a few pictures of duiker in a small zoo in Knysna, South Africa:

A little duiker taking a drink.
Another little duiker.
A little duiker house.
All nestled in the little house.

Aren’t these little duiker cute? I especially love their little houses!

The Geology of Gnoem Gnoemskloof near Robertson, Cape Fold Belt, South Africa

On our way to Gnoem Gnoemskloof!

Last weekend my geologist husband Jackie and I visited the Robertson area of South Africa. On Saturday morning we visited a lovely little place called “Gnoem Gnoemskloof” (pronounced like “Noom Noomskloof”) at the invitation of Francie, a woman who emailed me to ask if I could tell her more about the rocks on her family’s property. Jackie and I spent a couple of hours with Francie and her family looking at the various rocks on the property, which is nestled in the Breede River Valley.

The Breede River Valley is located in the Cape Fold Belt, and there’s a great description of the Breede River Valley’s geology (focused on how the geology affects vinticulture, but still a great article) located here. Jackie and I still need to take a look at a local geologic map, but we think that the sandstones exposed at Gnoem Gnoemskloof are part of the Cape Supergroup, specifically the Witteberg Group.

All of the rocks exposed at Gnoem Gnoemskloof are sandstones. If these sandstones do belong to the Witteberg Group as we suspect, then they are early Ordovician (490-439 million years) to early Carboniferous (363-290 million years)  in age. Originally deposited in a flat-lying, shallow marine environment, the sandstones were subsequently folded during the formation of the supercontinent Pangea (~300 million years ago). The folding is quite complex in places, leading to some beautiful scenery in the Robertson area.

Some of the beautifully folded sandstones at Gnoem Gnoemskloof.
Tilted and folded sandstones at Gnoem Gnoemskloof.
Sandstones at Gnoem Gnoemskloof... next to the fantastic swimming hole!
More sandstone terrain at Gnoem Gnoemskloof.

The sandstones exposed at Gnoem Gnoemskloof are fairly uniform. For the most part, they are comprised of pure quartz although in places they also contain a small amount of mica which makes them sparkly. One thing that surprised Francie and her family is the variety of colors found in the sandstone. The sandstone can be a white, slightly gray color (close to the original color of the sandstone) or a darker tan color or a rusty red color (caused by the oxidation of iron in the sandstone). The outside of the sandstone can also sometimes be dark black, probably due to surface weathering / precipitation of material similar to desert varnish.

Before Jackie and I visited, Francie and her family thought that perhaps the different colored rocks were different types of rocks. Jackie and I explained that all the rocks were the same type of rock: sandstone. Originally, most of the sandstones would have been similar in color (a white/gray color). However, post-depositional oxidation/reduction processes and weathering processes have changed the original color of many of the sandstones. Some of the sandstones also contain quartz veins, which formed when hot fluids circulated through the sandstones and re-precipitated some of the original quartz grains as quartz veins. Some sandstones contain dark black patches or nodules which are iron-rich concretions also formed during secondary alteration.

Here are some examples of the different colors found in the sandstones at Gnoem Gnoemskloof:

Sandstones of many colors #1.
Sandstones of many colors #2. You can see quartz veins (bright white) and iron-rich (black) bands in this picture.
Sandstones of many colors #3. Here you can see a rusty red, oxidized weathering zone and a lighter-colored, less-weathered interior.
Sandstones of many colors #4. The upper rock has black, iron-rich areas and the lower rock has a coarse (big crystals) quartz vein.
Sandstones of many colors #5. This sandstone contains several fine (small crystals) quartz veins.
Sandstones of many colors #6. This sandstone had a thin black coating on one side-- perhaps something similar to desert varnish?

I think the lesson to be learned from the above photos is to never identify a rock by its color– or at least not by its color alone. Many rocks, such as sandstones, come in several colors. Geologists must use several features– texture, morphology, grain size, hardness, reaction with acid, taste (yes, taste), and many others– to identify a rock. Color is one feature used to identify a rock– but only with caution since the colors of rocks and minerals often vary due to the presence of trace elements and can also be modified through weathering and reduction/oxidation processes.

Although the sandstones at Gnoem Gnoemskloof come in many colors and have also been folded and uplifted, some of the original sandstone features such as ripple marks, cross-bedding, and even trace fossils have been preserved in places.

