Analysis of the clay mineralogy of bottom and suspended sediment from Norton Sound and the adjacent Bering Sea shelf and from the Yukon and Kuskokwim Rivers suggests possible source areas, dispersal routes, and current patterns. Source areas include the Yukon and Kuskokwim Rivers, and possibly sites to the south or west.On June 20, 1975, clay mineralogy in the Yukon and Kuskokwim Rivers, respectively, averaged 50 and 52 percent illite, 48 and 48 percent chlorite+kaolinite, and 2 and 1 percent smectite. During the summer months of 1968-70 and 1976-77, the suspended sediment, which indicates short-term sediment supply, averaged 1 percent smectite, and the bottom sediment, which represents longer term deposition, averaged 21 percent smectite. Thus, smectite may be supplied to the northern shelf from a source to the south or west, perhaps the Aleutian Ridge or Chukotka Peninsula region of the U.S.S.R. In addition, the clay mineralogy of the Yukon River may change seasonally or annually; our sampling of the river represents only one moment in time. The detailed distribution of the clay minerals indicates that the dominant current in the Bering shelf is the northflowing Alaska Coastal Water. This current distributes fine-grained sediment northward from the Kuskokwim River into the Chirikov Basin, primarily around the western end of St. Lawrence Island and into Norton Sound, where the sediment is mostly masked by the Yukon River clay-mineral suite. Yukon detritus moves primarily to the northwest and enters the Chukchi Sea through the Bering Strait, but some sediment moves around Norton Sound in a sluggish counterclockwise gyre.Sediment-dispersal routes suggest that pollution in Norton Sound, such as an oil spill, could result in the rapid distribution of pollutants throughout the northern Bering Sea area.Because Norton Sound is shallow, resuspension of bottom sediments by tidal fluctuations and storm waves also could cause rapid distribution of pollutants.
