International Research Fellowship Program: The Break-up of the Rodinia Supercontinent and Snowball Earth: Paleogeography and Geochronology of the Western Amazon Craton

[0301807]国际研究奖学金计划使美国科学家和工程师能够在国外进行3至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持Eric Tohver博士与Wilson Teixeira博士在巴西圣保罗大学开展为期24个月的研究。该研究员将对巴西西部马托格罗索州和南马托格罗索州西部亚马逊克拉通的晚前寒武纪沉积物进行古地磁和地质年代学研究。这些沉积物记录了在罗丁尼亚超大陆分裂期间，北美洲祖先和亚马逊克拉通之间的Iapetus海洋的开放。在这个裂谷序列中发现的冰川沉积物被认为是雪球地球时期的产物，这一时期的极端气候条件与罗迪尼亚的分裂有关。利用40ar /39Ar技术对这些沉积物中的原生自生矿物进行放射性成因定年，以确定裂谷的时间和冰川事件的年龄。这些地质年代学结果将与古地磁数据结合使用，以确定冰川沉积物的古地理背景。此外，这些数据将与北美的数据进行比较，以记录土卫八海洋的开放情况。该项目将建立北美和南美前寒武纪的构造联系。这些沉积物提供了一个独特的机会来帮助解决关于前寒武纪末期极端气候的争论。主持人Teixeira博士是南美前寒武纪地质领域的权威专家，他最近建立了一个新的实验室，配有激光提取线，以补充现有的古磁学实验室，该实验室使用无磁场室和2G低温磁力计。

0301807TohverThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four month research fellowship by Dr. Eric Tohver to work with Dr. Wilson Teixeira at the University of Sao Paulo in Sao Paulo, Brazil.This fellow will undertake a paleomagnetic and geochronological study of the late Precambrian sediments of the western Amazon craton in the western Brazilian states of Mato Grosso and Mato Grosso do Sul. These sediments record the opening of the Iapetus Ocean between ancestral North America and the Amazon craton during the break-up of the Rodinia supercontinent. Glacial sediments found in this rift sequence have been ascribed to a snowball Earth episode, a period of extreme climatic conditions linked to the break-up of Rodinia. Radiogenic dating using the 40 Ar/39Ar technique will be carried out on primary, authigenic minerals from these sediments in order to determine the timing of rifting as well as the age of the glacial event. These geochronological results will be used in conjunction with paleomagnetic data to establish the paleogeographic context of the glacial deposits. In addition, these data will be compared with those from North America to document the opening of the Iapetus Ocean. This project will establish the tectonic link between North and South America Precambrian times. These sediments present a unique opportunity to help resolve the ongoing debate regarding extreme climates proposed for end Precambrian times.The host, Dr. Teixeira is a leading expert in the Precambrian geology of South America and has recently established a new laboratory with laser extraction lines to complement the existing paleomagnetic laboratory, which utilized a field-free room and a 2G cryogenic magnetometer.