A GEOPHYSICAL SURVEY OF THE MENDELEEV RIDGE, PROCESSING STEPS AND INTERPRETATION

In late summer 2005, a geophysical survey was conducted over the Mendeleev Ridge as part of a transarctic crossing. The Mendeleev Ridge is a broad, aseismic ridge that extends from the Siberian Shelf into the central Arctic Ocean. While physiographically it is attached to the Alpha Ridge and is inferred similarly to be an oceanic plateau, it may have had a distinct and separate history. During this survey ~730 km of seismic reflection data was recovered over the ridge along with co-registered gravity data and seismic refraction profiles. The seismic source was two 250 cu in G-guns. The streamer length was limited by ice conditions to 300 meters. Wear and tear caused by towing the streamer through the ice pack eliminated hydrophones, so the number of active channels ranged from 24 to as few as 11. The seismic reflection data requires significant trace editing to eliminate random electrical noise and frequency-wave number filtering to eliminate low velocity noise caused by the streamer traveling through heavy ice. After trace editing the data are stacked and migrated with constant water velocity. For future processing, stacking velocities will serve to create initial models for both gravity modeling and refraction data ray tracing. Derived boundary velocities from ray tracing models will be reapplied to the migration of reflection data and are expected to yield useful information about geologic origin. The origin of the Mendeleev ridge is not well understood due to the limited amount of both geological and geophysical data. The first order objectives of this survey are to determine whether the Mendeleev ridge is an oceanic or continental feature and whether it shares a geologic origin with the Alpha Ridge. Early brute stacked reflection images reveal pervasive extensional faulting of the basement and lower sediment layers, and a continuous 1/4sec sediment layer mantling the ridge, indicative of recent tectonic inactivity. The age of the unconformity underlying this layer should date the end of significant deformation within the Amerasian Basin.