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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Future Petroleum Provinces of Canada, Their Geology and Potential — Memoir 1, 1973
Pages 473-517

Shelves of Labrador Sea and Baffin Bay, Canada

N.J. McMillan

Abstract

The area of this study extends from 50°N to 78°N along the continental shelf and slope of eastern Canada. The shelf is between 25 and 200 miles (40-320 km.) wide and lies in water ranging in depth from 300 feet (100 m.), in a few places, to approximately 1,000 feet (300 m.). On an average, depth is between 450 and 800 feet (140-240 m.). Some exploration permits from the Canadian Government extend to beyond 6,000 feet (1,800 m.).

The mainland is mostly Precambrian with only a few remnants of Phanerozoic rocks. The land is high, rugged, and indented by fiords. The shelf, in contrast, is fairly smooth and “prairie-like”. The shallow shelf is, in many places, separated from the rugged mainland by a submarine channel marginal to the land. The western limit of coastal plain sediments generally is coincident with this channel. These soft sediments are Jurassic to Recent in age.

During the entire Paleozoic, Greenland and Canada were joined. Marine Ordovician rocks have been found in Labrador and western Greenland and also occur in Baffin, Devon, and Ellesmere Islands. This kind of fragmentary information allows the speculation that Ordovician seas, and others of the Paleozoic Era, covered the area from time to time. Possibly, the axis of the Labrador Sea-Baffin Bay oceanway had been weakened by Permian time and a shallow epicontinental sea spread over it. The Palisade Disturbance of the Late Triassic may have been the time of initial rifting but it is likely that new ocean floor was not formed until much later. A fossil mid-Labrador Sea ridge is present. Sufficient data about the floor of Bafin Bay are not available to clearly delineate such a feature there. The ridge ceased to be active during the Early Tertiary. During the last stages of sea-floor spreading, Orphan Knoll foundered to its present depth of 1,800 m. (5,500 ft.). A JOIDES core shows the section there to be, with breaks, mid-Jurassic to Recent. The sill between the Labrador Sea and Baffin Bay is roughly in the same position as a transform fault extending from Ungava Bay (Hudson Strait) northeastward to Greenland.

Paleozoic rocks under the coastal plain sediments of the northeastern shelf of Newfoundland are of Cambrian to possible Permian age. Those deposited since the Acadian Orogeny (Late Devonian) may be in part marine and relatively unaltered. Northward, it is envisaged that Paleozoic rocks are present as outliers under the coastal plain sediments, which are considered to be Jurassic to Recent in age. Older Mesozoics may contain evaporites, limestones, dolomites, and red beds but, higher in the section, sand and shale probably dominate. These sediments were deposited over a block-faulted terrain — Precambrian in the north and Appalachian Paleozoics south of 54°N. The faulting is assumed to have caused major lateral lithological variations in the rocks as well as creating structures. The climate was warm to warm temperature over the whole area for most of the Mesozoic and Tertiary.

The situation is ideal for entrapment of hydrocarbons. The only outcrops of marine coastal plain sediments are on western Greenland. Petroleum source rocks, bituminous shales and sandstones, as well as methane seeps are common there. The area in eastern Canada may be compared tectonically with the shelves on either side of the South Atlantic where oilfields have been found. Also, the Red Sea today may resemble the Labrador Sea-Baffin Bay oceanway as it was during mid-Jurassic. The only important hydrocarbon shows, or finds, in similar settings in the North Atlantic are at Sable Island (Nova Scotia Shelf) and in the Celtic Sea (south of Ireland).

One hole was drilled to 3,515 feet (1,100 m.) subsea on the Labrador Shelf in 1971. Its proposed ultimate depth is 7,200 feet (2,200 m.).

The main adverse effect to exploration and production is not geological but operational. Icebergs are always abundant and floe-ice partly covers the seas for three months of each year in the south and nine months in Baffin Bay. The problem is not insurmountable and probably will be solved by iceberg-towing during exploration, and emplacement of bottom installations for production.

The volume of sediments approximates 1,000,000 cubic miles under an area of 300,000 square miles. This volume could conservatively contain 30,000 million barrels of liquid hydrocarbons and 180 Tcf. of gas. A field containing 1,000 million barrels of oil, with high deliverability per well, may be economically viable at today’s prices.


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