Word: zircons
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Dates: during 1990-1999
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...uncovered a dramatic ledger of rock more than half a mile thick. In ancient seabeds near the mouth of the Lena River, they spotted numerous small, shelly fossils characteristic of the early Cambrian. Even better, they found cobbles of volcanic ash containing minuscule crystals of a mineral known as zircon, possibly the most sensitive timepiece nature has yet invented...
...Zircon dating, which calculates a fossil's age by measuring the relative amounts of uranium and lead within the crystals, had been whittling away at the Cambrian for some time. By 1990, for example, new dates obtained from early Cambrian sites around the world were telescoping the start of biology's Big Bang from 600 million years ago to less than 560 million years ago. Now, with information based on the lead content of zircons from Siberia, virtually everyone agrees that the Cambrian started almost exactly 543 million years ago and, even more startling, that...
...year term. A 69-year-old bachelor with a hot temper and a flair for the flamboyant, he made headlines in February by granting clemency to eight women convicted of murdering men who had abused them. In the notoriously corrupt politics of Maryland, he remains squeaky clean, an unpolished zircon who spends as many nights in the working-class row house he has lived in all his life as he does in the 53-room official mansion that was redecorated by his close friend of 35 years, Hilda Mae Snoops...