PALEOMAGNETIC INVESTIGATION OF SEDIMENT CORES RECOVERED DURING THE ATLANTIC MARGIN CORING PROJECT (AMCOR)

The paleomagnetic polarity in sediment from 10 cores recovered by the Glomar Conception during the Atlantic Margin Coring Project (AMCOR; Hathaway, et al., 1979) on the Atlantic Ocean continental shelf and slope was determined at the Woods Hole Oceanographic Institution. Two hundred seventeen samples encased in 6.4-cc plastic boxes were treated by alternating field demagnetization and measured in a cryogenic magnetometer. The cores have a diameter of 5.4 cm and were recovered in 9-m pieces that were cut into 1.5-m sections, split, and stored in sealed D tubes in a refrigerated van before transport to Woods Hole, MA. The most reliable data are from a 300-m core (6009B) from the New Jersey outer shelf in water depth 58.5 m at 38¢ª51.3'N, 73¢ª35.5'W where ~120 m of Pleistocene dark gray silty clay and fine sand (Hathaway, et al., 1979) record a possible change from normal to reverse polarity at ~ 90-m depth following demagnetization to 60 mT. The change in polarity is interpreted to be the Matuyama/Brunhes boundary ( ~ 0.78 m.y.) and is a marker horizon in the stratigraphy of the continental shelf.