Excavations in China helped to clarify the scale of the first glaciation in the history of the Earth
(ORDO NEWS) — An international team of geologists has discovered deposits of rocks of the Neoproterozoic era in southern China, indicating that the global glaciation of the Earth 720-630 million years ago was not as extensive as geologists and paleontologists now believe.
“Our excavations in the Nanto Formation in southern China provided the first evidence that potentially habitable ice-free areas of the ocean were present in the Snowball Earth era not only near the equator, but also in the middle latitudes.
These warm regions of the planet could serve as a refuge for the first multicellular organisms at the end of this ice age,” the researchers write.
Presumably, the first global glaciation in the history of our planet occurred approximately 720-630 million years ago, in the second half of the Neoproterozoic era.
During this epoch, the so-called cryogenic period, virtually the entire surface of the Earth, with the exception of its equatorial regions, was completely covered with ice at least twice and remained in this form for many tens of millions of years.
The exact reasons for the launch of this global ice age, which scientists call the “Snowball Earth” era, are still a matter of debate among geologists and climatologists.
Similar disputes raise questions related to how the planet managed to get rid of glaciation, how cryogeny influenced the evolution of terrestrial life, including the appearance of the first multicellular living beings.
Refined scales of the first glaciation of the Earth
A group of paleontologists led by Xiao Shuhai, a professor at Virginia Tech in Blacksburg (USA), took a big step towards obtaining such information while studying the rocks of the Neoproterozoic era occurring in the Hubei province in southern China.
Here are deposits of the so-called Nanto Formation, formed at the end of the cryogenian period, approximately 650-635 million years ago.
At that time, as noted by Professor Xiao Shuhai and his colleagues, the south of China was located in temperate latitudes, in the vicinity of 30 parallel north latitude.
For this reason, paleontologists and geologists in the past believed that this part of the continent and adjacent regions of the seas were covered with a thick crust of “eternal” ice, under which multicellular life could hardly exist.
Excavations in the Shennongjia forest in Hubei province have shown that these ideas were erroneous.
The researchers were able to find in local Proterozoic rocks a large number of algae imprints, supposedly growing on the bottom of shallow seas, as well as organic deposits and chemical traces of the presence of significant amounts of oxygen in the upper layers of sea water that covered this region of China in the distant past.
All this, as scientists note, indicates that at the end of the cryogenian period, this part of the Earth’s primary ocean was free of ice. This suggests that the ice sheet of the “Snowball Earth” either had a much smaller size than scientists had assumed in the past, or indicates the presence of large “holes” with warm water in it.
Both greatly expand the number of possible shelters of life in the first ice age on Earth, the geologists concluded.
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