AUTHIGENIC URANIUM IN ATLANTIC SEDIMENTS OF THE LAST GLACIAL STAGE - A DIAGENETIC PHENOMENON

被引:66
作者
THOMSON, J [1 ]
WALLACE, HE [1 ]
COLLEY, S [1 ]
TOOLE, J [1 ]
机构
[1] SCOTTISH UNIV RES & REACTOR CTR,E KILBRIDE G75 0QU,LANARK,SCOTLAND
关键词
D O I
10.1016/0012-821X(90)90061-2
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Cores from three different Atlantic localities (equatorial, Cape Verde Rise and Porcupine Abyssal Plain) are shown to have anomalous high U contents (5-8 ppm total) in sediments laid down during the last glacial stage (12-24 ky BP). Radiocarbon data demonstrate that the sediments hosting the peak U levels were accumulated at rates similar to those immediately above and below. All the cores exhibit maximum Mn levels, characteristic colour changes, and maximum U levels in the same sequence with increasing depth in core. On the evidence of the similarities between the cores, and pore water U data from a Porcupine Abyssal Plain site, it is proposed that the authigenic U enrichments are syndiagenetic and possibly active. No correlation is observed between sediment authigenic U and Corg contents. The source of enrichment is bottom water U which has diffused downwards into the sediments to be sorbed at a particular redox level, located 10-30 cm below the oxic/post-oxic boundary marked by the colour change. The magnitude of the enrichments is caused by the persistence of this boundary at a particular level as a result of the decrease in mean sediment accumulation rate between the last glacial stage (5.2 up to at least 19.1 cm ky-1) and the Holocene (2.2-4.1 cm ky-1). Similar accumulation rate contrasts are expected to be widespread in the Atlantic, and the implications for previous reported work, particularly from the Mid-Atlantic Ridge, are discussed. © 1990.
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页码:222 / 232
页数:11
相关论文
共 52 条
[1]   TH-234-U-238 DISEQUILIBRIUM IN NEAR-SHORE SEDIMENT - PARTICLE REWORKING AND DIAGENETIC TIME SCALES [J].
ALLER, RC ;
COCHRAN, JK .
EARTH AND PLANETARY SCIENCE LETTERS, 1976, 29 (01) :37-50
[2]  
ANDERSON RF, 1987, URANIUM, V3, P145
[3]  
ANDERSON RF, 1987, EOS T AM GEOPHYS UN, V68, P1780
[4]  
BACON MP, 1984, ISOT GEOSCI, V2, P97
[5]   ATLANTIC SEDIMENTS: GLACIAL/INTERGLACIAL COMPARISONS [J].
Balsam, William L. ;
McCoy, Floyd W., Jr. .
PALEOCEANOGRAPHY, 1987, 2 (05) :531-542
[6]  
BARNES C, 1988, RADIONUCLIDES : A TOOL FOR OCEANOGRAPHY, P162
[7]  
BATIURIN GN, 1973, GEOCHEM INT, V10, P1331
[8]   GEOCHEMISTRY OF THREE CORES FROM EAST PACIFIC RISE [J].
BENDER, M ;
BROECKER, W ;
BISCAYE, P ;
SUN, S ;
GORNITZ, V ;
MIDDEL, U ;
KAY, R .
EARTH AND PLANETARY SCIENCE LETTERS, 1971, 12 (04) :425-&
[9]   TIMING OF DEGLACIATION FROM AN OXYGEN ISOTOPE CURVE FOR ATLANTIC DEEP-SEA SEDIMENTS [J].
BERGER, WH ;
KILLINGLEY, JS ;
VINCENT, E .
NATURE, 1985, 314 (6007) :156-158
[10]   A NEW GEOCHEMICAL CLASSIFICATION OF SEDIMENTARY ENVIRONMENTS [J].
BERNER, RA .
JOURNAL OF SEDIMENTARY PETROLOGY, 1981, 51 (02) :359-365