März Christian

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März
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Christian
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  • Article
    Quantifying K, U, and Th contents of marine sediments using shipboard natural gamma radiation spectra measured on DV JOIDES Resolution
    (John Wiley & Sons, 2017-03-21) De Vleeschouwer, David ; Dunlea, Ann G. ; Auer, Gerald ; Anderson, Chloe H. ; Brumsack, Hans-Jürgen ; de Loach, Aaron ; Gurnis, Michael ; Huh, Youngsook ; Ishiwa, Takeshige ; Jang, Kwangchul ; Kominz, Michelle A. ; März, Christian ; Schnetger, Bernhard ; Murray, Richard W. ; Pälike, Heiko ; Expedition 356 Shipboard Scientists
    During International Ocean Discovery Program (IODP) expeditions, shipboard-generated data provide the first insights into the cored sequences. The natural gamma radiation (NGR) of the recovered material, for example, is routinely measured on the ocean drilling research vessel DV JOIDES Resolution. At present, only total NGR counts are readily available as shipboard data, although full NGR spectra (counts as a function of gamma-ray energy level) are produced and archived. These spectra contain unexploited information, as one can estimate the sedimentary contents of potassium (K), thorium (Th), and uranium (U) from the characteristic gamma-ray energies of isotopes in the 40K, 232Th, and 238U radioactive decay series. Dunlea et al. (2013) quantified K, Th, and U contents in sediment from the South Pacific Gyre by integrating counts over specific energy levels of the NGR spectrum. However, the algorithm used in their study is unavailable to the wider scientific community due to commercial proprietary reasons. Here, we present a new MATLAB algorithm for the quantification of NGR spectra that is transparent and accessible to future NGR users. We demonstrate the algorithm's performance by comparing its results to shore-based inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma-emission spectrometry (ICP-ES), and quantitative wavelength-dispersive X-ray fluorescence (XRF) analyses. Samples for these comparisons come from eleven sites (U1341, U1343, U1366-U1369, U1414, U1428-U1430, and U1463) cored in two oceans during five expeditions. In short, our algorithm rapidly produces detailed high-quality information on sediment properties during IODP expeditions at no extra cost.
  • Article
    Earthquake-enhanced dissolved carbon cycles in ultra-deep ocean sediments
    (Nature Research, 2023-09-11) Chu, Mengfan ; Bao, Rui ; Strasser, Michael ; Ikehara, Ken ; Everest, Jez ; Maeda, Lena ; Hochmuth, Katharina ; Xu, Li ; McNichol, Ann P. ; Bellanova, Piero ; Rasbury, E. Troy ; Kolling, Martin ; Riedinger, Natascha ; Johnson, Joel E. ; Luo, Min ; Marz, Christian ; Straub, Susanne ; Jitsuno, Kana ; Brunet, Morgane ; Cai, Zhirong ; Cattaneo, Antonio ; Hsiung, Kanhsi ; Ishizawa, Takashi ; Itaki, Takuya ; Kanamatsu, Toshiya ; Keep, Myra ; Kioka, Arata ; McHugh, Cecilia M. G. ; Micallef, Aaron ; Pandey, Dhananjai ; Proust, Jean Noel ; Satoguchi, Yasufumi ; Sawyer, Derek ; Seibert, Chloe ; Silver, Maxwell ; Virtasalo, Joonas ; Wang, Yonghong ; Wu, Ting-Wei ; Zellers, Sarah
    Hadal trenches are unique geological and ecological systems located along subduction zones. Earthquake-triggered turbidites act as efficient transport pathways of organic carbon (OC), yet remineralization and transformation of OC in these systems are not comprehensively understood. Here we measure concentrations and stable- and radiocarbon isotope signatures of dissolved organic and inorganic carbon (DOC, DIC) in the subsurface sediment interstitial water along the Japan Trench axis collected during the IODP Expedition 386. We find accumulation and aging of DOC and DIC in the subsurface sediments, which we interpret as enhanced production of labile dissolved carbon owing to earthquake-triggered turbidites, which supports intensive microbial methanogenesis in the trench sediments. The residual dissolved carbon accumulates in deep subsurface sediments and may continue to fuel the deep biosphere. Tectonic events can therefore enhance carbon accumulation and stimulate carbon transformation in plate convergent trench systems, which may accelerate carbon export into the subduction zones.