A study published in the journal Geology suggests that extinct volcanic contributed to the mass extinction of species toward the end of the Cretaceous.
The results confirm the notion that it was a major meteorite attack that caused a major biological crisis that ended with the extinction of non-bird dinosaurs and other marine and terrestrial creatures 66 million years ago.
The study was conducted by researcher Sietske Batenburg, from the Faculty of Earth Sciences of the University of Barcelona, and experts Vicente Gilabert, Ignacio Arenillas and José Antonio Arz, from the University Research Institute on Environmental Sciences of Aragon (IUCA-University of Zaragoza).
K / Pg border: Extreme extinction of Zuma’s Cretaceous coastline
The focus of this study was on the rocks of Zumaia (Basque Country), which has a different part of the line that reflects the geographical history of the Earth in the last 115-50 million years (Ma).
In this area, the team analyzed organisms and rocks rich in microfossils enclosed between 66.4 and 65.4 Ma, a time interval that included the well-known Cretaceous / Paleogene (K / Pg) boundary.
Set at 66 Ma, the K / Pg boundary separates the Mesozoic and Cenozoic periods and coincides with one of the five major extinct planets.
This study analyzed climate change that occurred shortly before and after the massive extinction marked by the K / Pg boundary, as well as its possible relationship to this major biological problem.
For the first time, researchers are investigating whether climate change is compatible with the timing and possible causes: the Deccan (India) volcano — one of the most violent volcanic eruptions in the history of planet Earth – and the atmospheric variation on Earth.
“The uniqueness of the landscape from Zumaia lies in the fact that two species have accumulated there – some rich in clay and some rich in carbonate – which we can now see as strata or marl and limestone alternating to create rhythm,” notes researcher Sietske Batenburg, from the Department of Lands. and Ocean Dynamics of UB.
“This strong rhythm of the pillars is related to the variation in the orbit of the Earth’s axis in the rotation motion, and in the translation movement around the Sun”.
This astronomical adjustment – cycles known as Milankovitch, which is repeated every 405,000, 100,000, 41,000 and 21,000 years – controls the amount of solar radiation they receive, balances our planet’s global temperature, and sets the type of sediment that reaches the oceans.
“Thanks to these times identified on the pillars of Zumaia, we have been able to determine the most significant period of the weather events that occurred during the settlement of the last dinosaurs,” said Ph.D. student Vicente Gilabert, from the UZ Department of Earth Sciences, who will present his defense at the end of the year.
Planktonic foraminifera: Reveals past climate
Carbon-13 isotopic analysis in rocks combined with research into planktonic foraminifera – microfossils used as highly accurate biostratigraphic indicators – has made it possible to reconstruct the paleoclimate and the chronological order in the Zuma pillars.
More than 90% of the Cretaceous planktonic foraminiferal species from Zumaia disappeared 66 Ma ago, accompanied by a major disruption in the carbon cycle and the collection of impact glass spherules from the asteroid that hit Chicxulub, on the Yucatan Peninsula (Mexico).
In addition, the results of this study reveal the existence of three tropical climate events – known as hyperthermal events – that have nothing to do with the impact of Chicxulub.
The first, known as LMWE and before the K / Pg boundary, is based on between 66.25 and 66.10 Ma. The other two events, after the mass extinction, are called the Dan-C2 (between 65.8 and 65.7 Ma) and LC29n (between 65.48 and 65.41 Ma).
Over the past decade, there has been a heated debate over whether the high blood pressure events mentioned above are due to an increase in the Deccan volcano, which emits high levels of electricity in the atmosphere.
“Our results show that all of these events are in line with the earth’s massive correction known as eccentricity maxima.
Only LMWE, which has produced an average temperature of 2-5 ° C, appears to be temporarily associated with the Deccan eruption. is a combination of the effects of volcanic eruptions and the recent magnitude of Cretaceous eccentricity maximum, “experts say.
Diversity of the earth around the sun
The global climate change that took place near the end of the Preteoous and the first Palaeogene – between 250,000 years before and 200,000 years after the K / Pg border – was due to the magnitude of the earth’s orbit around the Sun.
However, the orbital force influencing climate change before and after the K / Pg boundary is not related to the extinction of the Cretaceous species in the latter.
Climate change caused by eccentricity maxima and augmented by the Deccan volcano occurred gradually over a period of hundreds of thousands of years.
“These data will confirm that the extinction was caused by something completely outside the Earth’s system: the impact of the asteroid that occurred 100,000 years after the Cretaceous (LMWE) climate change,” said a team of researchers.
“Moreover, 100,000 years ago before the K / Pg border experienced high ecological stability without obvious disruption, and massive extinction of species took place immediately in the landscape,” they concluded.
