The Geology of Glaciated Sedimentary Basins

冰川沉积盆地地质

• 批准号: RGPIN-2015-05872
• 负责人: Eyles, Nicholas
• 金额: $ 2.4万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=685075
• 关键词: Geology; Glaciated; Sedimentary; Basins

The time interval from c. 750 to 600 million years ago (the Neoproterozoic) was dominated by the disintegration of the large supercontinent Rodinia. One unusual characteristic of the many extensional sedimentary basins that formed during continental rifting and breakup are exceptionally thick (~1 km) successions of diamictites that are poorly-sorted mixtures of particles ranging from mud to boulders. Despite decades of research their origin remains enigmatic. They are interpreted by some geologists as ancient glacial tills (`tillites') left by extensive ice sheets during world-wide ice ages (c. 770-735 Ma Kaigas, c. 715-680 Ma Sturtian, c. 660-635 Ma Marinoan, and c. 585-582 Ma Gaskiers events) with extremely low global temperatures (-50 °C) and frozen oceans. Other geologists argue that diamictites are glacially-influenced submarine debris flows deposited in open oceans akin to Pleistocene and modern glacially-influenced environments, or are entirely non-glacial and therefore lack climatic significance. The lack of agreement over the origin of diamictites is a fundamental data gap in understanding the history of Earth's climate and the evolution of the biosphere. It is also of direct economic importance. Exploration for stratiform copper hosted within thick (1.25 km) Neoproterozoic diamictites of the Katanga Basin in the Democratic Republic of Congo (DRC) by a Canadian mining company (Ivanplats) and for unconventional oil in such rocks in Brazil by Petra Energia SA has generated exceptional (and hitherto unavailable) basin-wide databases of drill core through Neoproterozoic diamictites and related facies, together with downhole geophysical and regional seismic and aeromagnetic data. This project identifies a plan to exploit these new databases by analyzing drill core and geophysical data in conjunction with the description and sampling of targeted surface outcrop exposures across DRC and Brazil. This will allow a clear methodology for the description and interpretation of diamictite facies and resolution of their origin and their tectonic significance within evolving Neoproterozoic basins. The project will provide key insights into the nature of Neoproterozoic hydrological cycles and the cryosphere and climate system at a time of rapid biological diversification linked by some to global ice ages. Substantial progress can be made in five years and results will be communicated in first class journals during the course of the project. This timely and ambitious research project will enhance Canadian expertise in mineral exploration and glacial sedimentology, accelerate resource exploration and investment in developing economies and promote opportunities for advanced student training and employment of Canadian geologists.**

在距今7.5 - 6亿年前（新元古代），以罗迪尼亚大超大陆的解体为主导。在大陆裂谷和破裂期间形成的许多伸展沉积盆地的一个不寻常的特征是异常厚（~1公里）的双晶岩序列，这些双晶岩是从泥浆到巨石的颗粒混合物，分类很差。尽管经过几十年的研究，它们的起源仍然是个谜。它们被一些地质学家解释为在全球冰期（约770-735 Ma Kaigas，约715-680 Ma Sturtian，约660-635 Ma Marinoan，约585-582 Ma Gaskiers事件）中广泛的冰盖留下的古冰川丘（“tillites”），全球温度极低（-50°c），海洋冻结。其他地质学家认为，二晶岩是冰川影响的海底碎屑流，沉积在开阔的海洋中，类似于更新世和现代冰川影响的环境，或者完全不是冰川影响的，因此缺乏气候意义。在了解地球气候历史和生物圈演化的过程中，对双晶岩的起源缺乏共识是一个根本性的数据缺口。它也具有直接的经济重要性。加拿大矿业公司Ivanplats对刚果民主共和国（DRC） Katanga盆地厚厚（1.25公里）新元古代双晶岩层状铜的勘探，以及巴西Petra Energia SA对这类岩石中的非常规石油的勘探，已经产生了非同寻常的（迄今为止无法获得的）全盆地范围的新元古代双晶岩及相关相岩心数据库，以及井下地球物理、区域地震和航空磁数据。该项目通过分析钻芯和地球物理数据，结合刚果民主共和国和巴西目标地表露头的描述和采样，确定了利用这些新数据库的计划。这将为描述和解释二晶岩相、确定其起源及其在演化的新元古代盆地中的构造意义提供一个明确的方法。该项目将为新元古代水文循环、冰冻圈和气候系统的本质提供关键见解，这一时期的生物快速多样化与全球冰河时期有关。五年内可取得实质性进展，并在项目过程中在一流期刊上发表成果。这个及时而雄心勃勃的研究项目将提高加拿大在矿产勘探和冰川沉积学方面的专业知识，加速发展中经济体的资源勘探和投资，并为加拿大地质学家提供高级学生培训和就业机会