--> Abstract: Gaspé Belt Subsurface Geometry as Revealed by an Integrated Geophysical and Geological Study, by Nicolas Pinet, Pierre Brouillette, Pierre Keating, Denis-Jacques Dion, and Denis Lavoie; #90039 (2005)

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Gaspé Belt Subsurface Geometry as Revealed by an Integrated Geophysical and Geological Study

Nicolas Pinet1, Pierre Brouillette2, Pierre Keating3, Denis-Jacques Dion4, and Denis Lavoie2
1 Institut National de la Recherche Scientifique, Quebec City, QC
2 Geological Survey of Canada, Québec
3 Geological Survey of Canada, Ottawa
4 Ministère des Ressources Naturelles de la Faune et des Parcs, Québec

Despite field-based studies which contribute to the understanding of the lithological framework and sedimentological evolution of the Gaspé belt in the northern Québec Appalachians, the overall sub-surface geometry remains elusive. A recent gravity survey and a high-resolution aeromagnetic survey cover the area at the basin-scale and clarify the picture. Integration of these data with geologic and recent seismic data, show the along-strike variability and tectonic complexity of the Gaspé belt.

Several northeast trending gravity highs (about 10 mGal above the regional field) located in anticlinal zones, divide the Siluro-Devonian basin in a western and eastern sub-basins with minima of –35 and –28 mGal respectively. This subdivision of the basin is also well expressed in the total magnetic field map as well as in filtered maps (low pass filter, pseudogravity, etc…) where sub-basins show contrasting regional magnetic anomalies. The NE trend dividing the sub-basins includes a complex network of, previously poorly constrained, faults identifiable on maps of the vertical derivative and analytic signal of the magnetic field. This trend extends NE (in Cambro-Ordovician rocks) and SW (in mainly Siluro-Devonian rocks of New-Brunswick).

We use a geologic-based forward modelling approach where potential field data are constrained by geologic and recent seismic data, and integrate a petrophysical database that show slight, but significant, changes between the various basin infill units and the underlying basement. This study reveals unexpected features and shows the importance of integrating geological and geophysical analysis in poorly exposed frontier basins.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005