Evolution of Tromsø Basin in the light of salt tectonics
MetadataShow full item record
Two dimensional (2D) seismic data was used for seismic interpretation of the main horizons in Tromsø Basin and mapping of the salt structures in the study area. Seismic data covers area of approximately 134x140 km comprising Tromsø Basin, East of the Sørvestsnaget Basin, North of the Harstad Basin, Senja Ridge and Ringvassøy Loppa Fault Complex. Study area is located within longitude 15ο05'37"E to 29ο02'27"E and latitude 69ο54'37"N to 73ο53'0"N. Ten horizons have been interpreted at different stratigraphic levels. Top Nordland Group (seabed), Top Miocene, Top Eocene, Top and Base Paleocene, Top Kolmule, Top Knurr, Top Hekkingen, Top Fuglen and Top Stø horizons were interpreted to understand the structural model of the area. Above thick Late Paleozoic salt mass, sedimentary packages have various thicknesses and each of them is not uniform across the field. Thickness maps show that TST (true stratigraphic thickness) of the formations can change in a very short distance dramatically. This is an evidence of the very complex processes took place in the basin.Fault reactivation and presence of radial fault due to salt upwelling caused accumulation of big thicknesses of syn-depositional sediments. It is worth to mention that Cretaceous sediments are represented with a very thick package in Tromsø Basin which is thinning towards the flanks of the study area.Nine salt structures (A-J) have been mapped in the area; three of them are located in the western part of the Senja Ridge. The rest of the salt bodies are located in the Tromsø Basin which played an important role in evolution of the basin. The salt structures area different in terms of shape, scale, but have been developed as passive diapirs, simultaneously with sedimentary accumulation. Salt structure A is the biggest salt body in Tromsø Basin and penetrates all of the layers and reaches up to Nordland Group. Most likely salt structure developed through continuously reactivating normal fault (with very big throw) in the central part of the basin. The other salt structures are smaller than A but also penetrated most of the overburden horizons. Salt tectonics has a huge role in the structural deformation history of the basin. The triggering factor of halokinesis is regional extensional forces. In order to understand the sequence of the processes took place shaping today s picture, backstripping method have been applied to restore the geological history of the basin. Using seismic section illustrated in Figure 4.15, 2D geological model of the area have been created. The model was the initiation point for the backstripping.