CARBONATITE ERUPTIONS OF SERRA NEGRA BRAZIL: A NEW MECHANISM FOR REGIONAL EXTINCTION

The area surrounding the Serra Negra region of central Brazil has a diverse and complex record of fossils and alkaline volcanics associated with surge deposits of the Bauru formation which extends 1500km north and 300km south into the Bauru basin. In previous work, the Bauru formation has been erroneously described as everything from a Tertiary laterite to a Cretaceous sandstone with numerous names for the same formation depending on the region.

The Bauru formation is of great interest as it is the most extensive Cretaceous continental sedimentary sequence in Brazil. The Bauru today is distributed on the hilltops forming plateaus or chapadas covering an area almost 4500km² north of the Serra Negra Crater.

Given the vast depth and overall volume of Serra Negra and other associated alkaline deposits in the region as well as the explosive nature of carbonatite eruptions, these would have been not only extensive in reach but catastrophic to the area surrounding the carbonatite eruption events.

Preliminary research suggests that vast amounts of CO₂ and lime ash would have been released from the eruption. We believe that carbonate phase change and a release of pressure resulted in multiple explosions over an unknown time span.

These explosions would have vaporized fauna near the eruption site, surge deposits, CO₂, lime, and ash would have suffocated and chemically burned organisms further away. Large volumes of ash and surge deposits blanketed the region, changing the environmental pH alkaline, causing a mass die off near the eruption site. This alkaline environment would have affected the area after each eruption resulting in a lack of life in the region.