Young scholars in China proposed a new mechanism of mass extinction at the end of the Ordovician period

Figure 1 460-430 MA paleomagnetic poles
in the world's major plates.
(a) Modern geographical coordinates; (b) Gondwana coordinates

Figure 2 450-440 MA global paleogeographic reconstruction

With the support of the National Natural Science Foundation of China (grant numbers: 91855216, 41230208, 42002208, 41888101), Dr.
Jing Xianqing and Professor Yang Zhenyu of Capital Normal University, Ross Mitchell and Wangbo Researcher, Institute of Geology and Geophysics, Chinese Academy of Sciences, Zhu Min, Researcher of Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, and Tong Yabo, Institute of Geomechanics, Chinese Academy of Geological Sciences, A new mechanism
for causing mass extinctions and environmental changes at the end of the Ordovician period is proposed.
The results, titled "Ordovician–Silurian true polar wander as a mechanism for severe glaciation and mass extinction," were published online in Nature Communications on December 26, 2022
。 Full text link: _istranslated="1">.

After the Cambrian explosion, the Earth's environment changed drastically at the end of the Ordovician period, with the first mass extinction since the Phanerozoic and the first serious ice age event
.
It has been suggested that special paleogeographical patterns and volcanic action may be the main reasons for
this mass extinction and ice age.
In this regard, there is still great controversy in the scientific community: first, whether there was a violent volcanic action during this period, and how did the volcanic effect affect this mass extinction? Second, the lack of key paleomagnetic data during this period makes it uncertain whether the paleogeographic reconstruction scheme can reflect the dispersion of global plates
.
Third, the latest high-precision chronology-paleontological data show that the start and end time of this extinction is longer than previously thought, and it does not show an obvious pattern
of two pulse extinctions.
As a result, the end-Ordovician mass extinction still lacks a perfect academic explanation
.

In order to more accurately establish the global late Ordovician paleogeographical pattern, the research team carried out a detailed paleomagnetic study of the Silurian Huixing Sentinel Formation in Xiushan County, Chongqing, South China (Figure 1).

Combined with the results of previous research, a highly reliable early Silurian paleomagnetic pole (438–435 Ma)
was obtained.
The global Odovician to early Silurian paleomagnetic results are systematically summarized, and it is found that almost all plates have a polar shift process
of about 50o during this period.
This multi-plate, large-scale, and rapid plate movement behavior cannot be explained by traditional plate tectonic theory, but is more consistent
with the phenomenon caused by the true polar shift of the earth.

After further ruling out other influencing factors (e.
g.
, equatorial–axial dipole field, non-dipole field, tectonic rotation), the research team concluded that a true polar shift event
of about 50o occurred on Earth between 450–440 Ma at the end of the Ordovician period.
The occurrence of the true polar shift event may be the mass collision and demise of the original Tethys, causing a large number of plates to subduct and sink and remain in the mantle transition zone, so that the mantle transition zone of the Tethys domain has a positive gravitational anomaly, causing a true polar shift and moving it towards the equator
.

Based on this true polar shift event, the research team further accurately reconstructed the paleogeographical pattern of the global 450–440 Ma plate (Figure 2), which can well explain the process and genesis
of glacial development at the end of the Ordovician.
At the same time, rapid geographical changes led to mass extinctions at the end of the Ordovician period
.