摘要
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.
