QUANTITATIVE RESOLUTION OF EOLIAN CONTINENTAL CRUSTAL MATERIAL AND VOLCANIC DETRITUS IN NORTH PACIFIC SURFACE SEDIMENT

Proxy records of continental climate and atmospheric circulation provi ded by analyses of eolian continental material extracted from marine s ediment have resulted in significant new information concerning the be havior of these climate systems on various timescales. These studies, however, currently are limited to certain geographic areas because no chemical or physical extraction procedure provides an unambiguous sepa ration of eolian continental crustal material from other contaminants like volcanic detritus. We employ a combined analytical and statistica l procedure in an effort to extract a more refined eolian ''signal'' f rom areas that may be affected by volcanic detritus. Bulk surface sedi ment samples from 33 locations in the North Pacific were treated using a conventional sequential extraction procedure to remove the carbonat e, silica and oxyhydroxide components, and the residue was analyzed by instrumental neutron activation analysis (INAA) for La, Ce, Sm, Eu, Y b, Ly Hf, Sc, and Th. Q-mode factor analysis of these data shows that > 99% of the variance is explained by two end-members, which we interp ret to be continental crustal material and volcanic detritus. Five lea st squares normative analysis models were evaluated to estimate the re lative amount of these end-members in each sample. The continental cru stal component was approximated using a fine-grained fraction of China loess and bulk loess. The volcanic component was approximated using t he compositions of average Kurile-Kamchatka volcanic material, a media n Ocean Drilling Program (ODP) Leg 145 Ash and a median Kurile basalt. The model based on average Kurile-Kamchatka volcanic material and the fine loess fraction gives the most accurate results. Central and east Pacific samples typically contain up to 100% of the eolian continenta l crustal component while samples near Japan, Kamchatka, and the Aleut ians contain a majority of volcanic detritus. However, the highly vari able composition of volcanic material can result in systematic errors up to 25% in samples dominated by volcanic detritus. The geographic di stribution of the compositional end-members is consistent with a conti nental dust source originating in Asia and being diluted by ash from t he volcanic arcs of the Pacific rim. This improved identification and resolution of the eolian continental component realized in this approa ch should permit paleoclimatic reconstructions to be developed from se diments in significant portions of the world that were previously prec luded from analysis because of limitations with chemical or physical e xtraction procedures.