Global dinoflagellate event associated with the late Paleocene thermal maximum

The late Paleocene thermal maximum, or LPTM (ca. 55 Ma), represents a geolo gically brief time interval (similar to 220 k.y.) characterized by profound global warming and associated environmental change. The LPTM is marked by a prominent negative carbon isotope excursion (CIE) interpreted to reflect a massive and abrupt input of C-12-enriched carbon to the ocean-atmosphere reservoir, possibly as a result of catastrophic gas-hydrate release, on tim e scales equivalent to present-day rates of anthropogenic carbon input. The LPTM corresponds to important changes in the global distribution of biota, including mass extinction of marine benthic organisms, The dinoflagellate cyst record indicates that surfaced-dwelling marine plankton in marginal se as also underwent significant perturbations during the LPTM. We report on t he dramatic response of representatives of the genus Apectodinium from two upper Paleocene-lower Eocene sections in the Southern (New Zealand) and Nor thern (Austria) Hemispheres, where the dinoflagellate records are directly correlated with the CIE, benthic foraminifera extinction event, and calcare ous nannofossil zonation. The results indicate that the inception of Apecto dinium-dominated assemblages appears to be synchronous on a global scale, a nd that the event is precisely coincident with the beginning of the LPTM. A pectodinium markedly declined in abundance near the end of the LPTM. This A pectodinium event may be associated with (1) exceptionally high global sea- surface temperatures and/or (2) a significant increase in marginal-marine s urface-water productivity, Such a globally synchronous acme of dinoflagella te cysts is unprecedented within the dinoflagellate cyst fossil record.