Rock-magnetic property of deep-sea sediments in the NE equatorial Pacific: a stratigraphic correlation tool

Abstract

To diagnose sedimentation environments through the geologic time, two sediments cores were recovered in the Northeast equatorial Pacific (PC120201: 9°57&#697 N and 131°42&#697 W in 5,080 m water depth KODOS 02-01-02: 16°12&#697 N and 125°59&#697 W in 4,550 m water depth). Successive AF demagnetization reveals a well constrained characteristic component between AF fields of 15&#8211 50 mT with the maximum angular deviation of <10°. The component flips eight times in PC120201 and three times in KODOS 02-01-02 showing distinctive antipodal declination and inclination. In the reference geologic time scale, the eight and three reversal events correspond to the age of about 4.5 Ma and 1.8 Ma, respectively. However, 10Be based age correction shows 13.4 Ma at 465 cm depth in PC120201 and variable sedimentation rates of 0.1&#8211 2.44 mm/kyr, indicating many of magnetic reversal records are buried. In KODOS 02-01-02, rock-magnetic properties (i.e., magnetic concentration, grain size, and mineralogy) above 250 cm, composed of siliceous ooze and pelagic red clay, show gradual down-core increase of magnetic concentration and grain size. Such variation is well correlated with the down-core variation to 215 cm of PC120201.5°59&#697 W in 4,550 m water depth). Successive AF demagnetization reveals a well constrained characteristic component between AF fields of 15&#8211 50 mT with the maximum angular deviation of <10°. The component flips eight times in PC120201 and three times in KODOS 02-01-02 showing distinctive antipodal declination and inclination. In the reference geologic time scale, the eight and three reversal events correspond to the age of about 4.5 Ma and 1.8 Ma, respectively. However, 10Be based age correction shows 13.4 Ma at 465 cm depth in PC120201 and variable sedimentation rates of 0.1&#8211 2.44 mm/kyr, indicating many of magnetic reversal records are buried. In KODOS 02-01-02, rock-magnetic properties (i.e., magnetic concentration, grain size, and mineralogy) above 250 cm, composed of siliceous ooze and pelagic red clay, show gradual down-core increase of magnetic concentration and grain size. Such variation is well correlated with the down-core variation to 215 cm of PC120201.