Upper Triassic Terrane Faunas and Their Use in Paleogeographic Comparisons within the Cordilleran Region

上三叠统地系动物群及其在科迪勒兰地区古地理比较中的应用本项目将采用野外考察、实验室研究和博物馆收藏研究相结合的方法来评估晚三叠世关键时期的无脊椎动物动物群。它试图记录来自阿拉斯加、加拿大西部、内华达州和墨西哥的各种热带到亚热带的shelly化石的分类组成、古生态学和古地理意义，并与世界其他地区（如西欧和前特提斯部分地区）的同时期化石进行比较。研究的化石包括珊瑚、海绵、水生动物、关节腕足类、双壳类和气足类。这些物种数量丰富，分布广泛，但对物种分类知之甚少。该研究将评估分类学和古生态关联。在三叠纪时期，这些无脊椎动物中的一些居住在北美西海岸，但其他许多居住在火山岛，现在被认为是移位的地。动物群将被提取出来的地形包括弗兰格利亚的阿拉斯加部分和告别地形，以及丘里特纳、瓦洛瓦、亚历山大和Junco地形。在三叠纪时期，这些地体分布在克拉通西海岸以外的未知距离，它们的动物群为测试和更好地解决古地理问题提供了无与伦比的机会，特别是研究了一些关键地体（如Wrangellia地体和Alexander地体）之间的古生物地理亲缘关系和关系。许多地体代表活跃的岛弧，在火山活动停止期间和之后，这些岛弧消退并被沉积所取代，从而形成了丰富的无脊椎动物海洋群落。一些待研究的化石出现在厚厚的碳酸盐沉积物甚至珊瑚礁组合中。这些生物曾经在古太平洋的热带至亚热带纬度地区发展。由于许多拟研究的生物组合是硅化的，化石将在稀酸中蚀刻，这有望释放出大量的化石供研究。对这些硅化动物群的分类研究将提供丰富的新的重要数据。该项目还有望通过与一些外部专家的合作而受益。统计古生物地理学方法将被采用，该项目也将受益于许多三叠纪分类群的电子古生物数据库的发展。这一古生物学项目有望为一般的古生物地理学综合提供必要的数据，并为检验一些大地关系的构造假设奠定基础。

Upper Triassic Terrane Faunas and Their Use in Paleogeographic Comparisons within the Cordilleran RegionGeorge Stanley, Robert Blodgett EAR0229795University of MontanaABSTRACTThis project will employ a combination of field work, laboratory, and museum collections research to assess invertebrate faunas during a critical time in the Late Triassic. It seeks to document the taxonomic composition, paleoecology and paleogeographic significance of various tropical to subtropical, shelly fossils from Alaska, western Canada, Nevada, and Mexico and to make comparisons with coeval fossils from other regions of the world, such as western Europe and parts of the former Tethys. Fossils to be studied are corals, sponges, hydrozoans, articulate brachiopods, bivalves and gasropods. These are abundant and widespread but little is known about the species taxonomy. The study will assess both taxonomy and paleoecological associations. During the Triassic time, some of these invertebrate faunas inhabited the western shores of North America but many others inhabited volcanic islands, now regarded as displaced terranes. The terranes from which faunas will be extracted, include the Alaskan portion of Wrangellia and the Farewell terrane, as well as Chulitna, Wallowa, Alexander and Junco terranes. In Triassic time, these terranes were located at unspecified distances off the western coast of the craton and their faunas provide unparalleled opportunities to test and better resolve the paleogeography, specifically to work out the paleobiogeographic affinities and relationships between some key terranes such as Wrangellia and the Alexander terrane. Many terranes represent active island arcs which, during and following cessation of volcanism, subsided and were replaced by sedimentary deposition, thus fostering rich invertebrate marine associations. Some of the fossils to be studied occur in thick carbonate deposits and even reefal associations. These organisms once developed at tropical to subtropical latitudes somewhere in the ancient Pacific ocean. Because many biotic assemblages proposed for study are silicified, fossils will be etched in dilute acids which are expected to free large numbers of fossils for study. Taxonomic study these silicified faunas will provide a wealth of new and important data. The project also is expected to benefit by collaboration with a number of outside specialists. Statistical paleobiogeographic methods will be employed and the project also will benefit from the development of an electronic paleontological database for many of the Triassic taxa. This paleontological project is expected to provide the necessary data for a general paleobiogeographic synthesis and to lay the foundation for testing some tectonic postulates for terrane relationships.