Old Trails: Hiking Up The Tufa

Hotel-Sized Tuffa, Namibia

We pulled up to the farmyard and stopped at the fence causing the cloud of dust to catch up and swirl past the gate towards the house. We got out, research permit from the Namibian Geologic Survey in hand, walked to the fence and waited. After a couple minutes passed a white farmer with a shaven head and sporty sunglasses stepped out of the house and approached us. We explained we were geologists from McGill University in Canada and asked permission to hike to the tufa, pointing across the graded dirt road which acted as Namibia’s highway system. I don’t remember the farmer saying much, if anything. He nodded, and went back into the farm house.

Recently, I started the gargantuan task of reorganizing and backing up all of my photos. This led me to dig through some archives and to revisit photos that I have not shared with many people. When we visited this tufa I had not yet been introduced to the sport of rock climbing. Looking at these tufa photos now, I see lines, unclimbed, begging for someone to clean and send. We didn’t climb the tufa, we hiked around. Here are some photos from that hike.

Hking through the grass to the tuffa.

After stopping at the farmhouse we pulled off the highway. Christie, my advisor, insisted that she needed a nap and waved us towards the tufffa while reclining the driver’s seat. We crossed the wire fence and made our way into the waist high grass. That two hundred meter walk through the grass was one of the most stressful moments of my life. There are snakes in Namibia. Pofadders, Cape Cobra, Black Cobra, and Black Mambas frequent my field area. At least when we’re out on the hill slopes there is less grass and we can see where we are stepping. Tanya, Ben, and I were all nervous and let out big sighs when we exited the high grass.

Namibian waterfall!

The tufa was gorgeous, huge, and loomed overhead. Yellow-green slim covered wet rock where water dripped down. A little waterfall ran sprinkled and slid over the tufa, collected in a pond, and trickled away in a stream that disappeared into the desert.

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We stepped to hike around and up the tufa where we got a special treat. Diamictite. B-E-A-utifully deformed diamictite. Diamictite is a rock that is a mix of rock clasts in a muddy matrix. These diamictites had since been deformed, shown by the elongate stretched, clasts.

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We turned and continued upward, following black plastic pipes that ran from some unseen spring above us.

Hiking up.

The hiking was steep, but not strenuous. Before we knew it the incline shoaled and we began topping out over the tufa. The top was like a geologist’s dream. A folded cap-carbonate could be seen on the mountainside framing the valley before us.

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We paused to look back towards the car, where our professor lazily dosed, probably dreaming of pseudotachylyte and fault gouge.

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Our tufa foray wasn’t over yet, we followed the stream that had built this tufa up. It takes time to build a deposit like this. Calcium carbonate precipitates from the water. We saw breccias too. Head-sized, angular clasts of limestone that had once been shot down the stream, maybe during a rainstorm, only to now be cemented in the tufa.

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Outside of the stream we spotted more folded limestone.

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The breccias become the tuffa, cemented in the streambed. Other rocks, with the power of water pushing them forward, polish and erode the surface of the cement. Ponds between trickling streams form. Desert life revolves around water. Where it is abundant so is life and green.

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Big tadpoles swam in the ponds we passed. I saw something unexpected in the desert: a bullfrog, quietly crouched near submerged rocks.

Namibian bullfrog

What other treasures would we find hidden in the hills? The only thing to do was follow the water.

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Finally we reached a point where the stream cut into rocks. To continue following it we had to leave it for higher ground. Unfortunately we hadn’t come prepared for canyoneering on this hike. Ahead and below us we caught glimpses of caves and pools hidden in tufa slot canyons.

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We ended the hike at this crystal blue pool. The water looked amazing, but strange yellow algae covered the surface of every rock below the water. Swarms of black water bugs oscillated in the turquoises liquid. We tossed a small rock in and watched as they scattered to the edges of the pool, then swam back into pulsing mosh pit.

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The pools were gorgeous, but so were the rocks. I’ve always been fascinated by structures in rocks, whether tectonic or diagenetic in origin. The limestone structures influenced their surficial weathering and thus the growth of lichen.

