| Co-Authors: | Cottrell, Rory D., University of Rochester, rory@earth.rochester.edu; Lippert, Peter, University of Rochester, pete@earth.rochester.edu; Friedman, Matt, University of Rochester |
| Abstract: | The Cretaceous of the Canadian High Arctic is represented by sedimentary and volcanic rocks of the Sverdrup Basin that are exceptionally well exposed on Axel Heiberg and Ellesmere Islands. These sequences contain evidence for short-term episodes of extreme warmth and cooling during the Late and Early Cretaceous, respectively.
Extreme Polar Warmth
A Turonian to Coniacian (~92 to 86 Ma) vertebrate assemblage from a site with a paleolatitude of approximately 71o N implies that polar climates were warm (mean annual temperature exceeding 14o C) (Tarduno et al., 1998). This episode may correlate with evidence for extreme high-latitude warmth from oxygen isotope paleotemperature estimates from the Southern Ocean (Huber, 1998). The Arctic assemblage includes large (over 2.4 meters long) champsosaurs, which are extinct crocodile-like reptiles. The vertebrate fossils overlie subaerially erupted flood basalts of the Cretaceous Strand Fiord Formation. These lavas are part of a large magmatic pulse (or large igneous province), that may include large parts of Ellesmere Island and the Arctic Ocean basin. This magmatism, coupled with coeval volcanism at six other large igneous provinces, suggests that volcanic carbon dioxide emissions may have helped cause the peak in global warmth.
Cool Polar Climate
In contrast to the extreme warmth of the Late Cretaceous, Arctic sedimentary rocks of mid- and Early Cretaceous age show evidence of cool conditions in the form of glendonite horizons. Glendonites (pseudomorphs after the hydrated calcium-carbonate mineral ikaite), are associated with glacial marine sediments of Permian to recent age. We are currently studying the biostratigraphy, magnetostratigraphy and geochemistry of Valanginian glendonite-bearing strata of the Canadian Arctic. Preliminary data suggest that the glendonite horizons represent relatively short ( less than 100-400 kyr) episodes at a time of low eustatic sealevel.
Huber, B.T., Tropical paradise at the Cretaceous poles?, Science, 282, 2199-2200, 1998.
Tarduno, D.B. Brinkman, P.R. Renne, R.D. Cottrell, H. Scher, P. Castillo, Evidence for extreme climatic warmth from Late Cretaceous Arctic vertebrates, Science, 282, 2241-2244, 1998. |