Dolding, PJD; (1996) Palynology and correlation of the Late Permian and Triassic sequences along North East Atlantic Margin. Doctoral thesis , University of London.

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Abstract

The use of microfossils as a biostratigraphic tool in commercial exploration wells is long established. They may be recovered from very small volumes of sediment, often in abundance, thus providing an alternative to microfossils which are rarely encountered during drilling. The highly resistant nature of palynomorphs means they are frequently the only microfossils group recovered from certain sediments. Palynomorphs occur in the marine and terrestrial realms, making them very useful for correlating continental and marine sequences. Since numerous global Permo-Triassic sequences are predominantly of terrestrial origin, spres and pollen offer one of the few reliable methods for dating and correlating. Palynological analysis has been undertaken on the Upper Permian and Triassic sequences along the North East Atlantic margin. The study are stretches from the North Porcupine Basin (west of Ireland) in the south-west to the Tampen Spur area (offshore Norway) in the north-east and total of twenty three commercial wells have been incorporated into the study. Over 430 examples have been analysed, of which 147 yielded palynomorphs. Over one hundred taxa have been recorded and a total of five in situ assemblages have been recognised, ranging in age from Late Permian (Kazanian - ?Tatarian) to Late Triassic (Rhaetian). These assemblages have been correlated with microfloras described from Europe and the Artic, which are dated by macrofauna (where possible). Rich and diverse palynological assemblages are illustrated and described from the Upper Permian (“Zechstein”) of the Unst Basin. These assemblages appear to represent a mixed European / Subangaran flora, since characteristic element of both areas are present, but the overall composition is distinct. Earliest Triassic ( Griesbachian) palynofloras occur in the Otter Bank Shale Formation in the west of Shetlands area. Palynomorphs of presumed fungal origin ( Chordecystia) are recorded in abundance and a new species – Chordecystia minuta, is formally described. These assemblages have more characteristic European aspect, as do the rest of the Triassic assemblages recorded here. The Late Permian and Early Triassic microfloras are dominated by taeniate bisaccate pollen and appear to represent an arid palacoenviroment. The Mid and Late Triassic assemblages recorded from Couny Antrim, Northen Ireland and the North Porcupine Basin respectively, contain a higher proportion of non-taeniate alete and trilete / monolete bisaccate pollen. Trilete spores are also more common in these younger assemblages. These younger assemblages suggest that conditions generally became less arid during Triassic.

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