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The Garn Formation (Bajocian to Bathonian) is interpreted as progradation of braided delta lobes over the mud dominated Not Fm. The Garn Fm is present over the central part of the Halten and Dønna Terraces and the Trøndelag Platform, except over structural highs (Nordland Ridge) where the entire formation may be eroded. In the Ylvingen Fault Zone (well 6510/2-1R), the Garn Fm contains more silt, and further north, siltstones and mudstones are the lateral equivalents of the sandstones in the Garn Fm. It must be noted that well control on the eastern part of the Trøndelag Platform and in the deeper areas to the west is limited.
Depositionally, the sandstones of the Garn Fm are interpreted as a wave-dominated shoreface system with marine mud-dominated sediments deposited towards the north and south. The thickness in the type well (6407/1-3) is 104m, and the formation may reach more than 100m on the Halten Terrace.
The thickness of the Garn Fm is about 150m on the Trøndelag Platform. In the Froan Basin the formation is sand dominated compared to the northern part, where it becomes more shale dominated.