Crustal magnetic anomaly data from the Orbiting Geophysical Observatories 2,4, and 6 (Pogo) satellites are compared with upward-continued aeromagnetic data between 59-85"N latitude and 220-260"E longitude. Agreement is good, both in anomaly location and in amplitude, giving confidence that it is possible to proceed with the derivation and interpretation of satellite anomaly maps in all parts of the globe. The data contain a magnetic high over the Alpha ridge suggesting continental composition and a magnetic low over the southern Canada basin and northern Canadian Arctic Islands (Sverdrup basin). The low in the Sverdrup basin corresponds to a region of high heat flow, suggesting a shallow Curie isotherm. A ridge of high field, with two distinct peaks in amplitude, is found over the northern portion of the platform deposits and a relative high is located in the central portion of the Churchill Province. No features are present to indicate a magnetic boundary between Slave and Bear Provinces, but a trend change is evident between Slave and Churchill Provinces. South of 60" latitude a broad magnetic low is located over very thick (40-50 km) crust, interpreted to be a region of low magnetization.On compare les donnees recueillies par les satellites OGO 2, 4 et 6 (Pogo) sur les anomalies magnetiques dans la crofite avec un prolongement vers le haut des donnees atromagnetiques situees entre les latitudes 50-85"N et les longitudes 220-26O0E. L'accord est bon a lafois pour la localisation des anomalies et leur amplitude, ce qui permet d'itre optimiste quant a la possibilite de proceder a la confection et a I'interpretation de cartes d'anomalies magnetiques par satellite dans toutes les parties du globe. Les donnees contiennent un pic magnetique sur la crkte Alpha suggerant une composition continentale et une depression magnetique sur le bassin du sud du Canadaet dans les iles de 1'Arctique canadien au nord (le bassin de Sverdrup). Ladepression dans le bassin de Sverdrup correspond a une region de flux thermique eleve ce qui laisse supposer une isotherme de Curie afaible profondeur. Une crite de champ intense avec deux pics distincts dans I'amplitude se retrouve dans la partie nord des depBts de plate-forme et un sommet relatif est localise dans la portion centrale de la province de Churchill. I1 n'y a rien qui indique une limite magnetique entre les provinces de 1'Esclave et de I'Ours, il y a un changement evident entre les provinces de Churchill et de I'Esclave. Au sud de la latitude 60°N, on observe une vaste depression magnetique situee sur une croDte tres epaisse (40-50 km) et qu'on interprkte comme une region de faible aimantation.

Stringent selection criteria using Kp indices, local magnetic activity estimates, and visual intercomparisons, followed by a statistical screening procedure have enabled the production of preliminary scalar and vector component magnetic anomaly maps derived from Magsat data at northern high latitudes, in spite of frequent external field disturbances. Comparisons between the maps and with other magnetic maps and geological information confirm their general validity.

Three-dimensional modeling of the prominent (2000 nT) magnetic anomaly at the center of the Manicouagan structure in Quebec indicates the presence of highly magnetic rocks close to the surface over an area roughly 8 x 12 km. The models depict a tabular body of variable thickness, the shallower parts forming a crude ringlike formation about the center. The depth to the base of the body is not well determined but may be less than 3 km. The direction of magnetization is not unique but is similar to paleomagnetic directions of Triassic age obtained from other rocks within the major structure. A localized, impact-generated magnetization produced in an underlying extensive mafic rock unit, with subsequent uplift, is suggested as the cause of the feature.

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.

A conroured map of vertical magnetic held residuajs (relative to the IGRF) over western Canada and adjacent Arctic regions has been produced by amalgamating new data with those from previous surveys. The measurements were made at altitudes between 3.5 and 5.5 km above sea level. The map shows the form of the magnetic field within the waveband 30 lo 5000 km. A magnetic feature of several thousand LiIomerres wavelength dominates the map. and is probably due in major part to sources in the earth's core. Superimposed on t h i~ are several groups of anomalies which contain wavelengths of the order of a thousand kilometres. The patterns of the rhort wavelen@h anomalies provide a broad view of major structures and indicate several regimes of di~tinctive evolutionary development. Enhancement of viscous magnetization at elevated temperatures may account for the concentration of in~enqe anomalies observed near the western edge of the craton.Une carte de contours residuels du champ magnetique vertical (par rapport au IGRF) du Canada de I'ouest et les regions contigues de I'Arctique a ete fabriquee par I'amalgamation des nouvelles donnees avec celles des leves anterieurs. Les mesures ont t t e faites a des altitudes entre 3.5 et 5.5 km au-dessus du niveau de la mer. La carte montre la forme du champ magnetique pourles longueurs d'onde de 30 b 5000 km. Une anomalie magndtique avec les longueurs d'onde de plusieurs milk kitomitres domine la carte, et probablement est due. en grande partie. i des sources dans le nayau terrestre. Rusieurs groupes d'anomalies de longueur d'onde de I'ordre de rnille kilornttres sont superposis sur I'anomalic dominante. LRs motifs des anomalies des longueurs d'onde courtes donnent une vue d'ensemhle des sauctures rnajeures e t indiquent quclqu~s rkgirnes de diveloppemenl ivolutiannaire distinctif, L'augmentation du mapnetisme visqueux i des ternpkralures Clevies peut expliquer les anomalies prononckes qu'on a observe pres du bord ouest du craton.