Prokopenko, Maria G.; Hammond, Douglas E.; Stott, Lowell (2006): Lack of isotopic fractionation of delta (super 15) N of organic matter during long-term diagenesis in marine sediments, ODP Leg 202, Sites 1234 and 1235. Texas A&M University, Ocean Drilling Program, College Station, TX, United States, In: Tiedemann, Ralf, Mix, Alan C., Blum, Peter, Abrantes, Fatima F., Benway, Heather, Cacho-Lascorz, Isabel, Chen, Min-Te, Delaney, Margaret L., Flores, Jose-Abel, Giosan, Liviu, Holbourn, Ann E., Irino, Tomohisa, Iwai, Masao, Joseph, Leah H., Kleiven, Helga F., Lamy, Frank, Lund, Steven P., Martinez, Philippe, McManus, Jerry F., Ninnemann, Ulysses S., Pisias, Nicklas G., Robinson, Rebecca S., Stoner, Joseph S., Sturm, Arne, Wara, Michael W., Wei, Wuchang, Proceedings of the Ocean Drilling Program; scientific results; Southeast Pacific paleoceanographic transects; covering Leg 202 of the cruises of the drilling vessel JOIDES Resolution; Valparaiso, Chile, to Balboa, Panama; Sites 1232-1242; 29 March-30 May 2002, 202, georefid:2007-051091

The isotopic composition of nitrogen in pore water ammonium and in sedimentary organic matter (N (sub org) ) was measured at Sites 1234 and 1235 in order to evaluate the impact of long-term (>100 k.y.) diagenesis on delta (super 15) N of preserved organic matter. At both sites, the average delta (super 15) N of pore water ammonium and N (sub org) are within 0.2ppm to 0.4ppm. The small difference is less than the analytical uncertainty, indicating that no significant isotopic fractionation is associated with decomposition of organic matter in these sediments. A mass balance for nitrogen was also computed, indicating that approximately 20% of the organic matter flux buried below 1.45 meters composite depth (mcd) is degraded between this depth and 40 mcd (Site 1235) to 60 mcd (Site 1234) depth. Two factors determine the absence of isotopic fractionation in these sediments: 1. A high degree of organic matter preservation due to rapid sediment accumulation rates at both sites. 2. The dominance of a marine component in the sedimentary organic matter (with only a small fraction contributed by a terrestrial component).
West: -73.4100 East: -73.3400 North: -36.1000 South: -36.1300
Expedition: 202
Site: 202-1234
Site: 202-1235
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