These findings generally confirm and complement those of Bhandari et al.
Argon-argon dating uses a mass spectrometer to measure the ratio of radioactive potassium in a sample of rock to its decay product, argon.
Shocked quartz granules and tektite glass spherules, indicative of an impact event, are also common in the K-Pg boundary, especially in deposits from around the Caribbean.
All of these constituents are embedded in a layer of clay, which the Alvarez team interpreted as the debris spread all over the world by the impact.
In an attempt to resolve the issue, an international team of scientists have determined the most precise dates yet for the dinosaur extinction 66 million years ago and for the well-known impact that occurred around the same time.
“The impact was clearly the final straw that provided the tipping point,” said Paul Renne, BGC director and professor in residence of earth and planetary science at the University of California, Berkeley.
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Mc Farland's record, though replete with experience, is spotted with light controversy. If you’re offered anything else, don’t take it; resign in six months and run for president." Petraeus was eventually offered the head JCS (Joint Chiefs post) position by President Obama, and thus did not run against him for president. Mc Farland's run was unsuccessful, which may have been partly due some career claims which were very publicly challenged, summarized as the following: "She had worked on President Ronald Reagan's 'Star Wars' speech and had been the highest-ranking woman at the Reagan Pentagon." Both of these assertions were found to be not completely true.