The fact the impact and mass extinction may have been virtually simultaneous in time supports the idea that the cosmic impact dealt the age of dinosaurs its deathblow.
"The impact was clearly the final straw that pushed Earth past the tipping point," Renne said. "We have shown that these events are synchronous to within a gnat's eyebrow, and therefore, the impact clearly played a major role in extinctions, but it probably wasn't just the impact."
The new extinction date is precise to within 11,000 years.
"When I got started in the field, the error bars on these events were plus or minus a million years," added paleontologist William Clemens at the University of California at Berkeley, who did not participate in this research. "It's an exciting time right now, a lot of which we can attribute to the work that Paul and his colleagues are doing in refining the precision of the time scale with which we work."
Final blow Although the cosmic impact and mass extinction coincided in time, Renne cautioned this does not mean the impact was the only cause of the die-offs. For instance, dramatic climate swings in the preceding million years, including long cold snaps in the general hothouse environment of the Cretaceous, probably brought many creatures to the brink of extinction. The volcanic eruptions behind the Deccan Traps might be one cause of these climate variations.
"These precursory phenomena made the global ecosystem much more sensitive to even relatively small triggers, so that what otherwise might have been a fairly minor effect shifted the ecosystem into a new state," Renne said.
The cosmic impact then proved the deathblow.
"What we really need to do is to understand better what was going on before the impact - what was the level of ecological stress that existed that allowed the impact to be the straw that broke the camel's back?" Renne said. "We also need better dates for the massive volcanism at the Deccan Flats to better understand when it first started and how fast it occurred."
The scientists detailed their findings in the Feb. 8 issue of the journal Science.
This article originally appeared on LiveScience.com.
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