Authors:Nguyen AV; Galloway JM, Poulton TP, et al. Abstract: AbstractQuantitative palynostratigraphy of the Middle to Upper Jurassic strata of the Sverdrup Basin is used to calibrate palynomorph signatures to Boreal ammonite occurrences to improve high-latitude chronostratigraphy and supplement a paucity of Upper Jurassic paleoclimatic data in Arctic Canada. Terrestrial palynological signatures of Middle and Upper Jurassic strata of the Sverdrup Basin, Arctic Canada, are assessed with associated Boreal ammonite occurrences to generate a multi-taxon biostratigraphic scheme to improve inter- and intra-basin correlations. Palynological analyses of two stratigraphic sections exposed on Axel Heiberg Island, Arctic Canada, generated a succession of six informal palynoassemblages related to closely co-occurring ammonite assemblages. The ammonite assemblages are a result of both endemic evolution of Boreal lineages within this relatively isolated Arctic basin (i.e. Middle and Upper Jurassic Cardioceratidae) and replacement at the superfamily level due to periodic incursions of southerly faunas into the basin. These migrations imply periods of connectivity with more southern basins that may be related to transgressive flooding, tectonic opening of north-south seaways and associated climate variation. Evidence for regional climate variation is supported by the taxonomic composition of terrestrial palynomorph groupings. Changes in the relative abundance of ecologically important spore and pollen taxa are consistent with a climatic shift from warm-temperate in the Late Toarcian–Early Bajocian to more arid and cooler conditions during the Middle Jurassic. Communities of Cupressaceae-Taxaceae and parent plants of Laricoidites magnus with an understory of ferns characterized the Late Toarcian–Early Bajocian, whereas the cooler conditions of the Middle Jurassic promoted expansion of coniferous plant communities in the hinterland. The latest Jurassic was characterized by the return of temperate conditions and Cupressaceae-Taxaceae conifer communities. PubDate: Tue, 01 Sep 2020 00:00:00 GMT
Open Access journal
[672 journals]
