Inauguration of the GSSP for the Jurassic System

Abstract

Formal definition of the Triassic-Jurassic boundary at a Global Stratotype Section and Point (GSSP) for the base of the Jurassic System proved to be difficult because of several geological factors. These include a major extinction event, a major global sea-level fall and the palaeogeographical and palaeoecological consequences of widespread tectonic and volcanic events. Historically the position of the boundary has been controversial. In 1984 the International Subcommission on Jurassic Stratigraphy (ISJS) set up a Working Group to investigate and document possible candidate sites and eventually select one to be proposed to ISJS as GSSP. At the end of the process six proposals, involving five sections and four possible key marker events were assessed and voted on by the members of the Working Group between February and April 2008. The Kuhjoch section in Austria, with key marker event the first occurrence of the ammonite Psiloceras spelae tirolicum, was proposed to ISJS. The proposal was accepted by ISJS in June 2008, by the International Commission on Stratigraphy in May 2009 and ratified by IUGS in April 2010. In August 2011 the GSSP was formally inaugurated during a ceremony on site by the placing of a permanent marker, the golden spike.