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Complications in the Canada Basin, Aerogeophysical Anomalies Lawrence A. Lawver 1 (+1-512-471-0433; lawver@ig.utexas.edu) John M Brozena 2 (+1-202-404-4346; john@qur.nrl.navy.mil) L. C. Kovacs 2 (+1-202-767-3013; skip@qur.nrl.navy.mil) Vicki Childers 2 (+1-202-404-1110; vicki@qur.nrl.navy.mil) 1L.A. Lawver, UT Institute for Geophysics 4412 Spicewood Sprgs Rd. #600, Austin, TX 78759 2J.M. Brozena, L.C. Kovacs and V. Childers, Naval Research Laboratory, Washington, DC 20375 Aeromagnetic data collected in the Amerasian Basin easily divides the basin into two regions. In the Canada Basin south of about $78\deg$N, the data are subdued with most anomalies less than 100 nT. North of $78\deg$N, and along Northwind Escarpment and west of Chukchi Plateau, the magnetic anomalies are much larger and have a range of well over 800 nT, peak to trough. An initial explanation might invoke the nearby Alpha and Mendeleev ridges, presumed hotspot traces, but the Alpha Ridge does not have a bathymetric signature in the eastern part of the Canada Basin south of $82\deg$N, almost 400 km distant, The greater amplitude of the magnetic anomalies to the west of Chukchi Plateau may in fact result from proximity to the Mendeleev Ridge and Arlis Plateau. A close inspection of the gravity data with the magnetics suggests that there may be a correlation between circular gravity highs and the large magnetic anomalies. The highest [$>$300 nT] and lowest [$<$-300 nT] magnetic anomalies are as much as 40 to 60 km wide and up to 200 km long. These amorphous magnetic anomalies do not resemble seafloor spreading generated anomalies but are suggestive of magnetic anomlies observed on land where large outpourings of magma can be traced to a single vent or line of vents. On land there is often a volcanic edifice. The gravity data do not show as great a disparity north and south of $78\deg$N. The overall amplitude of the gravity anomalies are not dissimilar but the gravity to the south is relatively smooth and clearly shows the abandoned spreading center in the southern Canada Basin. North of $78\deg$N, the gravity contains more bulls-eye features implying targets with wavelengths less than 30 km. We hope to correlate the suggested volcanic centers with bathymetric anomalies observed with the SCAMP system. The data used in this study consists of approximately 120,000 line km of aerogravity and aeromagnetic data collected by NRL in the Amerasian Basin, with some coverage of the nearby Siberian continental shelf. Data tracks were spaced approximately 12 nm (20 km) apart with cross track spacing of 50 nm (90 km). Nominal survey altitude and speed was 1500 ft and 250 kts, respectively, with data collected every 0.5 seconds (125 m). Navigation utilized long-baseline interferometric GPS. |
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