Palynology as a palaeoenvironmental indicator in the Brent Group, northern North Sea

Abstract

The Brent Group of the northern North Sea can be subdivided into a series of 12 assemblage units on the basis of palynomorph and kerogen abundances. These assemblages, which can be identified on a regional basis, have been recognized extensively throughout wells of the Brent Group depositional area. They represent changes in the environment, kerogen source and depositional setting and can be linked to lithostratigraphical units. Changes in assemblages through the Brent Group reflect an initial restricted marine environment followed by progradation in a regressive regime. Progradation ceased and the maximum point of regression occurred within the ‘Mid’ Ness Formation, after which deposition occurred within an abandonment and transgressive regime. These features are defined by palynological data, thus providing input into the regional understanding of Brent Group deposition. The palynological assemblages of the Brent Group are illustrated with reference to two wells: 211/18a-A31 from the Thistle Field and 3/3-5A from the Ninian Field. Palynomorph assemblages within the Brent Group are largely facies controlled and have an intimate relationship with lithofacies. The identification of these assemblages, therefore, allows for the positive identification of individual lithostratigraphical and reservoir units, particularly in problematic sections where stratigraphical interpretations based on other disciplines are hampered by faulting and truncation or lack of conventional core material and wireline log data, particularly where sidewall core samples are available.

Episodic river flooding events revealed by palynological assemblages in Jurassic deposits of the Brent Group, North Sea

“…McArthur et al, 2016a), and for the regional and large-scale stratigraphic and palaeoenvironmental interpretation of the Brent Group (e.g. Parry et al, 1981;Williams, 1992;Whitaker et al, 1992;Batten and Stead, 2005;Sawyer and Keegan, 1996). Here we use palynofacies analysis to provide more focussed interpretations based on targeted sampling of individual beds deposited under different depositional processes.…”

Effect of volcanic ash-fall on a Permian peat-forming environment, on the basis of palynology, palynofacies and paleobotany (Faxinal Coalfield, Brazil)

“…According to Crowley et al (1994), the water in peat mire often increased after deposition of volcanic ash, and palynological analysis could contribute significantly to determining if volcanic ash-fall affected the peat-forming vegetation in the mires, which formed the coals (Williams, 1992).…”

Maastrichtian island in the central European Basin—new data inferred from palynofacies analysis and inoceramid stratigraphy

“…(Prauss 2000), confirms the influence of fresh water, at least occasionally. Botryococcus algae are widely used in palynological studies to determine fresh water environments (lacustrine, fluvial, lagoon, and deltaic) (e.g., Batten and Lister 1988;Guy-Ohlson and Norling 1988;Riding et al 1991;Williams 1992). Subsequently, Botryococcus colonies may be transported by the rivers towards marine shelf facies (Combaz et al 1977;Caratini et al 1983;Guy-Ohlson 1986;Prauss 1989) and therefore often occur together with marine algae.…”