Major Climatic Change at the Smithian/Spathian Boundary – Evidence from Low Palaeolatitudinal Records

The delayed recovery of marine and terrestrial ecosystems after the end-Permian extinction event is still up for debate. Focusing on the Smithian/Spathian boundary, palaeoecological changes are reflected by a significant global faunal turnover as indicated by ammonoids (Brayard et al. 2006) and conodonts (Orchard 2007) as well as a change in the palynological associations of the Boreal realm. There, the Smithian/Spathian transition is marked by a conspicuous change from spore dominated assemblages in the Smithian to gymnosperm dominated assemblages in the Spathian (Galfetti et al. 2007a).

Here, we present the composition of the Early Triassic microfloras of Nammal, Salt Range, Pakistan. Ammonoids and conodonts provide the high resolution age control of the studied section (Brühwiler et al. 2007).

The late Smithian palynological assemblages are characterized by a general dominance of hygrophytic elements. Slightly below the Smithian/Spathian boundary, between the Anasibirites beds and the Glyptophiceras beds, the composition changes dramatically with a drastically increasing proportion of xerophytic elements. This event coincides with the onset of a positive shift in the δ¹³C record marking the Smithian/Spathian boundary (Galfetti et al. 2007b). Preliminary results from southern Tibet also indicate a similar trend from hygrophyte-dominated to xerophyte-dominated assemblages across the boundary.

Thus the Smithian/Spathian boundary climatic event can be traced from high to low latitudes, demonstrating its global significance.

Brayard, A. et al. 2006: PPP 239:374-395.

Brühwiler, T. et al. 2007: New Mexico Mus. Nat.Hist.& Sci. Bull. 41: 25-26.

Galfetti, T. et al. 2007a: Geology 35: 291-294.

Galfetti, T. et al. 2007b: EPSL 258: 593-604.

Orchard, M.J. 2007: PPP 252: 93-117