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Correlation Chart for Precambrian Rocks of the Eastern United States

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Correlation Chart for Precambrian Rocks of the Eastern United States Correlation Chart for Precambrian Rocks of the Eastern United States GEOLOGICAL SURVEY PROFESSIONAL PAPER 1241-E Correlation Chart for Precambrian Rocks of the Eastern United States By D. W. RANKIN, T. W. STERN, JAMES McLELLAND, R. E. ZARTMAN, and A. L. ODOM CORRELATION OF PRECAMBRIAN ROCKS OF THE UNITED STATES AND MEXICO Edited by J. E. HARRISON and Z. E. PETERMAN GEOLOGICAL SURVEY PROFESSIONAL PAPER 1241-E Lithdogy, distribution, correlation, and isotope ages of exposed Precambrian rocks in Eastern United States UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1983 UNITED STATES DEPARTMENT OF THE INTERIOR JAMES G. WATT, Secretary GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging-in Publication Data Main entry under title: Correlation chart for Precambrian rocks of the eastern United States. (Correlation of Precambrian rocks of the United States & Mexico) (Geological Survey professional paper ; 1241-E) Bibliography: p. Supt. of Docs, no.: 119.16:1241-E 1. Geology, Stratigraphic-Precambrian. 2. Stratigraphic correlation United States. I. Rankin, Douglas W. II. Series. III. Series: Geological Survey professional paper ; 1241-E. QE653.C68 551.7T0973 81-607917 ___________________AACR2_________________________________________ For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Page Abstract______________________________ El Geologic chronometric data Continued Introduction____________________________ 1 Western gneiss domes Continued Design of the correlation chart__________________ 2 Kings Mountain belt___________________ E9 Geologic chronometric data____________________ 3 Sauratown Mountains anticlinorium __________ 9 Adirondacks__________________________ 3 Baltimore Gneiss domes_________________ 9 Taconide zone _________________________ 4 Manhattan Prong ____________________ 9 Blue-Green-Long axis ____________________ 4 Central belt.....____._...._.._...._....___ 9 Older Precambrian rocks________________ 4 Charlotte belt.._.__...__.._____...._... 10 Stratified rocks along the Blue-Green-Long axis ___ 6 Bronson Hill-Boundary Mountain anticlinorium___ 10 West limb ._...._..__...__..__..._ _ 6 Merrimack synclinorium ________________ 10 East limb ______________________ 7 Avalonian zone ________________________ 10 Intrusive rocks younger than 1 b.y.___________ 7 Carolina volcanic slate belt _______________ 10 Allochthons of eastern rocks_________________ 7 Southeastern New England _______________ 11 Inner Piedmont and Smith River allochthons _____ 7 Southeastern metamorphic belt ____________ 12 Maryland and northern Virginia Piedmont allochthons_______________________ 8 Mineral resources_________________________ 13 Western gneiss domes ____________________ 8 Acknowledgments _________________________ 13 Pine Mountain belt__________________ 8 References cited __________________________ 13 ILLUSTRATIONS Page PLATE 1. Correlation chart for Precambrian rocks of Eastern United States_________________________________________________ In pocket 2. Map of terranes of Precambrian and selected Cambrian rocks of Eastern United States and adjacent Canada. In pocket TABLE Page TABLE 1. Ages of rocks from the Hudson Highlands . E5 in CORRELATION OF PRECAMBRIAN ROCKS OF THE UNITED STATES AND MEXICO CORRELATION CHART FOR PRECAMBRIAN ROCKS OF THE EASTERN UNITED STATES By D. W. RANKIN, T. W. STERN, JAMES McLELLAND1, R. E. ZARTMAN, and A. L. ODOM2 ABSTRACT pre-Appalachian crystalline basement consists of rocks In the Eastern United States, Precambrian rocks are exposed in the metamorphosed by, or formed during, pre-Appalachian Adirondack massif and in the Appalachian orogen. Rocks dated at orogenic events. In the Adirondack massif and along the 1,300-1,000 m.y. occur as outliers of the Grenville province of Canada. Blue-Green-Long axis, these rocks have isotopic ages These rocks constitute a western basement to the Appalachian orogen and appear in the Adirondack massif, in anticlinoria along the Blue- typically ranging from 1,250 to 1,000 m.y. old. Along the Green-Long axis, and in gneiss domes farther east. The Chain Lakes eastern margin of the exposed Appalachian orogen in massif in Maine, about 1,500 m.y. old, may represent a different block southeastern New England, the crystalline basement is of continental crust. Rifting of the Grenville continental mass, accom­ dated as 750-650 m.y. old. An eastern basement has not panied by anorogenic igneous activity, began about 820 m.y. ago. been identified with certainty south of the Potomac An eastern basement (750-650 m.y. old) has been identified in the Avalonian zone of the Appalachian orogen in southeastern New Eng­ River. land. It is intruded