Abstract
We used published biostratigraphic data on ranges of fusulinids and other foraminifera from Permian-Triassic boundary sections in the southern Alps, Italy, to test the effects of sampling and species abundance on the record of the timing of the latest Permian extinction. The number of last occurrences of taxa reaches a maximum close to the local base of the Tesero horizon of the Werfen Formation. Taxa that have ≤15% stratigraphic abundance (percent of sample intervals in which a taxon occurs) show last occurrences well before that level, whereas taxa with more complete records tend to disappear at or close to that level. These results are in agreement with simulations for abrupt extinctions, as opposed to gradual or steplike extinction scenarios, and support predictions of the Signor-Lipps effect, that errors in the end points of biostratigraphic ranges can produce range truncations and apparent gradual decline preceding a sudden extinction boundary. On the basis of estimated sedimentation rates for the Italian sections, the end-Permian extinctions could have been very sudden (≤30 k.y.), and the disappearance of most latest Permian foraminifers was most likely coincident with a worldwide ecological stress event, identified by a global negative δ13C anomaly that occurs in Italy near the base or within the time-transgressive Tesero horizon.
