Dinosaur abundance was not declining in a '' 3 m gap '' at the top of the Hell Creek Formation, Montana and North Dakota

An similar to 3 m stratigraphic interval that entirely lacks dinosaur fossi ls or has very few fossils has been reported at the top of the Hell Creek F ormation in the upper Great Plains of North America. The presence of the "3 m gap" in fossil distribution has been cited as evidence that dinosaurs ha d either become extinct or were on the verge of extinction prior to the bol ide impact at the end of the Cretaceous Period. A survey in two areas of No rth Dakota and Montana reveals that dinosaur fossils in the upper 3 m of th e Hell Creek Formation occur in numbers that are comparable to their abunda nce in other levels of the formation. Evidence for a gradual extinction is absent, and data are consistent with an abrupt extinction associated with a n impact.