A hadrosaur assemblage—found in the Paleocene Ojo Alamo Sandstone in the San Juan Basin straddling Colorado and New Mexico—suggests that perhaps an enclave of Dinosaurs survived into the Cenozoic.

Naashoibitosaurus

Initally it was thought that the fossil hadrosaur had been reworked—eroded form older sediment and redeposited in the Ojo Alamo, and that the lack of weathering to the specimen was due to a quick re-deposition near its initial burial site, or that the site was actually below the K-T boundary. But in a new study pubished in the online journal Paleontolgia Electronica, USGS emeritus scientist Jim Fassett analyzes the geochemistry of the bones, along with paleomagnetic, paleobotanical and palynological data—and concludes that they were indeed initially deposited in the Paleocene.

The dinosaurs were not wiped out in a wall of fire from a meteor's impact—as depicted here

Again—this is an assemblage of bones from a single individual of a single species, it doesn’t imply large herds of hadrosaurs roaming accross the American Southwest  in the Paleocene, or neccsessitate that other dinos must have survived also. But if this analysis is correct, a small breeding population of hadrosaurs must have survived into the Cenozoic—at least for a little while.

The impact event at chixalub would not have instantly vaporized the Dinosaurs as is widely believed. Globally the impact would have sent up a large cloud of debris and CO₂ from the carbonate rocks the asteroid impacted into. This would have dramatically altered climate and disrupted the Dinosaurs’ habitat—leading to their eventual extinction. So finding some holdouts, even close to the impact site is not unexpected. Also remember, just because they were there 1 million years after the impact doesn’t mean that they survuved the impact at that site. The hadrosaurs found could have established their Paleocene refuge well after the impact and ensuing chaos died down.

Emeritus USGS paleontologist Jim Fassett has published his findings in the April issue of the online journal Paleontolgia Electronica.