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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Structural Geometry of the
Taconic- Acadian Thrust System in the
Cambro-Ordovician of Western
Newfoundland
By
PanCanadian Petroleum
Limited, Calgary, Alberta, Canada
The Humber zone is the most external zone of the Appalachian orogenic belt in Western Newfoundland and records multiphase deformation of the Cambro-Ordovician passive margin and Ordovician to Devonian foreland basins by Taconic, Salinic and Acadian orogenic events.
The recent phase of exploration well
drilling in western Newfoundland has provided
new evidence for structural and
stratigraphic models of the region. The first
well drilled supported the hypothesis that
the Round Head thrust had an earlier extensional
history prior to the Acadian compressional
inversion that created the present-day structural high of the Port au Port
peninsula. The Port au Port #1 well penetrates
the footwall of the Round Head
thrust which has a significantly thinner
Middle Ordovician section than in the
hanging wall of the fault
. The structure
tested by the well is a small anticline
caused by a footwall shortcut
fault
from the
Round Head thrust. The second well was
drilled some 40 km to the NE to test the
triangle zone discussed by previous workers
in the area. This well demonstrates that
the frontal monocline at the western edge
of the triangle zone is elevated by a stack
of imbricate thrusts composed of rocks of
the Taconic allochthon. The age and facies
of these imbricates suggest that they may
have originated from the along strike
equivalents of the Cow Head group which
is exposed at outcrop some 130 km to the
NE. Some of the elevation of the triangle
zone is also due to inversion of basement
involved extensional faults which have
uplifted the Cambro-Ordovician carbonate
platform. The third well was drilled in
1996 to test the up-plunge portion of the
structure penetrated by the first well.
The structural model developed in the
Port au Port area with the aid of these
wells has been extended throughout the
Humber zone in Western Newfoundland.
The changes in structural style can be
illustrated by a suite of regional cross-sections
that show that prospective trap
geometries are only developed in the
southern part of the trend.
The reservoir model developed from
these wells invokes exposure and karsting
of platform carbonates on extensional fault
footwalls during the Middle Ordovician.
These structurally high
fault
footwalls
became the foci of the dolomitizing and
mineralizing fluids that utilized the major
faults as fluid conduits.
End_Pages 9 and 11---------------