Nemesis for Evolutionary Gradualism?

Abstract

During the Late Cretaceous Period, large areas of the continental land masses were covered by shallow seas, so rocks dating from that time are often chalk, a type of limestone composed of the fossilized remains and secretions of marine organisms, particularly planktonic coccolithophores. The White Cliffs of Dover provide an example of such a formation [1–5]. As previously noted, the name “Cretaceous” is derived from creta, the Latin word for chalk, which came in turn from an association with Crete, the Mediterranean island. The Greek and German words for chalk are krete and kreide, respectively, so on this basis the Cretaceous-Tertiary boundary is generally abbreviated as the K-T boundary, the use of the letter K avoiding possible confusion between the Cretaceous and the Cambrian or Carboniferous Periods [3, 5, 6].