High-resolution biochronology and diversity dynamics of the Early Triassic ammonoid recovery: The Dienerian faunas of the Northern Indian Margin

摘要: A new high resolution biozonation based on the Unitary Association (UA) method is constructed for Dienerian ammonoid succession of Northern Indian Margin. It includes 12 UA-zones and leads to subdivision into three parts (early, middle late). The corresponding diversity analyses, coupled with results previously obtained early Smithian ammonoids same regions, highlight four following phases: (1) a first modest peak in Dienerian; (2) very low persisting throughout (3) slow increase during late Dienerian, (4) marked diversification Smithian. Turnover rates are this entire time interval, boundaries between early–middle middle–late emphasised by complete renewals faunas. values concomitant an anoxic event outer continental shelves coincide warmer temperatures than those This pattern stands strong contrast credo protracted or stepwise recovery end-Permian mass extinction. Together end-Smithian extinction, crises were likely both radical setbacks Early Triassic ammonoids. However, these two do not necessarily imply identical environmental triggers that ultimately led bottom waters platforms cases.