2021-09-29

Research: the mass extinction of Late Cretaceous species was not caused by extreme volcanic activity

By yqqlm yqqlm

Research: the mass extinction of Late Cretaceous species was not caused by extreme volcanic activity </ P >

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p > k / PG boundary: Cretaceous mass extinction off the coast of sumaia </ P >

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p > the scene of this study is sumaia Cliff (Basque area), which has a special stratigraphic part, revealing the geological history of the earth in the period of 115-500 million years ago (MA). In this environment, the research team analyzed microfossil rich sediments and rocks deposited between 66.4 and 65.4ma, including the known Cretaceous / Paleogene boundary (K / PG). The time of K / PG boundary is 66 Ma, which divides Mesozoic and Cenozoic and coincides with one of the five mass extinctions on earth</ p>

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p > this study analyzes the climate change before and after the mass extinction marked by the K / PG boundary and its potential relationship with this large biological crisis. For the first time, researchers have studied whether this climate change coincides with its potential causes on a time scale: Deccan volcano (India) – one of the most violent volcanic events in the geological history of the earth – and changes in the earth’s orbit</ p>

Research: the mass extinction of Late Cretaceous species was not caused by extreme volcanic activity(1) </ P >

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p > “the particularity of sumaia outcrop is that there are two types of sediments accumulated there – some rich in clay and some rich in carbonate – we can now determine them as strata or marl and limestone, which alternate with each other to form rhythm.” Sietske batenburg, a researcher from UB’s earth and ocean dynamics system, pointed out that “this strong rhythm of deposition is related to the periodic changes of the direction and inclination of the earth’s axis in the rotation movement and the translational movement around the sun.” </ P >

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p > these astronomical configurations — the known Milankovitch cycle, every 405000 years, 100000 years 41000 and 21000 years repeat — regulating the amount of solar radiation they receive, regulating the global temperature of our planet, and regulating the type of sediment reaching the ocean. “Thanks to these periodicity found in the sumaia deposit, we have been able to determine the most accurate age of the climate events around the last dinosaurs,” said Vicente Gilbert, a doctoral student from the UZ Department of Geosciences. He will submit his thesis defense before the end of this year</ p>

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p > planktonic foraminifera: revealing the past climate </ P >

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p > the combination of carbon-13 isotope analysis on rocks and the study of planktonic foraminifera, microfossils used as high-precision biostratigraphic indicators, makes it possible to reconstruct the paleoclimate and chronology in sumaya sediments. More than 90% of Cretaceous planktonic foraminifera species in sumaia died out before 66 Ma, which is consistent with the large interruption of the carbon cycle and the accumulation of impact glass balls from the asteroid (Mexico) that hit Chicxulub</ p>

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p > in addition, the conclusion of the study reveals that there are three strong climate warming events – called high heat events – which have nothing to do with the Chicxulub impact. The first, called lmwe, has been measured between 66.25 and 66.10 Ma before the K / PG boundary. The other two events, which occurred after the mass extinction, are called dan-c2 (between 65.8 and 65.7 MA) and lc29n (between 65.48 and 65.41 MA)</ p>

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p > in the past decade, there has been a heated debate on whether the above-mentioned hyperthermic events were caused by the increase of Deccan volcanic activity. “Our results show that all these events are synchronized with the earth’s extreme orbital configuration known as the maximum eccentricity. Only lmwe produces global warming estimated at 2-5 ℃, which seems to be related to the Deccan volcanic eruption in time, indicating that it is caused by volcanic activity and the impact of the recent maximum Cretaceous eccentricity,” the experts added</ p>

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p > the change of the earth’s orbit around the sun </ P >

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p > the global climate change in the late Cretaceous and early paleomodern times – between 250000 years before and 200000 years after the K / PG boundary – is caused by the maximum eccentricity of the earth’s orbit around the sun</ p>

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p > however, the orbital eccentricity affecting climate change before and after the K / PG boundary has nothing to do with the mass extinction of species in the late Cretaceous. The climate change caused by the maximum eccentricity and enhanced by Deccan volcanism gradually occurred in the range of hundreds of thousands of years</ p>

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p > the research team pointed out: “these data will confirm that species extinction was caused by something completely outside the earth system: the impact of an asteroid occurred in this late Cretaceous climate change (lmwe) In addition, the last 100000 years before the K / PG boundary are characterized by a highly stable environment without obvious disturbance, and the mass extinction of species occurs instantaneously on the geological time scale. “