The K-Pg mass extinction event was primarily driven by an extraterrestrial source

It is most commonly accepted that a large planetary impact was the primary driver in the end-Cretaceous mass extinction.
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The K-Pg mass extinction event was primarily driven by a terrestrial source

Potential terrestrial drivers of the K-Pg mass extinction event include wide-spread volcanism, climate change, and the formation of flood basalts in the Deccan Traps in India.
Created at: 
2019-02-28
  Updated at: 
2020-04-22
Curator:
Leah O'Rourke   Subscribe ...

Background

Iridium Spike

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The iridium anomalies in the K-Pg boundary layer are not the result of a marine enrichment process or oceanic mass extinction.

eThe iridium (Ir) spike was observed in freshwater sediments.

Mineralogical Studies

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There was a large planetary impact 66 Ma.

eShocked quartz grains were found in the K-Pg layer.

eNanometer-sized diamonds containing a carbon isotope ratio similar to type C2 chondritic meteorites were found in K-Pg boundary layer rock.

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Shocked materials found in the K-Pg boundary originate from an extraterrestrial impact.

eZircon grains containing shock-specific crystallographic features were discovered in K-Pg layer rock samples.

eStishovite was detected in K-Pg layer samples.

Volcanic Activity

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Significant volcanic activity coincided with the K-Pg boundary.

e40Ar/39Ar dating places the deposition of the Deccan Traps basalt flows at 65-69 Ma.

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Volcanism was a primary factor affecting ecological survival and recovery.

eDeccan eruptions became much larger and less frequent for 500,000 years following the K-Pg boundary.

Marine Historical Record

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Global oceanic events have played a large role in extinction events and could have been a significant terrestrial factor in the K-Pg mass extinction.

eMarine regressions/transgressions appear to have coincided with multiple Phanerozoic extinction events.

eMarine fossils indicate a rapid sea level drop across 17,000 years before the K-Pg boundary.

eOcean environments were under high stresses concurrent with Deccan volcanism prior to the K-Pg boundary.