Late Quaternary development of the Java upwelling system (eastern Indian Ocean) as revealed by coccolithophores
Late Quaternary development of the Java upwelling system (eastern Indian Ocean) as revealed by coccolithophores
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DOI：
10.1016/j.marmicro.2007.11.005
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发表时间：
2008-10-01
影响因子：
1.9
通讯作者：
Staeger, Sabine
中科院分区：
文献类型：
--
作者：
Andruleit, Harald;Lueckge, Andreas;Staeger, Sabine
利用球石藻的古海洋学潜力分析了东印度洋近30万年的古生产力变化。S0139-74KL岩芯位于爪哇上升流体系下方的印度尼西亚大陆架弧前盆地向海边界。所有样品中都有球粒石，整个剖面的球粒石总浓度有明显的变化。丰度峰值每2万至2.5万年出现一次，最高峰出现在同位素阶段7。丰度在冰期增加，但丰度峰值也出现在间冰期。在大多数样品中，球粒石的保存良好至中等。丰度最高的是Florisphaera profunda，平均相对丰度为41.5%，其次是Gephyrocapsa ericsonii和Emiliania huxleyi （EhuxGeric）和Gephyrocapsa oceanica。这四个类群在整个岩心中占主导地位，平均占总类群的90.5%。物种组成表明，在整个调查时期，温暖的热带环境普遍存在，表明温度不是该地点组合变化的驱动力。现代和全新世海洋条件的地质记录似乎主要以高生产力和不稳定的水柱相结合为特征。少营养开放海洋条件的迹象很少。然而，在一年中的大部分时间里，少营养条件普遍存在，上升流只在短时间内反复出现，但上升流指示代用物在地质记录中占主导地位。与之形成对比的完全贫营养情景，其特征是总粒石藻、伞形藻的丰度峰值，以及EhuxGeric与G. oceanica的百分比比例峰值，每2万至2.5万年周期性出现一次。同时，高生产力指标、总有机碳和大洋洋的记录具有明显的最小值特征。我们认为，在这些时期，上升流完全被切断，并且在所有季节都存在明显的水柱分层的少营养条件。上升流停止时间与日照最小值之间的明显对应表明，地表水条件是由轨道强迫驱动的。(C) 2008 Elsevier B.V.版权所有
The paleoceanographic potential of coccolithophores was used to decipher the paleoproductivity changes in the eastern Indian Ocean during the past 300,000 years. Core S0139-74KL was taken at the seaward limit of a fore-arc basin of the Indonesian continental shelf located beneath the Java upwelling system. Coccolithophores occur in all samples, and total coccolith concentration exhibit distinct variations over the entire section. Peak abundances occur every 20,000 to 25,000 years with the highest peak at isotope stage 7. Abundances increase during the glacials but peak abundances also occur during interglacials. The preservation of coccoliths is good to moderate in most of the samples. The most abundant species is Florisphaera profunda with a mean relative abundance of 41.5% followed by Gephyrocapsa ericsonii and Emiliania huxleyi (EhuxGeric) and Gephyrocapsa oceanica. These four taxa dominate the assemblage throughout the core, forming on average 90.5% of the total assemblage. The species composition suggests that warm tropical conditions prevailed throughout the investigated time period indicating that temperature was not the driving force for the assemblage variations at this site. The geologic record for present-day and Holocene oceanographic conditions seemed to be predominantly characterised by high productivities in combination with an unstable water column. Indications for oligotrophic open ocean conditions were sparse. However, during most of the year oligotrophic conditions prevail and upwelling recurs only for a short time period but upwelling indicating proxies dominate the geological record. A contrasting fully oligotrophic scenario characterised by peaks in the abundances of total coccolithophores, Umbellosphaera irregularis, and in the percentage ratio of EhuxGeric to G. oceanica can be seen with a periodical recurrence every 20,000 to 25,000 years. Synchronously the records of the high productivity indicators total organic carbon and G. oceanica are characterised by distinct minima. We believe that upwelling was totally cut off during these times and oligotrophic conditions with a pronounced water column stratification prevailed throughout all seasons. An obvious correspondence between the shut down times of upwelling and insolation minima suggests that surface water conditions were driven by orbital forcing. (C) 2008 Elsevier B.V. All rights reserved.