Limestone structures

 

Time to head back. Christie had sent us up here to check out the tuffa and examine the diamictite, but we’d all become mesmerized by the pools and the life around them.

 

 

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I don’t remember which way we came down from the tufa. Nor do I recall if we trod through the waist-high grass or followed the stream to the road. I think at that point I was overwhelmed by the beauty of a little desert treasure.

 

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What’s in my in the field photo kit?

 

Self portrait via Brunton
Self portrait via Brunton

Field sciences such as geology, biology, anthropology, paleontology rely heavily on photographs to present evidence and convey the story that in the geologists case, is read and interpreted from the outcrop. Nowadays the camera is just as important as the hammer in the geologist’s toolkit.

In terms of cameras there are so many choices for what tools to take into the field. No set up is necessarily better than another… “the best camera is the one that’s with you”. I’d like to share with you the tools I bring into the field.

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Camera – Nikon D7000
Like every photographer just starting out, I had to make a decision on what brand to go with. I had long discussions with my dad, also a photographer about what camera to start with. Well, my dad is a Canon guy, but my grandfather was a Nikon guy. As a scientist that didn’t really get me closer to making a decision.

My dad and I researched the different camera packages on sale, some Nikon some Canon. When I had the models narrowed down I started digging into the technical specs. I primarily used the website Digital Photography Preview to dig into details. I also recommend Ken Rockwell’s camera and lens reviews.Two finalists remained, a Canon and the Nikon D7000.

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I decided to go with the D7000 because it had a magnesium-alloy body whereas the Canon had a plastic body. I wanted a camera that could stand up to the moderate to heavy hiking and traverses involved with field geology. The downside is that protection come with some added weight. Plus it came packaged with a great lens…

Lens – Nikon 18-200mm VR II AF-S Zoom Nikor ED, takes 72mm filters
This lens is a workhorse. I absolutely love it. Yes it is heavy, but the wide – telephoto range means that you only carry one lens, so no changing out lenses. The 18mm isn’t quite as wide as single purpose wide angle lenses, but with the help of photo stitching software it is possible to make some great panoramas and landscapes. On the other side of the range, the telephoto is extremely useful for getting close to the outcrop details. And for spontaneous portrait photography of animals and field assistants.

As for the lens hood. I almost never have it on, I keep it in my bag in case of rain.

Dolomitization front through interbedded limestone and shale
Dolomitization front through interbedded limestone and shale

Lens Filter
Always use a lens filter. The cost is small compared to the cost of the lens. I recently switched from the Nikon clear filter, which has gotten quite beat over three years, to a UV filter. Haven’t had too much of a chance to use it so I’ll report back on any differences.
Battery
I take two Nikon EN-EL15 batteries into the field with me. Always good to have a backup. I’ve switched out either battery for three years and they still hold a good charge.

Lens wipes

I carry a handful of these for keeping the lens clean. I travel to dusty, sandy, dirty places. These are a must to get clean photos.

Memory Card
These have gotten so cheap that it really is ridiculous. There’s no excuse for running out of pictures on your camera. I use two 16 GB in my D7000. If I’m out for a very long time the second SD slot is overflow. In other situations the second SD slot acts as a backup. I take that SD card out and keep it hidden away from the camera in case my camera is stolen.

I also recently got a little usb-miniSD reader so I can transfer photos from my camera to my phone. So I carry a couple miniSD with SD adapters now too.

Slickenlines on the Naukluft Thrust
Slickenlines on the Naukluft Thrust

Case
Get a case that will protect your camera and lens when you’re on the move. Just get one that fits your set up. I use a Lowepro Toploader Zoom 50 AW. Don’t bother with the strap, it broke pretty fast for me. I keep it at the top of my backpack for quick access. Otherwise my camera is on my neck or shoulder.

Strap
I use the standard Nikon strap that came with my camera. It is getting worn down so I’ll likely replace it soon.

Parting thoughts
Again, there is no right answer in terms of cameras and gear for the field. What suits me might not suit the next geologist.

What camera set up is in your field kit? Let us know in the comments!

Guest Post: The Pellaberg Traverse

Today’s post is a little campfire story from my friend Ben Melosh. Ben is a fellow Californian working here at McGill with Christie Rowe studying brecciation and earthquake processes. Check out his personal site HERE. Without further ado, here’s Ben.

