The Himalayas, the Asian mountain range that includes some of the tallest peaks in the world, turns out to be about 15 million years younger than geologists thought.
Various dating techniques have shown that many of the sediments deposited along the Himalayas' southern foothills are no more than 35 million years old. But in one area of northern Pakistan, an 8-kilometer-thick layer of otherwise fossil-free sediments--the so-called Balakot formation--includes several bands of sediment that contain 55-million-year-old fossils. This disparity led scientists to believe that some portions of the Himalayas were thrust up much earlier than others, says Yani Najman, a geologist at Edinburgh University in Scotland.
Najman and her colleagues analyzed 257 small grains of mica taken from samples at nine different locations within the Balakot formation's fossil-free sediments. They found that many of the individual mica grains were between 36 million and 40 million years old. Najman