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| COLLABORATIVE RESEARCH: Testing proposed rapid true polar wander in the Neoproterozoic Zavkhan Volcanics of Mongolia and the Banxi Group of South China | |
| 项目编号 | 1547434 |
| Nicholas Swanson-Hysell | |
| 项目主持机构 | University of California-Berkeley |
| 开始日期 | 2016-06-01 |
| 结束日期 | 2019-05-31 |
| 英文摘要 | Through geological time, Earth's crustal plates have moved through two distinct mechanisms. The first is the motion of Earth's plates relative to one another due to convection of the underlying mantle and the force balance on the plate - we call this "plate tectonics". The second mechanism is motion of all of the plates together due to shifting mass anomalies within the Earth and associated rotational imbalance, which can cause reorientation relative to Earth's spin axis. This reorientation motion is referred to as true polar wander, and the rate at it proceeds is dependent on the viscosity of Earth's interior, which is poorly constrained both today and through Earth History. This research targets a particular interval of time around 800 million years ago when it has been proposed that true polar wander was much faster than usual -fast enough that parts of Earth's surface may have moved the distance of the length of football field in around 100 years. The PIs seek to track ancient plate movement in Mongolia and China to test this hypothesis using rocks of this age. They will do so using the magnetic directions preserved in the ancient rocks combined with U/Pb radiogenic isotope dates to precisely determine their age. These data will be used constrain both the rate that plates were moving and the relative movement of different plates in order to determine if the motion is consistent with rapid true polar wander. The results will inform Earth Scientists about the drivers of apparent plate motion at this time and the past position of the continents. The data also have the potential to place constraints on the viscosity of Earth's interior through time. It has been proposed that large-scale, oscillatory true polar wander (TPW) occurred at ca. 800 Ma, associated with a carbon isotope interval known as the Bitter Springs Stage. Recent advances have led to a temporally quantified framework for the Bitter Springs Stage that enables this TPW hypothesis to be tested in non-carbonate-bearing lithologies, such as successions of extrusive volcanics. This project seeks to test the hypothesis through the development of new paleomagnetic and geochronological data from Mongolia and South China. The goal of the research is to robustly quantify Earth's rotational stability through this critical period of Earth history and allow for rates of TPW to be constrained. The Bitter Springs TPW hypothesis has become a central component of models for how continents aggregate into supercontinents, for fundamental inferences into the viscosity of Earth's mantle and the stabilizing effect of the remanent bulge and excess ellipticity, and for the planetary context of Neoproterozoic environmental change. Furthermore, the hypothesis of rapid TPW at ca. 800 Ma has become a significant component of models for the configuration of the supercontinent Rodinia. This project seeks to constrain the rate of pole movement during this interval through the development of new geochronological and paleomagnetic data from the Zavkhan Volcanics of Mongolia and the Banxi Group of South China in robust stratigraphic context. Importantly, these successions contain: (1) abundant volcanic rocks containing zircon from which high-precision U-Pb chemical abrasion-ion dilution-thermal mass spectrometry (CA-ID-TIMS) dates can be obtained and (2) paleomagnetic confidence tests indicating preservation of primary magnetization. Three years of field work, paleomagnetic analysis, and the development of CA-ID-TIMS U-Pb dates will focus on producing high quality pole paths for the Zavkhan Terrane of Mongolia and the South China craton from ca. 820 to 750 Ma. Such paths can be used to further test whether rapid oscillatory TPW occurred through this interval and, if so, at what rates. Testing and constraining this hypothesis is necessary for progress on the co-evolution of the solid earth and the surface through the time period and determining whether there were time periods in the Precambrian where it can be robustly shown that rates of TPW were higher than those resolved in the Phanerozoic. The broader impacts of the proposed research are four-fold: (1) the training and development of a UC Berkeley graduate student; (2) engagement of undergraduate students in basic research; (3) cultural exchange with Mongolian students in the field and in both of the PIs labs and (4) effective communication of a set of Earth systems history learning goals to K-12 communities through the construction of an educational display module in conjunction with the Harvard Museum of Natural History (HMNH). This educational exhibit will be focused on the geological record of Asia and will include: (1) large rock samples that can be touched; (2) photographs from field expeditions; (3) educational displays about geochronology and paleomagnetism; and (4) a video explaining the geophysical techniques used in this study. Following display in the Earth Science exhibit galleries at HMNH, the exhibit module will travel for display in the Earth and Planetary Science Department at UC Berkeley and then to the Mongolia University for Science and Technology in Ulaanbaatar. This work includes extensive international collaboration, and is co-funded by the Office of International Science and Engineering. |
| 学科分类 | 08 - 地球科学 |
| 资助机构 | US-NSF |
| 项目经费 | 95109 |
| 项目类型 | Continuing grant |
| 国家 | US |
| 语种 | 英语 |
| 文献类型 | 项目 |
| 条目标识符 | http://gcip.llas.ac.cn/handle/2XKMVOVA/69703 |
| 推荐引用方式 GB/T 7714 | Nicholas Swanson-Hysell.COLLABORATIVE RESEARCH: Testing proposed rapid true polar wander in the Neoproterozoic Zavkhan Volcanics of Mongolia and the Banxi Group of South China.2016. |
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