PALYNOLOGY OF THE NBP03-01A TRANSECT IN THE NORTHERN BASIN, WESTERN ROSS SEA, ANTARCTICA: A LATE PLIOCENE RECORD
PALYNOLOGY OF THE NBP03-01A TRANSECT IN THE NORTHERN BASIN, WESTERN ROSS SEA, ANTARCTICA: A LATE PLIOCENE RECORD
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南极洲西罗斯海北部盆地 NBP03-01A 断面的孢粉学：上新世晚期记录
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发表时间：
2006
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通讯作者：
R. Askin
中科院分区：
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作者：
S. Warny;J. Wrenn;P. Bart;R. Askin
摘要对南极罗斯海北部盆地大陆边缘样带采集的10个柱塞岩心的57个样品进行了形态分析。恢复了中等多样性的海洋微型浮游生物和陆生浮游生物组合。孢粉形态组合被细分为两大类：原位植物区系（包括针叶藻、鞭毛藻囊、球孢和主要由cymatiosphaerids组成的prasinophyte藻类）和改造植物区系（包括鞭毛藻囊、花粉和孢子）。高球是最丰富的异形。据报道，这种在相对丰度上的突出现象是今天在北极季节性冰和浮冰之间的界限发现的典型组合。原位鞭毛囊肿稀疏。它们主要以Lejeunecysta为代表，基于与开普罗伯茨的物种相似性，被认为是渐新世至上新世的。所有其他发现的鞭毛藻囊都是始新世到渐新世沉积物改造的结果。二次加工的孢子和花粉构成了第二丰富的群体。它们具有中等的多样性，包括始新世或更古老的Nothofagidites， Podocarpaceae和Proteaceae组合。其他分类群是温暖雨林植被的代表，渐新世和新近世的分类群包括生长在较冷的亚极地气候下的林地到草本/低灌木苔原植被的代表。这些组合表明不同时期的沉积或来自不同来源的改造。通过地震对比和硅藻分析，确定其沉积年代为晚上新世。在此基础上，我们假设Brancolini et al.（1995）的RSU 2或Bart et al.（2000）的un整合10 （U10）发生在2.3 Ma之前，这是在U10以上单元中原位物种恢复的最古老年龄。由于陆地和海洋的改造分类群都包括始新世至渐新世的组合，因此假设这些改造组分来自单一来源；最可能的是始新世至渐新世浅海地层被侵蚀，并通过位于Drygalsky和Joides盆地的冰流从罗斯岛地区转移到陆架边缘。
Abstract Fifty-seven samples taken from ten piston cores collected along a transect off the continental margin of the Northern Basin, Ross Sea, Antarctica were analyzed for palynomorphs. Moderately diverse assemblages of marine microplankton and terrestrial palynomorphs were recovered. The palynomorph assemblages have been subdivided into two main groups: the in-situ flora (including acritarchs, dinoflagellate cysts, leiospheres and prasinophyte algae mainly composed of cymatiosphaerids), and the reworked flora (including dinoflagellate cysts, pollen and spores). The leiospheres are the most abundant palynomorphs. This prominence in the relative abundance of leiospheres has been reported as typical of assemblages found today at the limit between seasonal and pack ice in the Arctic. In-situ dinoflagellate cysts are sparse. They are mainly represented by Lejeunecysta, which, based on species similarities to those from Cape Roberts, are believed to be of Oligocene to Pliocene age. All other dinoflagellate cysts recovered are the result of reworking from Eocene to Oligocene sediments. Reworked spores and pollen comprise the second most abundant group. They are of moderate diversity and include an Eocene or older assemblage of Nothofagidites, Podocarpaceae and Proteaceae. Other taxa are representative of warmer rainforest vegetation, with Oligocene and Neogene taxa that include representatives of woodland to herbaceous/low shrubby tundra vegetation growing in colder subpolar climates. These assemblages indicate either different periods of deposition or reworking from diverse sources. Through seismic correlation and diatom analysis, the sediments are believed to be Late Pliocene in age. On this basis, it is postulated that the major glacial advance, RSU 2 of Brancolini et al. (1995) or Unconformity 10 (U10) of Bart et al. (2000), occurred before 2.3 Ma, which is the oldest age of in-situ species recovered in units above U10. As both terrestrial and marine reworked taxa include assemblages of Eocene to Oligocene age, it is assumed that those reworked components were yielded from a single source; most probably Eocene to Oligocene shallow marine strata eroded and transported from the area of Ross Island to the shelf margin through ice streams located in the Drygalsky and Joides basins.