An exposure of sandstone. Along this exposure we observed ripple marks and trace fossils.
Ripple marks, with hammer for scale.
Cross-bedding, with my handsome husband Jackie for scale.
Jackie explains cross-bedding to Francie's husband and the rest of us (out of the picture).
A closer view of some cross-bedding. Look at how the red color (from iron oxidation) makes the cross bedding stand out! Neat, isn't it?
Trace fossils, located about 2 meters away from the ripple marks shown above.

We found the trace fossils particularly interesting, but neither Jackie nor I are fossil experts. Therefore, I sent the fossil pictures through to fellow geoloblogger Tony Martin, an ichnologist who blogs at Life Traces of the Georgia Coast. Tony identified the trace fossils as, “Zoophycos ( ‘witchbroom’ pattern) and probably Scolicia (tube with meniscae).”

Here’s an annotated version of the picture above:

Trace fossils, with labels.

I asked Tony to write up a little something about the Zoophycos trace fossil, and here’s what he wrote:

An All-Too-Brief Diagnosis of Zoophycos

Anthony Martin, @Ichnologist

Zoophycos is a beautiful, complex trace fossil with a wide geologic range, from the Lower Cambrian Period to the Holocene Epoch. It serves as the namesake of the Zoophycos ichnofacies, an assemblage of invertebrate trace fossils that mostly represent sediment feeding in deeper, quiet-water marine environments. But this trace fossil also occurs in shallow-water (shelf) deposits from the Paleozoic Era. I’ve encountered it in Ordovician shallow-marine rocks of Ohio-Kentucky and Carboniferous prodelta rocks of Kentucky. So for it to be in Ordovician prodelta rocks of South Africa is probably not too unusual, but might be worthy of further investigation by ichnologists who work specifically with Zoophycos. (Surprisingly, it’s more than one person!)

How was Zoophycos made, and what made it? That’s been the subject of lots of discussion among ichnologists, but everyone agrees that it is a systematic feeding trace, in which its maker repeatedly probed into the sediment and shifted its position each time, making “lobes.” These lobes then overlap and spiral in one direction or another, making what some researchers have described as a “Chinese hat” arrangement. Because of its long geologic range, it obviously has not been made by a single species of animal, but rather reflects an identical behavior expressed by many species over the past 500+ million years. These trace fossils were most likely made by a marine worm, and the best candidates so far are sipunculids, also known as peanut worms.

Thanks for the information, Tony! Fascinating! If you’re ever in South Africa, we’ll have to take you down to Gnoem Gnoemskloof to have a look at the trace fossils in person.

Here’s a few more pictures of the trace fossils:

Another view of the trace fossils.
Yet another view of the trace fossils.
And yet another view of the trace fossils.

Francie, thanks so much for inviting us out to Gnoem Gnoemskloof! We had a lovely time checking out your beautiful property and your rocks. I hope that Jackie and I were able to help you better understand the geology of your property. We’ll have to come back in the summertime to take a dip in your swimming hole!

A Weekend of Rainbows

Rainbow Picture #1.

This past weekend my husband and I left our cosy flat in Cape Town, South Africa and spent three days in the winelands. We went down to the Robertson area, where we were married back in October 2011, and also the Franschhoek area (Franschhoek means “French Corner” in Afrikaans). Since it is currently winter here in the southern hemisphere, the weather was cold and rainy for much of the weekend. The sun did come out periodically, however, and when the sun came out, there were rainbows! We saw five or six rainbows over the course of the weekend, and I thought I’d share a few rainbow pictures with you here on Georneys. Enjoy!

Rainbow Picture #2.
Rainbow Picture #3.
Rainbow Picture #4.
Rainbow Picture #5.
Rainbow Picture #6.
Rainbow Picture #7.
Rainbow Picture #8.
Rainbow Picture #9.
Rainbow Picture #10.
Rainbow Picture #11.
Rainbow Picture #12.
Rainbow Picture #13.
Rainbow Picture #14.
Rainbow Picture #15.
Rainbow Picture #16.
Rainbow Picture #17.
Rainbow Picture #18.
Rainbow Picture #19.