Insights into Late Cretaceous-Early Paleocene depositional systems from a heavy mineral study on the Tulipan well (6302/6-1), Møre Basin, Mid-Norway

During the Late Cretaceous-Early Paleocene the Norway Greenland rift was a deep water basin connecting the Arctic Ocean and the opening Atlantic Ocean to the south (Vergara et al., 2001). The fill of the basin is dominated by thick sequences of mudstone with thin beds or laminae of ripple cross laminated and parallel laminated fine- or very fine-grained sand and variable amounts of bioturbation. The presence of mud drapes on the foresets of ripple cross laminae favours deposition of the sand beds by bottom currents rather than sediment gravity flows. Locally, thick beds of sandstone showing grading, parallel stratification and parallel lamination and dish and pillow structures occur. These beds were deposited by sediment gravity flows. Beds composed of this facies combine to make up thick sandstone dominated units and form the reservoir units for the Ormen Lange and Nyk High gas accumulations (Kittilsen et al., 1999; Vergara et al., 2001). Sediment provenance studies indicate that the thick sandstone beds forming the Ormen Lange field were derived from western Norway, including the Western Gneiss Region. In contrast the thick beds of sandstone forming the Nyk High gas accumulation were supplied from the East Greenland side of the rift.

In the Tulipan well (6302/6-1) two facies are found in core in the Paleocene section. The first facies consists of clean, pale, graded, beds of well sorted sandstone. The second facies consist of sandy mudstones with discrete sand laminae showing variable degrees of bioturbation. Heavy mineral analysis reveals that the sand from the thick beds was derived from western Norway, whilst sand in the bioturbated sandy mudstones was derived from the Greenland margin. This surprising association indicates the interfingering of two depositional systems. The first consists of sediment gravity flows fed from the east. The second consists of episodic bottom currents reworking sediment derived from the west between periods of sediment gravity flow deposition. The interbedding of contrasting facies with different sand composition similar to that seen in well 6302/6-1 has also been observed at other locations in Norway-Greenland rift, including the Campanian of East Greenland and well 6505/10-1 (Helland Hansen).