A SERIES OF CRISES – THE EARLY TRIASSIC FLORAL RECORD (Invited Presentation)

The marine record of the Permian–Triassic event reflects the severest extinction event in Earth history. Subsequent disrupted recovery phases lead to the concept of protracted recovery during the Early Triassic. Similarly Early Triassic floras are believed to be depauperate, suffering from protracted recovery following the Permian–Triassic extinction event. Early Triassic floras are supposed to be dominated by herbaceous lycopods of reduced diversity and that the recovery of the gymnosperm dominated woody floras started at the onset of the Middle Triassic.

In the terrestrial realm most extinction events are reflected in the palynological record by high spore abundances. In Norway and Greenland the Permian–Triassic event is marked by a short lived abundance peak of lycopod spores falling within the global negative δ¹³C_org isotope shift characterising this event. This spore dominance was followed by a rapid gymnosperm recovery during the latest Permian. Griesbachian floras are characterized by diverse gymnosperm dominated assemblages. Palynological data from NE-Greenland show a fundamental floral turnover postdating the Permian–Triassic extinction event by about 500 kyrs. This event is marked by a swap in dominating floral elements, changing from gymnosperm pollen-dominated associations in the Griesbachian to lycopsid spore-dominated assemblages in the Dienerian. Again, this floral change coincides with a marked negative δ¹³C_org shift revealing a severe environmental crisis, probably induced by volcanic outbursts of the Siberian Traps, accompanied by a climatic turnover, changing from cool and dry in the Griesbachian to hot and humid in the Dienerian. A similar record from Pakistan indicates the global extent of this event. In contrast to the Permian–Triassic event spore dominance continues up to the middle Smithian. There, about 1myrs later, another distinct crisis followed, marked by extremely high spore abundances. Thus, the Early Triassic can be characterised as a time of successive environmental crises.