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We broke camp late and headed toward the long ridge. Our basecamp was along the abandoned mine road that led to the boarder past the game camps of Pellaburg. Just the night before, deep ground-shaking footsteps had silenced us, stealing a toast from our lips. In the dark imagination surrounding our small fire, what could have been a Zebra turned into a Rhinoceros pounding over scree just out of sight. The local farm hands had told us there were no Rhinos here, just in the surrounding game parks where they were harried by rich American hunters. They said that the game parks were all fenced off.

By the time evening came again our packs were heavy, but not with food, our food was gone, our water low. We carried rocks now in their place, rocks that tell an ancient story of struggle in the deep earth. The sun was at the horizon throwing shadows behind every stone. We guessed at an hour of dusk and then an hour of dark to carry our burden back to the truck. This was not going to be a hike for people who like to talk about hiking. I looked at Louis. My field partners’ loaded pack slipped from his shoulder and he caught it on his broken arm as he set it down. He quietly repeated the word: “ouch”. You can learn a lot about a person in the bush; Louis was tough. We were going to make it back.

We headed north up the largest ridge, from there we would just have to hike the ridge top to the west until we cut again toward the north, dropping partway down the ridge to a saddle were we had set basecamp. Simple enough. The steepest part of the hike came first and was the easiest. The sunset cast long African rays through purple-blue clouds. We reached the ridge crest as the sky turned dark purple-gray and a lone quiver tree silhouetted black against the rising ecliptic. The moon was a sliver. We took a moment to enjoy our progress and drank our remaining water; on the map it was smooth sailing from here on out.
Louis’ long legs seemed to gracefully hover over each stone and bush as we stepped from dusk to dark. It took more and more time and effort to place each footstep. In the dark the sharp boulders and loose scree became indiscernible from the surrounding hill slope save for the halo of our headlamps. And we had somehow lost the ridge. I secretly hoped my pack was heavier than Louis’, as an excuse for slowly falling further behind. But I knew that my pack was not heavier; Louis was tougher. Side slopping westward in the total dark, we could barely make-out the faint hint of the ridge crest way above us to our left. To our right was a deep ravine. Blackness.
Then we spied it, a faint white-silver glimmer in the distance, much further below us and off to the northwest, it was the truck. We regrouped, and started to doubt ourselves, staring intently into the darkness where the faint and occasional glimmer would appear. It was in the correct direction, at about the correct distance and some of these hill slopes looked familiar. Plus we had been hiking for about two hours; figuring it must be the truck we started down.
When we hit the game fence we knew we were lost. There wasn’t supposed to be a fence, we had planned to backtrack our course of two days prior and we had never crossed a fence. Out here a fence means game park. It sunk in fast, we were on the wrong hill and that glimmer of white-silver hope in the distance was not the truck. We had no choice but to follow the fence back up, back up to the ridge we should never have left. When the fence crossed over a cliff we had no choice but to throw our packs and crawl under, into the game park. We continued our way toward the ridge in what we hoped was the final up hill push, the weight of our packs and our pace now the least of our concerns.
When we reached the ridge top we were tired, thirsty, and starting to get cold. The wind blew hard and our headlamps cast narrow beams and broad shadows behind the low shrubs on the lunar sand blown crest. When we laid down our packs I was worried we would not be able to lift them again, although the prospect of sleeping in the park was not appealing.
Then I remembered, of course, I had waypointed the truck with my GPS two days before. I had made a habit of doing this in previous years, just for this occasion, but had almost forgot when it mattered. I flipped through my notebook and fired up the handheld GPS unit. I could feel the relief lifting our shoulders.
With the GPS running it still took us about another hour before we knew we were close. When we finally cleared the last hill and turned north less than half a kilometer from the waypoint, we still could not see the truck. It was pitch black and clouds had blown over the sliver moon. The final descent to the truck was much steeper in the dark than we remembered. We could not see the truck until we were within 20 meters and her beautiful license plate shone back at us.
After collapsing into our bags in the haze before sleep I realized that although we had crossed into the game park, we never crossed out. Footsteps.

