Salt Domes Under the Midnight Sun

The Sverdrup Basin in Nunavut, Arctic Canada, contains the world's second-largest concentration of emergent salt diapirs on Earth. More than 40 emergent diapirs are known on Axel Heiberg Island in the center of the Sverdrup Basin. As part of the Applied Geodynamics Laboratory (AGL) research program, Martin Jackson spent 3 weeks during June and July on Axel Heiberg Island and adjoining northern Ellesmere Island, collaborating with Dr. Christopher Harrison of the Geological Survey of Canada (Calgary). For 2 weeks, they mapped three diapirs using tent camps that were periodically moved and resupplied by helicopter. They also spent a week at Canada's Polar Continental Shelf Project base at the Eureka weather station on Ellesmere Island, from where they went on day trips to other diapirs and key outcrops by helicopter. Their work was part of a larger Arctic research program and workshop organized and led by Dr. Benoit Beauchamp of the Geological Survey of Canada (GSC). This program required 18 months of logistical preparation by the GSC, including laying in fuel caches for the helicopters the previous summer. In midsummer, even at a latitude of 80°, tundra around the diapirs is largely free of snow—fortunately for geologists—although the island contains a large permanent ice cap, innumerable glaciers, and frozen fiords.

The Carboniferous evaporite diapirs consist mostly of anhydrite, underlain by halite and weathering to a gypsum skin. The diapirs were squeezed by the early Tertiary Eurekan orogeny. Separating the diapirs are minibasins, which are also excellently exposed at the surface. Like the diapirs, they offer scientists an opportunity to investigate firsthand a geologic system similar to that in the Gulf of Mexico, which is either deeply buried or in deep water and thus inaccessible to direct observation.

Research results will first be presented in November at AGL's annual review meeting for sponsoring companies.

 
Moving camp by helicopter.   A fly camp on the shoulder of Expedition Diapir, overlooking the Thompson River and White Glacier on western Axel Heiberg Island.

 
Outlet glaciers draining one of the many ice caps on northern Ellesmere Island.   The main ice cap of Axel Heiberg Island, sporadically pierced by nunataks.

 
The central part of Muskox Ridge Diapir (pale-gray anhydrite ridge) overlain to the left by fluvio-deltaic sandstones and shales of the Cretaceous Isachsen Formation. Ice-covered Expedition Fiord in the background, western Axel Heiberg Island.   Strained nodular anhydrite (white) outlined by carbonaceous black streaks in Muskox Ridge Diapir.

 
Fiord cliff exposing upper Paleozoic succession on northern Ellesmere Island.   Christopher Harrison (left) and Benoit Beauchamp (right) on the shore of Otto Fiord, northern Ellesmere Island near the type section of the Otto Fiord Formation, which supplies evaporites to the numerous Sverdrup diapirs.

  Martin Jackson at Otto Fiord at 9:30 p.m.