SCIENCE REVIEW 1987 - Bedford Institute of Oceanography

The refraction data obtained with the
OBS provide important information on
acoustic velocity within the crustal layers
not obtained from reflection work where
the reflectors are deep.
The refraction data are used to confirm
variations in structure on the deep layers of
the crust and upper mantle, providing
additional control for predicting appropriate
geodynamic models. The successful
use of the OBS off the east coast of Canada
has resulted in considerable interest by the
oil and gas industry in other parts of the
world, providing the Atlantic Geoscience
Centre with opportunities for joint projects
in other sedimentary basin regions, and
Seastar Instruments with an opportunity to
market their services in a broader
marketplace.
Potential field surveys (gravity and
magnetic) provide the geophysicist with an
opportunity to map changes in crustal
structure over a broad area, starting from
known geology onshore, well information
or seismic information. Over the ocean
basins, magnetic field data provide us with
a chronology for the formation of the
ocean crust. Airborne magnetic surveys
provide coverage and a precision in data,
not available with conventional shipborne
surveys because of the difficulty in removing
temporal variations in the earth’s
magnetic field which can be confused with
crustal anomalies obtained from shipborne
measurements. Three major aeromagnetic
surveys of the Grand Banks and margins
have been completed as part of the Frontier
Geoscience Program. Together with earlier
work in the region of St. Pierre Bank and
the Laurentian Channel, these surveys
complete the aeromagnetic coverage of the
Grand Banks and margin (Figure 2). They
are a superb data set. They provide
accurate correlation of seafloor spreading
anomalies and thus the timing of formaion
of the ocean basins themselves, and so the
basis for relating oceanic events to the
development of the sedimentary basins.
The data constrain the age and location of
the ocean-continent boundary. They provide
a correlation of geological structures
between Nova Scotia and Newfoundland
across the Cabot Strait. Work is continuing
on the integrated interpretation of this
aeromagnetic data with available seismic
and gravity data across the major offshore
sedimentary basins.
Fig. 3 An example of two of the paleo-environment maps produced for the Labrador Basin Atlas.
Internal Geology of Basins
Study of the internal geology, and generation
and maturation of hydrocarbons in the
sedimentary basins, is carried out primarily
using industry seismic data and well
information available to the Geological
Survey through the offices of Canada Oil
and Gas Lands Administration or the
Offshore Petroleum Boards of Newfoundland
and Nova Scotia. New work has
concentrated on synthesizing data from the
Grand Banks and Scotian Shelf. However,
the first published synthesis which will
appear will be of the Labrador Sea, in the
form of an Atlas in early 1989. This atlas
will consist of some 60 compiled maps and
charts providing a composite of geophysical
and geological knowledge of the
Labrador shelf, margin and ocean basin
(Figure 3). The Atlas will include a
descriptive text for each map describing the
data sources used and the basis for the
interpretations included. A comprehensive
bibliography will be included as a reference
source to the subject content of each map
and the atlas as a whole. Similar atlases for
the Grand Banks and Scotian shelf and
margins will be published late in 1989 with
atlases for Hudson Bay and Gulf of St.
Lawrence scheduled for late in 1990 and
1991 respectively.
A primary emphasis in the basin studies
in all areas of the East Coast has been to
complete the biostratigraphic and lithostratigraphic
analyses of all key wells in the
region, to tie these analyses to the seismic
sections and establish a consistent stratigraphy
for the region. (Stratigraphy is the
study of the nature, distribution and
relations of the stratified rocks of the earth’s
crust. Biosfratigraphy uses the correlation
of fossils and lithostratigraphy uses the
correlation of sedimentary sequences.)
Organic geochemistry and maturation
studies are being carried out on well
samples and integrated with the other
geological information. These studies
provide key information on the nature and
origin of source rocks as well as the
potential total hydrocarbon generation.
Combining this information with studies of
the sedimentary sequences and their
porosity to understand the migration of
fluids in the rock sequences provides key
information on accumulation and preservation
of oil in the basin.
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