In situ δ18O and Mg/Ca analyses of diagenetic and planktic foraminiferal calcite preserved in a deep-sea record of the Paleocene-Eocene thermal maximum
In situ δ18O and Mg/Ca analyses of diagenetic and planktic foraminiferal calcite preserved in a deep-sea record of the Paleocene-Eocene thermal maximum
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DOI：
10.1002/palo.20048
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发表时间：
2013-09-01
期刊：
影响因子：
--
通讯作者：
Valley, J. W.
中科院分区：
文献类型：
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作者：
Kozdon, Reinhard;Kelly, D. C.;Valley, J. W.
我们报告的O-18和微量元素（Mg/Ca，Sr/Ca）的高分辨率，原位二次离子质谱（西姆斯）的数据，从南极有孔虫壳和100-500 μ m大小的成岩微晶恢复从深海记录（ODP网站865）的古新世-始新世热最大（PETM）。微晶（类似于1.2 Pee Dee Belemnite（PDB））的O-18类似于比南极有孔虫方解石（-3.6 PDB）高4.8，而微晶Mg/Ca和Sr/Ca比分别略高于和显著低于南极有孔虫方解石。集中的地层分布的微晶信号与PETM条件的关联，因此，我们把它们的形成早期成岩作用最初来源于海底溶解（烧毁），随后在较高的碳酸盐饱和度再沉淀。的Mg/Ca比的微晶是一个数量级低于无机沉淀实验，这可能反映了一定程度的继承从捐助者阶段的生物方解石，在沉积物柱中进行解决方案的预测。此外，在浮游有孔虫壳内进行的西姆斯O-18和电子微探针Mg/Ca分析得出，沿着与室壁上的muricae叶片一致的横向平行增加。O-18和Mg/Ca的平行增加表明叶片的成岩起源，但它们的O-18值（-0.5 PDB）低于微晶，表明这两个阶段的成岩碳酸盐形成于不同的时间。最后，我们认为，早期成岩作用的水平升高与沉积物混合和碳酸盐溶解，以减弱O-18减少信号PETM变暖的全壳记录发表的网站865。
We report O-18 and minor element (Mg/Ca, Sr/Ca) data acquired by high-resolution, in situ secondary ion mass spectrometry (SIMS) from planktic foraminiferal shells and 100-500 mu m sized diagenetic crystallites recovered from a deep-sea record (ODP Site 865) of the Paleocene-Eocene thermal maximum (PETM). The O-18 of crystallites (similar to 1.2 Pee Dee Belemnite (PDB)) is similar to 4.8 higher than that of planktic foraminiferal calcite (-3.6 PDB), while crystallite Mg/Ca and Sr/Ca ratios are slightly higher and substantially lower than in planktic foraminiferal calcite, respectively. The focused stratigraphic distribution of the crystallites signals an association with PETM conditions; hence, we attribute their formation to early diagenesis initially sourced by seafloor dissolution (burndown) ensued by reprecipitation at higher carbonate saturation. The Mg/Ca ratios of the crystallites are an order of magnitude lower than those predicted by inorganic precipitation experiments, which may reflect a degree of inheritance from donor phases of biogenic calcite that underwent solution in the sediment column. In addition, SIMS O-18 and electron microprobe Mg/Ca analyses that were taken within a planktic foraminiferal shell yield parallel increases along traverses that coincide with muricae blades on the chamber wall. The parallel O-18 and Mg/Ca increases indicate a diagenetic origin for the blades, but their O-18 value (-0.5 PDB) is lower than that of crystallites suggesting that these two phases of diagenetic carbonate formed at different times. Finally, we posit that elevated levels of early diagenesis acted in concert with sediment mixing and carbonate dissolution to attenuate the O-18 decrease signaling PETM warming in whole-shell records published for Site 865.