Meteor© Credit: Continental Dynamics Workshop/NSF

It’s not always an either/or proposition. Life is always too complicated to be that simple, whether today, or in the geological past. Since the 1980s scientists from many different fields of expertise have weighed in on what caused the extinction of the dinosaurs. The debate has been filtered down to this one question: was the extinction a gradual affair, spanning many millions of years; or was it catastrophically sudden, measured in 100s or 1000s of years? 

The geochemical markers that inform the catastrophic model cannot now be dismissed. Even in Saskatchewan, the marker beds are here, in support of an asteroidal impact in a crater called Chicxulub, off the tip of the Yucatan peninsula. However, there has always been a contingent of scientists who have read the geological record in India, regarding the giant lava flows from what is now called the Shiva impact structure. 

Longtime researcher Jack Lerbekmo from the University of Alberta released a study from Marine and Petroleum Geology journal, a quite unique study that links the Chicxulub and Shiva event as a ‘one-two punch’ 65 million years ago. His study, which was mostly completed before his passing, was bravely titled “The Chicxulub-Shiva extraterrestrial one-two killer punches to Earth” (2013).

He looks at the timing of the two events using paleomagnetic correlations. Since we know the Earth’s poles have reversed and normalized over time, paleomagnetic studies can provide a finer resolution to determine the timing of geological events. Lerbekmo, who has worked in Saskatchewan on many occasions, discovered that between the two events, the poles switched from north to south. In fact both events were only separated by about 400,000 years.

Considering the volume of ejecta, and atmospheric alterations caused by not one but two impactors, there could have been a greater destruction of species when we consider the complexity of life’s survival.