Collaborative Research: Comparative Studies of Circum-Arctic Neoproterozoic-Paleozoic Terranes

由于我们对环北极地质的了解不足，目前白垩纪美亚盆地开放的构造模型存在争议。这种不确定性源于缺乏来自北美北极大陆边缘偏远地区的实地观测和数据。更好地了解环北极地区的地质情况，对于检验与现在合并在北美科迪勒拉造山带内的外来地壳碎片的起源和演化有关的假设也至关重要。其中一些“可疑”地体具有古生代和新元古代基底，与Laurentia（北美西部）的西部边缘相比，它们记录了完全不同的进化史。这些难以捉摸的地壳碎片的起源一直是地质文献中一个长期存在的问题。除了先前提出的一些关于这些奇异地体起源的模型外，最近有人提出它们诞生于波罗的海和东劳伦西亚领域，随后由于它们被北美北部和西伯利亚之间形成的中古生代加勒比/斯科舍式俯冲系统夹带而迁移到劳伦西亚西部。在这些流离失所的陆地中，皮尔亚岛（北埃尔斯米尔岛）和北极阿拉斯加是离它们在波罗的海王国假定的家园最近的。目前，我们正在整合来自Ellesemere岛北部、阿拉斯加北极和育空地区的新元古代和早古生代岩石的详细地层学、古生物学、地球化学和年代学研究，为以下方面提供检验：1)最近提出的从波罗的海形成的外来地体的古生代西北通道模型；2) SAYBIA-Rubia假说，该假说认为北极阿拉斯加的南半部与其他“可疑”地体形成了带状大陆，这些地体在白垩纪增生之前对北美来说是外来的；3)北极阿拉斯加的北美起源。最终，梨亚和阿拉斯加北极地区新元古代和古生代地质特征将限制外来科迪勒拉地体起源的模型，并将为重建白垩纪美亚盆地的开放提供地质背景。该项目是哈佛大学和爱荷华大学研究人员的合作成果。哈佛自然历史博物馆（HNHM）的矿物学和地质博物馆是美国首屈一指的陨石和矿物收藏之一。每年约有33,000名学生团体参观HNHM，为学生介绍地球科学提供了一个独特的论坛。北极博物馆目前正在举办一个关于北极地质的展览。展览将包括：1)在西北布鲁克斯山脉的阿拉斯加国家野生动物保护区、北埃尔斯米尔岛和北极破冰船上拍摄的照片；2)各测点地层岩样，包括北坡烃源岩和储层岩；3)关于北极地质演化的教育展览。HNHM将提供一个儿童友好的显微镜和一个微软触摸桌，使学生能够与北极板块构造重建的动画互动，并放大北极卫星和地质数据。超越矿物学，拓展米高梅？该博物馆对现代地球科学，特别是北极地质演化的综合性和令人兴奋的性质进行了教育性的展示，有可能影响到33,000名到HNHM学习地球科学的学生中的一部分。该项目还为哈佛大学和爱荷华大学的两名博士生的培训做出了贡献，并为两所大学的本科生培训提供了支持。

Current tectonic models for the Cretaceous opening of the Amerasia Basin are controversial due to our poor understanding of circum-Arctic geology. This uncertainty is derived from a lack of field-based observations and data from remote portions of the North American Arctic continental margins. A better understanding of circum-Arctic geology is also critical to testing hypotheses related to the origin and evolution of exotic crustal fragments now incorporated within the Cordilleran orogen of North America. Some of these "suspect" terranes have Paleozoic and Neoproterozoic basement that record completely different evolutionary histories in comparison to the western margin of Laurentia (western North America). The elusive origination of these crustal fragments has remained a longstanding question in the geological literature. In addition to a number of previously proposed models for the origin of these exotic terranes, it has recently been proposed that they were born in the Baltic and eastern Laurentian realm and subsequently migrated to western Laurentia as a result of their entrainment in a mid-Paleozoic Caribbean/Scotia-style subduction system that formed between northern North America and Siberia. Of these displaced terranes, Pearya (Northern Ellesmere Island) and Arctic Alaska are the closest to their putative homeland in the Baltic realm. We are currently integrating detailed stratigraphic, paleontological, geochemical, and geochronological studies on Neoproterozoic and early Paleozoic rocks from northern Ellesemere Island, Arctic Alaska, and the Yukon to provide tests for: 1) The recently proposed model for the Paleozoic northwest passage of exotic terranes from their formation in Baltica; 2) The SAYBIA-Rubia hypothesis, which posits that the southern half of Arctic Alaska formed a ribbon continent with other "suspect" terranes that was exotic to North America until accretion in the Cretaceous; and 3) A North American origin for Arctic Alaska. Ultimately, the characterization of the Neoproterozoic and Paleozoic geology in Pearya and Arctic Alaska will constrain models for the origins of exotic Cordilleran terranes and will provide the geological background for reconstructing the Cretaceous opening of the Amerasian Basin. The project is a collaborative effort between researchers at Harvard University and the University of Iowa. The Mineralogical and Geological Museum at the Harvard Natural History Museum (HNHM) hosts one of the premier meteorite and mineral collections in the United States. HNHM is visited annually by approximately 33,000 school children in groups, presenting a unique forum to introduce students to the Geosciences. An exhibit on the geology of the Arctic is currently being developed at the HNHM. The exhibit will include: 1) photographs from expeditions in the Alaska National Wildlife Reserve of the NW Brooks Range, Northern Ellesmere Island, and on Arctic Icebreakers; 2) rock samples from formations at each of these localities including the North Slope oil source and reservoir rocks; and 3) educational displays about the geological evolution of the Arctic. The HNHM will provide a kid friendly microscopes and a Microsoft touch-table that will enable students to interact with animations of Arctic plate tectonic reconstructions and zoom in on Arctic satellite and geological data. Beyond mineralogy, expanding the MGM?s educational displays to the integrative and exciting nature of modern Geosciences, particularly the geological evolution of the Arctic, has the potential to influence a portion of the 33,000 students who visit the HNHM to pursue studies in the Geosciences. The project is also contribute to the training of two Ph.D. students, one at Harvard and one at the University of Iowa, and is providing support for training of undergraduate students at both universities.