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

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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.