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The AAPG/Datapages Combined Publications Database

Houston Geological Society Bulletin


Houston Geological Society Bulletin, Volume 48, No. 5, January 2006. Pages 43-43.

Abstract: Analysis of Previous HitMagneticNext Hit Anomalies from the South-Central Alberta Foothills, Canada


Christian Abaco

Interpretation of airborne and ground Previous HitmagneticNext Hit data from the south-central Alberta Foothills shows a remarkable correlation between surface geology and residual Previous HitmagneticNext Hit anomalies. The near-surface Previous HitmagneticNext Hit anomalies are not related to the topography and are induced by the Previous HitmagneticNext Hit properties of the rock units underlying the survey area.

Siliciclastic strata dominate the surface geology; they have low Previous HitmagneticNext Hit susceptibility (1025 to 1022 SI) and therefore induce small Previous HitmagneticNext Hit anomalies ranging between 9.8 and 210.8 nano Telsa. Most of the Previous HitmagneticNext Hit anomalies occur in uppermost Cretaceous sandstones (Brazeau and Lower Coalspur strata) and appear to increase in intensity at the contact with the Tertiary Upper Coalspur Formation and with the underlying marine shale of Alberta Group strata. The Albian Beaver Mines sandstone also exhibits higher Previous HitmagneticNext Hit anomalies, contrasting with the underlying lower Blairmore strata and the overlying shale of the Blackstone Formation.

Ground Previous HitmagneticNext Hit data show good correlation with highresolution aeromagnetic (HRAM) anomalies and the Previous HitmagneticNext Hit susceptibilities measured from the surface geology. The depth estimates to the Previous HitmagneticNext Hit sources that generate the Previous HitmagneticNext Hit anomalies indicate values ranging from 20 to 800 meters.

The occurrence of HRAM anomalies in the Beaver Mines, Brazeau and Lower Coalspur strata appears be related to their depositional history and petrographic compositional stages of the Middle and Upper Cretaceous sandstones from the southern and central Alberta Foothills. Cretaceous nonmarine sandstone from the study area contains up to 17% detrital opaque heavy minerals, which consist of magnetite, ilmenite and rare grains of chromite and pyrite.

The magnetization models constructed to reproduce the Previous HitmagneticNext Hit anomalies closely match both ground and airborne observed values. Seismic data interpretation constrains the Previous HitmagneticTop mapping results and suggests that HRAM data may be used in the early stages of exploration to assist in mapping lithology and structure between 2D seismic lines.

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