Salts as indicators of tectonic activity along Nesson anticline, North Dakota

The Nesson anticline is the major north-south-trending structure in the North Dakota portion of the Williston basin. The trace of the anticline is marked by nearly continuous production for 110 mi (175 km) from the Canadian border south to Dunn County; production is from 13 different stratigraphic zones. Previous studies have shown that the central and southern parts of the anticline, from Beaver Lodge field south to Rattlesnake Point field, consist of at least nine structurally independent areas, each of which has an individual tectonic history. Isopach patterns indicate that most of the areas underwent their greatest tectonic activity during the Devonian and Early Mississippian, although a few areas were active during the early Mesozoic as well. Ten traceable salts are present along the anticline in the Prairie (Devonian), Charles (Mississippian), Opeche (Permian), Spearfish (Triassic), and Pipe Formations (Jurassic). The isopach patterns of the individual salts indicate contemporaneous tectonic activity through thickening or thinning of the salt. Postdepositional activity is indicated by the absence of a salt; the timing of the activity may be estimated from the presence of compensating section above the level of the salt. Their results indicate that, in addition to the times given above, significant tectonicmore » activity took place along the anticline during the Late Mississippian, late Jurassic, and Early Cretaceous.« less