Paleogene Marine and Terrestrial Development of the West Antarctic Rift System
Paleogene Marine and Terrestrial Development of the West Antarctic Rift System
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DOI：
10.1029/2019gl085281
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发表时间：
2020-02-16
影响因子：
5.2
通讯作者：
Askin, R.
中科院分区：
文献类型：
--
作者：
Coenen, J. J.;Scherer, R. P.;Askin, R.
模拟西南极冰盖(WAIS)的早期发展取决于与西南极裂谷系统相关的古近纪陆地地貌的形态和演化。一项广泛应用但之前未经检验的始新世/渐新世界线古地形重建表明，当时西南极中部的大部分地区海拔高达1000米，构成了早期WAIS的关键成核地点。在这里，我们表明，在WAIS之下发现的沉积物中的古近纪海洋和陆地微化石组合和生物标志物提供了与这种广泛使用的“最大”古地形重建相反的直接证据。这些新的约束要求对构造和冰盖模型进行重大修改，并提供对整个西南极裂谷系统的现代差异抬升的洞察力。简而言之，在二氧化碳远高于今天的世界中，南极陆块的结构和海拔在早期冰盖发展中发挥了关键作用。几项研究试图重建3400万年前构造复杂的西南极的陆地景观，当时气候变冷导致南极冰盖增长。在这里，我们使用从西南极冰盖内部收集的沉积记录来测试已公布的地球历史上这一关键时期的景观重建。海洋微体化石(硅藻、甲藻、钙质超微化石和埃布里迪亚化石)被用来限制沉积沉积的年龄。此外，我们使用陆地花粉、孢子和淡水硅藻，以及海洋和陆地有机生物标志物，记录了过去的沉积盆地，并重建了从温暖的始新世(类似于5600万至3400万年前)到较冷的渐新世(类似于3400万至2300万年前)过渡期间的古环境。我们的研究结果极大地提高了人们对南极洲西部构造和地貌演化的认识，因此需要改进早期冰盖的模拟。
Modeling the early development of the West Antarctic Ice Sheet (WAIS) hinges on the configuration and evolution of Paleogene terrestrial landscapes associated with the West Antarctic Rift System. A widely applied but previously untested paleotopographic reconstruction for the Eocene/Oligocene boundary suggests that much of central West Antarctica was as much as 1,000 m above sea level at that time, constituting a key nucleating site for an early WAIS. Here we show that Paleogene age marine and terrestrial microfossil assemblages and biomarkers in sediments recovered from beneath the WAIS provide direct evidence contrary to this widely utilized "maximum" paleotopographic reconstruction. These new constraints call for significantly modified tectonic and ice sheet model parameterization and also provide insights into modern differential uplift across the West Antarctic Rift System.Plain Language Summary The configuration and elevation of Antarctic land masses played a key role in early ice sheet development in a world with CO2 much higher than today's. Several studies have attempted to reconstruct the terrestrial landscape of the tectonically complex West Antarctica 34 million years ago, a time when a cooling climate led to Antarctic ice sheet growth. Here we use sedimentary records collected from beneath the West Antarctic Ice Sheet interior to test published landscape reconstructions for this critical interval in Earth history. Marine microfossils (diatoms, dinoflagellates, calcareous nannofossils, and ebridians) are used to constrain the ages of sedimentary deposits. Additionally, we use terrestrial pollen, spores, and freshwater diatoms, as well as marine and terrestrial organic biomarkers, to document past sedimentary basins and reconstruct paleoenvironments during the transition from the warm Eocene (similar to 56 to 34 million years ago) to the cooler Oligocene (similar to 34 to 23 million years ago). Our results significantly advance knowledge of tectonic and landscape evolution across West Antarctica, thus calling for improved modeling of the early ice sheet.