Proceedings of the NATO Advanced Study Institute, Oslo, Norway, July 27-August 5, 1977

This work reviews the mechanism of rifting with a focus on pre-existing tectonic weaknesses in pre-rift and/or basement rocks, i.e., on tectonic inheritance. The passive margins that are studied in this book are the Norwegian Continental Shelf, the Eastern North America and the East and West Indian Continental Margins. The continental rifts that have been analysed are the East African Rift System, the Brazilian Continental Rift Systems and the European Cenozoic Rift System. It states how rifts and passive margins serve as valuable locations for hydrocarbon exploration. Tectonic inheritance/heritage examines the influence of pre-existing/pre-rift elements on the geometry, genesis and propagation of rift-related faults. Such elements include anisotropies in the shallow crustal levels, as well as the rheology of the lithosphere. Inheritance greatly influences the architecture of rifted passive margins including the attitude of faults and geometry of horsts, (half-) grabens, transfer zones etc. Inheritance is also a determining factor in the width of rifts and rift shoulder topography.

Proceedings of the NATO Advanced Study Institute, Oslo, Norway, July 27-August 5, 1977

This multi-author book has been prepared by an international group of geoscientists that have been active in rift research since the late 1960s. In 1984, an informal, grass-roots study group was initiated to compare individual research results and to explore in greater depth the apparent differences and similarities in the interpretations from various rift systems. The group became known as the CREST working group, an acronym of Continental Rifts: Evolution, Structure and Tectonics, which not surprisingly became the title of this book.Continental Rifts: Evolution, Structure, Tectonics presents an overview of the present state of understanding and knowledge of the processes of continental rifting from a multidisciplinary, lithospheric scale perspective. The chapters have been structured on each rift system in approximately the same synoptic sequence, so as to facilitate comparisons of rifts by the reader. The book complements its predecessors by presenting a more unified picture. It succeeds in presenting the status of a representative majority of the continental rift systems that have been at the forefront of recent research. For students and experienced researchers alike, this book will be of significant value in assessing the current state of knowledge and in serving as a framework for future research.

This volume contains papers giving an interdisciplinary review of 12 major rift systems from North and South America, Africa, Europe and Asia. These papers are written by an international group of academic and industrial specialists each of whom is most knowledgeable about the respective rift. The analyzed rifts were selected on the basis of availability of an as-complete-as-possible geological and geophysical data base. Thirteen papers deal with geodynamic processes governing the evolution of rifts.A comprehensive digest of the available stratigraphic, structural, geophysical and petrological data, together with an extensive list of references, is provided for each of the analyzed rift systems. The megatectonic setting and dynamics of evolution of each basin is discussed. Geodynamic models are tested against the record of the analyzed rifts.The question of "active" as against "passive" rifting is addressed. The rifts analyzed range in age from Precambrian to Recent and cover a wide spectrum of megatectonic settings. There is discussion of the evolution of rifts in a plate-tectonic frame. The case histories are followed by discussions addressing the global setting of rifts and geodynamic processes active during the development of rifted basins.

Subduction zones consume oceanic lithosphere and are an indispensible part of plate tectonics. Unlike the oceanic lithosphere production system which can be linked as a nearly continuous, albeit sinuous, strand around the earth, subduction zones are a rather dissociated group and are found in several isolated corners of the world. While plate tectonics can predict that subduction zones are required along certain plate boundaries, it does not stipulate how subduction zones initiate and develop. The preservation of newly created oceanic lithosphere and the propensity for spreading centers to fragment continents leaves a wealth of geological informa tion on the initiation and evolution of spreading. On the other hand, the subject of subduction initiation has little observational basis. To find such observations, we need to look at some muddled tectonic regimes. The Macquarie Ridge complex presents a natural laboratory for studies of subduction initiation. 2. Tectonics of the Macquarie Ridge Complex The Macquarie Ridge complex is a complicated physiographic feature that trends approximately north-south between South Island, New Zealand and the Pacific-Antarctica spreading center. This feature consists of a sequence of troughs and ridges, with Macquarie Island as the only exposed expression. The seismically active Macquarie Ridge complex (hereafter: MRC) is crudely continuous with the Tonga-Kermadec-New Zealand seismic activity. The basic physiographic features and seismicity of the MRC are shown in Figure I. The earthquake epicenters generally cluster about the bathymetric expression of the MRC.

Treatise on Geophysics: Crust and Lithosphere Dynamics, Volume 6, provides a comprehensive review of the state of knowledge on crust and lithosphere dynamics, which is defined as the study of how the outermost layers of the Earth respond to loads that are emplaced on, within, and below it and its implications for plate mechanics and mantle flow. The book begins with a chapter on plate kinematics, which shows how new observations and methodologies have improved the resolution of relative and absolute plate motions. This is followed by studies of plate mechanics, focusing on the long-term rheology of the plates and response of the plates to both relatively short-term and long-term loads. The book also includes chapters that examine the evidence from surface heat flow, borehole breakouts, and magma models for the thermal and mechanical structure of the lithosphere; the deformation of the lithosphere in extensional and compressional settings. The final two chapters deal with the structural styles of faulting in the shallow brittle part of the lithosphere, the brittle-ductile transition, and the shear zone in the ductile part of the lithosphere; and how developments in plate mechanics have impacted our understanding of geological processes. - Self-contained volume starts with an overview of the subject then explores each topic with in depth detail - Extensive reference lists and cross references with other volumes to facilitate further research - Full-color figures and tables support the text and aid in understanding - Content suited for both the expert and non-expert