New δ13Corg analyses of two
boundary sections between the late Permian Kapp Starostin
Formation and the early Triassic Vardebukta Formation of
western Spitsbergen confirm field evidence that
their contact is a conformable one. Thus, contrary to previous
reports, some Spitsbergen sections contain a
complete record of the environmental and faunal changes during
the crisis interval of the end Permian mass
extinction. No environmental deterioration is recorded in the
late Permian until near the end of the terminal
Changxingian Stage, whereupon the abundant siliceous sponge
fauna of the Kapp Starostin Formation disappears
along with the deep-burrowing fauna responsible for the
Zoophycus trace fossil. A low diversity
dysaerobic trace fossil assemblage is briefly developed before
a transition to finely laminated, pyritic facies
immediately beneath the Permo-Triassic boundary. Analysis of the
S/C ratios from the laminated strata suggests
that free H2S was present in the water column
(euxinic conditions) even in relatively nearshore settings
subject to storm sandstone deposition. The mass extinction
crisis in Spitsbergen is therefore coincident with
the extensive development of oxygen-poor conditions in the
water column and compares closely, both in
timing and nature, with the crisis seen in lower latitude
Tethyan settings. However, the subsequent aftermath
and recovery in the Boreal sections of Spitsbergen was more
rapid than in Tethys. Thus, a shoreface sandstone
body within the Dienerian Stage contains an appreciable
diversity of fauna (by the standards of the
early Triassic), including bryozoans, calcareous algae and
deep infaunal bivalves, that suggests the marine
ecosystem recovery began earliest in higher palaeolatitudes.
Unexpected Early Triassic marine ecosystem and the rise of the Modern evolutionary fauna
