Eocene-Miocene magnetostratigraphy of the southeast Greenland Margin and western Irminger Basin

Abstract

Shore-based paleomagnetic investigations were conducted on Eocene-Miocene sediments recovered during Ocean Drilling Program Leg 152 drilling of the southeast Greenland Margin and the western Irminger Basin. A total of 147 specimens was analyzed. In general, the magnetostratigraphy obtained from the shipboard whole-core magnetometer studies (spot demagnetization at 25 mT) has been confirmed. However, a number of specimens yielded polarities different from those obtained by the shipboard magnetometer, calling for some caution in the interpretation of the magnetostratigraphy. During Leg 152, it proved difficult to correlate the polarity records with the geomagnetic polarity time scale because of core recovery and the limited biostratigraphic information available at the time. Since then, the shore-based biostratigraphic studies have yielded many datum points useful for correlating the refined magnetozone sequences to the polarity time scale. In terms of seaward dipping reflector formation, the new data are particularly valuable in determining their subsidence history. At Sites 915 and 917, close to the southeast Greenland ocean/continent transition, intervals of 13 m.y. and 4 m.y., respectively, elapsed before marine sedimentation commenced. Sedimentation at Site 918, in the western part of the Irminger Basin, commenced almost immediately after seaward dipping reflector formation at about 54 Ma.