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

该奖项支持一个项目，研究横贯北极山脉中部的Beacon Supergroup的二叠纪和三叠纪部分的遗迹化石。横贯北极山脉中部的沉积序列表明，在二叠纪和三叠纪，冈瓦那古太平洋边缘的这一部分先后被大陆冰川(宝塔组)覆盖，被内海(麦凯勒组)淹没，被流经沙质辫状平原的河流沉积的沉积物(费尔柴尔德组)覆盖，并被辫状河道和泛滥平原(巴克利组和弗莱莫组)沉积的砂和粉砂所覆盖。这一系列事件是由气候的改善和构造体制的变化引起的。尽管巴克利和弗莱穆夫组丰富的植物群以及弗莱莫组保存完好的脊椎动物群是继续广泛研究的主题，但人们对生活在整个二叠纪和三叠纪广大内陆水域的底栖动物及其对气候变化的反应知之甚少。这些动物本身并没有作为化石保存下来，但生物起源结构，包括遗迹化石(遗迹化石；离散的足迹、踪迹和洞穴)和遗迹组构(生物活动造成的一般破坏)，提供了关于产生它们的底栖动物的信息。这些信息包括：1)生产者的大小和总体身体计划，给出他们身份的关键；2)动物多样性的近似值；3)生产者的行为；4)生产者的环境偏好；5)生产者对营养和空间资源的使用；以及6)底栖动物相对于物理和沉积过程的活动和丰度，如遗迹结构所反映的。在这项研究中，将描述和解释Mackella组、FairChild组、Buckley组和下Fremuw组不同水下相中的遗迹化石和遗迹组构，以形成二叠纪和最早的三叠纪底栖动物及其对气候变化的响应。将在野外描述和拍摄遗迹化石及其沉积学背景，收集有代表性的标本进行实验室研究，并评估动物对沉积物的破坏程度。样品将在实验室进行切割和抛光，以阐明痕迹形态并增强遗迹结构。人们对古代非海洋水生底栖动物群落和底栖动物知之甚少，尽管这些栖息地自古生代以来一直被占领。最近的研究表明，这些群落的主要变化发生在二叠纪和最早的三叠纪，当时洞穴动物变得更加丰富。这项研究将提供在水生底栖动物群落演化的关键时期不同水生环境中底栖生物(和间接动物)分布的罕见文献，并将独特地解决水生底栖动物如何响应冰川后气候改善的问题。同样重要的是，所收集的数据将用于评估南极洲与冈瓦那其他大陆，特别是南美洲和非洲之间相关单位的生物区系相似性，并检验关于海洋和非海洋环境中同等沉积制度中发现的生物区系之间的差异的假设。

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.