Seismic reflection profiles from Kane to Hall Basin, Nares Strait: Evidence for faulting

Report of the project:

• Marine geophysical investigations in the Nares Strait between Ellesmere and North-West Greenland

Leading edge of a linked strike-slip fault system. Source: BGR

Three major tectonic boundaries are predicted to be present beneath the waters ofthis segment of Nares Strait (see first figure):

1. the orogenic front ofthe Paleozoic Ellesmerian Foldbelt between thrust sheets on Ellesmere Island and fiatlying foreland rocks on Greenland,
   
2. the supposed sinistral strike-slip plate boundary of Paleocene age between the Ellemere Island section of the North America plate and the Greenland plate, and
   
3. the orogenic front of the Eocene to Oligocene Eurekan Foldbelt that must lie between thrust tectonics off Ellesmere Island and undeformed rocks of Greenland.

To understand this complicated situation and to look for direct evidence of the plate boundary, new seismic reflection profiles were collected and, together with industry data in the south, interpreted. The profiles are clustered in three areas controlled by the distribution of the sea ice. Bathymetry is used to extrapolate seismic features with a topographic expression between the regions. Based on high resolution boomer and deeper penetration airgun profiles five seismic units are mapped. These units are interpreted in the context of the adjacent onshore geology. Along Dobbin Bay there is a direct correlation between the seismic profile and three major onshore thrusts. Onshore changes observed in the amount of crustal shortening are related to the trend of the Eurekan structures as they adjust orientation from E—W to NE—SW Offshore of Ellesmere Island from just north of the Bache Peninsula to Hans Island, there is a linear sedimentary basin that follows the coast. In cross-section the basin is asymmetric shallowing towards Greenland. Several seismic sections illustrate the character of the steep fault that delimits the eastern margin of the basin. This basin bounding fault is interpreted to have originated as a linked strike-slip fault system that was reactivated during a compressional phase. Its near surface expression is hypothesized to be the leading edge of the plate boundary between the North American and Greenland plates

Three-dimensional structural fence-diagram and sub-surface interpretation of the Dobbin Bay area. Note the congruence of the interpreted thrusts in the seismic profile (NARES01-15) and the exposed thrusts in the geological cross-sections. Note also the climbing up-section of the Dobbin Bay Thrust towards the west and the consistent drop of the interpreted basement-surface below the Eurekan floor-thrust (Parrish Glacier Thrust). Source: BGR