Neritic isotope and sedimentary records of the Eocene–Oligocene greenhouse–icehouse transition: The Calcare di Nago Formation (northern Italy) in a global context
Neritic isotope and sedimentary records of the Eocene–Oligocene greenhouse–icehouse transition: The Calcare di Nago Formation (northern Italy) in a global context
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始新世-渐新世温室-冰室转变的浅海同位素和沉积记录：全球背景下的卡尔卡雷迪纳戈组（意大利北部）
DOI：
10.1016/j.palaeo.2012.11.003
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
S. Spezzaferri
中科院分区：
文献类型：
--
作者：
David Jaramillo‐Vogel;A. Strasser;G. Frijia;S. Spezzaferri
从始新世中期到渐新世早期，地球经历了新生代最显着的气候变冷。始新世-渐新世过渡（EOT）代表了这种气候变冷的顶峰，导致南极冰川作用的开始，从而导致当今冰库世界的开始。尽管深海系统对这种气候转变的响应已得到广泛研究，但其对浅水碳酸盐领域的影响却很少受到限制。这里展示了属于 Calcare di Nago 组的两个浅海碳酸盐岩层系（意大利北部的 Nago 和 San Valentino）中 EOT 的沉积表现。年代地层框架是通过整合岩石地层、生物地层和同位素地层数据（C 和 Sr 同位素）构建的，可以将这些浅海层序与意大利中部（马西尼亚诺）、坦桑尼亚（TDP 站点 12 和 17）以及印度洋（ODP 站点 744）的中上层剖面相关联。在意大利北部的几个地区，包括纳戈和圣瓦伦蒂诺，记录了普里亚波尼期（始新世晚期）海侵事件。 ODP 位点 744 的氧同位素显示出 0.4‰ 的同期负移，表明这种海侵的起源是冰川海平面上升。在 Nago 和 San Valentino 剖面中，没有检测到显着的层序边界，这表明海平面快速下降与定义 EOT-1 冷却事件的 δ18O 正向变化一起发生。相反，观察到沉积环境逐渐变浅。在 TDP 12 号和 17 号站点，EOT-1 之后出现 δ18O 约 0.4‰ 的负移，这与研究剖面中环境的相对加深相关，并表明 EOT-1 和渐新世同位素事件 1 (Oi-1) 之间存在熔融脉冲。与 Oi-1 相关的正 δ18O 变化在圣瓦伦蒂诺转化为碳酸盐工厂的变化，从以较大的底栖有孔虫、珊瑚和红藻为主的光生动物群落转变为以苔藓虫为主的杂虫群落。同样的苔藓虫相也出现在意大利始新世-渐新世边界附近的几个地区。该相被解释为代表现代冷水碳酸盐岩的类似物，并且是与 Oi-1 事件相关的至少区域范围的冷却脉冲的结果。
From the Middle Eocene to Early Oligocene, the Earth experienced the most significant climatic cooling of the Cenozoic era. The Eocene–Oligocene transition (EOT) represents the culmination of this climatic cooling, leading to the onset of the Antarctic glaciation and, consequently, to the beginning of the present-day icehouse world. Whereas the response of deep-sea systems to this climate transition has been widely studied, its impact on the shallow-water carbonate realm is poorly constrained. Here, the sedimentary expression of the EOT in two shallow-marine carbonate successions (Nago and San Valentino, northern Italy) belonging to the Calcare di Nago Formation is presented. The chronostratigraphic framework was constructed by integrating litho-, bio-, and isotope-stratigraphic data (C and Sr isotopes), allowing to correlate these shallow-marine successions with pelagic sections in central Italy (Massignano), Tanzania (TDP Sites 12 and 17), and the Indian Ocean (ODP Site 744). Within several sections in northern Italy, including Nago and San Valentino, a Priabonian (Late Eocene) transgression is recorded. Oxygen isotopes of ODP Site 744 show a coeval negative shift of 0.4‰, suggesting a glacio-eustatic origin for this transgression. In the Nago and San Valentino sections, no prominent sequence boundary has been detected that would indicate a rapid sea-level drop occurring together with the positive shift in δ18O defining the EOT-1 cooling event. Instead, a gradual shallowing of the depositional environment is observed. At TDP Sites 12 and 17, the EOT-1 is followed by a negative shift in δ18O of around 0.4‰, which correlates with a relative deepening of the environment in the studied sections and suggests a melting pulse between EOT-1 and the Oligocene isotope event 1 (Oi-1). The positive δ18O shift related to the Oi-1 translates in San Valentino into a change in carbonate factory from a photozoan association dominated by larger benthic foraminifera, corals, and red algae to a heterozoan association dominated by bryozoans. The same bryozoan facies occurs in several Italian localities near the Eocene–Oligocene boundary. This facies is interpreted to represent an analogue of modern cool-water carbonates and results from a cooling pulse of at least regional scale, associated to the Oi-1 event.
DOI：
10.1016/j.palaeo.2011.09.008
发表时间：
2011-11
期刊：
Palaeogeography, Palaeoclimatology, Palaeoecology
影响因子：
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作者：
L. Cotton;P. Pearson
通讯作者：
L. Cotton;P. Pearson
影响因子：
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作者：
Coxall, Helen K.;Wilson, Paul A.
通讯作者：
Wilson, Paul A.