[Rockhounds] New research links continents to key transitions in Earth's oceans, atmosphere and climate

[Kreigh Tomaszewski]

A new study led by University of Wisconsin Oshkosh geologist Timothy
Paulsen and Michigan Tech geologist Chad Deering advances the understanding
of the role that continents have played in the chemical evolution of
Earth's oceans, with implications for understanding atmospheric oxygenation
and global climate oscillations.

The team of researchers analyzed a global database of the chemistry of tiny
zircon grains commonly found in the Earth's continental rock record. The
research team includes other scientists from Michigan Technological
University and ETH Zurich in Switzerland.

The study was featured on the cover of the February issue of *GSA Today* by
the Geological Society of America.

"Oceans cover 70% of Earth's surface, setting it apart from the other
terrestrial
planets <https://phys.org/tags/terrestrial+planets/> in the solar system,"
said Paulsen, the lead author on the paper. "Geologists have long
recognized that there have been profound changes in ocean
<https://phys.org/tags/ocean/> chemistry over time."

Yet there are significant questions about the drivers for changes in ocean
chemistry in Earth's past, especially associated with the ancient rock
record leading up to the Cambrian explosion of life approximately 540
million years ago.

"Continents tend to be worn down by weathering and rivers tend to transport
this sediment <https://phys.org/tags/sediment/> to the oceans leaving
scattered puzzle pieces for geologists <https://phys.org/tags/geologists/> to
fit together," said Deering, a coauthor on the paper. "There is increasing
evidence that important pieces of the puzzle are found in the ancient beach
and river sediments produced through continental weathering and erosion."

The researchers' findings, based on an analysis of an exceptionally large
zircon data set from sandstones recovered from Earth's major continental
landmasses, may signify key links in the evolution of the Earth's rock
cycle and its oceans.
https://phys.org/news/2022-02-links-continents-key-transitions-earth.html