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首页> 外文期刊>Palaeogeography, Palaeoclimatology, Palaeoecology: An International Journal for the Geo-Sciences >Middle–late Miocene benthic foraminifera in a western equatorial Indian Ocean depth transect: Paleoceanographic implications
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Middle–late Miocene benthic foraminifera in a western equatorial Indian Ocean depth transect: Paleoceanographic implications

机译：赤道西部印度洋深度样带的中新世底栖有孔虫：古海洋学意义

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摘要

Middle through upper Miocene (17–5 Ma) benthic foraminiferal faunas (> 63 μm) from a depth transect in the western equatorial Indian Ocean (DSDP Site 237, ODP Sites 707, 709 and 710; water depth 1500–3800 m) underwent significant faunal changes at 14–13 Ma and 11–8 Ma. These faunal changes are not easily interpreted, because of the complex factors controlling benthic foraminiferal distribution and abundance. At 14–13 Ma, the relative abundance of ‘high-productivity’ taxa (Bolivina, Bulimina, Melonis and Uvigerina species), although highly variable, generally increased at the two shallower sites (237 and 707), as did the percentage of Epistominella exigua (indicative of seasonal productivity) and Nuttallides umbonifera (indicative of corrosive bottom waters) at the two deeper sites (709 and 710); the latter species had a peak in abundance at the deepest site (710) between 11 and 9 Ma. Benthic foraminiferal accumulation rates (BFARs) increased strongly at the shallower sites starting at 11 Ma, peaking between 9 and 8 Ma, and increased weakly at the deeper two sites starting at 11 Ma. Elongate, cylindrical taxa decreased in abundance between 12 and 11 Ma at all sites. The abundance of planktic foraminiferal fragments was, as expected, overall higher at the deeper sites, with some high values after 12–13 Ma at the shallower sites. The faunal changes suggest that overall the food supply to the sea floor increased, but also became more pulsed or seasonal, peaking at 9–8 Ma, while deep and intermediate waters may have become more ventilated. The first phase of faunal change (14–13 Ma) was coeval with the global increase in benthic foraminiferal oxygen isotope values, worldwide turnover in benthic foraminiferal faunas, and possibly increased production of Antarctic Bottom Water (AABW) and Northern Component Water (NCW). The overall faunal turnover may reflect the composite faunal response to increased food input resulting from heightened productivity and increased bottom water ventilation associated with a combination of monsoonal intensification, global cooling and changes in ocean circulation, but there is no unequivocal evidence for the presence of Tethyan Outflow Water (TOW) over the studied time and depth range, in contrast to earlier publications.
机译：在赤道西印度洋（DSDP站点237，ODP站点707、709和710;水​​深1500-3800 m）的深度断面中部至上中新世（17-5 Ma）底栖有孔虫动物区系（> 63μm）动物区系在14-13 Ma和11-8 Ma发生变化。由于控制底栖有孔虫分布和丰度的复杂因素，这些动物的变化不容易解释。在14-13 Ma时，“高产”类群（玻利维纳，Bulimina，Melonis和Uvigerina物种）的相对丰度虽然变化很大，但在两个较浅的地点（237和707）通常都增加了，而表皮藻的百分比也增加了两个更深处（709和710）的exigua（指示季节性生产力）和Nuttallides umbonifera（指示腐蚀性底水）;后一种物种在11 Ma至9 Ma之间的最深部位（710）的丰度峰值。底栖有孔虫的累积速率（BFARs）在较浅的站点从11 Ma开始强烈增加，在9和8 Ma之间达到峰值，而在较深的两个站点从11 Ma开始弱地增加。在所有地点，伸长的圆柱状类群的丰度在12到11 Ma之间下降。正如预期的那样，在较深的地点，有孔的有孔虫碎片的丰度总体较高，在较浅的地点在12-13 Ma之后具有较高的值。动物群的变化表明，总体而言，向海底的食物供应增加了，但也变得更加脉冲化或季节性变化，在9-8 Ma达到峰值，而深水和中层水可能已经通风了。动物区系变化的第一阶段（14-13 Ma）与底栖有孔虫的氧同位素值的全球增加，底栖有孔虫的动物群的全球营业额以及南极底水（AABW）和北部成分水（NCW）的产量增加同时出现。 。总体动物区系更新可能反映了季风集约化，全球变冷和海洋环流变化相关的生产力提高和底水通风增加对食物投入增加的综合动物区系响应，但尚无明确证据表明Tethyan的存在与早期出版物相比，在研究的时间和深度范围内的流出水（TOW）。

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