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Miospores From the Jurassic-Cretaceous Boundary Beds, Aklavik Range, Northwest Territories, Canada



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The boundary strata of the Jurassic and Cretaceous systems (?late Oxfordian - Hauterivian) of the Aklavik Range, Northwest Territories, contain abundant and diverse palynofloras. Comparison of taxa encountered with those previously described proved difficult owing to the confused state of Mesozoic miospore taxonomy; thus detailed reviews of many miospores groups had to be undertaken. Two new genera (Obscuritriletes and Globiporites) and five new species (Sculptisporis hamulatus, Roaalskaisoorites agmohalos, Retitriletes aklavikensis, Retitriletes quasitrabeculatus and Saxetia skolix) are proposed; 9 new names, 167 new combination;, 32 generic emendations and 36 specific emendations are proposed and 7 subgenera are raised to full generic rank. In addition, synonymies are presented for all taxa described. Many new forms of miospores appear in the Late Jurassic and earliest Cretaceous; these have great potential for biostratigraphic correlation, especially if the effects of evolutionary and ecological factors can be differentiated. A preliminary zonation is proposed which permits the marine and nonmarine strata of England to be correlated with the predominantly marine strata from the Aklavik Range. The following zones and subzones are recognized: Neoraistrickia truncata Interval Biozone (Late Oxfordian - early Late Kimmeridgian); Obscuritriletes vectensis Interval Sub-biozone (Early to early Late Kimmeridgian); Cicatricosisporites abacus Interval Biozone (Late Kimmeridgian to latest Portlandian); Cicatricosisporites purbeckensis Interval Biozone (latest Portlandian - ?Early Hauterivian); Pilosisporites delicatulus Range Sub-biozone (Late Brriasian to Early Valanginian). iv The diverse palynofloras obtained attest to a mild, humid climate for the area of the Aklavik Panae during Late Jurassic - Early Cretaceous times, despite its high northern palaeolatitude. The 'Palaeopacific' Ocean and its associated seaways evidently were sufficiently warm to induce ample precipitation over the cooler adjacent landmass during the long winters; the short summers were perhaps relatively dry. Classopollis-bearing Cheirolepidacean plants probably existed in a shoreline habitat. The coastal lowlands and maritime uplands were dominated by ferns and lycopods, with significant bryophyte floras in moister places; some conifers and possibly ginkgos, bennettitaleans and cycads also may have occurred in coastal areas. The vegetation of the dryer hinterland probably was dominated by pinaceans and other conifers.





Doctor of Philosophy (Ph.D.)


Geological Sciences





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