Incredible India: High Resolution Proterozoic Paleogeography through integrated studies of mafic dykes

大陆地壳在地球历史上的长期运动导致了被称为超级大陆的较大陆块的周期性聚集。 最近的超大陆泛古陆（Pangea）约在3亿年前合并，而较古老的超大陆则被假设在6亿年前（Pannotia）、10亿年前（Rodinia）和18亿年前（哥伦比亚/努纳）形成。 超大陆与地球历史上的一些重要发展有着一致的关系，包括经济矿藏的形成（哥伦比亚），严重的气候波动（Rodinia）和现代动物门的进化（Pannotia）。 由于现代大陆上有分散的古代地壳残余，确定超大陆的组装时间需要整个地球仪的古地磁学和地质年代学知识。 印度半岛是由五块古老的大陆地壳融合而成，分别是阿拉瓦利、本德尔坎德、辛格邦、达尔瓦尔和巴斯塔半岛。 本研究的重点是通过对火成岩中磁性方向的研究来确定五个板块的古地理组合。 多元化的研究团队，包括本科生，研究生和外国合作者，目标是在达尔瓦尔，Bundelkhand和Singhbhum的三个关键地区。 在这项调查中收集的古地磁数据被纳入全球古地理模型，这些模型是理解更大规模问题的关键，例如：所有大陆何时组装成更大的超级大陆？地球磁场是如何随时间变化的？古代的气候条件是什么，它们如何帮助我们了解未来的气候？ 这项研究的重要社会影响包括研究生和本科生在一个重要的STEM学科的培训，教育推广活动和与两年制社区学院的合作，K-12课堂推广，包括主要是非洲裔美国人和西班牙裔中学，以及涉及来自代表性不足群体的大学STEM学生的导师的努力。该项目还涉及与印度科学家的国际科学合作。调查人员概述了一系列旨在澄清印度半岛地质历史和解释全球构造影响的目标。 本提案中进行的工作是：1）完善导致印度组装的事件序列，2）阐明印度在拟议的哥伦比亚/努纳和罗迪尼亚超级大陆中的地位。 在全球构造模型的回顾中，注意到印度半岛在整个元古代被视为一个统一的块体，但现有的古地磁和地质年代学数据并不支持这样的结论。此外，来自中印度构造带的结构和年代学数据表明，直到~1100-900 Ma才实现统一。 将印度的古地磁记录与地球仪的结果进行比较，将建立元古代板块构造的克里思和模式，有助于回答现代构造何时开始的问题。 在回顾Rodinia和哥伦比亚的“传统”模型时，很明显，超级大陆的中心结构似乎没有什么变化。 如果罗迪尼亚构造只是代表了哥伦比亚/努纳的一个微小变化，这可能反映了与现代风格（古生代）板块构造的一些潜在差异，或者可能是整个地质时期板块组织规律的基本模式。 这些数据使研究人员能够评估印度次大陆的潜在“最近邻居”，如华北，南极洲东部，澳大利亚，波罗的海以及非洲和马达加斯加的部分地区。这些贡献为研究地球上的古代气候梯度、磁场的行为和强度、真正的极地漂移记录、以及在以前相邻的可能容纳重要成矿矿床的火山岩地区的鉴定。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准。

The motion of continental crust over long periods of Earth history results in the periodic assembly of larger landmasses referred to as supercontinents. The most recent supercontinent, Pangea, coalesced about 300 million years ago, whereas older supercontinents are hypothesized to have formed around 600 million years ago (Pannotia), 1000 million years ago (Rodinia), and 1800 million years ago (Columbia/Nuna). Supercontinents have a coincident relationship to some important developments in Earth history including the formation of economic mineral deposits (Columbia), severe climatic fluctuations (Rodinia) and the evolution of modern animal phyla (Pannotia). Because modern continents hold the dispersed remnants of ancient crust, determining the timing of supercontinent assembly requires paleomagnetic and geochronologic knowledge of the entire globe. Peninsular India is a fusion of five ancient pieces of continental crust known as the Aravalli, Bundelkhand, Singhbhum, Dharwar, and Bastar cratons. The research in this proposal is focused on determining the paleogeographic assembly of the five cratonic pieces by an investigation into the magnetic directions in igneous rocks. The diverse research team, including undergraduate students, graduate students and foreign collaborators, targets three key regions in the Dharwar, Bundelkhand and Singhbhum cratons. The paleomagnetic data being gathered in this investigation is incorporated into global paleogeographic models that are key to understanding larger scale questions such as: When were all continents assembled into larger supercontinents?, How has the Earth's magnetic field changed through time?, and What were ancient climatic conditions and how might they help us understand future climates?. Important societal impacts from this study include the training of graduate and undergraduate students in an important STEM discipline, educational outreach activities and collaboration with a 2-year community college, K-12 classroom outreach including predominantly African-American and Hispanic middle schools, and efforts that involve mentorship of university STEM students from underrepresented groups. The project also involves international scientific collaboration with scientists from India.The investigators outline a series of goals aimed to clarify the geological history of Peninsular India and interpret global tectonic implications. The work conducted in this proposal is generating that 1) refine the sequence of events that led to India's assembly, and 2) also elucidate India's place in the proposed supercontinents of Columbia/Nuna and Rodinia. In a review of global tectonic models, it is noted that Peninsular India is treated as a unified block during the entire Proterozoic, but available paleomagnetic and geochronologic data do not support such a conclusion. Additionally, structural and geochronological data from the Central Indian Tectonic Zone suggest that unity was not achieved until ~1100-900 Ma. Comparing a robust paleomagnetic record from India with results from around the globe will establish the tempo and mode of plate tectonics in the Proterozoic, helping answer the question of when modern style tectonics began. In reviewing "traditional" models of Rodinia and Columbia, it is apparent that the central structure of the supercontinents appears to show little change. If the Rodinia configuration represents only a slight variation on Columbia/Nuna, this might reflect some underlying difference from modern-style (Phanerozoic) plate tectonics, or perhaps fundamental mode of plate organization regularity throughout geologic time. These data allow the researchers to evaluate potential "nearest neighbors" to the Indian cratons such as North China, East Antarctica, Australia, Baltica, and parts of Africa and Madagascar. The contributions add an important component to studies of ancient climatic gradients across the Earth, behavior and strength of the magnetic field, the record of true polar wander, and the identification of large igneous provinces in formerly adjacent cratons that may host important metallogenic ore deposits.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.