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Author : Paul Kibler Sime
Publisher :
ISBN 13 :
Total Pages : 11 pages
Book Rating : 4.:/5 (92 download)
Download or read book Great Lakes Tectonic Zone--revisited written by Paul Kibler Sime and published by . This book was released on 1993 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Paul Kibler Sime
Publisher :
ISBN 13 :
Total Pages : 20 pages
Book Rating : 4.3/5 (91 download)
Download or read book Great Lakes Tectonic Zone--revisited written by Paul Kibler Sime and published by . This book was released on 1993 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Great Lakes tectonic zone (GLTZ) is a Late Archean crustal boundary (paleosuture) at least 1,200 kilometers long that juxtaposes a Late Archean greenstone-granite terrane (Wawa subprovince of Superior province) on the north and an Early to Late Archean gneiss terrane (Minnesota River Valley subprovince) on the south. Recent mapping of an exposed seg- ment in the Marquette, Michigan, area provides new data on the vergence of the structure. These data necessitate reexami- nation of the COCORP seismic-reflection profiling in central Minnesota, which has been the principal basis for past views on the vergence of the GLTZ. In the Marquette area, the GLTZ is a northwest-striking mylonite zone about 2.3 kilometers wide that is superposed on previously deformed rocks of both Archean terranes. Shear zone walls strike N. 55°-60° W., and foliation in mylonite within the GLTZ strikes (average) N. 70° W. and dips 75° SW. A stretching lineation plunges 42° in a S. 43° E. direction. Hinges of tight to open (sheath?) folds of both Z- and S-symmetries plunge parallel to the lineation. The attitude of the lineation (line of tectonic transport and X finite strain axis), together with asymmetric kinematic indicators, indicates that collision at this locality was oblique; the collision resulted in dextral- thrust shear along the boundary, northwestward vergence, and overriding of the greenstone-granite terrane by the gneiss terrane. In contrast, the seismic-reflection profiling in central Minnesota has been interpreted by several investigators to indicate that the GLTZ is a shallowly north dipping (=30°) structure, which implies southward vergence on a north-dipping subduction zone. We suggest, alternatively, that the shallow- dipping reflectors in the seismic profiles indicate lithologic contacts related to recumbent and gently inclined folds (D1), perhaps enhanced by ductile deformation zones, and that the Morris fault is indeed the GLTZ. The Morris fault strikes about N. 70° E., dips steeply southeastward, is transparent in seismic profiles, appears to be narrow, and coincides with the inferred position of the GLTZ as shown on earlier maps. The oblique collision along northwest-trending segments of the GLTZ would be expected to produce dextral transpression across a large region north of the GLTZ, and may have produced an early nappe-forming event (D1) as well as younger upright folds (D2), and as a later, more brittle event, the numerous dextral faults and conjugate sinistral faults that are widespread in the Wawa and adjacent subprovinces.
Author : Paul Kibler Sime
Publisher :
ISBN 13 :
Total Pages : 11 pages
Book Rating : 4.:/5 (92 download)
Download or read book Great Lakes Tectonic Zone--revisited written by Paul Kibler Sime and published by . This book was released on 1993 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: He Great Lakes tectonic zone (GLTZ) is a Late Archean crustal boundary (paleosuture) at least 1,200 kilometers long that juxtaposes a Late Archean greenstone-granite terrane (Wawa subprovince of Superior province) on the north and an Early to Late Archean gneiss terrane (Minnesota River Valley subprovince) on the south. Recent mapping of an exposed seg- ment in the Marquette, Michigan, area provides new data on the vergence of the structure. These data necessitate reexami- nation of the COCORP seismic-reflection profiling in central Minnesota, which has been the principal basis for past views on the vergence of the GLTZ. In the Marquette area, the GLTZ is a northwest-striking mylonite zone about 2.3 kilometers wide that is superposed on previously deformed rocks of both Archean terranes. Shear zone walls strike N. 55°-60° W., and foliation in mylonite within the GLTZ strikes (average) N. 70° W. and dips 75° SW. A stretching lineation plunges 42° in a S. 43° E. direction. Hinges of tight to open (sheath?) folds of both Z- and S-symmetries plunge parallel to the lineation. The attitude of the lineation (line of tectonic transport and X finite strain axis), together with asymmetric kinematic indicators, indicates that collision at this locality was oblique; the collision resulted in dextral- thrust shear along the boundary, northwestward vergence, and overriding of the greenstone-granite terrane by the gneiss terrane. In contrast, the seismic-reflection profiling in central Minnesota has been interpreted by several investigators to indicate that the GLTZ is a shallowly north dipping (=30°) structure, which implies southward vergence on a north-dipping subduction zone. We suggest, alternatively, that the shallow- dipping reflectors in the seismic profiles indicate lithologic contacts related to recumbent and gently inclined folds (D1), perhaps enhanced by ductile deformation zones, and that the Morris fault is indeed the GLTZ. The Morris fault strikes about N. 70° E., dips steeply southeastward, is transparent in seismic profiles, appears to be narrow, and coincides with the inferred position of the GLTZ as shown on earlier maps. The oblique collision along northwest-trending segments of the GLTZ would be expected to produce dextral transpression across a large region north of the GLTZ, and may have produced an early nappe-forming event (D1) as well as younger upright folds (D2), and as a later, more brittle event, the numerous dextral faults and conjugate sinistral faults that are widespread in the Wawa and adjacent subprovinces.
