Ancient mud from the high Andes

4th July – Dispatch from the Andes
Thanks in large part to Matt, an undergraduate from Pacific Lutheran University in Washington, we now have more than sixty samples for surface-exposure dating. This is no easy feat, for collecting these samples requires a great deal of hammering on granite boulders with nothing more than a hammer and chisel. There are other ways of doing it, such as using small explosive charges, rock saws, or splitting wedges, but we find that good old-fashioned hammering is by far the safest way. I say ‘we’ but really this means Matt. He has a gift for removing large amounts of rock, be it a soft shale or the hardest quartzite. And best of all, he doesn´t complain. So in all, we have sixty four samples from the Aricoma region, from moraines of all ages. In addition to the hammering, the process includes detailed descriptions of each boulder and measurement of location, altitude, and how much of the surrounding sky is obscured by mountains. It can take a while but we have it down to an art now, as the ton or so of granite in the back of our vehicle attests!

We´re also collecting sediment cores from bogs within the moraines, so as to provide radiocarbon ages for the deposits. Just yesterday we extracted a two-meter core from a basin near camp that lies between two long moraine ridges. It was a messy business, taking the three of us to punch the core barrel through the malodorous slime and into the stiff glacial clay, going as and as far as the rocks below. When all was said and done, each of us was fairly bloody and covered with ancient mud, but the core was extracted and the day was ours. Now the core is neatly contained in plastic tubing, sealed from the air and ready for shipment to Lamont where it will be analyzed.

Gordon