Uranium-series disequilibrium techniques have been applied to sediments and phosphate nodules sampled from the Peru-Chile continental margin in order to decipher growth histories of the nodules and time scales of diagenetic processes occurring within the sediment. / Uranium-series analysis of 11 series of contiguous slices from individual phosphate nodules consistently show unidirectional growth at rates of 0.1 to 10 mm/Kyr with a trend of slow but persistent radium leakage with time. Estimated radium fluxes from these phosphate nodules are 1-3 orders of magnitude less than those calculated for deep-sea sediments and manganese nodules. / Growth curves based upon ('226)Ra and ('230)Th radiometric ages of sequential layers in a buried phosphate crust show that this crust grew upward toward the sediment-water interface at a rate of 12-13 mm/Kyr. Crystallographical analyses of this crust display a trend of enhanced crystallinity as a function of sample age. / An intercomparison of uranium-series and ('14)C ages of 9 phosphorite samples show that both methods agree reasonably well with each other for samples younger than 30 Kyr. A pelletal phosphorite displayed the greatest discrepancy between the two ages, probably due to post-depositional adsorption of thorium and/or carbon onto pellet surfaces. / A radiochemical study of sediments associated with these phosphorites produced ('210)Pb-derived sedimentation rates on the order of a few mm/yr in the vicinity of the most intense upwelling (12(DEGREES)S and 15(DEGREES)S) decreasing by a factor of approximately 100 on the shelf further north (7(DEGREES)S and 10(DEGREES)S). Particle mixing coefficients estimated from excess ('234)Th and excess ('210)Pb profiles were on the order of 10('1) cm('2)/yr near the center of intense upwelling and decreasing to about 10('-1) cm('2)/yr at the 7(DEGREES)S and 10(DEGREES)S sites. Several cores display evidence of mass movement of sediment on a time scale of decades. / Source: Dissertation Abstracts International, Volume: 46-01, Section: B, page: 0090. / Thesis (Ph.D.)--The Florida State University, 1984.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75505 |
| Contributors | KIM, KEE HYUN., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 229 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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