Twenty-two trace elements in 355 sediment samples from Site 997 on the Blake Ridge were examined by inductively coupled plasma-optical emission spectrometry and inductively coupled plasma-mass spectrometry, for respective fractions of acid-soluble and insoluble compositions. Downhole profiles of these elements exhibit complicated fluctuations throughout late Miocene to Pleistocene, principally due to the variations in the acid-soluble fraction. Noncarbonate composition is given from the acid-insoluble residues, which permits us to recognize secular feature of selected element variance for four intervals. These intervals (I: 0-183 mbsf; II: 183- 440 mbsf; III: 440-618 mbsf; and IV: 618-750 mbsf) are interpreted to have originated from changes in the suite of sediments of particular sources and chemical composition, sedimentation rate, dilution of biogenic carbonate abundance, and possibly the current system that controlled deposition and reworking of the terrigenous materials.
1Paull,
C.K., Matsumoto, R., Wallace, P.J., and Dillon, W.P. (Eds.), 2000. Proc. ODP,
Sci. Results, 164: College Station, TX (Ocean Drilling Program).
2Mineral and Fuel
Resources Department, Geological Survey of Japan, Tsukuba, Ibaraki 305-8567,
Japan. nabe@gsj.go.jp
3Geological
Institute, School of Sciences, The University of Tokyo, Hongo, Tokyo 113, Japan.
4Present address:
Technology Research Center, Japan National Oil Corporation, 1-2-2, Hamada,
Mihama-ku, Chiba 261-0025, Japan.
Date of
initial receipt: 5 May 1998
Date of acceptance: 4 October 1998
Ms 164SR-223