Rate-dependent distributions of Lead-210 and interstitial sulfate in sediments of the Mississippi River Delta /

Bibliographic Details
Main Author:	Shokes, Robert Francis
Other Authors:	Rowe, M. W. (degree committee member.), Sackett, W. M. (degree committee member.), Schink, D. R. (degree committee member.), Scott, R. B. (degree committee member.)
Format:	Thesis Book
Language:	English
Published:	[College Station, Tex.] : Shokes, 1976.
Subjects:	Marine sediments > Louisiana > Mississippi River Delta. Sediments (Geology) > Louisiana > Mississippi River Delta. Oceanography Marine sediments. Sediments (Geology) Louisiana > Mississippi River Delta. Academic theses
Online Access:	Link to ProQuest copy Link to OAKTrust copy

Description
Abstract:	Vertical distributions of excess Pb-210 and interstitial sulfate were measured in a suite of sediment cores from the Mississippi River Delta. Although geochemically independent, both species have kinetically-controlled distributions which can be related to the high and extremely variable sedimentaton rates in this area. Pb-210 activity profiles yield sediment accumulation rates from < .1 gm/cm²-yr on the Delta's contiguous continental slope up to about 1.5 gm/cm²-yr on the shelf approaching the river mouths. Accumulation rates are unobtainable from Pb-210 in the very near-shore areas of the Delta due to increases in the sedimentary coarse size fraction and the rates themselves (> 2 gm/cm²-yr). In the areal extremities of the Delta two cores have Pb-210 profiles which indicate surface sediment mixing in enough detail to model as an "eddy diffusivity" process (GOLDBERG and KOIDE, 1962; GUINASSO and SCHINK, 1975). A method is developed to calculate mixing coefficients for these profiles and, in general, for profiles of any radioisotope decaying at a rate comparable to the rate of mixing. Surface sediment Pb-210 activities vary from 6-15 dpm/gm over most of the Delta's shelf environment but drastically increase at the shelf break to as high as 85 dpm/gm. The lower values closer to shore indicate that the Pb-210 flux to the sediments is controlled by the detrital sediment flux, while the higher values in deeper water indicate substantially increased pelagic contributions of Pb-210. Interstitial sulfate profiles show increased depletion gradients in going from the Delta extremities toward the river outlets..
Item Description:	"Major Subject: Oceanography." Vita.
Physical Description:	x, 123 leaves : illustrations ; 28 cm
Bibliography:	Includes bibliographical references (leaves 92-96).