by calc-alkaline granitic rocks roughly 600-640 In places along the western margin of the Appalach­ m.y. old that are nonconformably overlain by Lower and Middle Cam­ ian metamorphic belt (the Blue-Green-Long axis), a brian strata. Extensive Precambrian stratified rocks (mostly younger thick-to-thin sequence of stratified rocks lies uncon- than 610 m.y. but possibly including rocks as old as 725 m.y.) crop out formably on Precambrian crystalline basement and is in the Carolina volcanic slate belt and probably in the higher grade metamorphic belt east of that. These rocks include large volumes of overlain conformably by fossiliferous Lower Cambrian felsic volcanic rocks and probably were deposited on a continental strata. These upper Precambrian and overlying Cam­ crust. brian stratified rocks are interpreted as marking the The eastern terranes were sutured to ancestral North America dur­ ancient eastern continental margin of North America ing the Appalachian orogenic events that closed the lapetus Ocean and recording the breakup of a larger continental mass basin. The location of the suture is uncertain, but it probably lies just east of the gneiss domes containing rocks older than 1 b.y. by rifting and the formation of the lapetus Ocean basin (Rankin, 1975). Prominent bends in the structural INTRODUCTION trends of the Appalachian orogen are thought to be inherited from the irregularities developed at the time Precambrian rocks are exposed in the Adirondack of this late Precambrian continental breakup (Rodgers, Mountains, N.Y., in the core of a large dome flanked by 1975). Because upper Precambrian or Eocambrian rhyo- lower Paleozoic sedimentary rocks. These high-grade lites are restricted to three bends convex toward the metamorphic and intrusive rocks are contiguous with craton, Rankin (1976) suggested that the bends devel­ similar rocks of the Grenville structural province in oped at triple junctions over hot spots. Thomas (1977) Canada. amplified Rodgers' (1975) suggestion that the irregu­ The Eastern United States is dominated by the Paleo­ larities originated as a rift broken by transform faults. zoic Appalachian orogen, the product of collisional He called the bends that were convex toward the craton events between at least two continental masses. Differ­ reentrants, rather than salients, and the bends that ences between the Cambrian fauna on opposite sides of were concave toward the craton promontories, rather the orogen are important evidence for the former exist­ than recesses. ence of an ocean basin called lapetus, between the two As a framework in which to discuss the Precambrian flanks. These Cambrian faunal realms are referred to as rocks, we accept that a rifting event in late Precambrian- Pacific or Ottenelus on the west and as Acado-Baltic or early Paleozoic time created an ocean basin (lapetus) in Paradoxides on the east (Theokritoff, 1968; Wilson, eastern North America. The ocean basin probably devel­ 1969). Oceanic crust is preserved as ophiolites within oped to the east of a series of early ensialic rifts, much the lower Paleozoic rocks. as the present Atlantic opened to the east of the earlier Rocks stratigraphically beneath Lower Cambrian ensialic Late Triassic-Early Jurassic rifts still exposed strata are recognizable on each flank of the orogen. A in eastern North America. The Appalachian orogen 1 Colgate University, Hamilton, NY 13346 was formed by the closing of the lapetus Ocean basin 2 Florida State University, Tallahassee, FL 32306 and the subsequent continent-continent collision. The El E2 CORRELATION OF PRECAMBRIAN ROCKS OF THE UNITED STATES AND MEXICO continental mass that collided with the North American rane older than the Carolina volcanic slate belt; that is, craton, however, may not have been the same con­ an eastern basement. tinental mass that separated during the formation of Finally, the Coastal Plain of southwesternmost Geor­ the lapetus Ocean. The location of the suture between gia and northern Florida is underlain by nonfolded and the continental masses is one of the unresolved prob­ nonmetamorphosed clastic rocks containing fossils lems of Appalachian geology. The Adirondack massif is ranging in age from Early Ordovician to probably Mid­ entirely west of the area affected by Appalachian (Pale­ dle Devonian (Rodgers, 1970). These rocks have not been ozoic) metamorphic events. Potassium-argon mica ages deformed by Appalachian orogenic events, and they from the Adirondacks reflect uplift and cooling follow­ contain a pelecypod fauna closely resembling that of ing metamorphic events > 1 b.y. ago. central Bohemia and Poland but also with similarities The metamorphic and deformational history of the to that of Nova Scotia, North Africa, and South Amer­ Appalachian orogen is complex, commonly polyphase. ica (Pojeta and others, 1976).
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