Magnetostratigraphy of ODP Sites 114-699 and 114-700

• Main Authors: Hailwood, Ernie A, Clement, Bradford M
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1991
• Subjects: 114-699A; 114-700B; DRILL; Drilling/drill rig; Joides Resolution; Leg114; Ocean Drilling Program; ODP; South Atlantic Ocean; Antarc*; Antarctica
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.734978; https://doi.org/10.1594/PANGAEA.734978

ODP Sites 699 and 700 were drilled within the East Georgia Basin primarily to explore the paleoceanographic and sedimentary history of this region during the early stages of separation of South America from Africa and Antarctica. Determination of the timing of the various events represented in the sedimentary record of these sites requires the establishment of a high-resolution stratigraphic framework. This was achieved through combined magnetostratigraphic/biostratigraphic studies of the sediments recovered from Holes 699A and 700B. The magnetostratigraphic data are presented in this paper. They are based on a combination of shipboard whole-core paleomagnetic determinations made at 10-cm intervals on all archive core halves and involving AF demagnetization in fields of 5 and/or 9 mT together with shipboard and post-cruise incremental AF demagnetization analyses of some 450 discrete samples. A generally continuous magnetostratigraphic record has been obtained for the Pliocene-Pleistocene and Oligocene sequences recovered from Hole 699A. A record of the Brunhes, Matuyama, and late Gauss Chrons has been identified in the Pleistocene to late Pliocene age sediments cored in the upper 30-m section of this hole. However, interpretation of the magnetostratigraphic record observed for the Pliocene sediments in the interval from 30 to 70 mbsf is complicated by the possible presence of hiatuses. A well-defined sequence of normal and reverse polarity magnetozones was identified for the Oligocene sequence of Hole 699A in the interval from 85 to 219 mbsf. Although there are few biostratigraphic datums for this interval, the observed polarity sequence shows a good correlation with geomagnetic polarity Chrons C6CR to C11R. As a result of poor core recovery, the magnetostratigraphic sequence for the early Oligocene to early Eocene age sediments from 243 to 468 mbsf in Hole 699A is discontinuous. However, available biostratigraphic datums allow the identification of Chrons C13N and C13R in the depth interval from 270 to 306 mbsf ...