Journal of Petroleum Geology, Vol.7, No.2, pp.169-188, 1984

©Copyright 2000 Scientific Press, Ltd.

SEDIMENTOLOGICAL AND PALEONTOLOGICAL ANALYSES OF
JURASSIC NORTH SEA DEPOSITS FROM DELTAIC ENVIRONMENTS

J. Nagy*, H. Dypvik* and T. Bjaerke*

*Institutt for Geologi, Universitetet 1 Oslo, Postboks 1047, Blindern, Oslo 3, Norway.

Abstract

Core samples from Well 33/9-3, Norwegian North Sea, have been analysed sedimentologically, palynologically and micro-paleontologically. The cores cover the Toarcian Drake Member of the Dunlin Formation, and nearly the whole thickness of the Middle Jurassic Brent Formation. The Drake Member is characterized by pro-deltaic depositional conditions. In the Brent Formation, five members are recognized (from below): the Broom, Rannoch and Etive Members represent distributary mouth bar facies; while the Ness and Tarbert Members are recognized as interdistributary bay fill sequences. The composition of the kerogen assemblages is controlled by the changing energy regimes of the different depositional facies. Terrestrial plant débris are dominant throughout the studied interval. Marine palynomorphs are present in the Drake Member and in the lower part of the Broom Member. The development of rich, arenaceous foraminiferal assemblages in the Drake Member are interpreted as a response to shallow, pro-deltaic conditions. Calcareous foraminifera constitute only a small, accessorial part of these assemblages.