Palynological zonation and stratigraphy of the Jurassic section in the Gassum No. 1-borehole, Denmark

The Jurassic section of the Danish onshore borehole Gassum No. 1 has been investigated palynologically. 126 palynomorph-taxa have been recognized, consisting mainly of microspores and gymnosperm pollen. The palynomorphs are treated morphosystematically. 71 samples were prepared and the relative abundances determined in 32 representative samples. 5 spore- pollen zones, A to E, have been defined based on the stratigraphical ranges and abundances of specific taxa. Correlating with data from Northwest Europe allows the zones to be dated as follows: Zone A: Late Rhaetian, Zone B: Hettangian, Zone C: Early Sinemurian to ?Pliensbachian/foarcian, Zone D: Kimmeridgian/ Early Volgian, Zone E: Middle Volgian. The relative abundances of the main morphological groups of palynomorphs have been calculated and their stratigraphical variations correlated with previously proposed Early Jurassic sea-level changes.