THE TRIASSIC-JURASSIC BOUNDARY EVENT: LINKING THE TERRESTRIAL AND MARINE RECORDS

Major extinctions took place across the Triassic-Jurassic (T-J) boundary in both terrestrial and marine environments, but the relative timing of these events, and relationships to other major environmental changes are poorly known. On the land, a major floral and faunal turnover is evident principally from lacustrine successions, in eastern North America and Greenland. In the sea there is a good record of significant relative sea-level changes that accompany faunal changes in regions bordering the central Atlantic. Here we present carbon-isotopic data from two key sections across the T-J boundary (Jameson Land, East Greenland, and St Audrie’s Bay, England) which demonstrate significant positive and negative isotopic excursions coincident with floral turnover. At St Audrie’s Bay (a candidate global stratotype for the base of the Jurassic) the event horizon is at a lower level than most previously proposed T-J boundary levels but coincides with a unique horizon of soft sediment deformation and shallow-water deposition. Shallow-water deposition resulted from rapid but not instantaneous regression and extraterrestrial explanations are inconsistent with the whole range of observed phenomena: more plausible are mechanistic linkages with the Central Atlantic Magmatic Province.