Chemical composition of ferromanganese crusts and manganese nodules from the Indian and Southern Ocean, supplement to: Andersen, M E (1978): Accumulation rates of manganese nodules and sediments - An alpha track method. Master thesis, University of California, San Diego, USA, unpublished


Excess 230Th dominates the alpha activity of the surface regions of manganese nodules and deep sea sediments. If uranium series eguilibrium is maintained, total alpha activity depth profiles should be as useful in determining sedimentation rates as are 230Th measurements. We have used cellulose nitrate alpha track recorders pressed against manganese nodule slabs to record high resolution alpha activity "maps' of a large number of nodules. Total alpha activity profiles have also been obtained for several sediment cores. From the approximately 90 nodule profiles measured to date, 73 show simple, approximately exponential depth dependence; about 2/3 of these have inferred deposition rates of 4-10 mm/10power6 yr. Ten profiles show statistically significant breaks in slope, suggesting growth rate changes. Within single dredge hauls there is little variation in growth rates, although different portions of the same nodule sometimes exhibit different growth rates. There is no correlation between depth and measured growth rate, except for a general tendency for the few Atlantic Ocean nodules we have measured to have slightly lower rates than Pacific or Indian Ocean samples. For a number of nodules and sediments the alpha track results have been compared with 230Th-based deposition rates measured by other workers. Two nodules have 230Th rates (W. S. Broecker et al., pers. comm.) identical within errors to the alpha track determinations. A third nodule (S. Krishnaswami, pers. comm. ) and two sediment cores previously measured by Goldberg and Koide (E. Sci. and Meteoritics, 1963, p. 90} all have much slower rates based on 230Th measurements compared with the alpha track results.

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Metadata Access
Creator Andersen, M E
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 1978
Rights Creative Commons Attribution 3.0 Unported
OpenAccess true
Language English
Resource Type Supplementary Dataset
Format text/tab-separated-values
Size 789 data points
Discipline Earth System Research
Spatial Coverage (-119.837W, -62.092S, 55.165E, 6.872N); Arabian Sea; Indian Ocean
Temporal Coverage Begin 1968-01-01T00:00:00Z
Temporal Coverage End 1975-06-19T00:00:00Z