Facies Relations at Edge of Early Mid-Devonian Carbonate Shelf, South Nahanni River Area, N.W.T1
Published:January 01, 1973
A broad area of shallow-shelf carbonate beds of the Nahanni Formation (Eifelian-Givetian) borders the Canadian shield in the District of Mackenzie, N.W.T. To the west, in the region of Deadman's Valley in the South Nahanni River area, the carbonate rocks grade into a basinal facies within about 3 mi (5 km).
Examination of the sediments and fauna across this transition permitted correlation between the shelf and the basin and recognition of several faunal communities. On the basis of (1) environmental deductions interpreted for these faunal communities and (2) lithosome geometry and the character of the sediments, it is concluded that the Nahanni sediments were deposited on a broad, slightly restricted, shallow shelf, and that their basinal equivalents were deposited in a marginal cratonic trough. The shelf and trough were separated by a moderately steep shelf edge, or epeiric slope. A shoal was developed near the edge of the shelf.
The boundary between the shelf and the deeper basin during deposition of the Arnica sediments (Eifelian and earlier) was much more abrupt, and was defined by the Manetoe barrier reef.
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Following the discovery of Prudhoe Bay oil field in 1968, much attention was turned to the Arctic in the search for giant hydrocarbon accumulations. The Soviets had already proved giant reserves in their West Siberian Basin, and exploration was moving ahead quickly in the Canadian Arctic. Plans were drawn up for an AAPG Symposium on Arctic Geology and held in February 1971. Papers were selected from the Symposium for this publication and cover seven topical groupings: Regional Arctic Geology of Canada, Regional Arctic Geology of the Nordic Countries, Regional Arctic Geology of the USSR, Regional Arctic Geology of Alaska, Comparisons in the North Atlantic Borders, Evolution of the Arctic Ocean Basin, and Economics of Petroleum Exploration and Production in the Arctic.