Palaeomagnetism And The Continental Crust

A comprehensive introduction to palaeomagnetism offering a comprehensive treatment of theory and practice. Written in a clear and concise style that will be understandable to undergraduate students and researchers alike, it analyzes the palaeomagnetic record over the whole of geological time, from the Archaean to the Cenozoic, and goes on to examine the impact of past geometries and movements of the continental crust at each geological stage. Topics covered include theory of rock and mineral magnetism, field and laboratory methods, growth and consolidation of the continental crust in Archaean and Proterozoic times, Palaeozoic palaeomagnetism and the formation of Pangaea, the geomagnetic fields, continental movements, and configurations and mantle convection since Archaean times, and more.

One of the most interesting results obtained in the last two decades in the study of crustal deformation has been the recognition that large regions of continental crust undergo rotations about vertical axis during deformation. Proof of such rotations has come through the paleomagnetic studies, which reveal rotations when paleomagnetic declinations within the deforming region arc compared with those found in coeval rocks in the stable regions outside the deforming zone. Such rotations were first described in Oregon then in the North American Cordilleras and in Southern California and were a surprise to everyone. Even in California which, as a result of oil exploration, was among the best geologically explored regions in the world, no one could claim to have predicted that these rotations would be found. Rotations have subsequently been found in other areas of recent continental tectonic activity, notably in the Basin and Range province, New Zealand, the Andes, Greece and Western Turkey, so that they appear as an important feature of continental deformation.

Paleomagnetism is the study of the fossil magnetism in rocks. It has been paramount in determining that the continents have drifted over the surface of the Earth throughout geological time. The fossil magnetism preserved in the ocean floor has demonstrated how continental drift takes place through the process of sea-floor spreading. The methods and techniques used in paleomagnetic studies of continental rocks and of the ocean floor are described and then applied to determining horizontal movements of the Earth's crust over geological time. An up-to-date review of global paleomagnetic data enables 1000 million years of Earth history to be summarized in terms of the drift of the major crustal blocks over the surface of the Earth. The first edition of McElhinny's book was heralded as a "classic and definitive text." It thoroughly discussed the theory of geomagnetism, the geologic reversals of the Earth's magnetic field, and the shifting of magnetic poles. In the 25 years since the highly successful first edition of Palaeomagnetism and Plate Tectonics (Cambridge, 1973) the many advances in the concepts, methodology, and insights into paleomagnetism warrant this new treatment. This completely updated and revised edition of Paleomagnetism: Continents and Oceans will be a welcome resource for a broad audience of earth scientists as well as laypeople curious about magnetism, paleogeography, geology, and plate tectonics. Because the book is intended for a wide audience of geologists, geophysicists, and oceanographers, it balances the mathematical and descriptive aspects of each topic. Details the theory and methodology of rock magnetism, with particular emphasis on intrepreting crustal movements from continental and oceanic measurements Outlines Earth history for the past 1000 million years, from the Rodinia super-continent through its breakup and the formation of Gondwana to the formation and breakup of Pangea and the amalgamation of Eurasia Provides a comprehensive treatment of oceanic paleomagnetism Provides a set of color pateogeographic maps covering the past 250 million years Written by two internationally recognized experts in the field

This volume focuses on Late Mesoproterozoic to early Cambrian events related to Gondwana assembly and break up. The nineteen papers provide a comprehensive review including advanced knowledge and new data from all critical areas of East Gondwana. The recent knowledge of the evolution of East Gondwana, which was regarded as an integral part of the Mesoproterozoic supercontinent Rodinia, is the major theme of the volume, which is reinforced by highlighting this radical and new understanding of the evolution of this region.

Developments in Geotectonics, 10: The Expanding Earth focuses on the principles, methodologies, transformations, and approaches involved in the expanding earth concept. The book first elaborates on the development of the expanding earth concept, necessity for expansion, and the subduction myth. Discussions focus on higher velocity under Benioff zone, seismic attenuation, blue schists and paired metamorphic belts, dispersion of polygons, arctic paradox, and kinematic contrast. The manuscript then ponders on the scale of tectonic phenomena, non-uniformitarianism, tectonic profiles, and paleomagnetism. Concerns cover global paleomagnetism, general summary of the tectonic profile, implosions, fluid pressures, pure shear, crustal extension, simple shear with horizontal axis, geological examples of scale fields, and length-time fields of deformation. The publication explores the cause of expansion, modes of crustal extension, and rotation and asymmetry of the earth, including dynamic asymmetry, precessions, nutations, librations, and wobbles at fixed obliquity, variation of rate of rotation, and categories of submarine ridges. The text is a dependable source of data for researchers wanting to study the concept of expanding earth.