Mineralogical and geochemical compositions of the eolian dust from the northeast equatorial Pacific and their implications on paleolocation of the Intertropical Convergence Zone

Abstract

[1] Eolian components of a 328-cm-long piston core collected from the northeast equatorial Pacific at 16°12 0 N and 125°59 0 W were investigated for mineral and geochemical compositions in order to constrain the sources of dust and determine the latitudinal position of the Intertropical Convergence Zone (ITCZ) recorded in the core. The eolian components below 250 cm are characterized by smectite-and phillipsite-rich mineral composition, depleted rare earth elements (REEs), and high Eu/Sm ratios, indicative of volcanic-rich composition. These characteristics are found in equatorial and south Pacific surface sediments, of which eolian particles are supplied from Central and South America. In contrast, eolian components above 250 cm are characterized by quartz-and illite-rich mineralogy, and more shale-like REE and trace element compositions, which are common in surface sediments of the central Pacific north of the ITCZ, where eolian particles are sourced from the Asia and North America. The observed changes are attributed to the shifting of its eolian sources from the Central and South America to the China and North America across the hemispheric dust barrier of the ITCZ. This result suggests that smectite-illite transition, a phenomenon that smectite amount increases over illite at a depth, can be used as a tracking tool for the paleolocation of the ITCZ in the northeast and central Pacific. Backtrack path construction of Pacific plate indicates paleolocation of the ITCZ north of 12°N (±2°) prior to late Miocene.

Geochemical approaches to the quantification of dispersed volcanic ash in marine sediment

“…Factor 1 is interpreted as lower crust island arc volcanic arc material and Factor 2 is similar to upper continental crust. T1, T2, and T3 are eolian dust samples classified based on REE patterns, Eu/Sm, and La/Sc ratios from Hyeong et al (2005). URC upper red clay; LRC lower red clay (Fig.…”

Thorium-derived dust fluxes to the tropical Pacific Ocean, 58Ma

“…However, this interpretation is at odds with long-term records of dust provenance based on REE and radiogenic isotope geochemistry (Kyte et al, 1993;Pettke et al, 2002;Hyeong et al, 2005).…”

“…1) indicates two sources of dust to the central Pacific during the early Cenozoicolder terrigenous material interpreted to be from Asia (e Nd = À10) and younger volcanic material thought to originate in the Americas (e Nd > À5) (Kyte et al, 1993;Pettke et al, 2002). The variations in dust provenance are interpreted to reflect migration of the paleo-location of the inter-tropical convergence zone (ITCZ) (Pettke et al, 2002;Hyeong et al, 2005). Enhanced precipitation along the ITCZ forms an effective barrier to dust transport between hemispheres (Rea, 1994).…”

Modern modes of provenance and dispersal of terrigenous sediments in the North Pacific and Bering Sea: implications and perspectives for palaeoenvironmental reconstructions

“…Sediment cores from that region are suitable for the reconstruction of past aeolian dynamics, as has been demonstrated in earlier investigations (e.g. Morley et al 1987;Rea and Leinen 1988;Pettke et al 2000;Hyeong et al 2005).…”