Salt Tectonics of the Norwegian Barents Sea and the NE Greenland Shelf
The present southern Norwegian Barents Sea and NE Greenland shelf formed a complex salt basin during the Pennsylvanian to Early Permian. Although the tectonic history is relatively well known, little has been published on the salt tectonics. Here, we address three topics: (1) the nature of the salt sequence; (2) the relationship between evaporite deposition and crustal rifting; and (3) the initiation and evolution of salt structures. The Gipsdalen Group of the Barents Sea is a layered evaporite sequence comprising interbedded halite, anhydrite, carbonates, and siliciclastics. When present on basement highs, it generally forms a thin, polygonal pattern of carbonate buildups separating lagoonal evaporites and mudstones. In some cases, buildups loaded the salt, creating small pillows in between. The salt was thicker over basement lows, with multiple levels dominated by halite and intervening competent layers that became disrupted in diapirs. Although the Greenland equivalent also comprises a layered evaporite sequence, the carbonate buildups are not apparent on seismic data. The relationship between evaporite deposition and crustal extension varied because of differences in the timing of rifting. In the Tiddlybanken Basin, the salt largely filled a postrift sag basin. In contrast, the Nordkapp Basin comprised a series of half graben filled with syn- to early postrift salt. Farther west, the confinement of salt to the lows and its absence on highs, for example in the Tromsø Basin area, suggests that it was synrift. Salt in NE Greenland was thicker in the Danmarkshavn and Thetis basins but was also deposited on the Danmarkshavn Ridge, suggesting that it was syn- to postrift salt. The triggers for salt movement and the styles of salt tectonics also varied widely. In the Barents Sea, the Haapet and other domes did not form until the Cenozoic due to regional basin inversion. The Tiddlybanken Diapir is a collapsed-anticline diapir triggered by Triassic contraction and erosion. In the Nordkapp Basin, many diapirs were initiated in the Early Triassic by progradational loading, consequent local salt inflation, and breakthrough after erosional thinning of the pillow roofs. In the Tromsø and Danmarkshavn basins, diapirism was triggered by partially decoupled thick-skinned extension in the Mesozoic, with drape folds and reactive diapirs. Greenland was also characterized by linked thin-skinned deformation, with salt rollers and contractional salt-cored anticlines.
AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017