Late Cenozoic Evolution of the Continental Margin Offshore Troms, North NO

Tom Arne Rydningen

A new incentive in the form of greatly improved data coverage (2D and 3D seismic) has resulted in increased focus on the continental margin offshore Troms, North NO. Here, Trough Mouth Fans are found seaward of glacial troughs. In this study we address the depositional environment during the evolution of the fans. Four regionally correlated reflectors, named T4 (oldest) to T1, defining four seismic units, named S4 to S1 have been identified. We define the stratigraphically deepest angular unconformity, T4, as the onset of Trough Mouth Fan growth. Sediment thicknesses above T4 reach up to 1.2 seconds (two-way time), corresponding to ~1 km using available well data (from north of the study area). During deposition of the fans the shelf edge has prograded some 20, 15, and 8 km in the Andfjorden, Malangsdjupet and Rebbenesdjupet troughs, respectively. In contrast, the inter-fan areas show only 2-5 km of progradation in the same time period. Within the oldest unit (S1), several canyons and channel-like features occur. Their occurrence and complex cut-and-fill character points to an early fluvial/glacifluvial paleoenvironment. The overlying two units consist of stacked westward prograding clinoforms infilling the canyons and channel-like features, with an increase in clinoform steepness above reflector T2. These units mark the onset and gradual transition to a more glacially influenced sedimentation and is inferred to be dominated by a muddy diamicton. Glacial landforms (e.g. mega-scale glacial lineations) at the T1 reflector and internally within the uppermost unit S4 give conclusive evidence of grounded ice at the palaeo-shelf. During this period the trough mouth fans have been affected by submarine landslides resulting in an irregular morphology. In the inter-fan areas, channel systems leads into canyons routing sediments into the deep-sea basin.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013