Abstract

Campbell et al. (1992) suggest that the Permian/Triassic extinction resulted from the eruption of the Siberian Traps, producing dust and SO₂ aerosols which induced instant cooling, polar ice caps and low sea level before dissipating in acid rain; whereupon CO₂ warming melted the ice and raised sea level. Confirmatory sedimentary evidence is the sudden cooling at the P/Tr boundary indicated by permafrost structures (“stone-rolls”) in the floor of the topmost Bulli Coal of the eastern Australian coal measures and by coldwater facies in Arctic Canada, followed by warming indicated in Australia by a drop in δ¹³C_org in coastal barren measures and the first appearance of redbeds. In Tethys warming was indicated by a fall in δ¹³C_co, and a rise in the ⁸⁷Sr/⁸⁶Sr ratio.

The stone-rolls occur in swarms of subparallel linear ridges of expanded and disrupted floor strata that have a mean relief of about 1 m, widths of 4 m and lengths of 1.5 km. The rolls are hummocky in cross-section and are separated by linear zones of unexpanded floor strata and thicker coal, 10 to 30 m apart. The swarms are analogous to modern minerogenic string-palsamires of sub-Arctic zones of continuous and discontinuous permafrost, as found today in Arctic Eurasia and North America.

Permafrost structures in the floor of the Wongawilli Coal, 40 m below the Bulli Coal, register severe, spatially continuous permafrost at the end of the Permian Ice Age, and the Bulli rolls a less severe, spatially discontinuous, permafrost during the SO₂-induced snap freeze at the P/Tr boundary.