Terrestrial Paleoecology and Sedimentary Environment of the Meyer Desert Formation, Beardmore Glacier, Transantarctic Mountains

跨南极山脉迈耶沙漠地层、比尔德莫尔冰川的陆地古生态和沉积环境

• 批准号: 0230696
• 负责人: Allan Ashworth
• 金额: --
• 依托单位: North Dakota State University Fargo
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2010-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0230696&HistoricalAwards=false
• 关键词: Terrestrial; Paleoecology; Sedimentary; Environment; Meyer

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a study of the paleobiology of the late Cenozoic Meyer Desert Formation. Terrestrial fossils recovered from the Beogene Meyer Desert Formation (Sirius Group) are providing paleoclimatic information about the interior of Antarctica before the growth of the great ice sheets. The site is located on the Upper Beardmore Glacier at latitude 85S, about 500 km from the South Pole. Fossils of numerous types of organisms occur in siltstone, marlstone and lithified peat that are interbedded with lodgment tills. Wood and leaves of Nothofagus (southern beech) were discovered many years ago but since 1995 the fossils now include seeds of several species of vascular plants, including Ranunculus (buttercups), the stems and leaves of several species of mosses, body parts of beetles, including two weevil species, a puparium of a higher fly, shells of freshwater mollusks, including a lymnaeid gastropod and sphaeriid clam, valves of an ostracod, and the tooth of a fish. The largest fossils at the site are cushions of vascular plants buried in their growth positions by sediments of glacial outwash. The sediments were deposited in stream channels and shallow pools associated with moraines that had been colonized by a tundra-like vegetation in that harbored insects and mollusks. Mean summer temperatures are estimated to have been about 4-5C for at least three months per year. The fossils provide the best evidence so far obtained of how much heat the atmosphere near the South Pole can hold.The fossils represent organisms that inhabited Antarctica until climate change forced their extinction. The fossils are fragmentary but hold the promise that better-preserved specimens are available for phylogenetic and biogeographic studies. They are more closely related to living terrestrial and freshwater organisms than any other fossils so far discovered in Antarctica. They are most probably the direct descendants of an ancient Antarctic biota that was part of Gondwana. Until the discovery of the Meyer Desert Formation, no fossils of terrestrial organisms, except for pollen and spores, were available to answer questions about evolutionary relationships between organisms distributed in southern South America, Australia, New Zealand, and the subantarctic islands.The research team will revisit Meyer Desert Formation exposed in the Oliver Bluffs on the Beardmore Glacier. Several studies will be conducted including locating and sampling new fossiliferous horizons, constructing an accurately scaled and correlated cross-section of the complex facies, and collecting samples for a pilot project to directly date the deposits using an approach involving a combination of several cosmogenic nuclide systems. Paleontological studies will focus on enhancing paleoenvironmental interpretations and on integrating the fossils in biogeographic studies. The startigraphic and dating studies will focus on resolving differences between interpretations of sedimentary environments. Collectively, the studies will provide information that should help to address larger questions about the size and the dynamics of the East Antarctic Ice Sheet during the Neogene.There is extensive public interest in Antarctica in part because of the romance of exploration but also because of the threat of global warming and the potential instability of the West Antarctic Ice Sheet. That interest has been fueled recently by reports of the collapse of the Larsen B Ice Shelf and the release of huge icebergs, like B17, to the Southern Ocean. Because Antarctica exerts a huge influence on the Earth's climate, oceanic circulation and sea level, knowledge about warmer climates during the Neogene is of broad interest. Media, educators and researchers will be able to access information about the studies, including a photographic archive for the fossils, through links to "Biota Austarlis Terrestris," an existing searchable database for the terrestrial and freshwater organisms of Antarctica and the subantarctic islands.

该奖项由极地计划办公室南极地质和地球物理计划提供，支持对晚新生代迈耶沙漠形成的古生物学研究。 从Beogene Meyer沙漠组（天狼星群）中发现的陆地化石提供了大冰盖生长之前南极洲内部的古气候信息。 该地点位于南纬85度的上比尔德摩尔冰川上，距离南极约500公里。 许多类型的生物化石出现在粉砂岩、泥灰岩和岩化泥炭中，与沉积冰碛物互层。 假山毛榉属的木材和树叶（南方山毛榉）是许多年前发现的，但自1995年以来，化石现在包括几种维管植物的种子，包括毛茛（毛茛属）、几种苔藓的茎和叶、甲虫的身体部分（包括两种象鼻虫）、一种高等蝇的蛹、淡水软体动物的壳（包括一种拟腹足类和球壳类蛤），介形虫的瓣膜和鱼的牙齿。 该地点最大的化石是被冰川沉积物掩埋在其生长位置的维管植物垫。 这些沉积物沉积在与冰碛有关的河道和浅池中，冰碛被一种像苔原一样的植被殖民化，其中有昆虫和软体动物。 据估计，每年至少有三个月的夏季平均气温约为4- 5摄氏度。 这些化石提供了迄今为止获得的关于南极附近的大气可以容纳多少热量的最佳证据。这些化石代表了在气候变化迫使它们灭绝之前一直居住在南极洲的生物。 这些化石是零碎的，但有希望保存更好的标本可用于系统发育和地理学研究。 它们与陆地和淡水生物的关系比迄今为止在南极洲发现的任何其他化石都要密切。 它们很可能是古南极生物群的直系后代，古南极生物群是冈瓦纳的一部分。 在发现迈耶沙漠组之前，除了花粉和孢子外，没有陆地生物化石可以回答有关分布在南美洲南部、澳大利亚、新西兰和亚南极洲岛屿的生物之间进化关系的问题。研究小组将重新访问暴露在比尔德摩尔冰川上的奥利弗布拉夫斯的迈耶沙漠组。 将进行几项研究，包括对新的含矿层进行定位和取样，制作复杂相的精确比例和相关横截面，并为一个试点项目收集样本，以便使用涉及几种宇宙成因核素系统组合的方法直接确定矿床的年代。 古生物学研究将侧重于加强古环境解释，并将化石纳入地理学研究。 星图和测年研究将侧重于解决沉积环境解释之间的差异。 总的来说，这些研究将提供信息，应该有助于解决更大的问题，在新第三纪东南极冰盖的大小和动态。有广泛的公众对南极洲的兴趣，部分是因为探险的浪漫，但也因为全球变暖的威胁和西南极冰盖的潜在不稳定性。 最近有报道称，拉森B冰架崩塌，巨大的冰山（如B17）被释放到南大洋，这进一步激发了人们的兴趣。 由于南极洲对地球的气候、海洋环流和海平面有着巨大的影响，有关新近纪温暖气候的知识引起了广泛的兴趣。 媒体、教育工作者和研究人员将能够通过与“Biota Austarlis Terrestris”的链接获得有关研究的信息，包括化石的照片档案，“Biota Austarlis Terrestris”是一个现有的可搜索的南极洲和亚南极洲岛屿陆地和淡水生物数据库。