This recent study focuses on the asteroid impact which eradicated 75% of life including non-avian dinosaurs. Analysis of rock and debris that fell in the first 24 hours following the impact is giving an insight into conditions during the immediate aftermath of the impact.
An international team led by the University of Texas analysed more than 130 metres of rock that had built up over just one day, the day after the asteroid struck. The rock record here includes bits of charcoal, jumbles of rock brought in by the tsunami’s backflow and importantly an absence of sulfur.
“They are all part of a rock record that offers the most detailed look yet into the aftermath of the catastrophe that ended the Age of Dinosaurs”
– Sean Gulick, a research professor at the University of Texas Institute for Geophysics (UTIG) at the Jackson School of Geosciences.
Gulick led the study and co-led the 2016 International Ocean Discovery Program scientific drilling mission that retrieved the rocks from the impact site offshore of the Yucatan Peninsula. The research, published in the Proceedings of the National Academy of Sciences builds on earlier work co-led and led by the Jackson School that described how the crater formed and how life quickly recovered at the impact site.
The aftermath
In just one day 130 meters of material built up inside the crater, this rate is amongst the highest ever encountered in the geological record. Most of this material was deposited within hours of the impact or was carried into the crater by seawater from the Gulf of Mexico. This rapid accumulation of rock means there is an excellent record preserved of the conditions in and around the crater in the immediate aftermath of the impact and this record contains clues on the longer-lasting effects of the collision.
Researchers estimate the asteroid hit with the equivalent power of 10 billion atomic bombs. The blast set trees and plants ablaze that were thousands of miles away and triggered a massive tsunami that reached as far inland as Illinois. Inside the crater, researchers found charcoal and a chemical biomarker relating to soil fungi associated with layers of sand that shows signs of being deposited by resurging waters. It is therefore hypothesised that the charred landscape was pulled into the crater with the receding waters of the tsunami.
Mysterious sulfur
It was not only the physical findings of this study that are aiding our understanding of this time but also what was missing. Despite the area surrounding the crater being heavily comprised of sulfur-rich rocks, there was no sulfur found in the cores taken from the crater itself.
This lack of sulfur is evidence that supports the theory that the asteroid impact vapourised sulfur present at the impact site and released it into the atmosphere where it proceeded to reflect sunlight away from the planet and cause global cooling.
The 1883 eruption of Krakatoa released 60 teragrams of sulfur and the resultant cooling of the Earth was an average of 2.2 degrees Fahrenheit for 5 years. Comparatively, researchers estimate that the dinosaur destroying impact released 4 orders of magnitude more than this at 325 billion tons of sulfur so the effect on climate would have been colossal.
Although the asteroid impact created mass destruction at a regional level with wildfires and tsunamis, it was this global climate change that caused the mass extinction that saw the demise of the dinosaurs along with most other life on the planet at the time.
“The real killer has got to be atmospheric,” …”The only way you get a global mass extinction like this is an atmospheric effect.”
– Sean Gulick, a research professor at the University of Texas Institute for Geophysics (UTIG) at the Jackson School of Geosciences.
This research has given scientists the most detailed look yet of the aftermath following the eruption providing key evidence to existing theories and has consequently provided a unique insight into the dawn of the dinosaurs’ demise.
-GeologyHub
References
Sean P. S. Gulick, Timothy J. Bralower, Jens Ormö, Brendon Hall, Kliti Grice, Bettina Schaefer, Shelby Lyons, Katherine H. Freeman, Joanna V. Morgan, Natalia Artemieva, Pim Kaskes, Sietze J. de Graaff, Michael T. Whalen, Gareth S. Collins, Sonia M. Tikoo, Christina Verhagen, Gail L. Christeson, Philippe Claeys, Marco J. L. Coolen, Steven Goderis, Kazuhisa Goto, Richard A. F. Grieve, Naoma McCall, Gordon R. Osinski, Auriol S. P. Rae, Ulrich Riller, Jan Smit, Vivi Vajda, Axel Wittmann, and the Expedition 364 Scientists. The first day of the Cenozoic. PNAS, 2019 DOI: 10.1073/pnas.1909479116
University of Texas at Austin. “Rocks at asteroid impact site record first day of dinosaur extinction.” ScienceDaily. ScienceDaily, 9 September 2019. <www.sciencedaily.com/releases/2019/09/190909160102.htm>.
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