PALEOCURRENT ESTIMATION BY ANISOTROPY OF MAGNETIC SUSCEPTIBILITY FOR THE CORE MD982196 FROM THE EAST CHINA SEA

*Hirokuni Oda[1] ,Yurika Ujiie [2]
National Institute of Advanced Industrial Science and Technology[1]
Ocean Research Institute, University of Tokyo[2]

IMAGES IV cruise was operated in 1998 by R/V Marion Dufresne and was composed of a series of three legs along the western Pacific marginal seas. Leg 3 was operated along the Okinawa Trough through East China Sea with special reference to the history of Kuroshio Current and East Asian monsoon. In this presentation, we will show paleocurrent estimation by anisotropy of magnetic susceptibility (AMS) of the core MD982196 obtained during leg 3.

The core MD982196 was retrieved close to the northern end of Okinawa Trough (29d52.58'N, 128d36.50'E) at a water depth of 951 m. The length of the core is 38.8 m and the estimated sedimentation rate is 20 cm/kyr. The sediment is mainly composed of clay to clayey silt with some turbidite and ash layers. AMS show vertically aligned magnetic fabric for the top 4 m suggesting the vertical extention by the piston coring. Paleomagnetic declination show that the core is twisting anticlockwise downcore for about 180 degrees from top to bottom. The core spans oxygen isotopic stages 1 through 7.

Directions of maximum axes of susceptibility anisotropy ellipsoide (Kmax) are statistically processed on rose diagrams after correcting the twisting of the core separately between stages. The results show that during stages 2, 4 and 5, and substage 6a, paleocurrent directions were E-W. During substage 6b, the paleocurrent was NE-SW, whereas it was N-S during stage 7. During stage 3, the current direction seems not stable. Paleocurrent directions of N-S and NE-SW during stage 7 and substage 6b might represent the different depositional system from the later stages after 6a.