CONSTRUCTION AND DEVELOPMENT OF A PALEOMAGNETIC AND AN ENVIRONMENTAL MAGNETIC RECORD FROM NE PACIFIC CORE EW9504-12PC

Dating is an essential component in the reconstruction of Earth's history recorded in the marine sediment records. Piston core EW9504-12PC from the Northeast Pacific Ocean is part of a series of Pacific margin cores that are being analyzed for their paleoclimatological and magnetic properties. The site's location was 34.547° N, 121.108° W at a water depth of 938m. To obtain a time scale for this specific core, paleomagnetism was employed. U-channel samples were taken from EW9504-12PC. The natural remament magnetization was studied by progressive alternating field (AF) demagnetization at the Paleomagnetism Laboratory at the University of California, Davis. Laboratory magnetization, anhysteretic remanent magnetization (ARM) and isothermal remanent magnetization (IRM) were also applied and demagnetized at the same AF as the NRM. This record showed a change in inclination and declination at a depth of ~ 8.3 m, that is interpreted to reflect the Bruhnes-Matuyama magnetic reversal. This interpretation is supported independently, by the environmental magnetic and the carbonate record, that preserves changes in the concentration (of magnetic material and CaCO₃) suggestive of glacial and interglacial variations. When these were compared with a global benthic oxygen isotope stack using the interpretation of the Bruhnes-Matuyama magnetic reversal (~780ka) as a single tie point, a clear correlation between the three records (oxygen isotope, carbonate, magnetic concentration) are observed. From these indicators the core's basal age can be estimated at ~900ka with a sedimentation rate of ~1.1cm/ka. The paleomagnetic and environmental magnetic significance of these studies will be presented.