Precambrian sedimentary assemblages: keys to understanding ocean-atmosphere evolution and tectonic processes on the young earth

前寒武纪沉积组合：了解年轻地球海洋-大气演化和构造过程的关键

• 批准号: 1388-2007
• 负责人: Fralick, Philip
• 金额: $ 1.62万
• 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: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=363296
• 关键词: Precambrian; sedimentary; assemblages; keys; understanding

Most people tend to view the natural world as constant. Sure, 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 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 ten 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 under the ice. The further back in time we go, the more different things were. Two thousand seven hundred million years ago the central area of Canada consisted of volcanic islands similar to the Carribean region; North America did not exist; a world ocean dominated the planet; the most advanced life were bacteria; and the atmosphere had no oxygen, but lots of carbon dioxide. 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 discouver what the geography looked like when the Earth was a young planet. I am particularly interested in the composition of the atmosphere and ocean during the time period 2.7 to 1.8 thousand million years ago when photosynthesizing organisms first started to add significant amounts of oxygen to the atmosphere and oceans. I analyse minerals in sedimentary rock that formed from chemicals precipitated in the ocean at that time. These minerals grew on the bottom of the ocean and are now contained in two billion year old sedimentary rocks. The composition of the minerals provides me with the information I need to form conclusions on how the chemistry of the oceans developed through time.

大多数人倾向于认为自然界是恒定的。当然，一场风暴可能会吹倒一棵树，或者一个海崖可能会慢慢地被海浪侵蚀，但是海洋和山脉是永恒的。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，受到我们短暂寿命的限制。然而，海洋和山脉也有寿命，而且寿命要长得多。仅在一万年前，加拿大大部分地区还被冰覆盖着。我们今天看到的一切要么不在这里，要么，如果它是大而坚实的，在冰下。我们越是追溯到过去，事情就越不一样。27亿年前，加拿大中部地区由类似于加勒比地区的火山岛组成;北美不存在;世界海洋主宰着地球;最先进的生命是细菌;大气层没有氧气，但有大量的二氧化碳。我们之所以知道这一点，是因为当时火山爆发形成的岩石，以及岛屿侵蚀产生的沉积岩，都是加拿大中部大面积地区的基岩。我的研究利用沉积岩中留下的线索来发现地球年轻时的地理状况。我特别感兴趣的是27亿至18亿年前的大气和海洋的组成，当时进行光合作用的生物第一次开始向大气和海洋中添加大量的氧气。我分析了沉积岩中的矿物，这些矿物是由当时海洋中沉淀的化学物质形成的。这些矿物生长在海底，现在包含在20亿年前的沉积岩中。矿物的组成为我提供了所需的信息，使我能够得出海洋化学是如何随着时间的推移而发展的结论。