The Sixth Extinction: An Unnatural History

Landman has his office in a turret overlooking Central Park, and, together
with a pair of graduate students, headed south to the Lincoln Tunnel.
Driving through northern New Jersey, we passed a succession of strip
malls and car dealerships that seemed to repeat every few miles, like
dominoes. Eventually, in the general vicinity of Princeton, we pulled into
a parking lot next to a baseball field. (Landman would prefer that I not
reveal the exact location of the field, for fear of attracting fossil
collectors.) In the parking lot, we met up with a geologist named Matt
Garb, who teaches at Brooklyn College. Garb, Landman, and the graduate
students shouldered their gear. We circumnavigated the baseball field—
empty in the middle of a school day—and struck out through the
underbrush. Soon we reached a shallow creek. Its banks were covered in
rust-colored slime. Brambles hung over the water. Fluttering from these
were tattered banners of debris: lost plastic bags, scraps of newspaper,
the rings from ancient six-packs. “To me, this is better than Gubbio,”
Landman announced.
During the late Cretaceous, he explained to me, the park, the creek
bed, and everything around us for many miles would have been under
water. At that point, the world was very warm—lush forests grew in the
Arctic—and sea levels were high. Most of New Jersey formed part of the
continental shelf of what’s now eastern North America, which, as the
Atlantic was then much narrower, was considerably closer to what’s now
Europe. Landman pointed to a spot in the creek bed a few inches above
the water line. There, he told me, was the iridium layer. Although it
wasn’t in any way visibly different, Landman knew where it was because
he’d had the sequence analyzed a few years earlier. Landman is stocky,
with a wide face and a graying beard. He had dressed for the trip in khaki
shorts and old sneakers. He waded into the creek to join the others, who
were already hacking at the bed with their pickaxes. Soon, someone found
a fossilized shark’s tooth. Someone else dug out a piece of an ammonite. It
was about the size of a strawberry and covered in little pimples, or
tubercles. Landman identified it as belonging to the species Discoscaphites