ridges. Such studies would require the deployment of ocean-bottom seismometers along the ridge.

Earthquake focal mechanisms suggest that rifting associated with the Arctic Mid-Ocean Ridge continues at least 600 to 700 km into the Eurasian continent (Fujita et al., 1990). The North America-Eurasia pole of rotation lies near the rift zone, which is a major plate tectonic boundary. This provides an opportunity to investigate seismically variations in the rupture processes along a rift as a function of spreading rate. Examination of detailed source parameters and of Soviet geologic data along this boundary would provide insight into the mechanics of the rifting process and place constraints on material properties of the crust. These data would also provide an opportunity to study the geometry and kinematics of the junction of this transpressive boundary with the convergent structures of the Pacific Rim. These studies would require geologic fieldwork in addition to deployment of fixed and portable seismic stations in the northeastern USSR and marine geophysical surveys on the adjacent continental shelf.

Pistal compressional effects of Pacific subduction on the overriding plate appears to have extended into the Arctic Ocean Basin in northeastern Alaska, the northern Yukon Territory, and the southeastern Canada Basin (Grantz et al., 1990c). This deformation provides an opportunity to study the distal structural effects of modern subduction in continental crust and the differing mechanical responses of continental and oceanic crust to compression. In contrast, virtually all previous comparisons of continental and oceanic crustal strength have been confined to responses to extension. Both thin-skinned (i.e., a deformed, detached upper plate) and thick-skinned tectonic models have been proposed for this arctic deformation. Although the seismotectonic regime of northeastern Alaska has been studied, the short duration of local seismic network data combined with the low frequency of moderate to large earthquakes in the area provide an inadequate data base. An adequate seismotectonic analysis of this region, including the subsurface structure of the deformation front and its hinterland and the location and character of the stress regime boundary, would require the reinstallation of a local seismograph network.

The Arctic Ocean Basin encompasses a great variety and complexity of submarine landforms that are known only from sparse bathymetric profiles and soundings. Nevertheless, enduring insights into the tectonics, sedimentology, and oceanography of the Arctic Ocean Basin have been derived from our present imperfect knowledge of its morphology. Thus, S.W. Carey (1955) suggested largely on morphologic grounds that the Amerasia Basin is a sphenochasm that opened by rotational rifting of Alaska away from the Canadian Arctic Islands, and morphology led Tuzo Wilson (1963) to suggest that the Lomonosov Ridge was separated from the Barents Shelf by rifting along an arctic extension of the Mid-Atlantic Ridge.

More accurate and detailed knowledge of the bathymetry of the Arctic Ocean Basin would help to understand its geologic structure, sedimentation, and oceanography, especially when supplemented by continuous, overlapping side-scan sonar imagery. Such data would, for example, provide the first definitive information on the character, depth, and morphology of the Arctic Mid-Ocean Ridge and end speculation about the presence and character of associated transform faults. The data would delineate the young extensional structures that disrupt the continental shelf and slope of the Laptev Sea where the Arctic Mid-Ocean Ridge enters the Eurasian continent, the fault scarps that offset the seabed on the Alpha and Mendeleev Ridges, and any of the distal compressional structures that were produced in the eastern Beaufort Sea by Pacific-North American convergence. Detailed bathymetric mapping and imagery would also map the seamounts that occur in the region of anomalously high heat flow in the northwest part of the Canada Basin and Mendeleev Plain, provide insight into the structural significance of the linear ridged topography that lies between the Alpha and Lomonosov Ridges, and map the

Front Matter (R1-R12)

Executive Summary (1-4)

1 Introduction (5-6)

2 Physiography (7-8)

3 Role of the Arctic in Global Solid-Earth Geoscience (9-13)

4 Rationale for Focusing on the Arctic Ocean Basin and Its Margins (14-18)

5 The Next Stage of Arctic Solid-Earth Geoscience Research (19-45)

6 Logistic Realities and Opportunities (46-55)

7 Research Priorities (56-58)

8 Special Concerns (59-60)

References (61-67)