Foraminiferal distribution patterns in the northern Gulf of Alaska are interpreted as representing seven faunal assemblages. Three sublittoral and three bathyal

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assemblages define depth zones. A seventh faunal assemblage occurs within two sublittoral depth zones where it is restricted to shelly, gravelly mud on submarine banks of truncated Pleistocene rocks. The study is based on 112 stained samples from stations between 15 and 1,350 m depths along transect lines across the shelf and slope between Cape Yakataga and Yakutat, and from within Yakutat Sea Valley and Yakutat Bay. Where data are adequate for depth zonation on live populations, zones determined on live and live-plus-dead populations are approximately the same.

The Yakataga-Yakutat area shelf and slope foraminiferal depth-zonation assemblages correspond in depth to depth-zonation assemblages from other areas of the northeast Pacific margin; the only marked difference is the deeper limit of the inner and middle sublittoral zone transition at 40-50 m, approximating the limit of inner-shelf sandy substrates. This depth limit is the same as that off Washington-Oregon and is significantly deeper than off southern California, reflecting the deeper reach of winter storm waves in the higher latitudes in the northeast Pacific.

Yakutat Sea Valley, a glaciated trough with a floor 100 to 150 m below the shelf, arcs across the shelf toward the mouth of Yakutat Bay. Yakutat Sea Valley is inhabited by outer sublittoral and upper bathyal benthic assemblages associated with abundant planktons. The distribution pattern of the assemblages is related more importantly to factors that vary with depth than to factors that vary with distance from shore or substrate type.

Yakutat Bay is a deep glacial bay with a sill depth of 75 m. The Yakutat Bay fauna developed between depths of 55 and 260 m resembles the open shelf fauna from between 50 and 75 m, suggesting that foraminiferal distribution in the bay is controlled by sill depth.

There are some notable differences in species distribution patterns between faunas in the Gulf of Alaska and those farther south in the northeast Pacific. For example, in the Gulf of Alaska, Epistominella pacifica is an outer sublittoral to bathyal species instead of being exclusively bathyal, and Uvigerina peregrina remains costate instead of changing to hispido-costate with increasing depth in the bathyal zone.

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