کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8906721 | 1634658 | 2018 | 10 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Diagenetic overprint on authigenic Nd isotope records: A case study of the Bering Slope
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
علوم زمین و سیاره ای (عمومی)
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چکیده انگلیسی
Neodymium isotope ratios (143Nd/144Nd, εNd) have been used as a quasi-conservative water mass tracer in the Atlantic and Southern oceans. However, boundary exchange and diagenesis can limit their use in areas where extensive interactions between seawater, pore water and bottom sediments can overwrite the original water mass signature. To avoid the misapplication of this proxy and to provide a new perspective on the application of Nd isotopes to authigenic phases, we present εNd records covering the past 2.4 Myr for the authigenic (εNd,âauth) and detrital (εNd,âdet) phases of sediments from Integrated Ocean Drilling Program site U1343 (â¼1950 m water depth) on the Bering Slope. The εNd,âdet values range from â9.0 to â2.3 (n=70), showing binary mixing between Alaskan and Aleutian sediments. Glacial-interglacial variations are muted in the εNd,âdet record because sediment delivery pathways from both source areas exist regardless of climatic conditions. The εNd,âauth values range from â5.9 to â0.2 (n=153) and show a strong correlation (r=0.58, n=60) with εNd,âdet in the deeper part of the core (>160 ka), where authigenic carbonate layers are frequently observed. We attribute this covariation to diagenetic overprinting by pore water Nd during late diagenesis. The pore water Nd that is incorporated into authigenic carbonates was initially released by marine silicate weathering, therefore indicating that sediment lithology exerts a first-order control on the εNd values of the pore water in deeply buried sediments. In the shallower part of the core (<160 ka), there is no correlation between εNd,âauth and εNd,âdet (r=â0.23, n=10). Here, εNd,âauth is typically radiogenic during interglacial periods, which may be due to the diagenetic flux from the relatively stagnant N. Pacific or the incongruent chemical weathering of freshly ground sediments on the Bering Shelf. The effect of dense water formation on εNd,âauth seems to be minimal when we compare the εNd,âauth records at three different depths of the Bering Sea. Our εNd dataset provides a unique perspective on the behavior of εNd,âauth during late diagenesis. To apply εNd,âauth as a water mass tracer to long cores containing volcanogenic sediments or in productive regions, we recommend testing for deep authigenesis using pore water profiles.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 498, 15 September 2018, Pages 247-256
Journal: Earth and Planetary Science Letters - Volume 498, 15 September 2018, Pages 247-256
نویسندگان
Kwangchul Jang, Youngsook Huh, Yeongcheol Han,