Abstract The Eocene-Oligocene transition represents the latest greenhouse-icehouse shift faced by Earth, a major global climate change associated with carbon cycle perturbation. In this paper, we investigate the Massignano stratigraphic section (northern Apennines, Italy), GSSP of the Eocene-Oligocene boundary, by X-ray diffraction analysis of clay minerals and carbon and oxygen stable isotopes to explore the link among climate, paleoweathering and runoff, and carbon cycle in the Neotethys across this major climatic transition. We examine the interplay between global climate forcing and orogen evolution controlling the Massignano hemipelagic sedimentation. The late Eocene clay mineral assemblages indicate that the Neotethys was sensitive to global eustatic changes as well as changes in composition and rates of weathered sediments accumulating into the basin. The carbon isotope record matches with the global signal, showing productivity pulses linked to cooling phases and sea-level drops before 34.8 Ma. Subsequently, a constant negative trend is recorded, which is consistent with the global carbon isotope curve, and attests for a decrease of primary productivity linked to decreasing atmospheric CO2. This negative trend ends at the Eocene-Oligocene boundary, when the onset of the global carbon isotope positive excursion is recorded also within the Massignano hemipelagic succession. On the contrary, the clay mineral assemblage is quite constant across the Eocene-Oligocene boundary reflecting the complex interplay among fluvial discharge, sea level changes and orogen dynamics which clouded the global climate shift. In this context, the enhanced fluvial discharge likely contributed to sustain high trophic conditions in the Adriatic waters and, in turn, the Oligocene positive carbon isotope shift. These results highlight how clay minerals proved to be a useful proxy to identify the interplay between global and regional controlling factors on hemipelagic sedimentation and, their integration with the carbon isotope record, provides insights into carbon cycle dynamics.

中文翻译：

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Massignano 剖面（意大利亚平宁北部）始新世-渐新世过渡的营养、气候和古风化条件

摘要 始新世-渐新世转变代表了地球面临的最新温室-冰库转变，这是与碳循环扰动相关的主要全球气候变化。在本文中，我们研究了始新世-渐新世边界的 Massignano 地层剖面（意大利亚平宁山脉北部）、GSSP，通过粘土矿物和碳氧稳定同位素的 X 射线衍射分析，探索气候、古风化和径流之间的联系。 ，以及在这一重大气候转变中新特提斯群岛的碳循环。我们研究了全球气候强迫和造山带演化控制 Massignano 半远洋沉积之间的相互作用。晚始新世粘土矿物组合表明，新特提斯对全球海平面变化以及风化沉积物在盆地中积累的成分和速率的变化很敏感。碳同位素记录与全球信号匹配，显示了与 34.8 Ma 之前的冷却阶段和海平面下降相关的生产力脉冲。随后，记录了一个持续的负趋势，这与全球碳同位素曲线一致，证明初级生产力下降与大气 CO2 减少有关。这种负面趋势在始新世-渐新世边界结束，当时全球碳同位素正偏移的开始也在 Massignano 半远洋序列中被记录。相反，整个始新世-渐新世边界的粘土矿物组合相当稳定，反映了河流流量、海平面变化和造山带动力学之间复杂的相互作用，这些相互作用使全球气候变化蒙上阴影。在这种情况下，增强的河流排放可能有助于维持亚得里亚海水域的高营养条件，进而导致渐新世正碳同位素转移。这些结果突出说明了粘土矿物如何被证明是确定全球和区域控制因素对半远洋沉积的相互作用的有用代理，并且将它们与碳同位素记录的整合提供了对碳循环动力学的见解。增强的河流排放可能有助于维持亚得里亚海水域的高营养条件，进而导致渐新世正碳同位素转移。这些结果突出说明了粘土矿物如何被证明是确定全球和区域控制因素对半远洋沉积的相互作用的有用代理，并且将它们与碳同位素记录的整合，提供了对碳循环动力学的见解。增强的河流排放可能有助于维持亚得里亚海水域的高营养条件，进而导致渐新世正碳同位素转移。这些结果突出说明了粘土矿物如何被证明是确定全球和区域控制因素对半远洋沉积的相互作用的有用代理，并且将它们与碳同位素记录的整合，提供了对碳循环动力学的见解。