Evolution after the Chicxulub Asteroid Impact: The Rapid Response of
Life to the End-Cretaceous Mass Extinction Event
Boulder, Colo., USA: The impact event that formed the Chicxulub crater
(Yucatán Peninsula, México) caused the extinction of 75% of species on
Earth 66 million years ago, including non-avian dinosaurs. One place that
did not experience much extinction was the deep, as organisms living in the
abyss made it through the mass extinction event with just some changes to
community structure.
New evidence from International Ocean Discovery Program (IODP) Expedition
364 of trace fossils of burrowing organisms that lived in the seafloor of
the Chicxulub Crater beginning a few years after the impact shows just how
quick the recovery of the seafloor ecosystem was, with the establishment of
a well-developed tiered community within ∼700,000 years after the event.
In April and May 2016, a team of international scientists drilled into the
Chicxulub impact crater. This joint expedition, organized by the
International Ocean Discovery Program (IODP) and International Continental
Scientific Drilling Program (ICDP) recovered an extended syn- and
post-impact set of rock cores, allowing study of the effects of the impact
on life and its recovery after the mass extinction event. The end
Cretaceous (K-Pg) event has been profusely studied and its effect on biota
are relatively well-known. However, the effect of these changes on the
macrobenthic community, the community of organisms living on and in the
seafloor that do not leave body fossils, is poorly known.
The investigators concluded that the diversity and abundance of trace
fossils responded primarily to variations in the flux of organic matter
(i.e., food) sinking to the seafloor during the early Paleocene. Local and
regional-scale effects of the K-Pg impact included earthquakes of magnitude
10–11, causing continental and marine landslides, tsunamis hundreds of
meters in height that swept more than 300 km onshore, shock waves and air
blasts, and the ignition of wildfires. Global phenomena included acid rain,
injection of aerosols, dust, and soot into the atmosphere, brief intense
cooling followed by slight warming, and destruction of the stratospheric
ozone layer, followed by a longer-term greenhouse effect.
Mass extinction events have punctuated the past 500 million years of
Earth’s history, and studying them helps geoscientists understand how
organisms respond to stress in their environment and how ecosystems recover
from the loss of biodiversity. Although the K-Pg mass extinction was caused
by an asteroid impact, previous ones were caused by slower processes, like
massive volcanism, which caused ocean acidification and deoxygenation and
had environmental effects that lasted millions of years.
By comparing the K-Pg record to earlier events like the end Permian mass
extinction (the so-called “Great Dying” when 90% of life on Earth went
extinct), geoscientists can determine how different environmental changes
affect life. There are similar overall patterns of recovery after both
events with distinct phases of stabilization and diversification, but with
very different time frames. The initial recovery after the K-Pg, even at
ground zero of the impact, lasted just a few years; this same phase lasted
tens of thousands of years after the end Permian mass extinction. The
overall recovery of seafloor burrowing organisms after the K-Pg took
~700,000 years, but it took several million years after the end Permian.
FEATURED ARTICLE
Rapid macrobenthic diversification and stabilization after the
end-Cretaceous mass extinction event
AUTHORS: Francisco J. Rodríguez-Tovar, Christopher M. Lowery, Timothy J.
Bralower, Sean P.S. Gulick, and Heather L. Jones
CONTACT: Francisco J. Rodríguez-Tovar, fjrtovar@ugr.es
URL:
https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G47589.1/588088/Rapid-macrobenthic-diversification-and
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