Prof. Shen Yan’an and a research team hailing from the University of Science and Technology of China (USTC) within the Chinese Academy of Sciences (CAS) have conducted a comprehensive exploration of South China’s interglacial stratigraphy. Employing high-precision sulfur and mercury isotope analyses, their study has brought forth a fresh perspective suggesting a correlation between the melting of the enigmatic “Snowball Earth” and widespread volcanic activities. Moreover, this research furnishes compelling evidence indicating that the gradual oxidation of interglacial oceans engendered favorable environmental conditions crucial for the development of early, intricate life forms. The findings from this endeavor have been documented in the journal Science Advances.
The primary focus of this research team was the Datangpo Formation in South China, where their aim was to delve into the transformations occurring in the Earth’s surface environment and climate system post the “Snowball Earth” thaw. The Datangpo Formation not only stands as a significant repository of extensive sedimentary manganese deposits in China but also serves as an almost complete archive of climate and environmental shifts bridging two distinct “Snowball Earth” events.
Following numerous field surveys and in-depth investigations, the team meticulously selected a drill core from the Datangpo Formation, spanning hundreds of meters in depth. This core served as the basis for geological, stratigraphic, and geochemical analyses. The findings from these studies indicate that during the initial phases of the “Snowball Earth” thaw, the chemical composition of seawater was chiefly influenced by hydrothermal venting on the ocean floor. This revelation indirectly highlights the stark disparities between the ocean during the “Snowball Earth” epoch and a typical ocean, with severely restricted substance exchange and circulation among the ocean, atmosphere, and land during that time.
Furthermore, variations in non-mass-dependent mercury isotopes supply evidence pointing to heightened volcanic activity during the deglaciation of the “Snowball Earth.” In light of this revelation, the research team introduces a novel viewpoint, suggesting that the swift thawing of the “Snowball Earth” triggered a sudden reduction in surface pressure, subsequently setting off magmatic activity deep within the Earth, ultimately leading to volcanic eruptions.
The researchers also identified peculiarities in the sulfur isotope composition of pyrite within interglacial sediments, including slight non-mass-dependent sulfur isotope fractionation. Nevertheless, the sedimentary sequence evidently indicates that this minor non-mass-dependent sulfur isotope fractionation isn’t causally tied to volcanic activity. Instead, the team posits that the “Snowball Earth” itself altered the sulfur isotope composition of seawater sulfates, giving rise to this phenomenon.
Additionally, temporal fluctuations in sulfur isotopes illustrate a gradual upswing in sulfate concentration in interglacial seawater, signaling a progressive oxidation of the atmospheric and oceanic systems during this era. Considering shifts in atmospheric chemistry, a gradual dip in surface temperatures, and the advancing oxygenation of the oceans during the interglacial era, the research team suggests that the alterations in environmental and climatic conditions on Earth’s surface during this interglacial phase spurred the evolution of early, intricate life forms.