Palynostratigraphic and Paleoenvironmental Characterization of Upper Miocene Sediments from Western Ross Sea, Antarctica

南极洲西罗斯海上中新世沉积物的孢粉地层和古环境特征

• 批准号: 0230001
• 负责人: Sophie Warny
• 金额: $ 9.2万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-04-15 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0230001&HistoricalAwards=false
• 关键词: Palynostratigraphic; Paleoenvironmental; Characterization; Upper; Miocene

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a project to investigate the interaction of the Antarctic ice sheet and the Southern Ocean during the late Miocene time period. Numerous lines of geological evidence show that the Earth climate system changed dramatically during the late Miocene. These changes include the largest pre-Pleistocene glacioeustatic sea-level low stands during the Cenozoic, a 300-km northward shift of the Polar Front, multiple pulses of ice rafting, a global carbon isotopic (d13C) shift, a global reduction in ocean salinity, and several episodes of Southern Ocean abyssal-plain erosion. Primarily on the basis of deep-sea proxy data, it has been inferred that late Miocene climatic changes were related to Antarctic glacial intensification.Although these proxy data interpretations are based on fundamentally sound geological and geochemical principles, the conclusions concerning linkages to the Antarctic cryosphere are equivocal because the specific environmental conditions at the Antarctic continental margins have not yet been established. The fundamental purpose of this palynological study is to address the following question: What were the environmental conditions (i.e. salinity, temperature, and sea ice-cover) during late-Miocene interglacials and glacials on the western Ross Sea inner and outer continental shelf?The secondary goals are to:1. Enhance the existing Ross Sea palynostratigraphy developed from the Cape Roberts Project.2. Determine if the major glacial advance to the Northern Basin shelf edge, described by Brancolini and colleagues in 1995 and Bart and colleagues in 2000, was indeed a late Miocene event, and if so, what were the environmental conditions existing during this glacial period.3. Determine the effect of Antarctic environmental changes on low-latitude climate change, focusing on linkage with the Messinian Salinity Crisis and the reason behind the global salinity reduction. Indeed, new palynological data from the Atlantic coast of the paleo-Gibraltar threshold suggests that a significant Antarctic-linked lowering of sea level occurred during the late Miocene, restricting Atlantic inflow into the Mediterranean Sea at the beginning of the crisis.In the first part of this study, the palynology of the well-dated, inner continental shelf cores DVDP 10 and 11 will be analyzed. Prior work by others showed, on the basis of benthic foraminifer and diatom distribution, that cycles of open-marine/glacial conditions existed on the Ross Sea inner continental shelf during the Mio-Pliocene. Dinocyst distribution should test this theory. In the second part of this study, a palynological analysis of previously acquired material from the Northern Basin outer continental shelf will be conducted. Recent seismic-stratigraphic analyses indicated that the sediments associated with a major late Miocene (?) glacial advance are exposed over a broad area, on the northwestern Ross Sea outer continental shelf. Palynomorphs contained in these sediments should test if indeed, the outcrops were deposited during the late Miocene. Because basic types of Antarctic and Arctic marine palynomorphs are similar, paleoenvironmental reconstruction will be based on existing ecological data from the Arctic, as well as that from Antarctic waters. The oxygen isotopic (d18O) record recently generated for DVDP sites 10 and 11 should provide a reasonable proxy for Antarctic ice-volume changes and evaluate if environmental changes were related to ice-volume changes. In addition to the environmental aspect, the biostratigraphic information generated by this study should provide improved chronostratigraphic support for future proposed Antarctic geological drilling programs, such as SHALDRIL and ANDRILL.

该奖项由极地计划办公室的南极地质与地球物理学计划提供，支持一个项目，以调查中新世晚期的南极冰盖和南方大洋的相互作用。大量地质证据表明，中新世晚期地球气候系统发生了巨大变化。这些变化包括在酸中心期间最大的丙酸式海平面远离海平面的低位，在极地朝北300公里，冰裂多脉冲，全球碳同位素（D13C）偏移，一种全球降低的海洋盐度盐度降低，以及南部大洋深渊的几集侵蚀。主要基于深海代理数据，已经推断中新世晚期的气候变化与南极冰川强化有关。尽管这些代理数据解释是基于基本上是合理的地质和地球化学原理，是与与南极冰lossosphere crypsopter的结论的结论是模棱两可的，因为尚未建立南极大陆边缘的特定环境条件。这项孤生研究的基本目的是解决以下问题：在西部罗斯海内部和外大陆架上的晚期冰川和冰川期间，环境条件（即盐度，温度和海冰覆盖）是什么？次要目标是：1。增强现有的罗斯·帕尔纳森地层学，从罗伯茨角（Cape Roberts）项目开发。2。确定Brancolini及其同事在1995年以及2000年的Bart及其同事所描述的北盆地架架边缘的主要冰川前进是否确实是中新世晚期事件，如果是这样，那么在这个冰川期间存在的环境条件是什么。33.3 。确定南极环境变化对低纬度气候变化的影响，重点是与弥赛亚盐度危机的联系以及全球盐度降低背后的原因。确实，古勃里巴尔特阈值的大西洋海岸的新载生学数据表明，在中新世晚期，海平面发生了大量的南极链接降低，限制了大西洋流入危机开始时进入地中海的大西洋流入。在这项研究中，将分析良好的，内部大陆架核心DVDP 10和11的烷学。其他人的先前工作表明，在底栖有孔虫和硅藻分布的基础上，在小单元期间，在罗斯海内部大陆架上存在开放盐/冰川条件的周期。 dinocyst分布应检验该理论。在这项研究的第二部分中，将对先前从北部盆地外部大陆架的材料进行孢粉学分析。最近的地震 - 地层学分析表明，与重大中新世晚期（？）冰川前期相关的沉积物在西北罗斯海外大陆架上暴露在广阔的地区。这些沉积物中包含的palynomorphs应该测试是否确实在中新世晚期沉积了露头。由于南极和北极海洋palynomorphs的基本类型相似，因此古环境重建将基于来自北极的现有生态数据，以及来自南极水域的生态数据。最近针对DVDP位点10和11生成的氧同位素（D18O）记录应为南极冰量变化提供合理的代理，并评估环境变化是否与冰量变化有关。除了环境方面，这项研究产生的生物地层学信息还应为未来提议的南极地质钻探计划（例如Alldril and Andrill）提供改进的年度地层学支持。