Bomb-proof sample packing

Geologists travel near and far in search of rocks. We measure sedimentary bed dip, record structural data, and collect samples. Lots of samples. This summer during my Namibian field season I collected 70.3 kg of rock samples (which is considered a light load), some small some large. The geologist is then faced with the problem of getting the rocks back safely to our home institution. Partly this is running around town acquiring the necessary export and shipping permits. The other part is packing the samples to ship. Geologists all have their own methods. I would like to share mine. I was indocturated with the CRowe method of sample shipping.

Here we’ll be packing our samples in used paint buckets and securing them with a silicon foam.

Materials and Tools Needed

Materials:

  • Large paint buckets (used can be acquired for free or cheap. New is $$) with lids
  • Black heavy duty garbage bags
  • PU-Foam (silicon foam)
  • Duct-tape

Tools:

  • Hammer

How to pack your samples

I’m assuming you have already placed your samples in sample bags and written sample name, ect on the bag. I like to secure that bag with duct-tape to keep the samples from moving within its bag. 


  1. Place the sample in a black heavy duty garbage bag. Only the heavy duty black bags will work in the case. Lesser bags will be dissolved by the PU-Foam. Several smaller samples may be placed together in the same bag. I usually pack no more than three samples in the same trash bag. Close of this bag and wrap excess bag around itself. Place it in the bottom of the paint bucket. Repeat until you have a layer of rocks on the bottom of the bucket.

  2.  Shake shake shake that PU-Foam can. Install the applicator straw. Be very careful to not get any foam on you when packing samples. It’s hell to clean off. The only effective method of removal seems to be acetone. Some PU-Foam cans come with plastic gloves, but these can be annoying to use, so best just be careful. Apply the PU-Foam to gaps between the samples and the bucket wall. The foam will expand, but no reason not to apply liberally.

      

       

    1. Wait for the foam to set. The PU-Foam cans usually recommend waiting 2 hours or more. This is a tad long, but the more time the foam has to set before adding the next layer the better. If the foam is not allowed to set fully, it will morph into a sticky ooze. For this reason I will pack multiple buckets at the same time.

    2. Now that the layer has set. Repeat steps 1-3 until the bucket is full. Don’t forget to let the foam set between layers. Relax, have a beer while you wait.

    3. Now we’re going to seal up the bucket. Slap the lid on and use a hammer to bang down the lid’s side tabs. Be sure the lid is totally secure and doesn’t spin. Finish off the bucket by going around the lid with duct tape.

    How do you pack your samples for shipping? Is this too extreme? 

    Rock n Roll fault rocks: a pictorial journey aka my Namibian field season

    So my last post was a tiny tiny update. I should write more about what I’ve been up to the past month and a half. First off, this has been an incredible adventure. Namibia is amazing. This was my second time to Africa (South Africa and Namibia). I’m currently living in the Geo department flat at UCT. Thank you to the department staff, and Tanya and Jacq for helping Ben and I get settled.

    EDIT: Click any of the pictures below for a larger view!

    I know, I know, you want to see rocks. Bear with me. Let me give you some context.
    So where in Namibia was I? Where the hell is Namibia!?

    Let’s zoom in:
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    Naukluft Nappe Complex
    That’s about 200km South-Southeast of the capital city of Windhoek as the crow flies. 

    The Naukluft Nappe Complex is a thrust fault system associated with the Damara Orogen (~550Ma) that emplaced meta-sedimentary rocks in a roughly Southeast vergence on undeformed basin sediments. This area was originally studied by two German geologists, Henno Martin and Herrmann Korn, in the 1930s. These two geologists would later live two years in the Namib desert hiding (and mapping!) during World War 2 (blag post on that coming soon). They divided the complex into three different nappes, though more recent mapping has established five nappes. Korn and Martin also made the observation of a fault rock they describe as the “Unconformity Dolomite”. You know how geologists love to name stuff. First it was “Unconformity Dolomite”, then other authors called it “Lubricating Layer”, then other authors called it “Sole Dolomite”. From now on let’s agree to stick with the sole dolomite convention.

