ABSTRACT

Although modern very fine-grained sands and silts are deposited seaward of the delta of the Yukon River, sediment derived from the Yukon today is a more dominant component of bottom sediments in the Chukchi Sea than in the Bering Sea where the river debouches. Between the area of the delta and the Bering Strait entrance to the Chukchi Sea is the Chirikov Basin, which is floored by relict sands and has a pattern of bottom topography leading into the Chuckchi Sea that suggests a former route of the Yukon. Analyses of bottom-sediment texture and mineralogy, however, indicate that the Holocene Yukon sand has not reached the Chirikov Basin. Only after the opening of Shpanberg Strait approximately 11,800 B.P. did Yukon-derived sediment enter the northernmost Bering Sea. From 11,800 to 5,000 B.P. fine-grained sand was carried onto Norton Plain by the recently strengthened coastal current. This sand is now relict. Since 5,000 B.P. the modern Yukon very fine sand and silt have been accumulating near the delta. Future studies may show that the opening of Shpanberg Strait represents a more marked change in the sedimentary history of the adjacent parts of the Bering and Chuckchi seas than does the earlier opening of Bering Strait and the Strait of Anadyr that formed the initial connection of the seas.