Alvarez hypothesis
Crucially, the cores also showed a near-complete absence of gypsum, a sulfate-containing rock, which would have been vaporized and dispersed as an aerosol into the atmosphere, confirming the presence of a probable link between the impact and global longer-term effects on the climate and food chain.
[8] In April 2019, a paper was published in PNAS which describes evidence from a fossil site in North Dakota that the authors say provides a "postimpact snapshot" of events after the asteroid collision "including ejecta accretion and faunal mass death".
"[10] According to a high-resolution study of fossilized fish bones published in 2022, the Cretaceous-Paleogene asteroid which caused mass extinction impacted during the Northern Hemisphere spring.
[17] Prior to Keller's research, the timeframe of the Deccan Traps' eruptions had a significantly large range of error, making it difficult to draw strong conclusions regarding their connection to the K-Pg extinction.
[18] Along with ocean acidification, ozone reduction, acid rain, and a release of harmful gases, she asserts that these conditions were sufficient to have initiated the mass extinction.
[14][17] Keller has specifically rejected the Alvarez hypothesis, pointing to evidence she gathered from the Chicxulub crater in 2009 revealing that twenty inches of sediment separates the impact from the extinction.
[14][15] This, however, contrasts the range of 33,000 years determined by Paul Renne in 2015,[19][20] as well the more recent assertion that a tsunami generated by the impact created the unusual sediment layer.
[15][18] A more recent theory combining both Deccan volcanism and the impact hypothesis has been developed by teams at UC Berkeley led by Paul Renne and Mark Richards.
[21] Debate regarding the cause of the K-Pg extinction has proven to be extremely controversial among researchers, and the resilience of its intensity has earned it the moniker of the "dinosaur wars."
Verbal accusations have been thrown both by and toward many prominent researchers including Gerta Keller and Luis Alvarez, discouraging civil debate and in some cases threatening careers.
This global dispersal of dust and sulfates would have led to a sudden and catastrophic effect on the climate worldwide, large temperature drops, and devastated the food chain.
