Planktic foraminiferal response to early Eocene carbon cycle perturbations in the southeast Atlantic Ocean (ODP Site 1263)
Planktic foraminiferal response to early Eocene carbon cycle perturbations in the southeast Atlantic Ocean (ODP Site 1263)
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DOI：
10.1016/j.gloplacha.2017.09.007
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发表时间：
2017-11-01
影响因子：
3.9
通讯作者：
Wade, Bridget S.
中科院分区：
文献类型：
--
作者：
Luciani, Valeria;D'Onofrio, Roberta;Wade, Bridget S.
在北方低纬度地区，两个主要的南极有孔虫属Morozovella和Acarinina的相对丰度和多样性的显着变化，已被称为发生接近早始新世气候最佳期（EECO;类似于49-53 Ma）。下始新世富含碳酸盐的沉积物在大洋钻探计划（ODP）网站1263沉积在水深高（沃尔维斯岭）在类似的40 ° S，并提供了一个机会，研究这种南极有孔虫组合的变化在温带南半球设置。我们在这里提出了定量计数早始新世寒武纪有孔虫组合从孔1263 B，沿着与散装沉积物稳定同位素分析和碳酸盐溶解的替代测量。1263号站点的大量沉积物三角洲C-13记录类似于其他地方生成的类似记录，因此可以很容易地识别已知和推断的超高温事件。虽然发生了一些碳酸盐溶解，但保存完好的南极有孔虫组合大多代表了环境条件的初步变化。我们的研究结果记录的Morozovella丰度的永久性减少，并在EECO的开始增加蜱螨目丰度，虽然这种开关发生类似165 kyr后，在低纬度北方半球的位置。这表明，在EECO开始时对morozovellids不利的环境条件，例如持续通过温度阈值或地表沃茨的其他变化，首先发生在低纬度地区。从Morozovella到Acarinina的显着营业额在地理上广泛分布，尽管因果机制仍然难以捉摸。此外，在网站1263，我们记录的虚拟消失内的EECO的bischiloguembelinids，通常被认为是居住在中间的水深处，并减少丰度的温跃层居住subbotinids。我们将这些变化解释为地下水特性的信号，也许是变暖，以及相关的生态位收缩。
At low latitude locations in the northern hemisphere, striking changes in the relative abundances and diversity of the two dominant planktic foraminifera genera, Morozovella and Acarinina, are known to have occurred close to the Early Eocene Climatic Optimum (EECO; similar to 49-53 Ma). Lower Eocene carbonate-rich sediments at Ocean Drilling Program (ODP) Site 1263 were deposited on a bathymetric high (Walvis Ridge) at similar to 40 degrees S, and afford an opportunity to examine such planktic foraminiferal assemblage changes in a temperate southern hemisphere setting. We present here quantified counts of early Eocene planktic foraminiferal assemblages from Hole 1263B, along with bulk sediment stable isotope analyses and proxy measurements for carbonate dissolution. The bulk sediment delta C-13 record at Site 1263 resembles similar records generated elsewhere, such that known and inferred hyperthermal events can be readily identified. Although some carbonate dissolution has occurred, the well-preserved planktic foraminiferal assemblages mostly represent primary changes in environmental conditions. Our results document the permanent decrease in Morozovella abundance and increase in Acarinina abundance at the beginning of the EECO, although this switch occurred similar to 165 kyr after that at low-latitude northern hemisphere locations. This suggests that unfavourable environmental conditions for morozovellids at the start of the EECO, such as sustained passage of a temperature threshold or other changes in surface waters, occurred at lower latitudes first. The remarkable turnover from Morozovella to Acarinina was widely geographically widespread, although the causal mechanism remains elusive. In addition, at Site 1263, we document the virtual disappearance within the EECO of the biserial chiloguembelinids, commonly considered as inhabiting intermediate water depths, and a reduction in abundance of the thermocline-dwelling subbotinids. We interpret these changes as signals of subsurface water properties, perhaps warming, and the associated contraction of ecological niches.