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Dinosaurs Extinction Due to a “One-Two Punch”

Scientists from the University of Michigan and a colleague from the University of Florida have used new technology to determine that the extinction of the dinosaurs and other creatures 66 million years ago was due to two catastrophic events.

They reconstructed temperatures spanning 3.5 million, at the end of the Cretaceous period and the beginning of the Paleocene period. They found two abrupt heating spikes (temperatures jumping 14-degrees Fahrenheit) in ocean temperatures that coincide with the two major events: volcanic eruptions in India’s Deccan Traps and the asteroid impact on Mexico’s Yucatan Peninsula.

Sierra Peterson, a postdoctoral researcher in the University of Michigan’s Earth and Environmental Sciences Department says,

These two extinction pulses coincide with the two warming spikes we identified in our new temperature record, which each line up with one of the two “causal events.”

The new study supports the “press-pulse mechanism theory.” In this theory, the “press” of gradual climate change due to volcanic activity, was followed by the “pulse” of the asteroid’s impact.

Peterson adds,

This new temperature record provides a direct link between the volcanism and impact events and the extinction pulses – that link being climate change.

The fossil shells of the clam-like bivahos

The fossil shells of the clam-like bivahos

The scientists analyzed the isotopic composition of 29 well-preserved shells of the clam-like bivalves. These 2-5-inch long creatures lived 65.5-69 million years ago in the coastal delta near the Antarctic Peninsula. Their shells incorporated atoms/isotopes of oxygen and carbon that revealed the temperature of the surrounding seawater. The scientists used a new technique, the carbonate clumped isotope paleothermometer, that showed the two temperature spikes. These temperature increases were likely the result of huge amounts of heat-trapping carbon dioxide gas released from the volcanic eruption. The second warming event, that occurred about 150,000 years later, happened when the Chicxulub asteroid hit Mexico.

The size of the study subjects, bivahos fossils

The size of the study subjects, bivahos fossils

The study states,

The cause of the end-Cretaceous (KPg) mass extinction is still debated due to difficulty separating the influences of two closely timed potential causal events: eruption of the Deccan Traps volcanic province and impact of the Chicxulub meteorite. Here we combine published extinction patterns with a new clumped isotope temperature record from a hiatus-free, expanded KPg boundary section from Seymour Island, Antarctica.

Peterson sums up,

We find that the end-Cretaceous mass extinction was caused by a combination of the volcanism and meteorite impact, delivering a theoretical “one-two punch.”