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

该奖项由极地项目办公室的南极地质和地球物理项目提供，为研究横贯南极山脉中部的化石植物提供资金，以了解植物多样性和进化，并改善对古环境条件的了解。在过去的30年里，横贯南极山脉中部的陆相岩石是发现杰出植物化石的来源，包括二叠纪和三叠纪的过矿化泥炭，生长位置硅化的化石森林，以及表皮保存的压缩植物区系。罕见的并列遗址包括许多不同类型的植物保存（过矿化，压缩/印象，原地森林，木乃伊化木材），植物保存的卓越质量和遗址的丰富性使该地区在世界上独一无二。这个项目的重点是收集来自比尔德莫尔冰川地区的二叠纪和三叠纪植物巨型化石。预计将在2003-2004年实地考察季与其他研究人员一起作为小型营地的一部分进行实地考察。收集将包括压缩植物群，特别是来自石墨峰的植物群，以及来自沃尔科特Neve附近的Skaar Ridge和Fremouw Peak的过矿化泥炭。这些过矿化反应代表了植物化石保存的最罕见形式。由于它们保存了植物区系的三维记录，因此对于了解植物化石的基本形态和解剖结构以及类群之间的详细关系非常重要。同时保存为过矿化和压缩的植物化石的并置所提供的额外数据，已经对我们对古生代晚期-中生代早期植物进化的理解作出了很大的贡献。该项目将通过进一步收集材料，结合已经处理的材料，解决几个重要的系统发育假说。二叠纪和三叠纪代表了植物进化的一个重要时期，但我们对它的了解相对较少，尤其是在南半球。二叠系的舌蕨类（叶片型）和三叠系的伞蕨（叶片型）是冈瓦纳的优势植物类群。由于这两个类群都有以某种方式封闭的种子，因此曾有人提出它们可能是开花植物的祖先，并在种子植物的系统发育分析中占有重要地位。只有将过矿化作用和压缩作用结合起来，才能全面揭示植物化石的形态和结构，更重要的是了解这些植物类群在种子植物进化中的地位。将从石墨峰剖面收集植物和硅化原木，该剖面被认为包含二叠纪/三叠纪边界。这些植物化石将被用来测试一些关于植物和古气候变化的假设，这些变化可能发生在这一边界之外。这些问题包括：Dicroidium植物群是在三叠纪多早出现的？舌蕨是否和其他冈瓦纳植物区系一样出现在双子母科？是否有证据表明，像一些孢粉学证据所表明的那样，有一个由石松类动物主导的巨型植物群？在该地点的巴克利组下部（二叠纪中期）发现了硅化原木，这些原木将被收集起来，并通过树木年轮进行古气候数据的研究。这些也可以与附近阿切纳尔山的晚二叠世木材（上巴克利）的树木年轮进行比较。晚二叠纪被认为比早中二叠纪温暖得多，这应该反映在树木年轮的宽度和结构上的差异上。该项目有望对二叠纪至三叠纪关键时期的植物进化和古环境条件的理解产生重大影响。

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.