Permian and Triassic Floras of the Beardmore Glacier Area: Icehouse or Greenhouse?

该奖项由极地计划办公室南极地质和地球物理计划提供资金，用于研究横贯北极山脉中部的植物化石，以了解植物的多样性和进化，以及改善对古环境条件的了解。在过去的30年里，横贯北极山脉中部的陆相岩石一直是杰出植物化石发现的来源，包括二叠纪和三叠纪过矿化泥炭，生长位置硅化的化石森林，以及角质层保存的压缩植物群。遗址罕见地并列在一起，包括许多不同类型的植物保存(过矿化、压缩/印记、原生森林、木乃伊)、非凡的植物保存质量和丰富的遗址使该地区在世界上独一无二。该项目主要收集比尔德莫尔冰川地区的二叠纪和三叠纪植物巨型化石。作为与其他研究人员一起的小型夏令营的一部分，预计将在2003-2004年的野外季节进行实地考察。收藏品将包括压缩植物群，特别是那些来自石墨峰的植物群，以及来自Skaar Ridge和Fremuw Peak的永久矿化泥炭，这两个地方都位于沃尔科特Neve附近。这些过矿化作用代表了植物化石保存的最稀有形式。由于它们保存了植物区系的三维记录，因此它们对于了解植物化石的基本形态和解剖学以及详细描述类群之间的关系非常重要。同时保存为过矿化作用和挤压作用的植物化石的并置提供的额外数据，已经为我们理解晚古生代-早中生代植物演化做出了很大贡献。这个项目将通过进一步收集材料以及已经处理的材料来解决几个重要的系统发育假说。二叠纪和三叠纪代表着植物进化的一个重要时期，我们对此仍然知之甚少，特别是在南半球。冈哇那的优势植物群是二叠纪的舌翅目种子蕨类(叶型)和三叠纪的子生蕨类(叶型的双生蕨属)。由于这两个类群都有以某种方式封闭的种子，它们曾一度被认为是开花植物的可能祖先，并在种子植物的系统发育分析中发挥了重要作用。只有通过过矿化作用和压缩作用的结合，才有可能揭示化石植物的形态和结构的完整图景，但更重要的是，了解这些植物类群在种子植物进化中的位置。植物和硅化原木将从石墨峰的部分收集，该部分据信包含二叠系/三叠系界线。这些植物化石将被用来检验关于这一边界上可能发生的花卉和古气候变化的几个假说。这些问题包括：在三叠纪多早的时候出现了双沟藻植物群？Glossopteris是否像在冈瓦那的其他几个植物区系中一样，与DMicro dium一起出现？有没有证据表明，就像一些孢粉学证据所表明的那样，存在由石龙科动物主导的巨型绿藻？硅化测井已在巴克利组下部(中二叠世？)在这个地点，这些将被收集并检查来自树木年轮的古气候数据。这也可以与附近山上晚二叠世木材(上巴克利)中的树木年轮进行比较。阿切纳尔。晚二叠世比早-中二叠世温暖得多，这应该反映在树木年轮的宽度和结构上的差异。这一项目有望在关键的二叠纪至三叠纪期间对植物演化和古环境条件的理解取得重大进展。

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, provides funds for research to investigate fossil plants from the central Transantarctic Mountains toward an understanding of plant diversity and evolution as well as an improved understanding of the paleoenvironmental conditions. The terrestrial rocks of the central Transantarctic Mountains have been a source of outstanding plant fossil discoveries over the last 30 years, including Permian and Triassic permineralized peat, fossil forests silicified in growth position, and compression floras with cuticular preservation. The rare juxtaposition of sites that include many different types of plant preservation (permineralization, compression/impression, in situ forests, mummified wood), the exceptional quality of the plant preservation, and the richness of the sites make this area unique in the world. This project centers on the collection of Permian and Triassic plant megafossils from the Beardmore Glacier area. Fieldwork is anticipated in the 2003-2004 field season as part of a mini-camp with other researchers. Collections would include compression floras, especially those from Graphite Peak, and permineralized peats from Skaar Ridge and Fremouw Peak, both in the vicinity of Walcott Neve. These permineralizations represent the rarest form of plant fossil preservation. Since they preserve a three-dimensional record of the flora, they are important in understanding the basic morphology and anatomy of fossil plants, as well as detailing relationships among groups. The additional data provided by the juxtaposition of plant fossils preserved both as permineralizations and compressions have already contributed a great deal to our understanding of late Paleozoic-early Mesozoic plant evolution. This project will address several important phylogenetic hypotheses through further collection of material, coupled with material already processed. The Permian and Triassic represent an important time in plant evolution, and one about which we still know relatively little, especially in the southern hemisphere. The glossopterid seed ferns in the Permian (leaf type, Glossopteris), and the corystosperms in the Triassic (leaf type, Dicroidium) were the dominant plant groups in Gondwana. Since both of these groups bore seeds which were enclosed in some manner, they have been proposed at one time or another as possible ancestors of the flowering plants, and have figured prominently in phylogenetic analyses of seed plants. Only through a combination of permineralizations and compressions is it possible to reveal a complete picture of the form and structure of fossil plants, but more importantly, to understand the position of these plant groups in seed plant evolution. Plants and silicified logs will be collected from the section at Graphite Peak, which is believed to contain the Permian/Triassic boundary. These plant fossils will be used to test several hypotheses concerning the floral and paleoclimate changes that may have occurred across this boundary. These include: How early in the Triassic does the Dicroidium flora appear? Does Glossopteris occur with Dicroidium as it does in several other Gondwana floras? Is there any evidence of a megaflora dominated by lycopods, as some of the palynological evidence suggests? Silicified logs have been noted in the lower Buckley Formation (mid-Permian?) at this site and these will be collected and examined for paleoclimate data from tree rings. These can also be compared with tree rings in Late Permian wood (upper Buckley) from nearby Mt. Achernar. The Late Permian has been assumed to be much warmer than Early-Middle Permian and this should be reflected in differences in the width and structure of the tree rings.This project is expected to lead to significant improvements in understanding of both plant evolution and paleoenvironmental conditions during the critical Permian to Triassic interval.