Update on lab projects and notes from geomorph lab

Hi all,

This is Gaby writing again, it has been a while since my last post. Since the beginning of the semester, the lab group has run quite a few of the samples that Dom and I are working on. In fact, I think we have less than 10 samples to go, which is pretty exciting. Another good news is that the samples that the team collected in China this January arrived today! We are going to be pretty busy this spring with all the projects.

So, what are the next steps after running the samples for our watershed? Well, after inputting the first wave of data into our excel sheets (excel is incredibly useful!), we need to record the energy peak information to make sure all is going well, and that the channel that the detector has assigned to particular energies is not moving around and giving us misleading results. We want to make sure that we are always measuring the right “spot” or the right energy peak, so that results are more consistent, but also it makes it easier when subtracting background noise from the raw data. The step after this one would be to learn how to use a software called Angle, which helps us calculate further corrections that regard the volume and shape of the sample (more on this when we start using it).

Since I’m taking the geomorphology class this semester, there have been a lot of interesting connections that have occurred these past weeks between our work at lab and the class. One of the most basic but important concepts that I had an interesting time working through is that soils are not just simply deposited in sedimentary layers. This might seem pretty basic, but in geology there is strong emphasis on the idea that newer stuff deposits on top and that things are in chronological layers, with the deeper stuff at the bottom.

Soils do not fit this model very well. In fact, soils can be easily deposited or eroded, and they also can form “from the bottom” of the soil horizon, adding new soil that won’t necessarily receive radionuclides if it is deep enough. Besides all this ways soils can be moved around, there are also processes of bioturbation and other types of mixing that also conflict with the idea of chronological deposition. Just the fact that the “soils” are on top of each other is not an assurance about how the landscape formed. Like I said before, this might seem pretty basic, but realizing this did shatter a lot of my assumptions about landscapes. From now on I’ll be having a more critical mind on both the work that I do and the papers we read for lab.

Looking forward more connections and findings this spring semester, write to you soon,

Gaby

Summary of “Sediment accumulation determined with Pb-210 geochronology for Strickland River flood Plains, Papua New Guinea”

In this 2005 paper, Rolf Aalto and William Dietrich give a fascinating introduction to their fieldwork on the Strickland River flood plains in Papua New Guinea. This paper focuses on the timing and rate of sediment accumulation in the river. Most of the paper describes the Pb-210 geochronology methods they use to date sediment accumulation. The experiment involves a dating approach this team of scientists have used more than once called CIRCAUS (constant initial river-reach clay activity). This method starts by taking 8-20 measurements of clay-normalized excess Pb-210 activity and many depths in each core .

Aalto and Dietrich use clay normalized pb-210 activity because clay preferentially absorbs mobile Pb-210. They are then able to deduce how much of the pb-210 activity is caused by meteoric rain out and soil radon decay. This allows them to exclusively use mobile pb-210 to measure the rate and timing of sediment accumulation. At the time this paper was written, the two writers had only analyzed 36 of about 200 cores taken from diverse locations in the floodplains. From the 36 cores the analyzed, the authors saw that most of the floodplain has received little to no accumulation over the past 100 years. This is most clearly represented in figure 3, which shows two graphs of DPM/G as a function of Depth (cm) and % Abundance (clay and sand ).

 Although one chart is for a terrace well above the floodplain and one is for a core taken from the flood plain, neither shows significant sediment accumulation. In the future, Aalto and Dietrich plan to expand upon their preliminary findings with data from more cores and a better understanding of the way that floods affect their geochronology procedures .

Hotel standards and driving in China

I promised this post ages ago and have now been back in the US for over a week. Sorry.

Quickly:

Nearly 10 years ago, during my first year in graduate school, my mom and I went on a trip for her 50th birthday. We went to Kunming, Dali, Lijiang, and Tiger Leaping Gorge, all in Yunnan, China. It was my first trip to Yunnan. I told Mom she could only go with me if she promised to travel "my way". I had fantasized about backpacking around China and meeting cool people and I didn't want to be hampered by a mother insisting on staying in fancy hotels. So we each had a small backpack (you can see pictures of mine in our field work photos from January - it's the blue and black one) and took a flight from Shenzhen airport to Kunming. We stayed in a youth hostel and bought train tickets (only soft sleepers available, darn it). We bicycled around Kunming. We stayed in hotels where beds cost 10 RMB (about $1.25 at the time) and I refused to upgrade to rooms with beds for 15 RMB. I wouldn't let Mom hire a horse to carry her or her stuff on the hike, even though I now realize she was suffering from altitude sickness... we were at elevations close to 10,000 ft.

On this trip to China, Yue found us the fanciest hotel she could in most towns we stayed in (not Dali or Kunming, but everywhere else). We stayed in hotels with breakfast buffets that sometimes even had western food like cereal, a waffle bar, and an omelet bar. One hotel had rose petals in the toilet and a bathtub in the bathroom. I think hotels averaged about 250 RMB (about $45) a room. We would never dream of staying in rooms with shared bathrooms or in dorms.

How my standards have changed!

Another note I promised:

It's amazing how quickly I remember how to drive in China. Honking on every turn, passing whenever the corner is less blind, slamming on brakes when you see traffic cameras that will catch you speeding (but I did get a speeding ticket and a parking ticket anyway). I always worry that I'll forget how to drive in the US when I get back, but I seem to have done ok. The places we were driving in Yunnan, especially the main east-west highway from Kunming towards the Myanmar border, seem to be particularly prone to accidents, so there were graphic signs on the road about what happens at different driving speeds. Burned and crashed cars were on pedestals on the side of the road as a warning. One had inflatable feet and legs dangling out of it. I only had two close calls, one of them on my 3rd to last day of driving. But they still scare me. The last thing I need is to have me and possibly a student in a hospital in rural Yunnan. I have to admit that towards the end of my nearly 6000 km of driving (in under 3 weeks), I was starting to get a little wigged out. Colby needs a mom and the new baby needs to be born and to have a mom. I was happy to return the rental car. And I'm happy to report that I took a few cab rides in Chengdu and Shanghai and survived them fine, and, more importantly, I remembered that one can't pass on blind corners in the US and you shouldn't honk on every corner or each time you pass.