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°57ʹN and 131°42ʹW in 5,080 m water depth; KODOS 02-01-02: 16°12ʹN and 125°59ʹW in 4,550 m water depth). Successive AF demagnetization reveals a well constrained characteristic component between AF fields of 15–50 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 0.1–2.44 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. From the correlation, the estimated age at 215 cm depth of KODOS 02-01-02 is ~7 Ma and a sedimentation rate is ~0.36 mm/kyr. At this time, we test the possibility of rock-magnetic properties as an alternative age dating tool for deep-sea sediments. When detailed mineralogical data are complemented, rock-magnetic properties will answer the question about sediments provenance in spatial and temporal terms.