Linked Aspects of Nonmarine Cretaceous–Tertiary Boundary Events

Abstract

Here I attempt to weave together a few strands of knowledge about the Cretaceous–Tertiary asteroid collision and its biological effects. The sheer enormity of kinetic energy involved in the collision and the immediate conversion of the energy to infrared radiation upon worldwide reentry of suborbitally lofted debris is not adequately appreciated by most paleontologists who deal with nonmarine organisms. Consideration of the physics of such a collision leads to the conclusion that there should have been no live Paleocene nonavian dinosaurs, but a view that nonavian dinosaurs survived into the Paleocene has been accepted by some students on the basis of “Paleocene pollen” found stratigraphically beneath specimens of nonavian dinosaurs. However, investigation of the biostratigraphic basis of dating “Paleocene” dinosaurs points to flaws in palynological dating of Late Cretaceous and early Paleocene strata in Rocky Mountain basins of deposition. The argument for “Paleocene” pollen occurring with or stratigraphically beneath non-reworked nonavian dinosaurs is not acceptable because palynological zone P1 and most or all of zone P2 occur in Upper Cretaceous strata in the Hell's Half Acre area of central Wyoming where the palynological scheme of zonation originated, not in Paleocene strata. Although said to conflict, palynological occurrences are actually compatible with results from dinosaurs. Finding P1 and/or P2 pollen stratigraphically beneath nonavian dinosaur remains does not push those dinosaurs up into Tertiary strata. Populations of sheltering organisms, provided that they were of small enough individuals, would have survived the K–T calamity easily. However, manifestations of Mayr's “founder effect” would have altered the equilibria of genetic composition of populations forever. “Molecular clocks” would have temporarily run fast, giving the impression that phylogenetic branch points lie deeper in the Cretaceous than was actually the case.