Author : Paul Kibler Sims
Publisher :
ISBN 13 :
Total Pages : 20 pages
Book Rating : 4.:/5 (359 download)
Download or read book Archean and Early Proterozoic Tectonic Framework of North-Central United States and Adjacent Canada written by Paul Kibler Sims and published by . This book was released on 1995 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 372 pages
Book Rating : 4.:/5 (319 download)
Download or read book U.S. Geological Survey Bulletin written by and published by . This book was released on 1983 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 1592 pages
Book Rating : 4.:/5 (31 download)
Download or read book Monthly Catalogue, United States Public Documents written by and published by . This book was released on 1994 with total page 1592 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monthly Catalog of United States Government Publications written by and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Paul Kibler Sims
Publisher :
ISBN 13 :
Total Pages : 268 pages
Book Rating : 4.3/5 (243 download)
Download or read book U.S. Geological Survey Bulletin written by Paul Kibler Sims and published by . This book was released on 1983 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Early Proterozoic Michigamme Formation of northern Michigan was deposited in the southeastern part of the Animikie basin. The formation conformably overlies the Goodrich Quartzite and comprises three widespread members a lower member of thin-bedded shale, siltstone, and sandstone; the Bijiki Iron-formation Member; and an upper member of tur- biditic graywacke, siltstone, and mudstone and a few local members. The Goodrich Quartzite is interpreted as having been deposited in a tidally influenced shallow marine environ- ment. The lower member of the Michigamme is interpreted as having been deposited in a tidally influenced environment, the iron-formation member as having been deposited below wave base in somewhat deeper water, and the upper member as having been deposited in still deeper water with turbidity currents being a major depositional mechanism. Several lines of evidence including paleocurrents, paleo- geographic setting, and neodymium isotopes suggest that the graywacke of the southern part of the outcrop area was derived from the south (Early Proterozoic Wisconsin magmatic terranes, Archean miniplates, and older Early Proterozoic sedimentary units formed on the continental margin), and that the graywacke in the northern area was derived from an Archean terrane to the north. The tectonic model that best fits the available data is a northward-migrating foreland basin.
Author : Richard W. Ojakangas
Publisher :
ISBN 13 :
Total Pages : 40 pages
Book Rating : 4.3/5 (91 download)
Download or read book Sedimentology and Provenance of the Early Proterozoic Michigamme Formation and Goodrich Quartzite, Northern Michigan written by Richard W. Ojakangas and published by . This book was released on 1994 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Early Proterozoic Michigamme Formation of northern Michigan was deposited in the southeastern part of the Animikie basin. The formation conformably overlies the Goodrich Quartzite and comprises three widespread members a lower member of thin-bedded shale, siltstone, and sandstone; the Bijiki Iron-formation Member; and an upper member of tur- biditic graywacke, siltstone, and mudstone and a few local members. The Goodrich Quartzite is interpreted as having been deposited in a tidally influenced shallow marine environ- ment. The lower member of the Michigamme is interpreted as having been deposited in a tidally influenced environment, the iron-formation member as having been deposited below wave base in somewhat deeper water, and the upper member as having been deposited in still deeper water with turbidity currents being a major depositional mechanism. Several lines of evidence including paleocurrents, paleo- geographic setting, and neodymium isotopes suggest that the graywacke of the southern part of the outcrop area was derived from the south (Early Proterozoic Wisconsin magmatic terranes, Archean miniplates, and older Early Proterozoic sedimentary units formed on the continental margin), and that the graywacke in the northern area was derived from an Archean terrane to the north. The tectonic model that best fits the available data is a northward-migrating foreland basin.
