2021-06-11

Radiation from seed plants may be the direct cause of the late Paleozoic glacial period

By yqqlm yqqlm

In recent years, climate issues have attracted much attention, among which global warming has become one of the most concerned climate issues. But this time we live in is not the hottest time on the earth, would you be surprised? Since the industrial revolution, the concentration of carbon dioxide in the atmosphere has risen rapidly, and significant global warming is taking place. However, for the blue planet we live in with a”ball age” of 4.6 billion years, it is normal for us to alternate between cold and warm!

In fact, for the past billion years, the earth has been dominated by a greenhouse climate, and the glacial period can only occupy less A quarter of the time. In the Late Paleozoic Great Ice Age, the longest lasting and largest ice-forming event since the Phanerozoic occurred. This glacial period caused significant changes in the global paleo-ocean, paleo-climate, and paleo-ecology, and is a key turning point in the evolution of the earth’s climate and environment. period.

The prologue of this ice age can be traced back to the earliest Carboniferous 355 million years or so), when the global climate became drastically cold and accompanied by significant carbon cycle fluctuations, the so-called”Mid-Dune carbonIsotope positive drift event”, this event is the late Paleozoic global climate caused by the”greenhouse”An important landmark event for the transition from”to the ice room”.

For a long time, the landing and large-scale prosperity of vascular plants, especially seed plants, have been considered to be one of the important reasons for triggering the Late Paleozoic glacial period, but there has been a lack of direct evidence to reveal the causal connection between them. In response to this problem, Chinese Academy of Sciences Nanjing Institute of Geology and Palaeontology Young Scientists Chen Bo, Chen Jitao, Qie Wenkun, Huang Pu And others have carried out systematic research in cooperation with domestic and foreign counterparts. Through the research of South China and Vietnam and other places 5 Carry out detailed carbon, strontium, and oxygen isotope analysis (respectively indicating carbon cycle, continental weathering, and paleotemperature changes) in the Early Carboniferous section, and systematically sort out the global seed plants from the Late Devonian to Early Carboniferous. class=”candidate-entity-word” data-gid=”17744530″ qid=”6596472650929804558″>Diversity and changes in geographic distribution.

The study found that the strontium isotope ratio of seawater began to decrease in the middle of the Dunet period (about 355 million years ago), and was accompanied by the increase of carbonate carbon isotope and conodont oxygen isotope (Figure 1) The coupling change of the three isotopic systems of carbon, oxygen and strontium coincides with an important radiation event in the early evolution of seed plants.

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Fig.1 The relationship between the changes of carbon, oxygen, and strontium isotopes in the early Carboniferous sub-Dune stage and the evolution of seed plants

During the incident, the diversity of seed plants increased rapidly and their distribution range expanded significantly, and it is likely to quickly occupy the previous vegetation Arid and high latitude areas with sparse or no vegetation cover (Figure 2). This coincidence in time indicates to a certain extent that the radiation and expansion of seed plants in the Dune stage may lead to the mainland Silicate, especially basaltic silicate, increases weathering intensity (Sr/87 86SrSr value decreases), thereby bringing a large amount of terrestrial nutrients such as phosphorus to the ocean. Promote the increase of the global ocean’s original productivity and the increase of organic carbon burial (δ13Ccarb value rises); while silicate weathering and organic carbon burial will consume a lot of The carbon dioxide in the atmosphere eventually leads to the cooling of the climate (the value of δ18Oapatite rises) and the transition of the global climate from the”greenhouse” to the”ice chamber” period.

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Figure 2 Late Devonian-Early Carboniferous seed plant genus diversity and distribution range changes

The hypothesis that the expansion triggered the Late Paleozoic glacial period provides direct evidence for our understanding of the rise of terrestrial ecosystems and their role in shaping the global climate.

Relevant research results were published online in the journal”Earth and Planetary Science Letters” (Earth and Planetary Science Letters). This research was jointly funded by the Special Category B project of the Chinese Academy of Sciences’ Leading Strategy and the National Natural Science Foundation of China.

Related information about the paper:Bo Chen*, Jitao Chen, Wenkun Qie, Pu Huang, Tianchen He, Michael M. Joachimskic, Marcel Regelous, Philip AE Pogge von Strandmannd, Jiangsi Liu Xiangdong Wang, Isabel P. Montanez , Thomas J. Algeo. (2021). Was climatic cooling during the earliest Carboniferous driven by expansion of seed plants? Earth and Planetary Science Letters Volume 565, 116953. https://doi.org/10.1016/j.epsl.2021.116953.

Source:Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences