East Antarctic glacial history through microfossil analyses of the Pagodroma Group

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Pagodroma群沉积物进行微古生物调查，以补充和加强先前对这些东南极新生代冰川沉积物的地层和古环境研究。初步结果表明，存在渐新世(？)、中中新世、上中新世和上新世-更新世冰晶地层，这些地层对我们理解南极东部冰盖(EAIS)过去的波动范围和特征具有重要意义。这些地层是在一个冰川系统中沉积的，包括通过兰伯特冰川的EAIS排水和反复的海洋入侵和冰缘/接地线撤退，跨越800多公里的距离。这些地层中存在的古生物和沉积学信息有可能提供与EAIS历史有关的基线气候信息。Pagodroma Group层序将提供新近纪大陆内陆冰川玛利亚沉积的记录，这将扩大已知的干谷地区和维斯特福尔德丘陵地区钻芯和露头的情况。这些矿床的生物地层年龄是由硅藻和有孔虫组合的产状决定的，这些硅藻和有孔虫组合赋存于硅藻质海相泥岩的横向连续岩层中，位于一系列斜长英云母中。这些化石与南大洋和罗斯海的生物地层学方案有直接的年龄关联。在Pagodroma组的几个矿床中发现了开阔的海洋硅藻生产和原位硅藻沉积，这些矿床距离目前的海岸线至少内陆300公里。这项新的研究将集中于通过原位和冰川改造微化石组合的研究来确定Pagodroma群不同沉积的时代。这将有助于重建EAIS-兰伯特冰川-阿莫利盆地-普里兹湾系统的复合历史。这项建议的主要目标是：(1)开发新近纪EAIS变异性的时间和空间记录，以及(2)利用地质数据检验预测EAIS未来变化的假设，以响应全球气温上升。此外，生物地层学和古生态分析可以揭示沉积时的海表面温度、海平面和海冰条件以及其他环境参数。通过对新生代南极含硅藻类沉积物的持续研究，测年和解释这些古环境条件的能力正在稳步提高，但仍有许多工作要做。将对1997/98年度野外季节收集的250份Pagodroma Group样本进行分析。目前，从距离现代海岸内陆250公里的阿莫里绿洲的沉积物中可以获得116个样品；从内陆500公里的斯特林纳山获得5个样品；从内陆600公里的孟泽斯山获得84个样品。该项目的大部分将由一名博士后科学家进行，他将继续改进硅藻的生物地层和古生态利用，并进一步扩大他在新生代南极硅藻古生物学方面的教育和经验。许多国际南极项目计划在南极陆架和边缘进行未来的地层钻探项目，这些项目将需要几名经验丰富的硅藻古生物学家的技能，为回收的物质提供年龄和环境控制。总之，该项目将为博士后研究人员提供有关重要材料的进一步经验和培训，这些材料将有助于回答目前关于南极东部冰盖新近纪变化以及未来可能对全球气温升高作出反应的问题。

0089899HarwoodThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a micropaleontological investigation of Pagodroma Group sediments to complement and enhance prior stratigraphic and paleoenvironmental studies of these Cenozoic glacial deposits of East Antarctica. Preliminary results indicate the presence of Oligocene (?), middle Miocene, upper Miocene and Pliocene-Pleistocene glaciomarine strata that have the potential to contribute significantly to our understanding of the past fluctuations in the extent and character of the East Antarctic Ice Sheet (EAIS). These strata were deposited in a glacial system involving EAIS drainage through the Lambert Glacier and repeated marine incursion and ice margin/grounding line retreat across a distance of more than 800 km. Paleontological and sedimentological information present within these strata have the potential to provide baseline climate information bearing on the history of the EAIS. The Pagodroma Group sequences will provide a Neogene record of glaciomarine deposition on the continental interior that will expand what is already known from drill cores and outcrops in the Dry Valley region and the Vestfold Hills. These deposits are dated biostratigraphically by the occurrence of in situ diatom and foraminifera assemblages that occur in laterally-continuous beds of diatomaceous marine mudstone within a sequence of diamictite. These fossils provide direct age correlation to Southern Ocean and Ross Sea biostratigraphic schemes. Open marine diatom production and in situ diatom sedimentation is noted in several deposits of the Pagodroma Group that are at least 300 km inland from the current coastline. This new research will focus on establishing the age of different deposits of the Pagodroma Group through the study of in situ and glacially reworked microfossil assemblages. This will aid in the reconstruction of a composite history of the EAIS-Lambert Glacier-Amery Basin-Prydz Bay system. Primary objectives of this proposal are: (1) to develop a temporal and spatial record of Neogene EAIS variability, and (2) to test hypotheses that predict future changes in the EAIS in response to elevated global temperatures with geologic data. In addition, biostratigraphical and paleoecological analyses can reveal sea-surface temperature, sea level and sea-ice conditions, among other environmental parameters at the time of deposition. The ability to date and interpret these paleoenvironmental conditions is improving steadily through continued study of Cenozoic Antarctic diatom-bearing deposits, yet much remains to be done. Analyses will be undertaken on 250 Pagodroma Group samples collected during the 1997/98 field season. Currently 116 samples are available from deposits on the Amery Oasis, which is 250 km inland from the modern coast; 5 samples from Mt Stinear, 500 km inland; and 84 samples from Mt Menzies, which is 600 km inland. The bulk of this project will be conducted by a post-doctoral scientist, who will continue to improve the biostratigraphic and paleoecological use of diatoms and further extend his education and experience in Cenozoic Antarctic diatom paleontology. Future stratigraphic drilling programs that are planned for the Antarctic shelf and margin by numerous international Antarctic programs will require the skills of several experienced diatom paleontologists to provide age and environmental control for recovered materials. In summary, this project will provide further experience and training for a postdoctoral researcher on important materials that will help to answer current questions about Neogene variability of the East Antarctic Ice Sheet and the likely response to elevated global temperatures in the future.