颗石藻对中中新世气候转型事件的响应

RESPONSE AND MECHANISM OF COCCOLITHOPHORES TO THE MIDDLE MIOCENE CLIMATE TRANSITION

本文以南海大洋发现计划U1501站颗石藻属种组合及形态分析为基础,通过与太平洋和大西洋其他站位颗石藻群落分析数据作对比,探讨了颗石藻对中中新世气候转型事件的响应。结果表明,颗石总丰度在17–12 Ma期间缓慢增加,其中Reticulofenestra逐渐成为优势属种,而Sphenolithus, Discoaster以及Cyclicargolithus的适应能力随着气候变冷逐渐降低。颗石长度高值与蒙特利碳位移的CM3-CM5事件对应良好。由此推测, MCO时期较高的温度和大气CO_(2)浓度使得海平面上升,海洋CO_(2)增加,从而增加了表层海洋溶解无机碳(DIC)浓度和有机碳埋藏,引起了碳同位素的广泛偏重。同时,当溶于海水的CO_(2)浓度较高时,颗石藻将更多地HCO3-用于钙化作用,最终表现为颗石长度的增加。

Based on species composition and morphology analysis of coccolithophores at site U1501 in the South China Sea, this paper discussed the response of coccolithophores to the middle Miocene climate transition by comparing them with those at other stations in the Pacific and Atlantic. The results showed that the total abundance of coccolith increased slowly during 17–12 Ma, and Reticulofenestra gradually became the dominant species, while the fitness of Sphenolithus,Discoaster, and Cyclicargolithus gradually decreased with the cooling of the climate. The high value of coccolith length corresponds well to the CM3-CM5 events of the “Monterey Carbon Excursion”. Therefore, it is speculated that the higher temperature and atmospheric p CO2 during the MCO period led to the rise of sea level and the increase of marine CO2, which increased the concentration of dissolved inorganic carbon(DIC) and organic carbon burial, resulting in the positive carbon isotope drift. At the same time, when the concentration of CO2 dissolved in seawater increases,coccolithophores will make full use of HCO3-for calcification, which ultimately shows an increase in the length of coccolith.