Collaborative Research: Permian-Triassic Basin History of Southern Victoria Land and the Darwin Mountains

合作研究：维多利亚州南部土地和达尔文山脉的二叠纪-三叠纪盆地历史

• 批准号: 9909637
• 负责人: John Isbell
• 金额: $ 23.45万
• 依托单位: University of Wisconsin-Milwaukee
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-06-01 至 2004-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9909637&HistoricalAwards=false
• 关键词: Collaborative; Research; Permian; Triassic; Basin

9909637IsbellThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a collaborative sedimentological, palynological, and paleomagnetic study of Permian and Lower Triassic strata in southern Victoria Land (SVL) and the Darwin Mountains (DM), Antarctica. Results of the study will help constrain the paleoenvironmental, tectonic, biotic, and paleogeographic histories of southern Pangea and provide a unique polar view of the world during an icehouse to greenhouse transition.The assembly and drift of Pangea resulted in heightened orogenic activity and associated development of numerous depositional basins. One of the largest basins was the 10,000+ km long "Gondwanide foredeep" that extended across southern South America, South Africa, the Falkland Islands, Antarctica, and Australia. Antarctica's centralized location between South Africa and Australia, make SVL and DM key areas for testing paleogeographic and paleoclimatic models.Upper Paleozoic and Lower Mesozoic rocks in SVL and DM were deposited during Gondwanaland's drift across the south pole. Based on present plate reconstructions, SVL and DM were located higher than 75 degrees south latitude from 320 to 210 Ma. Despite the putative high latitude position, SVL and DM sedimentary successions record a change from Lower Permian glacial deposits, to Permian fluvial coal measures, to Lower Triassic non-carbonaceous fluvial deposits, and finally to Middle and Upper Triassic fluvial coal measures, with well-developed vegetation during much of this time. Present climatic simulations suggest seasonal climatic extremes within Pangea's polar interior. Discrepancies between the geological evidence and the climate simulations need to be resolved, and may be magnified by incomplete understanding of the influence of paleotopography, large lakes, and river systems at the time of deposition, as well as by incomplete documentation of paleoenvironmental conditions. Furthermore, Late Permian and Triassic mean pole positions for Gondwanaland are not tightly constrained. Paleomagnetic signatures will be recovered from Permian and Triassic petrified wood, silicified peat, and coal, which were cemented during early diagenesis (preliminary results indicate stable remnant magnetizations). Palynological analyses will provide time control for the succession.Objectives of this study include:1) Determination of a late Paleozoic glacial/deglaciation history for SVL and DM as Gondwana drifted over the south pole,2) Documentation of Permian strata as a means to better understand the environments of high latitude fluvial coal-bearing deposits,3) Documentation of Triassic lithofacies as a means to better understand high latitude conditions during the Early to Middle Triassic "coal gap" interval,4) Providing a well-constrained stratigraphic framework for the Permian to lower Triassic succession,5) Testing the diachronous and inversion tectonic models for the Panthalassan Margin of southwestern Pangea, and6) Constructing better paleogeographic models for Gondwana by obtaining new Gondwana reference poles for the Permian and Triassic.

该奖项由极地计划办公室南极地质和地球物理计划提供，支持对南维多利亚大陆(SVL)和南极洲达尔文山脉(DM)的二叠纪和下三叠纪地层进行沉积学、孢粉学和古地磁合作研究。研究结果将有助于约束盘古大陆南部的古环境、构造、生物和古地理历史，并提供一个独特的冰库向温室过渡期间的世界极地图景。盘古大陆的组装和漂移导致造山活动增强，并伴随着众多沉积盆地的发育。其中最大的盆地之一是横跨南美洲南部、南非、福克兰群岛、南极洲和澳大利亚的10,000多公里长的“冈德瓦尼德深渊”。南极洲集中在南非和澳大利亚之间，这使得SVL和DM成为检验古地理和古气候模型的关键地区。SVL和DM的上古生界和下中生界岩石是在冈瓦瓦兰德漂移穿过南极期间沉积的。根据目前的板块重建，在320~210 Ma期间，SVL和DM位于南纬75度以上。尽管推测处于高纬度位置，但SVL和DM沉积序列记录了从下二叠统冰川沉积到二叠系河流煤系，再到下三叠统非碳质河流相沉积，最后到中上三叠统河流煤系的变化，在这段时间的大部分时间里，植被发育良好。目前的气候模拟表明，盘古大陆两极内陆地区存在季节性气候极端。地质证据和气候模拟之间的差异需要解决，而且可能会因为对沉积时古地形、大湖和河流系统的影响的不完全了解以及对古环境条件的不完整记录而被放大。此外，冈瓦瓦兰晚二叠世和三叠纪的平均极点位置并没有受到严格的限制。将从二叠纪和三叠纪石化木材、硅化泥炭和煤中恢复古地磁特征，这些木材在早期成岩作用期间被胶结(初步结果表明剩余磁化作用稳定)。这项研究的目的包括：1)确定晚古生代SVL和DM的冰川/消冰史，因为冈瓦纳漂移到南极；2)二叠纪地层的记录，作为更好地了解高纬度河流含煤矿床的环境；3)三叠纪岩相的记录，作为更好地了解早、中三叠世的高纬度条件的手段；4)为二叠纪到下三叠世层序提供一个良好的约束地层格架；5)检验盘山西南边缘的历时和反转构造模型，6)通过获取二叠系和三叠系的新冈瓦那参照柱，建立了更好的冈瓦那古地理模型。