The Geology of Glaciated Sedimentary Basins

从约7.5亿年到6亿年前(新元古代)的时间间隔主要是大型超大陆罗迪尼亚的解体。在大陆裂谷和解体期间形成的许多伸展沉积盆地的一个不同寻常的特征是异常厚(约1公里)的硅质岩序列，它们是从泥土到巨石的各种颗粒的不良分选混合物。尽管经过几十年的研究，它们的起源仍然是个谜。一些地质学家将它们解释为全球冰期(约770-735 Ma Kaigas、约715-680 Ma Sturtian、约660-635 Ma Marinoan和约585-582 Ma加斯基山事件)在极低的全球温度(-50℃)和冰冻的海洋中留下的古老冰川碎屑。其他地质学家认为，硅质岩是受冰川影响的海底泥石流，沉积在类似于更新世的开阔海洋和现代受冰川影响的环境中，或者完全不是冰川的，因此缺乏气候意义。在理解地球气候历史和生物圈演化方面，缺乏关于透辉石起源的一致意见是一个基本的数据差距。它还具有直接的经济重要性。加拿大矿业公司(Ivanplats)在刚果民主共和国加丹加盆地厚(1.25公里)新元古代闪长岩中赋存的层状铜，以及巴西国家石油公司(Petra Energia SA)在此类岩石中进行的非常规石油勘探，产生了通过新元古代闪长岩和相关相建立的异常(迄今无法获得的)盆地范围钻探岩心数据库，以及井下地球物理和区域地震及航磁数据。该项目确定了一项开发这些新数据库的计划，方法是分析钻探岩心和地球物理数据，并对刚果民主共和国和巴西的目标地表露头暴露进行描述和抽样。这将为描述和解释辉绿岩相及其成因及其在新元古代演化盆地中的构造意义提供一种明确的方法。该项目将对新元古代水文循环的性质以及冰冻圈和气候系统的性质提供关键的见解，因为有些人认为生物多样性与全球冰河时代有关。在五年内可以取得实质性进展，结果将在项目过程中在一流期刊上发表。这一及时而雄心勃勃的研究项目将增强加拿大在矿产勘探和冰川沉积学方面的专业知识，加快发展中经济体的资源勘探和投资，并促进加拿大地质学家的高级学生培训和就业机会。

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.