Permian and Triassic Biogenic Structures in the Shackleton Glacier Area,Transantarctic Mountains: Record of Nonmarine Benthic Communities and their Response to Climate Change

该奖项支持了一个研究横贯南极山脉中部灯塔超群二叠纪和三叠纪部分化石的项目。横贯南极山脉中部的沉积序列表明，在二叠纪和三叠纪期间，冈瓦纳古太平洋边缘的这一部分先后被大陆冰川覆盖（宝塔组），被内陆海淹没（麦盖勒组），被流经砂质辫状平原的河流沉积的沉积物覆盖（仙子组），并被沉积在辫状河道和洪泛平原上的沙和粉砂所覆盖（巴克利和弗雷莫地层）。这一系列事件是由气候的改善和构造制度的变化引起的。尽管丰富的Buckley和Fremouw组的植物群和保存完好的Fremouw组的脊椎动物群是持续广泛研究的主题，但人们对居住在二叠纪和三叠纪广泛内陆水域的底栖动物群及其对气候变化的反应知之甚少。这些动物本身并没有以化石的形式保存下来，但生物成因结构，包括痕迹化石（石栖动物；离散的足迹、足迹和洞穴）和石栖结构（生物活动造成的普遍破坏），提供了产生它们的底栖动物的信息。这些信息包括：1)生产者的体型和总体平面图，这是他们身份的钥匙；2)近似的动物多样性；3)生产者的行为；4)生产者的环境偏好；5)生产者对营养资源和空间资源的利用；6)与物理和沉积过程相关的底栖动物的活动和丰度，反映在技术结构上。本研究将对Mackellar、Fairchild、Buckley和lower Fremouw组中不同水下相的微量化石和技术结构进行描述和解释，以描绘二叠纪和最早三叠纪底栖水生动物及其对气候变化的响应。痕量化石及其沉积学背景将在实地描述和拍摄，有代表性的标本将被收集用于实验室研究，并将评估动物对沉积物的破坏程度。样品将在实验室中切割和抛光，以阐明痕迹形态并增强技术结构。人们对古代非海洋水生底栖生物群落和鱼栖动物知之甚少，尽管这些栖息地自古生代以来就有人居住。最近的研究表明，这些群落的主要变化发生在二叠纪和三叠纪早期，当时穴居者变得更加丰富。本研究将为水生底栖动物群落进化的关键时期不同水生环境中的鱼-动物（和间接动物）分布提供罕见的文献资料，并将独特地解决水生底栖动物如何应对冰川后气候改善的问题。同样重要的是，收集的数据将用于评估南极洲和其他冈瓦纳大陆，特别是南美洲和非洲之间相关单元的鱼群动物群相似性，并检验关于在海洋和非海洋环境中相同沉积制度中发现的鱼群之间差异的假设。

This award supports a project to study trace fossils in the Permian and Triassic portions of the Beacon Supergroup in the central Transantarctic Mountains. The sedimentary sequence in the central Transantarctic Mountains indicates that during the Permian and Triassic this portion of the paleo-Pacific margin of Gondwana was successively covered by a continental glacier (Pagoda Formation), flooded by an inland sea (Mackellar Formation), blanketed with sediment deposited by rivers flowing across a sandy braid plain (Fairchild Formation), and covered with sands and silts deposited in braided river channels and floodplains (Buckley and Fremouw Formations). This sequence of events was induced by amelioration of the climate and changes in tectonic regime. Although the rich floras of the Buckley and Fremouw Formations and well preserved vertebrate fauna of the Fremouw Formation are the subject of continuing extensive studies, little is known about the benthic fauna that inhabited the widespread inland waters throughout the Permian and Triassic and its response to climate change. The animals themselves are not preserved as fossils, but biogenic structures, including both trace fossils (ichnofauna; discrete tracks, trails and burrows) and ichnofabric (general disruption caused by biologic activity), give information about the benthic fauna that produced them. This information includes: 1) the size and general body plan of the producers, giving keys to their identity; 2) an approximation of the faunal diversity; 3) the behavior of the producers; 4) the environmental preferences of the producers; 5) the use of trophic and spatial resources by the producers; and 6) the activity and abundance of the benthic fauna relative to physical and depositional processes, as reflected by ichnofabric. In this study, the trace fossils and ichnofabric in diverse subaqueous facies within the Mackellar, Fairchild, Buckley and lower Fremouw Formations will be described and interpreted t o develop a picture of the Permian and earliest Triassic benthic aquatic fauna and its response to climate change. Trace fossils and their sedimentological context will be described and photographed in the field, representative specimens will be collected for laboratory study, and the extent of sediment disruption by animals will be evaluated. Samples will be cut and polished in the laboratory to elucidate trace morphology and enhance ichnofabric. Very little is known about ancient nonmarine aquatic benthic communities and ichnofaunas, in spite of the fact that these habitats have been occupied since the Paleozoic. Recent work suggest that major changes in these communities occurred during the Permian and earliest Triassic when burrowers became more abundant. This study will provide rare documentation of ichnofaunal (and indirectly faunal) distributions in diverse aquatic environments at a crucial time during evolution of aquatic benthic communities, and will uniquely address the question of how aquatic benthic faunas responded to climate amelioration after glaciation. Equally important, data collected will be used to assess the ichnofaunal similarity in correlative units between Antarctica and other Gondwana continents, particularly South America and Africa, and to test hypotheses regarding differences between ichnofaunas found in equivalent depositional regimes in marine and nonmarine environments.