Evolution Of New Life Forms In 'Cambrian Explosion' Linked With Increase In Atmospheric Oxygen Levels And Concomitant Fossil Fuel Formation

Evolutionary biologists suggest a connecting link between optimum atmospheric oxygen levels during the Cambrian era with the origin of new life forms and refer it as the "Cambrian explosion."

According to the results obtained from a recently conducted study done by a group of geologists from the University of Wisconsin-Madison, the upsurge in the atmospheric oxygen levels that occurred 500 million years ago was because of increased burial of natural plant based sediments.

If not buried, the carbon content of the dead plant material starts getting oxidized, which leads to the formation of carbon dioxide. Burial of these dead plants restricted the oxidation of carbon and thus indirectly facilitated increased accumulation of atmospheric oxygen.

The study was published online in the Earth and Planetary Science Letters journal. It clearly states that even though photosynthesis has been considered the chief source of supply of atmospheric oxygen, it was insufficient in generating the atmospheric oxygen levels required for the sustenance of animal life forms.

Shanan Peters, Professor of Geoscience at the University of Wisconsin-Madison, who was the co-author of the study, said that sediment storage helped in blocking oxidation of carbon in prehistoric times. Furthermore, the buried plant materials were subjected to natural heat and pressure conditions, which helped in fossil fuel formation, according to Phys org.

Shanan Peters and Jon Husson, post-doctoral fellow at the university, carefully studied the Macrostrat data set, which is an accumulation of previously recorded geologic data in the North American region. They mapped the increase in atmospheric oxygen level in relation to sediment burial, as well as with the formation of sedimentary rock. The graph obtained from the analysis suggests an increase in oxygen concentration 500 million years ago.

Jon Husson said, "When you store sediment, it contains organic matter that was formed by photosynthesis, which converted carbon dioxide into biomass and released oxygen into the atmosphere. Burial removes the carbon from Earth's surface, preventing it from bonding molecular oxygen pulled from the atmosphere."

In-depth analyses also suggested that the surge of oxygen coincided with the event of formation of vast fossil fuel fields that are mined till date for coal and petroleum, e.g., oil-rich Permian Basin, Texas, and the Pennsylvania coal fields, Appalachia.

The data obtained from the study have been recorded in a database and may be helpful in studying similar patterns of fossil fuel formation and increase in atmospheric oxygen levels, specifically during the Cambrian explosion, in various other regions of the world.