Monday, 5 September 2005

This presentation is part of: Poster Session I

10Be variation in surficial sediments of the Central Indian Basin

B. N. Nath1, A. Aldahan2, K. Selvaraj3, M. B. L. Mascarenhas-Pereira1, and G. Possnert4. (1) National Institute of Oceanography, Dona Paula, Goa-403 004, India, (2) Department of Earth Sciences, Uppsala University, SE-752 36 Uppsala, Sweden, (3) Institute of Marine Geology & Chemistry, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, (4) Tandem Laboratory, Uppsala University, Box 529, SE-751 20 Uppsala, Sweden

The distribution of 10Be in systematically collected (1x1 degree grid interval at 10 to 16šS; 73.5 to 76.5šE) surficial siliceous ooze, siliceous clay and pelagic clay sediments from the abyssal Central Indian Basin is used to decipher sediment transport pathways, sediment depocenters and erosional areas. 10Be concentrations display a significant variation from 0.12 to 5.56 x 109 atoms/g with a mean of 3.58 x 109 atoms/g. The distributional pattern suggests a broad area of enrichment in the north and two patches in the eastern and western parts of the study area. When compared to surficial sediments from the Andaman Back-Arc Basin situated in the northern Indian Ocean (concentrations ~1.5 x 109 atoms/g), the abyssal sediments indicate higher 10Be concentrations. However, some of the abyssal sediments show low values (0.125 to 0.169 x 109 atoms/g) and are comparable to the eolian dust in the Pacific Ocean (0.1 to 0.5 x 109 atoms/g). The aluminum concentrations in the abyssal sediments are about 3-5% and suggest dominant non-lithogenic composition. Accordingly, a large part of 10Be could be supplied from water column in addition to eolian dust and minor riverine detritus. Furthermore, both the 10Be concentrations and those normalized to Al, and Ti (indicators of lithogenic material), and Mn (to represent adsorption from water column and authigenic formation) show similar distribution patterns. These are interpreted as indicating mixed sources with contribution from both lithogenic and biogenic material. In addition to variable supply through water column and detrital particles, bottom topographic changes seem to exert control on the longitudinal variation seen in southern part of the studied area. Sediments deposited in valleys or topographic depressions seem to have higher 10Be concentrations probably forming depocenters in contrast to the erosion-dominated areas at the slopes that may also expose older sediments that are depleted in 10Be.

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