Author : S. R. Hemming
Publisher :
ISBN 13 :
Total Pages : 24 pages
Book Rating : 4.3/5 (91 download)
Download or read book Precambrian Crustal Blocks in Minnesota written by S. R. Hemming and published by . This book was released on 1995 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sm-Nd survey of Precambrian granitic and metasedimentary rocks collected from several geophysically defined blocks in central Minnesota confirms the presence of some fundamental geologic boundaries previously mapped on the basis of structure. The Malmo discontinuity an Early Proterozoic structure separates the Archean Minnesota River Valley ter- ranes from an Early Proterozoic (Penokean magmatic) terrane and the McGrath Gneiss dome of east-central Minnesota North of this boundary, the Penokean fold-and-thrust belt can be divided into fault-bounded terranes that were assembled during the Penokean orogeny. Each terrane within the study area has distinct crust formation ages.
Author : S.B. Lucas
Publisher : Geological Society of America
ISBN 13 : 0813754461
Total Pages : 395 pages
Book Rating : 4.8/5 (137 download)
Download or read book Geology of the Precambrian Superior and Grenville Provinces and Precambian Fossils in North America written by S.B. Lucas and published by Geological Society of America. This book was released on 1998 with total page 395 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains a description of the geology and mineral deposits of the Superior Province of the Canadian Shield, an overview of Grenville Province geology, and a synopsis of Precambrian fossil occurrences in North America. Six large plates include a geological map of Canada, geological map of the Grenville Province, lithotectonic map of the Superior Province, Archean mineral deposit map of the Superior Province, and more.
Author : Geological Survey (U.S.)
Publisher :
ISBN 13 :
Total Pages : 370 pages
Book Rating : 4.:/5 (319 download)
Download or read book New Publications of the U.S. Geological Survey written by Geological Survey (U.S.) and published by . This book was released on 1993 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 64 pages
Book Rating : 4.:/5 (319 download)
Download or read book New Publications of the U.S. Geological Survey written by and published by . This book was released on 1993 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 360 pages
Book Rating : 4.:/5 (319 download)
Download or read book U.S. Geological Survey Professional Paper written by and published by . This book was released on 1984 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Geological Survey (U.S.)
Publisher :
ISBN 13 :
Total Pages : 836 pages
Book Rating : 4.3/5 (91 download)
Download or read book New Publications of the Geological Survey written by Geological Survey (U.S.) and published by . This book was released on 1989 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Martin J. Van Kranendonk
Publisher : Elsevier
ISBN 13 : 0080552471
Total Pages : 1331 pages
Book Rating : 4.0/5 (85 download)
Download or read book Earth's Oldest Rocks written by Martin J. Van Kranendonk and published by Elsevier. This book was released on 2007-10-26 with total page 1331 pages. Available in PDF, EPUB and Kindle. Book excerpt: Earth’s Oldest Rocks provides a comprehensive overview of all aspects of early Earth, from planetary accretion through to development of protocratons with depleted lithospheric keels by c. 3.2 Ga, in a series of papers written by over 50 of the world's leading experts. The book is divided into two chapters on early Earth history, ten chapters on the geology of specific cratons, and two chapters on early Earth analogues and the tectonic framework of early Earth. Individual contributions address topics that range from planetary accretion, a review of Earth meteorites, significance and composition of Hadean protocrust, composition of Archaean mantle and deep crust, all aspects of the geology of Paleoarchean cratons, composition of Archean oceans and hydrothermal environments, evidence and geological settings of early life, early Earth analogues from Venus and New Zealand, and a tectonic framework for early Earth. * Contains comprehensive reviews of areas of ancient lithosphere on Earth, of planetary accretion processes, and of meteorites* Focuses on specific aspects of early Earth, including oldest putative life forms, evidence of the composition of the ancient atmosphere-hydrosphere, and the oldest evidence for subduction-accretion* Presents an overview of geological processes and model of the tectonic framework on early Earth
Author :
Publisher :
ISBN 13 :
Total Pages : 996 pages
Book Rating : 4.F/5 ( download)
Download or read book Petroleum Abstracts written by and published by . This book was released on 1994 with total page 996 pages. Available in PDF, EPUB and Kindle. Book excerpt:
