Minimal influence of recrystallization on middle Miocene benthic foraminiferal stable isotope stratigraphy in the eastern equatorial Pacific
Minimal influence of recrystallization on middle Miocene benthic foraminiferal stable isotope stratigraphy in the eastern equatorial Pacific
复制标题
DOI：
10.1002/2015pa002822
复制
发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Janett Voigt;E. Hathorne;M. Frank;A. Holbourn
中科院分区：
文献类型：
--
作者：
Janett Voigt;E. Hathorne;M. Frank;A. Holbourn
有孔虫测试的稳定碳和氧同位素（δ 13 C和δ 18 O）是古海洋学中最重要的工具之一，但重结晶可以改变测试的同位素组成的程度还不清楚。在这里，我们比较了三个中中新世（16-13马）的底栖有孔虫稳定同位素记录从赤道东太平洋网站不同的成岩历史，以探讨重结晶的影响。为了测试一个极端的情况下，我们分析了底栖有孔虫的稳定同位素组成的综合大洋钻探计划网站U1336，散装碳酸盐和相关的孔隙沃茨的地球化学表明，在沉积物中持续的成岩蚀变> 14.7 Ma。尽管有这种成岩叠加，分析的U1336稳定同位素的振幅和绝对值与附近保存较好的U1337和U1338站点的高分辨率记录一致。我们的研究结果表明，虽然底栖有孔虫测试的所有三个网站显示一定程度的纹理变化，由于重结晶，他们保留了原来的稳定同位素签名。底栖有孔虫稳定同位素记录的良好一致性表明，沉积后重结晶发生得非常迅速（< 100 kyr）。这一点得到了U1336稳定同位素数据中轨道旋回性的保存和δ 18 O值与在后期重结晶过程中从U1336孔隙沃茨中沉淀的无机方解石不同的证实。这两个站点之间的底栖有孔虫稳定同位素记录非常相似，因此可以将站点U1336的高分辨率古地磁结果转移到站点U1337和U1338，从而改进全球地质时标。
Stable carbon and oxygen isotopes (δ13C and δ18O) of foraminiferal tests are amongst the most important tools in paleoceanography, but the extent to which recrystallization can alter the isotopic composition of the tests is not well known. Here we compare three middle Miocene (16–13 Ma) benthic foraminiferal stable isotope records from eastern equatorial Pacific sites with different diagenetic histories to investigate the effect of recrystallization. To test an extreme case, we analyzed stable isotope compositions of benthic foraminifera from Integrated Ocean Drilling Program Site U1336, for which the geochemistry of bulk carbonates and associated pore waters indicates continued diagenetic alteration in sediments > 14.7 Ma. Despite this diagenetic overprinting, the amplitudes and absolute values of the analyzed U1336 stable isotopes agree well with high-resolution records from better preserved Sites U1337 and U1338 nearby. Our results suggest that although benthic foraminiferal tests of all three sites show some degree of textural changes due to recrystallization, they have retained their original stable isotope signatures. The good agreement of the benthic foraminiferal stable isotope records demonstrates that recrystallization occurred extremely rapidly (< 100 kyr) after deposition. This is confirmed by the preservation of orbital cyclicities in U1336 stable isotope data and δ18O values being different to inorganic calcite that would precipitate from U1336 pore waters during late recrystallization. The close similarity of the benthic foraminiferal stable isotope records between the sites allows the well-resolved paleomagnetic results of Site U1336 to be transferred to Sites U1337 and U1338 improving the global geological timescale.