Sains Ma1aysiana 26(2): 103-113 (1997)                                                                Sains Bumi/                                                                                                                                                                              Earth Sciences

Natural Radionuclides Contents in Marine Sediment:

Evidence for the Paleoproductivity

Che Abd. Rahim Mohamed

Faculty of Natural Resource Science

Department of Marine Science

43600 UKM Bangi, Selangor D.E.

E-Mail: carmohd@pkrisc.cc.ukm.my

ABSTRACT

A sediment core was obtained at one station in the North Pacific region, and for analyzed uranium, thorium and their daughter nuclides, and combustible fraction. Their concentrations vary considerably in the surface layer but was constant at deeper depth. This variation could be due to the temporal changes on the seabed before being buried in the sediment column. The dilution of aluminosilicate detritus in uranium and thorium nuclides may be occurred. However, the constant concentrations of ²³⁰Th at the deeper (30 cm to 110 cm) are due to the past abruption. The calculated sedimentation rate was 1.56 mm/kyr at the surface (0 cm to 30 cm) and 4.55 mm/kyr at the bottom (110 cm to 180 cm) layer.

ABSTRAK

Analisis uranium, thorium, rangkaian nuklid dan pembakaran organik dilakukan ke atas teras sedimen yang diperolehi pada satu stesen di utara Lautan Pasifik. Kepekatan unsur-unsur ini adalah berbeza di bahagian permukaan dan seragam di bahagian yang lebih dalam. Perbezaan yang ketara ini disebabkan oleh perubahan yang berlaku di dasar lautan iaitu sebelum unsur-unsur ini berkubur di dalam sedimen. Pengcairan alumonisilicate detritus ke atas uranium dan thorium mungkin berlaku. Keseragaman kepekatan ²³⁰Th di bahagian bawah (30 cm ke 110 cm) adalah disebabkan oleh faktor fizikal yang berlaku pada masa lampau. Kadar pemendapan yang diperolehi ialah 1.56mml kyr di lapisan permukaan (0 cm ke 30 cm) dan 4.55 mm/kyr di lapisan yang lebih dalam (110 cm ke        180 cm).

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