The Late Triassic represents records many of the most critical biotic crises in life-history (from Carnian to the end-Triassic extinction, ETE). Some hypotheses propose that these life changes were linked with shifts in the environmental setting during the initial stages of the Pangea breakup. These crises were likely not sudden events but a series of step-changes that reached their peak at the end of the Triassic. The Carnian-Norian Ischigualasto Formation is a world-renown terrestrial sequence that records both the Triassic Dinosaur Diversification Event (DDE) and at least one crucial terrestrial environmental and biotic turnover. A notable increase in humidity and volcanism was the setting of critical faunal replacement represented by the passage of the Hyperodapedon-Exaeretodon-Herrerasaurus to Exaeretodon tetrapod biozones. That environmental modification, together with the paleofaunistic turnover, has been accurately constrained by a new high-precision CA-TIMS U/Pb zircon age of 228.91 ± 0.14 Ma obtained from a tuff layer located in the exact stratigraphic position of the major biotic-paleoenvironmental disturbance in the middle part of the Valle de la Luna Member, at ~310 m from the base of the Ischigualasto Formation. Palynological assemblages containing the first records in westernmost Gondwana of European Tethyan and Onslow palynological species are also recognized close to the dated tuff level. Thus, this age is the first isotopic record for the Onslow Microflora diagnostic species in Gondwana. Moreover, the CA-TIMS date promotes a discussion about the accurate chronostratigraphic position for the beginning (after the Carnian Pluvial Event) of a series of environmental-biological disturbances that culminated at the end of the Triassic.

晚三叠世记录了生命史上许多最关键的生物危机（从卡尼阶到三叠纪末灭绝，ETE）。一些假设提出，这些生命变化与泛大陆分裂初期的环境变化有关。这些危机很可能不是突发事件，而是在三叠纪末达到顶峰的一系列阶跃变化。Carnian-Norian Ischigualasto 组是世界著名的陆地序列，它记录了三叠纪恐龙多样化事件 (DDE) 和至少一个关键的陆地环境和生物周转。湿度和火山活动的显着增加是关键动物群更替的背景，表现为Hyperodapedon-Exaeretodon-Herrerasaurus到外齿象四足生物区。这种环境改变，连同古动物群的周转，已被新的高精度 CA-TIMS U/Pb 锆石年龄 228.91 ± 0.14 Ma 准确约束，该锆石年龄为 228.91 ± 0.14 Ma，该年龄是从位于主要生物古环境准确地层位置的凝灰岩层中获得的。 Valle de la Luna 段中部的扰动，距 Ischigualasto 组底部约 310 m。包含欧洲特提斯和昂斯洛孢粉物种最西端冈瓦纳的第一批记录的孢粉组合也接近于过时的凝灰岩水平。因此，这个年龄是冈瓦纳大陆 Onslow Microflora 诊断物种的第一个同位素记录。而且，