Sand-silt Petrology and Sediment Dispersal in the Gulf of Alaska

Abstract

ABSTRACT Variations in the heavy and light mineralogy of Pliocene-Quaternary sands and coarse silts in Deep Sea Drilling Project holes in the Gulf of Alaska and eastern Aleutian Trench have been studied. Diagenesis is unimportant. Grain size has a strong influence on both heavy and light mineralogy. Pyroxene and volcanic lithic fragments are concentrated in coarser sands; amphibole and coarser crystalline lithic fragments in finer sands. This variation is partly provenance dependent. The sands are derived from two sources. Coarse pyroxene rich sands, with lithic fragments of volcanic and sedimentary rocks, have been transported by ice rafting from the Alaskan Peninsula and south-central Alaska. An amphibole-altered grain assemblage, associated with a wide range of lithic fragments, including m tamorphic and plutonic rocks, is transported by turbidity currents from south-eastern and south-central Alaska. The ice-rafted material is of lesser importance in Pliocene sediments, but is present in substantial amounts through the Pleistocene.