Tectonically, the Amerasian Basin of the Arctic Ocean is in many ways the last unknown in the global system. In the Eurasia Basin of the Arctic Ocean, to the east of the Lomonosov Ridge, Karasik (1973) was the first to identify very slow spreading, Cenozoicage magnetic anomalies that connect to the North Atlantic spreading center. In about 1970, Irv Tailleur and Warren Hamilton deduced a rotational opening of the Canada Basin about a pivot point in the Mackenzie Delta based on matching geological histories of the Alaskan Arctic margin and the Canadian Arctic Islands. Aerogeophysical data collected by the Naval Research Laboratory in the 1990s did not find easily correlatable magnetic anomalies in the Canada Basin as hoped. A simple rotational opening of the Amerasian Basin is hampered by the large Chukchi Borderland including the Northwind Ridge northwest of Alaska and the Mendeleev and Alpha ridges to the west of the Chukchi Cap. The two ridges are thought by many to be manifestations of a hot spot that formed either before, during or after the Amerasian Basin opened. If the ridges formed after the basin opened they are not a problem to a rotational opening.

All these features have recently become important not only as tectonic problems but also in a legal framework. The United Nations Convention on Law of the Sea (UNCLOS) Article 76 allowed exceptions to the standard 200 nautical mile exclusive economic zone (EEZ). The Russians filed the first claims to an extended EEZ in the Arctic under the idea that the Lomonosov, Alpha and Mendeleev ridges are all continental and that much of the remainder of the Amerasian and the Eurasian basins is continental. They have even asserted that the Amerasian Basin formed by “oceanization of continental crust” and therefore virtually all of the Arctic Ocean belongs to one of the five bordering, claimant nations.

In summer 2006, scientists at the Institute for Geophysics undertook a seismic refraction experiment to study the crustal structure of the Northwind Ridge, Chukchi Cap and Mendeleev Ridge. Previous cores taken along the Northwind Ridge recovered sediments as old as Cambrian, so at least parts of the Chukchi Borderland are believed to be continental. Aerogravity data indicate that while much of the Chukchi Cap may be continental, substantial parts may be extended continental crust; the 2700 m deep, 15 km wide Chukchi Trough that separates the Chukchi Cap from the Northwind Ridge appears to be some form of rift.

The 2006 season for seismic work along the Alaskan margin turned out to be a difficult one for acquiring the necessary permits. In the recent past very little seismic work has been done but upcoming lease sales have prompted a number of companies to undertake substantial

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seismic reflection surveys in both the Beaufort and Chukchi seas. The Alaska Eskimo Whaling Commission (AEWC) has established itself as the arbitrator for seismic permitting. There is even talk of a seismic noise budget that will set seasonal limits to the total amount of seismic noise allowed in a given area. This presentation will cover these issues as well as the primary focus of the tectonic history of the Arctic Ocean.

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