African Sands

backstory African sands Pieter Vermeesch enjoyed training for a marathon in an empty two-dimensional space, with his eyes closed, in-between sampling aeolian dunes in the Namib Sand Sea.

■■ What was the objective of the work? mining activities. I ended up collecting the We wanted to measure the average residence sample under the bridge in the no man’s time of sand grains in the Namib Sand Sea, land between the two countries with the but the results of this study actually exceeded permission of the friendly South African my own expectations. In my proposal for border guards. funding, I had included a so-called ‘banana plot’, a schematic diagram with predicted ■■ any encounters with dangerous results. The actual measurements fitted these animals? predictions almost exactly. It is a rare pleasure No, but while discussing the dangers of to see this happen in geomorphology! doing desert field work in Namibia, my field companion Giles Wiggs told me a chilling ■■ Why did you choose this location? story. Climbing a dune in the Kalahari desert The Namib Sand Sea is a unique natural to survey the crestal movement, on his own laboratory for the study of aeolian processes, and with no-one else knowing where he was, for two reasons. First, sediment is derived Giles came across two lionesses sitting under from a single source, the Orange River at the a tree opposite, staring at him. He gently and southern boundary of Namibia, and the winds very slowly backed down and kept very low (and therefore the sand transport) occur in a so the crest of the dune rose up between him constant northward direction. This makes the and the lions. With their heads craning up to boundary conditions less complex than those get a better view as he slowly disappeared, he of most other deserts. Second, Namibia is a ran like the clappers 300 m back to the car. peaceful country and the Namib Sand Sea is easily accessible in contrast to, for example, ■■ What was your personal highlight? most sand seas in the Sahara. I was training for a marathon during the expedition. Running in the desert is a ■■ What sort of samples were you after? wonderful experience. Back home, I am I collected 12 samples of aeolian sand at the constrained to running on one-dimensional crests of large dunes, all around the edges trails, but the desert (or at least the interdune of the sand sea, plus one sample of river area) is a two-dimensional space in which I sand from the mouth of the Orange River, could just close my eyes and run without fear on the border of Namibia and South Africa. of hitting any obstacles. On return to the United Kingdom, we used bromoform to separate the light minerals ■■ How did you get the samples back? from the dense ones. Zircon in the dense I brought some 50 kg worth of samples fraction was dated using the U–Pb method, back to Windhoek airport, for which the and quartz in the light fraction was dated with airline wanted to charge me a ridiculous cosmogenic nuclides. $2,000 surcharge. Fortunately, I managed to convince one of the airline staff to let the ■■ Did you encounter any difficulties? samples through for a fraction of that price — It was not easy to get the Orange River cash paid in the men’s room. These are the samples. I first tried to get to Oranjemund advantages to working in Africa. through the Sperrgebiet diamond mining area, but was stopped at a checkpoint not far ■■ any ideas for future research projects? from Rosh Pinah for lack of a permit. I then During the trip, we encountered a German had to make a 500-km desert guide taking tourists from Luderitz at detour to Alexander the southern end of the sand sea to Walvis Bay in South Africa Bay in the north, straight through the heart of s through Vioolsdrif, the desert. I would like to return to Namibia GG only to discover to collect samples along that route, to find out

that both the whether the sand sea has been continuously Giles Wi Namibian and or episodically active. the South African Top of the dune. To avoid possible sampling bias, sides of the border This is the Backstory to the paper by all aeolian samples were collected on the summits were off limits P. Vermeesch and colleagues, published on of large dunes, which involved climbing up to because of diamond page 862 of this issue. 200 m in the soft sand.

876 nature geoscience | VOL 3 | DECEMBER 2010 | www.nature.com/naturegeoscience