Montagnais Submarine Meteorite Impact Structure, Offshore Nova Scotia, Canada

Otto R. Friedenreich

Seismic oil exploration recordings (originally in a 4-mi grid shot in 1970, later filled in during 1971) on the Le Havre Bank of the Scotian basin revealed a nearly circular structurally deformed area about 40 km in diameter. The center of the structure is located at 42°53^primeN, 64°13^primeW, and 200 km south of Halifax, Nova Scotia, near the edge of the shelf in water depths of 115 m. The structure has a central domal uplift, 12 km across, of Cambrian-Ordovician metasedimentary rocks (Meguma Formation) uplifted 1.8 km above regional level, surrounded by a circular synclinal area. The structure, named Montagnais, was interpreted to be an astrobleme (meteorite impact crater). A panel of seismic sections and a time structure map on the Eocene unconformity illust ate the character of the Montagnais structure. An oil exploration well, Union et al Montagnais I-94, was drilled in 1974 near the crest of the structure. No hydrocarbons were found. Drilling results confirmed however the seismic interpretation of an impact crater. Rocks penetrated by the 1,646-m well can be subdivided into three sequences: (1) Holocene to Eocene marine sediments (540 m), (2) early Eocene to Cretaceous beds (547 m) containing three basaltic melt zones, and (3) the Meguma basement. K-Ar dating provides ages of 49-51 Ma for the melt zones, which is in agreement with the early Eocene age of the overlying sediments and the regional seismic-stratigraphic calibrations and correlations of the sequences.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.