Causes and Consequences of the Triassic-jurassic Mass Extinction as Seen from the Hartford Basin

One of the most severe mass extinctions of the Phanerozoic, the Triassic-Jurassic event is greater or equal in magnitude to that at the more famous K-T boundary (Benton, 1994) (Fig. 1). Such severity, at least for marine families is also supported by Foote’s (2003) statistical revaluations, although there remain dissenters (e.g. Hallam, 2002; Lucas et al., 2002). The cause of this mass-extinction remains hotly debated; explanations include sea-level change (Hallam, 1990), a methaneand CO2generated super-greenhouse triggered by flood basalt eruptions (McElwain et al., 1999; Hesselbo et al., 2002), and bolide impacts (Olsen et al., 1987). During the Triassic, all major extant groups of terrestrial vertebrates evolved, including dinosaurs (whose descendants survive as birds) and mammals. The Triassic-Jurassic mass extinction may have cleared ecological space for the rise of dinosaur dominance much as the K-T mass extinction prepared the way for mammalian ecological ascent (Olsen et al., 2003a).