Enhanced primary productivity and magnetotactic bacterial production in response to middle Eocene warming in the Neo-Tethys Ocean
Enhanced primary productivity and magnetotactic bacterial production in response to middle Eocene warming in the Neo-Tethys Ocean
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DOI：
10.1016/j.palaeo.2014.08.009
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发表时间：
2014-11
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通讯作者：
J. Savian;L. Jovane;F. Frontalini;R. Trindade;R. Coccioni;S. Bohaty;P. Wilson;F. Florindo;A. Roberts;R. Catanzariti;F. Iacoviello
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作者：
J. Savian;L. Jovane;F. Frontalini;R. Trindade;R. Coccioni;S. Bohaty;P. Wilson;F. Florindo;A. Roberts;R. Catanzariti;F. Iacoviello
地球的气候在大约40 Ma时经历了一个被称为中始新世气候适宜期（MECO）的变暖事件，这是一个长期始新世冷却趋势的突然逆转。该事件的特征是在南大洋、大西洋、太平洋和印度洋的深海中，δ 18 O明显负漂移超过50万年。我们报告的高分辨率古生物学，地球化学和岩石磁性调查的新特提斯Monte Cagnero（MCA）部分（东北亚平宁山脉，意大利），这可以是相关的基础上的磁性和生物地层学结果记录在深海部分的MECO事件的结果。在MCA部分，富营养超微化石类群的相对增加（和贫营养类群的丰度降低）的间隔跨越了MECO变暖的高潮及其后果，并与正的碳同位素偏移相吻合，磁铁矿和赤铁矿/针铁矿浓度的峰值。磁铁矿峰反映了推定的磁化石的外观，而赤铁矿/针铁矿顶点是由于增强碎屑矿物的贡献，可能是风成尘埃从邻近新特提斯洋的大陆在干燥，更季节性的气候在峰值MECO变暖。根据我们新的地球化学，古生物和磁性记录，MECO变暖高峰及其直接后果被解释为一个时期的高初级生产力。据推测，海面铁施肥刺激了浮游植物的高生产力，增加有机碳出口到海底，促进增强趋磁细菌的生物矿化，这是保存在最温暖的时期的MECO事件在MCA部分的推定磁化石。与以前的研究一起，我们的工作加强了超高温气候事件和沉积记录中推定的磁化石的发生（或增加丰度）之间的联系。
Earth's climate experienced a warming event known as the Middle Eocene Climatic Optimum (MECO) at ~ 40 Ma, which was an abrupt reversal of a long-term Eocene cooling trend. This event is characterized in the deep Southern, Atlantic, Pacific and Indian Oceans by a distinct negative δ18O excursion over 500 kyr. We report results of high-resolution paleontological, geochemical, and rock magnetic investigations of the Neo-Tethyan Monte Cagnero (MCA) section (northeastern Apennines, Italy), which can be correlated on the basis of magneto- and biostratigraphic results to the MECO event recorded in deep-sea sections. In the MCA section, an interval with a relative increase in eutrophic nannofossil taxa (and decreased abundances of oligotrophic taxa) spans the culmination of the MECO warming and its aftermath and coincides with a positive carbon isotope excursion, and a peak in magnetite and hematite/goethite concentration. The magnetite peak reflects the appearance of putative magnetofossils, while the hematite/goethite apex is attributed to an enhanced detrital mineral contribution, likely as aeolian dust transported from the continent adjacent to the Neo-Tethys Ocean during a drier, more seasonal climate during the peak MECO warming. Based on our new geochemical, paleontological and magnetic records, the MECO warming peak and its immediate aftermath are interpreted as a period of high primary productivity. Sea-surface iron fertilization is inferred to have stimulated high phytoplankton productivity, increasing organic carbon export to the seafloor and promoting enhanced biomineralization of magnetotactic bacteria, which are preserved as putative magnetofossils during the warmest periods of the MECO event in the MCA section. Together with previous studies, our work reinforces the connection between hyperthermal climatic events and the occurrence (or increased abundance) of putative magnetofossils in the sedimentary record.