The Jurassic/Cretaceous system boundary is an impasse. Why do not go back to Oppel’s 1865 original an historic definition of the Tithonian?

Abstract

The lack of an absolute and persistent opinion regarding definition of the base of the Berriasian Stage, i.e., its instability over the past 50 years, casts grave doubts on its suitability to be the Jurassic/Cretaceous System boundary. The question "when does the Jurassic ends?" is addressed in a discussion on the highest Jurassic stage, the Tithonian of Oppel. The Berriasian of Coquand that came later was, amongst other options, considered either as Cretaceous and to be its lower stage, or as Jurassic and to be the upper substage of the Tithonian. The first option, the Kilian view, was so far the most popular but it is most debatable because the base Berriasian is not accurately correlated over long distances and across domains (Austral, Tethyan, Boreal, basin, ramp or platform, land). In contrast, the second option, which is known in the literature as the Oppel view, although it should be called the Toucas view, has recently been resurrected from oblivion. As a matter of fact, the base Valanginian, which corresponds to biotic crises affecting the ammonites and other groups, is far the better alternative to be selected as the Jurassic/Cretaceous System boundary.