Study links Korean crater to oxygen rise

South Korean researchers say they have uncovered a key clue on the Korean Peninsula that could help explain the Great Oxidation Event, a surge in atmospheric oxygen about 2.4 billion years ago.

The Korea Institute of Geoscience and Mineral Resources said on April 15 that a team led by Lim Jae-su, head of its Planetary Geology Laboratory, has discovered stromatolites, among the oldest known evidence of life on Earth, at the Hapcheon meteorite impact crater in South Gyeongsang Province. Stromatolites are dome-shaped sedimentary structures formed in shallow water as primitive microorganisms such as cyanobacteria trap and bind sediment.

The team identified several stromatolites measuring 10 to 20 centimeters in diameter in the northwestern part of the crater, the only known meteorite impact site on the Korean Peninsula. Detailed analysis showed that as the microorganisms built up layers of sediment, they incorporated material derived from the meteorite along with fragments of surrounding rock. The researchers also detected minerals that form only in high-temperature water, indicating the structures developed in a hydrothermal environment fed by hot, rising fluids. These minerals were most concentrated toward the core, where growth first began.

Taken together, the findings show for the first time that stromatolites formed in a hydrothermal lake created by heated groundwater rising after a meteorite impact. The study was published in Communications Earth & Environment.

The researchers also suggest that hydrothermal lakes formed by frequent meteorite impacts on early Earth may have supported the spread of photosynthetic microorganisms, creating localized “oxygen oases” that supplied oxygen to surrounding environments.

Lim Jae-su said the study offers the first comprehensive explanation of stromatolite formation. He added that confirming the possibility of oxygen oases and providing a new perspective for Mars surface exploration made the findings especially meaningful.


Jae-Hyeng Kim monami@donga.com