SEMINAR: GEOTOPICS: Uranium-series Isotopes, Sediment Fluxes, and Climate Change

[Andrew Jo <ajo@rsmas.miami.edu>]

Uranium-series Isotopes, Sediment Fluxes, and Climate Change

Speaker: Dr. Franco Marcantonio 

(Professor, Texas A&M)  

Monday, November 12, 2012

3:30 PM, SLAB Seminar Room, S/A 103

Abstract

Unsupported ²³⁰Th has been proposed as a constant-flux proxy with which to study past sedimentary fluxes. However, a controversy exists over its use in the equatorial Pacific. The proponents of the ²³⁰Th technique maintain that sediment focusing is widespread in the West, Central, and East Equatorial Pacific, and that the flux of laterally advected sediment can surpass the vertically rained flux by up to 2-4 times.  Another viewpoint is that although the ²³⁰Th proxy is a valuable tool, the ²³⁰Th depositional model may have incorrect assumptions associated with it.  Proponents of the latter viewpoint maintain that ²³⁰Th-normalized burial fluxes can underestimate true vertical fluxes due to a) significant lateral transport of ²³⁰Th in the water column without transport of sediment, or b) preferential transport of fine particles during sediment redistribution processes.  The crux of the disagreement amounts to how one explains the larger-than-expected inventories of sedimentary ²³⁰Th along the equator in the Pacific, inventories that are above those expected from a constant water column production rate.  We have conducted a new oceanographic survey in the eastern Equatorial Pacific, in the Panama and Peru Basins, which includes mapping and seismic reflection data acquisition.  In addition, we have collected water and new sediment cores to assess the budget of ²³⁰Th along water flow paths into the Panama Basin, from the tops of the surrounding ridges, and in the Panama Basin proper. We find that the extent of lateral movement of ²³⁰Th in the water column is not enough to explain the large sedimentary ²³⁰Th inventories.  On the other hand, we do find evidence for preferential transport of ²³⁰Th-rich fine particles during hydrodynamic redistribution processes.

 

Hope to see you all there!

Geotopics coordinator,

Mandy Mulcan and Andrew Jo