Sprecher
Beschreibung
Palynology and palynofacies are central to stratigraphic and palaeoenvironmental interpretation of the Middle Jurassic Brent Group, one of the main reservoir intervals of the North Sea. However, several parts of the succession are dominated by anomalous palynological assemblages, including leiosphaerid-like forms, indeterminate spheromorphs, degraded bisaccate-like structures, and palynomorph-sized plant fragments of possible bryophytic affinity. These intervals have commonly been treated as poor-recovery horizons or taphonomic noise, although they may preserve evidence of salinity stress, organic-matter sourcing, and coastal ecosystem instability.
Here we present new data from Well 30/11-14, Norwegian Sector, based on 52 core samples spanning a c. 210 m interval through the Heather, Tarbert, and Ness formations. More than 12,000 palynomorphs and 13,350 organic particles were counted, yielding 103 palynological taxa, including 74 terrestrial and 29 marine taxa. Quantitative palynological and palynofacies data reveal strong stratigraphic variation in marine, brackish, and terrestrial components. Spheromorph-rich assemblages, locally exceeding 80%, occur in tidal-flat, tidal-channel, and offshore facies, whereas amorphous palynomorphs reach more than 90% in selected levels. These patterns suggest repeated shifts in restriction, salinity, oxygenation, and terrestrial input.
Ongoing SEM and TEM analyses indicate that these problematic forms are not taxonomically or environmentally uniform. Some bisaccate-like structures are unlikely to represent true pollen, dominant spheromorphs may include algal forms linked to salinity-stressed conditions, and several Dissiliodinium willei-like specimens show low-relief sutural features only visible under SEM. This study reframes problematic assemblages as palaeoenvironmental evidence rather than analytical noise.