SALT DIAPIRS OF THE SOUTHWEST NORDKAPP BASIN - ANALOG MODELING

The geometry and evolution of the salt diapirs in the southwestern seg ment of the Nordkapp Basin (SW NKB) were interpreted on reflection sei smic data. Reflection seismic profiles were used to build a dynamicall y scaled model analogue to study salt tectonics of the basin. The mode l was prepared using lengths, densities, and sedimentary histories obt ained from seismic and well data. Model results suggest that the salt structures in the SW NKB were influenced by basement faults that horiz ontally stretched and faulted their overburden and induced salt flow b y differential loading. Model diapirs rose only where the overburden w as faulted. The salt structures are aligned in two NE-SW rows that par allel the major basement faults that outline the basin. Carboniferous salt in the SW NKB formed conformable pillows in the Early Triassic (S cythian), which became diapiric during the late Early and Middle Trias sic. The salt diapirs spread to form asymmetric broad overhangs at sup erficial levels during slow sedimentation in Late Triassic and/or Jura ssic. Diapir overhangs were later reactivated because of burial by Cre taceous and Tertiary sediments. Basement faults were mapped by compari ng thickness of the sediments and/or level of the reflectors on either side of the diapirs that had relatively narrow overhangs. Depth conve rsion and restoration of velocity pull-up of reflectors beneath salt d iapirs suggest that the salt diapirs of the SW NKB have broad overhang s above narrow stems.