One goal in the coring project is exact dating of the wavy band of rock about three feet below Olsen, a few inches thick, marking the break between reddish rocks above and whitish ones below. Composed of tangled, cylindrical strands that could be tree roots or other debris, he thinks it may be the remains of a sudden mass extinction. It could line up with a well-dated giant meteorite that hit what is now southern Canada 215.5 million years ago—but only data provided by the core will tell. Olsen and others also intend to inspect this layer for other signs of a connection, including microscopic diamonds created on impact, and the rare element iridium, carried by asteroids. If his idea proves correct, it would represent the only known biological prelude to an even larger impact believed to have wiped out the dinosaurs 149 million years later.