A GEOPHYSICAL
SURVEY OF THE MENDELEEV RIDGE, PROCESSING STEPS AND
INTERPRETATION
DOVE, Dayton, Dept. of Geology and Geohysics, University of Alaska
Fairbanks, P.O. Box 755780, Fairbanks, AK 99775, [email protected], COAKLEY,
Bernard J., Geophysical
Institute, Univ of Alaska Fairbanks, Fairbanks, AK, and
HOPPER, John, Department of Geology and Geophysics, Texas A&M University,
College Station, TX 77843
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.