Magsat scalar magnetic anomalies at northern high latitudes

Abstract

A new scalar magnetic anomaly map derived from Magsat data at high northern latitudes shows important correlations with major geologic and tectonic features. Positive magnetic anomalies over some high‐grade metamorphic Precambrian terranes contrast with negative anomalies over lower‐grade Precambrian terranes. A positive anomaly is associated with the Aleutian arc‐trench system, a region of active plate convergence. Negative anomaly fields are associated with the Nansen‐Gakkel Ridge, a region of plate accretion in the Arctic Basin, with its extension into the seismically active Cherskiy Mountains in eastern Siberia, and with the Labrador Sea, an extinct spreading center. However, a positive anomaly occurs over Iceland, on the mid‐Atlantic spreading ridge system, and an intense positive anomaly occurs over the Alpha Ridge in the Arctic Basin. The relations among the Magsat orbit, the rotation of the earth, and the movements of the auroral oval have major effects on the spatial distribution of acceptable data and, therefore, on map resolution.

Canadian expedition to study the Alpha Ridge complex: results of the seismic refraction survey

“…Velocities beneath the eastern CESAR south Ridge match those beneath Iceland itself and velocities underlying the central CESAR south ridge resemble those associated with the small volcanic island of Heimaey a little to the south of Iceland. Our interpretation of the Alpha Ridge complex as the product of a mantle plume is supported by (a) its enormous satellite magnetic anomaly, which is similar in many respects to the satellite magnetic anomaly over Iceland (Taylor 1983;Coles 1985;Forsyth et al 1986b), (b) its gravity expression, which has led Weber (1986) to conclude that it may be composed of a large pile of mafic rock, (c) heat flow (Taylor et al 1986) and bathymetric (Weber 1986) data that are consistent with the existence of a hotspot beneath the Amerasian Basin in Cretaceous times and (d) the basement alkalic basaltic rocks that were recovered during the CESAR project (Van Wagoner et al 1986). (5) The Alpha Ridge complex and Iceland may be products of the same mantle plume.…”

An assessment of long-wavelength magnetic anomalies over Canada

“…Positive anomalies over sddimentary basins associated with the failed arms of ancient rifts are coincident in each data set occurring over the Peace Rjver and Lake Superior basins (cf. Arkani-, Hamed et al 1984, 1985. The magnetic low associated with dominantly revejsed oceanic crust in the Labrador Sea (Arkani-Hamed 1990) is also well correlated in the two maps.…”

“…6) due to t ighly magnetized thick oceanic crust is present in both maps (cf. Coles 1985). To the south, lows coincide with the southern Canada Basin to the west and the Sverdrup Basin to the east.…”

The Canadian Geomagnetic Reference Field 1995

“…Careful selection criteria, as described by Coles et al (1982) and Coles (1985), resulted in a set of quiet data that were then variably decimated to produce a relatively uniform areal distribution north of 40°N, with an approximate density of 1 point per (150 km)2. The latter procedure has been described by Haines (1985b).…”