The following is my project description and answers to the survey form questions. I would also like to thank you for making this summer so enjoyable for me by running such a wonderfully educational internship program. I hope next yearís is just as great so that even more students can get an awesome perspective on what geology can entail as a science and a career.

My research project this past summer of 2003 was primarily concerned with dating marine terraces using cosmogenic radionuclides (CRNs). It began along the coast of Northern California, with collecting soil samples at two sites on marine terraces located near the Mendocino Triple Junction. These sites were named Windy Point and Needle Rock and we took GPS and GPR measurements at these sites as well, but this data was processed by Lincoln Weller and is to be used in conjunction with my results. The soils samples were taken by auger and so represent the profile of soil down to bedrock. However, augering at Needle Rock was rather unsuccessful since we werenít able to get down far enough (we got down ~2.5 m). So the rest of my work was focused on the samples from Windy Point, where we augered down an outstanding 6 meters!

The samples were taken back to the University of Minnesota to be processed in the lab. For CRN dating, a certain grain size is desired and then must be rid of all material except quartz. The quartzís Si and O atoms react to cosmogenic radionuclides (which rain down from outer space) and get transformed into 10Be and 26Al isotopes, respectively. So the samples were sieved and the 250 mm ? 500 mm range of grain size of several select samples was taken for further processing. I selected several samples that would sufficiently represent the entire soil profile, so about one sample for every half meter. These samples were then leached with hydrogen peroxide, hydrochloric acid, and then thrice with a solution of hydrofluoric acid and nitric acid to end up with just quartz. The quartz of each sample was then weighed and spiked with a known mass of 9Be because the accelerator mass spectrometer measures the ratio of 10Be to 9Be and so to find the concentration of 10Be, we need to know that of 9Be. We also made a blank of just 9Be. The spiked quartz sample and the blank were then dissolved in hydrofluoric acid on hot plates and run through anion and cation filter columns. These last two steps isolate the Beryllium isotopes for each sample so that they are ready to be packed for analysis in an accelerator mass spectrometer. The concentration of 10Be is found and so that data is used to calculate the age of the samples.

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