Sedimentology of Precambrian Depositional Systems: Understanding the Earth's Surface in Deep Time

前寒武纪沉积系统的沉积学：深入了解地球表面

• 批准号: RGPIN-2018-04051
• 负责人: Fralick, Philip
• 金额: $ 3.13万
• 依托单位: Lakehead University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=712729
• 关键词: Sedimentology; Precambrian; Depositional; Systems; Understanding

Most people tend to view the natural world as constant. A storm may blow a tree down or a bluff may be slowly eaten away by the waves, but the oceans and the mountains are viewed as forever. When people think of forever in this way, they are approaching the concept from a human point of view, limited by our short lifespans. However, the oceans and mountains also have lifespans and these are much longer. Only twenty thousand years ago most of Canada was covered by ice. Everything we see today was either not here or, if it was large and solid, was all or mostly under the ice. The further back in time we go, the greater the difference from the present. Two thousand seven hundred million years ago the central area of Canada consisted of volcanic islands similar to the Caribbean region; North America did not exist; a world ocean dominated the planet; the most advanced life was bacteria; and the atmosphere had no oxygen. We know this because the rocks that were formed at this time from volcanic eruptions, and the sedimentary rocks produced by the erosion of the islands, occur as bedrock under large areas of central Canada. My research uses clues left behind in sedimentary rocks to discover what the geography looked like and what sedimentary processes were operating, when the Earth was a young planet. I am particularly interested in the composition of the atmosphere and ocean during the time period 3.0 to 1.4 thousand million years ago. In approximately the middle of this time period photosynthesizing organisms added significant amounts of oxygen to the atmosphere and oceans. I analyse minerals in sedimentary rocks that formed from chemicals precipitated in the ocean during this time period. These minerals grew on the bottom of the ocean and are now contained in sedimentary rocks. The composition of the minerals provides me with the information I need to form conclusions on how the chemistry of the ocean-atmosphere system developed through time. The importance of this work is not limited to understanding how the oceans and atmosphere were transformed over time. The chemistry of the surface of the Earth was a major control on the evolution of various forms of life on Earth. Understanding ocean-atmosphere chemistry is essential to unraveling life's early history.

大多数人倾向于认为自然世界是恒定的。暴风雨可能会吹倒一棵树，或者悬崖可能会被海浪慢慢吞噬，但海洋和山脉被视为永恒。当人们以这种方式思考永远时，他们是从人类的角度来看待这个概念的，受到我们短暂的寿命的限制。然而，海洋和山脉也有寿命，而且寿命更长。仅两万年前，加拿大大部分地区还被冰雪覆盖。我们今天看到的一切要么不在这里，要么，如果它大而坚固，则全部或大部分都在冰下。时间越久远，与现在的差异就越大。 27亿年前，加拿大中部地区由与加勒比地区类似的火山岛屿组成；北美并不存在；世界海洋主宰着这个星球；最高级的生命是细菌；大气中没有氧气。我们之所以知道这一点，是因为当时火山喷发形成的岩石，以及岛屿侵蚀产生的沉积岩，在加拿大中部大片地区以基岩的形式出现。我的研究利用沉积岩中留下的线索来发现地球还是一颗年轻行星时的地理状况以及正在发生的沉积过程。我对 3.0 至 1.4 亿年前的大气和海洋的组成特别感兴趣。大约在这个时期的中期，光合作用生物向大气和海洋添加了大量的氧气。我分析了沉积岩中的矿物质，这些矿物质是由这段时期海洋中沉淀的化学物质形成的。这些矿物质生长在海底，现在包含在沉积岩中。矿物质的成分为我提供了所需的信息，以得出关于海洋-大气系统的化学成分如何随时间发展的结论。这项工作的重要性不仅限于了解海洋和大气如何随着时间的推移而发生变化。地球表面的化学性质是地球上各种生命形式进化的主要控制因素。了解海洋-大气化学对于解开生命的早期历史至关重要。