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首页> 外文期刊>Journal of the Geological Society of India >Paleoceanographic significance of changes in Miocene deep-sea benthic foraminiferal diversity on the Wombat Plateau, eastern Indian Ocean
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Paleoceanographic significance of changes in Miocene deep-sea benthic foraminiferal diversity on the Wombat Plateau, eastern Indian Ocean

机译：印度洋东部温巴特高原中新世深海底栖有孔虫多样性变化的古海洋学意义

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摘要

In the present work, late Oligocene to latest Miocene (-28-6.5 Ma) deep-sea benthic foraminifera (over 149 Am size fraction) were studied from ODP sites 760A and 761B on Wombat Plateau in the eastern Indian Ocean to understand the faunal diversity pattern. The samples were commonly examined at about 0.75rn interval at both the sites. The benthic foraminiferal species diversity was measured in terms of Shannon-Weaver Index [H(S)], Hurlbert's Diversity Index (S-100), Alpha Index (alpha) and Equitability (E'), all of which show almost similar trends with few exceptions. The Miocene section at both the sites show marked fluctuations in the values of various diversity indices of deep-sea benthic foraminiferal assemblages. Distinctly low values of diversity indices across the Oligocene-Miocene transition Correspond well with the higher values of benthic delta O-18 and delta(13)c reflecting relatively cold, nutrient depleted, young bottom waters which possibly indicate the influence of Antarctic Circumpolar Current (ACC) in this region. Faunal diversity reached to maximum values at both the sites near the end of Miocene climatic optimum at about 15 Ma reflecting warm bottom waters with low trophic levels. The low bottom water temperature, expansion of East Antarctic Ice Sheet (EAIS) and possibly higher trophic level appear to be responsible for less diverse fauna during the middle Miocene i.e. similar to 14Ma and younger. Further, decrease in the values of diversity during latest Miocene (similar to 7.5-6.5 Ma) is Suggested to be due to increased surface water productivity in response to the intensified monsoonal activity in the eastern Indian Ocean.
机译：在目前的工作中，从印度洋东部温巴特高原的ODP站点760A和761B研究了晚渐新世至最新的中新世（-28-6.5 Ma）深海底栖有孔虫（大小超过149 Am）。模式。通常在两个位置以大约0.75rn的间隔检查样品。底栖有孔虫物种多样性是根据Shannon-Weaver指数[H（S）]，Hurlbert多样性指数（S-100），Alpha指数（alpha）和公平性（E'）来衡量的，所有这些都显示出与很少有例外。两个地点的中新世剖面显示深海底栖有孔虫组合的各种多样性指数的值都有明显的波动。渐新世-中新世转变的多样性指数值极低，与底栖三角洲O-18和delta（13）c的较高值很好地对应，这反映了相对寒冷，营养物质耗尽的年轻底水，这可能表明了南极绕极洋流的影响（ ACC）。在中新世最佳气候结束时的两个地点，大约15 Ma处的动物多样性都达到了最大值，这反映了低营养水平的温暖的底水。较低的底部水温，南极东部冰盖（EAIS）的扩张以及可能更高的营养水平似乎是造成中新世中期动物种类较少的原因，即与14Ma或更年轻。此外，建议在最新中新世（类似于7.5-6.5 Ma）期间降低多样性值，这是由于响应东印度洋季风活动的增强增加了地表水生产率。

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