Abstract

L. M. Fält & R. J. Steel write: Richards et al. 1988 have offered a new palaeogeographic reconstruction for the Middle Jurassic of the northern North Sea. We consider their suggestions as an interesting contribution to a continuing debate about Jurassic sand-body development and evolution in the northern North Sea basin. Nevertheless, we suggest from the perspective of the Norwegian sector that they are mistaken in some of their main points and, at best, they have not documented any convincing case. Richards et al. 1988 reject the ‘traditional’ model for the Middle Jurassic deltaic system of the Brent Group, one of general northwards progradation with a broadly convex deltaic-front morphology. They suggest instead a more complex model with an axial estuary (without any trunk river system!) and deltaic flanks with sediment supplied primarily from the East Shetland Platform and from the Horda Platform (Richards et al. 1988, fig. 1).

Our main problems with the suggestions of Richards et al. 1988 are as follows.

(1) They have attributed, to the ‘traditional’ model, a greater degree of precision than it has ever had. The nation of a general northwards progradation of Brent delta system, as developed through the works of Eynon (1981), Johnson and Stewart (1985), Graue et al. 1987, Brown et al. 1987, Helland-Hansen et al. 1989 and Fält et al. 1990 has never been dependent on the presence of a southerly dome as principal source area. There has been an increasing awareness of the likelihood of sediment contribution from the

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