Precambrian Crustal Blocks in Minnesota
Precambrian Crustal Blocks in Minnesota

Author: S. R. Hemming

Publisher:

Published: 1995

Total Pages: 24

ISBN-13:

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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.

U.S. Geological Survey Bulletin
U.S. Geological Survey Bulletin

Author: Paul Kibler Sims

Publisher:

Published: 1983

Total Pages: 268

ISBN-13:

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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.

Great Lakes Rocks
Great Lakes Rocks

Author: Stephen E Kesler

Publisher: University of MICHIGAN REGIONAL

Published: 2019-05-01

Total Pages: 369

ISBN-13: 0472053809

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The geologic story of the Great Lakes region is one of the most remarkable of any place on Earth. Great Lakes Rocks takes readers on this fascinating journey through geologic history, beginning with an investigation of the surface features—the hills and valleys, waterfalls and caves, and the Great Lakes themselves—that we encounter on a daily basis. From there the book digs deeper into the past, and readers learn about the amazing techniques geologists have used to reconstruct the events that shaped this region millions and even billions of years before humans set foot on Earth. Throughout, the book gives special attention to the link between the region’s geology and its modern history, including the impacts of geology on settlement patterns as well as the development of industries and the present-day economy. Other discussed topics include natural hazards that are geologic in nature, including earthquakes, floods, landslides, and coastal erosion, as well as information on rocks, minerals, and ancient life seen in fossils. Written for nonspecialist readers, this book provides a detailed but easy-to-follow introduction to the geology of the Great Lakes region, and it is an ideal fit for introductory geology courses, including those aimed at nonscience majors.

Precambrian Geology of China
Precambrian Geology of China

Author: Mingguo Zhai

Publisher: Springer

Published: 2015-08-11

Total Pages: 389

ISBN-13: 3662478854

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This book is the first contribution to the overview of Precambrian geology of China. It covers Precambrian geology of the North China Craton, the South China Craton and the Tarim Craton, as well as other smaller blocks in the Chinese orogenic belts. It provides systematic concepts of the Chinese paleo-continents and incorporates the most up-to-date achievements. Edited by many of the active researchers working at the forefront of the related fields, it contributes greatly to the international Precambrian geology community and would be of interest to geoscientists working in the research field of geology of China and Precambrian geodynamics.