Earth's orbital changes have influenced climate, life forms for at least 215 million years
Every 405,000 years, gravitational tugs from Jupiter and Venus slightly elongate Earth's orbit, an amazingly consistent pattern that has influenced our planet's climate for at least 215 million years and allows scientists to more precisely date geological events like the spread of dinosaurs, according to a Rutgers-led study.
The scientists linked reversals in the Earth's magnetic field - when compasses point south instead of north and vice versa - to sediments with and without zircons (minerals with uranium that allow radioactive dating) as well as to climate cycles.
The scientists studied the long-term record of reversals in the Earth's magnetic field in sediments in the Newark basin, a prehistoric lake that spanned most of New Jersey, and in sediments with volcanic detritus including zircons in the Chinle Formation in Petrified Forest National Park in Arizona. They collected a core of rock from the Triassic Period, some 202 million to 253 million years ago. The core is 2.5 inches in diameter and about 1,700 feet long, Kent said.
Prior to this study, dates to accurately time when magnetic fields reversed were unavailable for 30 million years of the Late Triassic. That's when dinosaurs and mammals appeared and the Pangea supercontinent broke up. The break-up led to the Atlantic Ocean forming, with the sea-floor spreading as the continents drifted apart, and a mass extinction event that affected dinosaurs at the end of that period, Kent said.
"Developing a very precise time-scale allows us to say something new about the fossils, including their differences and similarities in wide-ranging areas," he said.
The findings are published online today in the Proceedings of the National Academy of Sciences.
Source: Columbia University [May 07, 2018]
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