Distribution and behavior of /sup 230/Th and /sup 231/Pa at an ocean margin, Baja California, Mexico

Journal Article · Sat Nov 01 04:00:00 EST 1986 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(86)90032-3· OSTI ID:7193210

Shimmield, G B; Murray, J W; Thomson, J; Bacon, M P; Anderson, R f; Price, N B

Uranium, Th and Pa isotopes were measured in sediments collected by box core along a transect normal to the Baja California continental margin. Six cores were analyzed, ranging in depositional environment from manganese nodule-bearing, pelagic, red clay to hemipelagic sediments displaying Mn reduction in the upper 5 cm. In the hemipelagic cores, solid-phase Mn peaks due to diagenetic remobilization occur within the upper layers which are well mixed with respect to unsupported /sup 230/Th and /sup 231/Pa. The fact that /sup 230/Th and /sup 231/Pa are not concentrated at the Mn peaks suggests that little mobility of these nuclides occurs within the sediment column. Unsupported /sup 230/Th//sup 231/Pa activity ratios in the biomixed layer of the sediments range from 10.9 to 6.6, generally decreasing towards the inshore stations. The flux of /sup 230/Th and /sup 231/Pa across the sediment/water interface is almost in balance with the theoretical water column supply in the most distal core, but rapidly increases inshore. This evidence from the sediment column confirms that enhanced /sup 230/Th and /sup 231/Pa removal occurs at ocean margins, and that /sup 231/Pa is removed from the water column to the sediments in preference to /sup 230/Th.

• Research Organization: Univ. of Edinburgh, England
• OSTI ID: 7193210
• Journal Information: Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 50:11; ISSN GCACA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ALPHA DECAY RADIOISOTOPES
CHEMISTRY
CONTINENTAL MARGIN
EVEN-EVEN NUCLEI
GEOCHEMISTRY
GULF OF CALIFORNIA
HEAVY NUCLEI
ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
PACIFIC OCEAN
PROTACTINIUM 231
PROTACTINIUM ISOTOPES
RADIOISOTOPES
SEAS
SURFACE WATERS
THORIUM 230
THORIUM ISOTOPES
YEARS LIVING RADIOISOTOPES