Oxygen is necessary to support life on Earth. A recent study using Geochemical proxies,high resolution data collated from sea water formed carbonated rocks and their chemical signatures points towards a boost in levels of oxygen between 445 and 485 million years ago which had resulted in a threefold increase in biodiversification during that period. Using these data researchers were able to identify the increase in oxygen during the Darriwilian Stage- 460 to 465 million years ago to the Late Ordovician Period, specifically during the mid Katian stage 450 to 455 million years ago. The Katian is the second stage of the upper Ordovician.
This study suggests that this oxygenation is supported by two different approaches that are mostly independent from each other. Use of different sets of geochemical records pointed towards the same amount of oxygenation occurring roughly at the same time as the diversification. Another link between biodiversification and oxygen levels were noted during the Ordovician where near modern levels of oxygen were reached to 455 million years ago. The biodiversification was enhanced due to changes taking place during those times such as ocean cooling, an increase in nutrient supply to the oceans and predation pressure. All these factors together were conducive for animal life to diversify over millions of years.
This study thus suggests, the oceans reached modern levels of oxygen millions of years after Cambrian explosion which was traditionally represented as the most important evolutionary event in the history of life on earth.
By: Madhuchanda Saxena