    Carrying on, this sole dolomite is the a layer of rock that separates the footwall sediments, blue limestone and shale, from the hanging wall, which is a charlie foxtrot of dolostone, quartzites, and shales. Want a photo of what this thrust looks like? Check out the header for this blog! Oh, you’re too lazy to scroll back up? Okay, here you go:

    Naukluft Thrust

    and at another location:

    Naukluft Thrust

    Did you spot the fault yet?

    I have so many pictures of this thing it is ridiculous. Tons of panorama shots too. Sadly, the GigaPan uploader can’t get through the UCT firewall, so we’re all going to have to wait until I’m back in Montreal to see those panoramas. It’ll be worth the wait. I’m getting ahead of myself.

    So what does this sole dolomite look like? It’s the brown-tan bed on the blue limestone in the above photos, but let’s move a little closer…

    Ben (Dr. Choff) for scale

    The limestone at the fault margin is mylonitized. Enough teasing, let’s look at the rock.

    Slicks!

    As you can see there is a foliated zone of dolomite at the fault surface. How about that rock above it though? That’s called “Gritty Dolomite.” It is a “cataclasite-like” fault rock that has dolomite phenocrysts, lithics, and silica. It looks like this:

    Gritty dolomite with silica banding.

    But sometimes it looks like this:

    Discrete gritty dolomite layer between sole dolomite (below) and a dolomite breccia (above).

    Or even this:

    Uhm, what? Laminated and folded (flow-folds?) gritty dolomite. Some silica banding.

    But sometimes it does this:

    Footwall limestone clasts in a gritty dolomite / sole dolomite breccia. A brown silica cortex surrounds footwall clasts.

    And how about up on the ridge (picture from this blog’s header and picture #2)… BAM!

    That is a RocknRoll breccia if I’ve ever seen one.

    Sometimes the gritty dolomite will inject upsection/downsection off of the fault, sometimes looking like this, often found with neocrystallized dolomite, sometimes doubly-terminating neocrystalline quartz on the surface:

    This rock is from part of a clastic gritty dolomite injection.

    And these photos are only on the eastern side of the nappe. Okay, okay, so WHAT were we doing out there? We were mapping this fault with a pair of these:

    Ben desires more satellites.

    The Trimble GeoXH. We set one up as a base station. The other is a rover. We walked the fault, making observations, taking measurements, ect. Once home I load the rover file with the corresponding base station file into the Trimble TerraSync software and presto! Centimeter GPS accuracy! As a first order question, I’ll be looking at how the geometry of the basal fault relates to the type of fault rock observed, injections, and make interpolations of the fault surface.

    In the eastern side of the Nappe typical fault dip is betwee 15-25 degrees, but varies widely. Now on the West side…

    Tsams Ost locality

    Can you spot the fault? Hmm… that looks a bit different. Typical fault dip here is ~3 degrees. The foot wall is typically blue shales, and there is no gritty dolomite to be found. We do observe the occasional footwall shale injecting up into sole dolomite…

    Footwall shale injecting up into sole dolomite.

    There’s also some fantastic folding in the hanging wall.

    Hanging wall folds.

    I feel like I could continue on and on posting pictures, so I’m going to force myself to stop. I’ll put up a gallery of photos on my Google+ page in the near future. I’m incredibly eager to get back to Montreal to look at the GPS data and start piecing this puzzle together.

    Special thanks to Ben Mapani for his invaluable assistance and advice. Thanks to Ben Melosh, Jodie Miller, Clint Isaacs, Rangers of Tsams Ost, and my advisor Christie Rowe. An extreme thank you goes out to the Naukluft 9 park staff for their generous hospitality and assisting with charging of our GPS batteries.

    Desert graffiti. 

    Back on the grid

    I’ve returned from my field work in Namibia. Currently I am at UCT where I will be doing SEM work,  sample prep and writing. Expect updates in the future + tons of field photos. Until then…

    Naukluft Thrust, Namibia

    The simple things

    We’re prepping to leave for South Africa and Namibia. I’m pretty much in full panic mode trying to get everything ready for launch.

    It’s good to stop and appreciate the simple things in life… such as successfully extracting data from your differential GPS system and viewing the test path on Google Earth.