Origin of Continental Margin
Published:January 01, 1972
To understand the Mesozoic-Cenozoic development of the North American continental margin, it is of prime importance to gain a knowledge of the tectonic framework of the continent. A review of this framework provides the foundation for discussion of the evolution of the continental margin. The northern part of the North American continent is dominated by the Canadian shield (Fig. 321), a tectonic province consisting mainly of metamorphic and plutonic infracrustal rocks. These rocks are divided into several fold belts that are the products of the Grenville orogeny (880–1,000 m.y.; Grenville fold belt), the Hudsonian orogeny (1,640–1,820 m.y.; Churchill, Southern, Bear, and Nain fold belts), and the Kenoran orogeny (2,390–2,600 m.y.; Superior, Slave, and Nain fold belts; P. B. King, 1969b). On top of these fold belts are less disturbed postorogenic sedimentary and volcanic (Fig. 321) Precambrian platform deposits. This Precambrian terrane was depressed toward the south to form the foundation for Paleozoic and younger platform deposits.
East of the platform tectonic province is the Appalachian system that was deformed during the Paleozoic, with major deformations occurring during the Taconic (Ordovician) and Acadian (Devonian) revolutions and the Allegheny (Permian) disturbance. The deformed belt consists of a narrow miogeosyncline in the northwest composed of folded and thrust-faulted sedimentary rocks. Southeast of the miogeosyncline is a broad eugeosyncline of de-formed and metamorphosed sequences of sedi-mentary and volcanic rocks intruded by plutonic masses. Between these two geosynclines are long strips of Precambrian rocks that are uplifted parts of the basement
Figures & Tables
Western North Atlantic Ocean: Topography, Rocks, Structure, Water, Life, and Sediments
The Atlantic coast of North America was the first part of the New World to be described by maps and texts; its exploration begain with the Vikings nearly a thousand years ago. Since then, the pace of exploration of both land and ocean floor has increased steadily. The concern during the 1960s was with details of geology, water, and life that largely were bypassed during earlier stages of discovery and exploration. The accumulation of knowledge was expressed approximately by the publication of charts, articles, and tabulations of data. This publication is concerned with the Atlantic continental margin of the United States, and it necessarily includes some information about the adjacent land and ocean areas. It is a summary of the existing knowledge of the ocean floor, the water above it, and the life that is in the water or at the bottom. The chapters contained within the publication fall into seven categories: Physiography, Rocks, Structure, Water, Life, Sediments, and Origin of Continental Margin.