UT professor says tectonic shift triggered biological explosion

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New research from geosciences professor Ian Dalziel suggests the cause of rising sea levels and biological expansion 530 million years ago was a major
tectonic shift. 

Dalziel’s study, which was published in the November issue of The Journal of Geology, suggests that the shift resulted in the emergence of major multicellular organisms, such as fish and mollusks during this era, the Cambrian period.

According to Dalziel, he had been collecting geological evidence on various continents, primarily in Antarctica, when he discovered a link between the evidence he had been collecting and existing research that indicated the Pacific and Atlantic Oceans were once a single body of water. 

“One night, I thought there had to be a connection between the two oceans,” Dalziel said. “I’d been
concentrated on the continents and not on the ocean.”

Dalziel proposed a reconstruction of Earth involving the supercontinent called Gondwanaland that was composed of Australia, Antarctica, Africa, India, and South America and Laurentia, the geological ancestor of North America. In Dalziel’s model, Gondwanaland and Laurentia oceans were separated by the Pacific and ancestral Atlantic oceans.

“I’ve been working on the study of the Earth before Cambrian for quite a number and in Antarctica,” Dalziel said. “North America and Antarctica were
previously joined.”

Dalziel said a rift opened up between the Pacific and ancestral Atlantic oceans, which led to the rise in sea levels. Dalziel said he utilized previous research to come to his conclusions.

“We know the chemistry of the Atlantic Ocean affected the chemistry of the Pacific,” Dalziel said. “[This has made possible] the
connection between the previous, well-documented research and what’s been done recently.”

John Goodge, environmental sciences professor at the University of Minnesota who read Dalziel’s paper, said that this tectonic shift caused the buildup of oxygen in the environment, which made prime conditions for the rise of modern species.

“We have shallow seas encroaching on land,” Goodge said. “North America [had a] warm climate and nutrient-rich waters. It’s possible that that’s what set the stage for the expansion of these living organisms.”

As research on this topic continues, Dalziel said he would like for more people to piece together evidence supporting his claims.

“There are students and faculty around the world that will be able to collect evidence,” Dalziel said. “I hope they continue piecing it together and understand this far-reaching problem.”