The PRIME Lab external research program

PRIME Lab has a multidisciplinary external research program with projects in geomorphology, hydrology, ocean science, planetary science, environmental science and biology. Introduction PRIME Lab is a national AMS facility for measurement of the long lived cosmogenic nuclides Be, C, Al, Cl, Ca, and I [1]. Since its inception in 1991 we have chemically processed over 2000 samples and have measured over 5000 research samples. Currently there are a total of about 125 external users conducting research using AMS data obtained at PRIME Lab. There are about 20 internal and 160 external ongoing research projects. About 60% of the samples measured at PRIME Lab belong to the external research program and about 40% of these are prepared in the PRIME Lab chemistry laboratory. About 40% of the samples are measured under a special seed analyses program to attract new users and to allow them to obtain preliminary data for proposals. 10 14 26 36 41 129 The multidisciplinary research program is centered in areas of atmospheric science, ocean science, hydrogeology, planetary science, glacial chronology and geomorphology, soil science, archaeology, anthropology, environmental science, and biology. About 50% of the research projects are focused around applications of in-situ produced cosmogenic nuclides ( Be, Al and Cl) for geomorphology and climate change. Applications include glacial chronology, erosion and paleolake shorelines; determining tectonic uplift rates and seismic hazards; dating of landslides, volcanic lava flows, rock art, and paleoearthquakes events. 10 26 36 Other research applications include: radionuclide fallout and mapping across the U.S.A.; soil dynamics and chronology; cosmic ray intensity variations; diagenesis of ferromanganese crusts; distribution of I and carbon cycling in the oceans; groundwater tracing; assessment of low level and high level radioactive waste repositories; release of radioactivity from fuel reprocessing facilities and reactors; toxicity and uptake of Al by plants and animals; determination of neutron energy spectra from atomic bombs at Hiroshima and Nagasaki; and exposure histories and terrestrial ages of meteorites and tektites. A few examples are given below to indicate the breadth of the PRIME Lab external research program. 129 Geomorphology 36 2/24/04 1:10 PM The PRIME Lab external research program Page 1 of 6 http://amos.physics.purdue.edu/web/primelab/papers/sh97a/sh97A.html Cl production rates in terrestrial rocks Since Cl is applicable to a wide variety of rock types and does not require mineral separation, there has been a rapid increase in the use of in-situ produced cosmogenic Cl for geomorphological studies. To determine it's production rate, Cl was measured in 33 rock samples having known exposure histories and ages [2]. The Cl production rates were estimated by minimizing the squared deviations between the Cl and independent ages, yielding the following production rates (applicable to surface at sea level and latitude >60). 36 36 36 36 36 Spallation and -production from Ca = 2940+/-200 atoms Cl (mole Ca) a , Spallation from K = 6020+\-400 atoms Cl (mole K) a , Neutron production in air = 586+/-40 fast neutrons (g air) a . The new production parameters on Ca and thermal neutron activation are in good agreement with previous results, but that for K spallation is ~50% larger [3]. 36 -1 -1 36 -1 -1 -1 -1 Fault Scarp Fault scarps contain information on timing and frequency of paleoseismic activity. Dating is important to assess the stability of an area. A series of samples from a late Quaternary bedrock fault scarp at Lake Hebgan, Montana have been dated by Cl build up [4]. The scarp shows multiple surface ruptures as bands of similar weathering characteristics in limestone bedrock. Cosmogenic Cl dating of the fault has been shown to be feasible. The Cl ages for the bedrock fault face are consistent with seismic stratigraphy, i.e. they increase consistently and predictably toward the top of the face. This method promises to become an important tool for quantitative paleoseismology. 36