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首页> 外文期刊>Paleoceanography >Carbon isotopic fractionation (ε_p) of C_(37) alkenones in deep-sea sediments: Its potential as a paleonutrient proxy
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Carbon isotopic fractionation (ε_p) of C_(37) alkenones in deep-sea sediments: Its potential as a paleonutrient proxy

机译：深海沉积物中C_（37）烯酮的碳同位素分馏（ε_p）：其作为古营养替代物的潜力

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摘要

We compared ocean atlas values of surface water [PO_4~(3-)] and [CO_2(aq)] against the carbon isotopic fractionation (ε_p) of alkenones obtained from surface sediments of the South Atlantic and the central Pacific (Pacific data are from Pagani et al. [2002]). We observed a positive correlation between ε_p and 1/[CO_2(aq)], which is opposite of what would be expected if the concentration of CO_2(aq) were the major factor controlling the carbon isotopic fractionation of C37:2 alkenones. Instead, we found inverse relationships between ε_p and [PO_4~(3-)] for the two ocean basins (for the Atlantic, ε_p = -4.6~*[PO_4~(3-)] + 15.1, R = 0.76; for the Pacific, ε_p = -4.1~*[PO_4~(3-)] + 13.7, R = 0.64), suggesting that ε_p is predominantly controlled by growth rate, which in turn is related to nutrient concentration. The similarity of the slopes implies that a general relationship between both parameters may exist. Using the relationship obtained from the South Atlantic, we estimated surface water nutrient concentrations for the past 200,000 years from a deep-sea sediment core recovered off Angola. Low ε_p values, indicating high nutrient concentrations, coincide with high contents of total organic carbon and C37 alkenones, low surface water temperatures, and decreased bulk δ15N values, suggesting an increased upwelling of nutrient-rich cool subsurface waters as the main cause for the observed ε_p decrease.
机译：我们将地表水[PO_4〜（3-）]和[CO_2（aq）]的海洋地图集值与从南大西洋和中太平洋的表层沉积物获得的烯酮的碳同位素分馏（ε_p）进行了比较（太平洋数据来自Pagani等人[2002]。我们观察到ε_p与1 / [CO_2（aq）]之间存在正相关，这与如果CO_2（aq）的浓度是控制C37：2烯酮的碳同位素分馏的主要因素的预期结果相反。相反，我们发现两个海盆的ε_p和[PO_4〜（3-）]之间存在反比关系（对于大西洋，ε_p= -4.6〜* [PO_4〜（3-）] + 15.1，R = 0.76;对于太平洋地区，ε_p= -4.1〜* [PO_4〜（3-）] + 13.7，R = 0.64），表明ε_p主要受生长率控制，而生长率又与养分浓度有关。斜率的相似性暗示两个参数之间可能存在一般关系。利用从南大西洋获得的关系，我们估算了过去20万年来自安哥拉海域的深海沉积物核心的地表水营养物浓度。较低的ε_p值表示较高的养分含量，同时有机碳和C37烯酮的总含量较高，地表水温度较低，总δ15N值降低，这表明富含营养的冷地下水的上升流是造成这种现象的主要原因ε_p减小。

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