Events around the Triassic–Jurassic boundary in northern and eastern Spain: A review

Abstract

More than 20 successions containing the Triassic–Jurassic (T–J) boundary were studied in five of the major geological units of Spain. The data are from outcrop, cored boreholes, and interpreted well-logs. A consistent −3.4‰ δ13Corg isotope excursion, starting in the Rhaetian and continuing in the Hettangian, was recorded in Asturias. Climate changes in the T–J transition show a warming episode in the early Hettangian. Other climate changes are indicated by an increase in hygrophytic miospores above the T–J boundary; this reflects a more humid episode at the beginning of the Hettangian. The Messejana Dyke in southeastern Iberia is part of the Central Atlantic Magmatic Province (CAMP). CO2 outgassing related to extensive magmatic activity in the CAMP is thought to be one of the possible factors responsible for the end-Triassic mass extinction. No major sea-level changes or unconformities were recorded at the T–J boundary. Only in the Asturias area was there a well-defined shallow carbonate platform during the T–J transition. The other areas of eastern and northern Spain were occupied by coastal playas and sabkhas that developed in arid climatic conditions. The biotic crisis around the T–J boundary is reflected in the palynomorph record. In Asturias, seven species do not persist beyond the late Rhaetian, and only six appeared in the Triassic–Jurassic transition. However, 22 taxa appeared in the early Hettangian.