Nuussuaq Basin of West Greenland: Subsidence and Structural Inversion in an Albian - Early Tertiary Pull-Apart Basin

Anthony Tankard, Tai Ng, and Ted Renner

The western margin of Greenland consists of a complex of linked extensional basins which formed during opening of Labrador Sea and Baffin Bay in Albian - early Tertiary time. The Nuussuaq basin, which straddles Nuussuaq peninsula and Disko Island, is onshore. Its sedimentary succession is generally hidden beneath a cover of early Tertiary extrusives. Slim-hole exploration drilling has been based on an integrated basin analysis and magnetotelluric data acquisition. Nuussuaq basin developed at a left-lateral releasing stepover at the end of the Ungava fault, an interplate strike-slip fault zone. SW-directed extension was accommodated by several transfer faults which compartmented the Nuussuaq basin. Although the principal depocenter is only 1500 sq. km² in area, nterpretation of the magnetotelluric data shows basin depths greater than 10 km. Persistent overpressuring and the low resistivity lower basin fill are believed to be typical of a young basin which has subsided rapidly. The Cretaceous - lower Tertiary succession is indicative of a resticted, underfilled basin. In contrast, the mid-Paleocene paleogeography was controlled by dextral slip along the basement strike-slip fault zones, broadscale structural inversion of the earlier extensional faults, and widespread volcanism. Catastrophic crestal collapse of inversion anticlines is reflected in sudden incision and rapid filling of a suite of paleovalleys. In Paleocene time, the Nuussuaq basin was generally overfilled and dominated by terrestrial depositional systems. Oil seeps are associated with crestal collapse and fracturing of inversion structures. Biomarkers suggest a source rock of Paleocene age.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California