- Email: [email protected]
Geology of Greenland
292
reported than horizontal movement, but the horizontal studies present some results of great interest. For example, measurements of extension in Iceland, while in general accord with the spreading rate suggested by marine magnetic anomalies, show that, on a short-time scale, the movement is 'jerky' and irregular, with contraction occurring in some years. Other notable examples of horizontal movement measurements are from the highly-instrumented Garm areas in Central Asia and across the San Andreas fault in California. The vertical movement studies include those by the conventional methods of repeated precise levelling and geomorphology, but also some studies by new techniques. As an example, there is, for the Alps, a comparison between the present rate of uplift given by precise levelling and that indicated by fission-track ages, which are reset when rock temperature drops below 120°C, and which therefore give the date at which an uplifted sample was raised above the 120°C isotherm. The conclusion is that uplift proceeded, 6 - 1 0 million years ago, at a rate similar to that of the present day. Other regional studies include the measurement of in-situ stresses, by the methods described in the general papers. In summary, this is a well-produced, well-organized volume, providing a broad view of the place of recent movement studies in modern tectonics. G.D. Garland, Toronto, Ont.
GEOLOGY OFGREENLAND A.Escher and W.S. Watt, 1976. Geology of Greenland. Geological Survey of Greenland, Copenhagen, 603 pp., DKr. 195.00. Geology of Greenland is a lavishly produced, comprehensive review. Magnificent exposures and explicit geological relationships available in Greenland have attracted geologists from many universities who have worked, with mutual benefit, with those from the Geological Survey. Results of much of this modern work have become dispersed in the journals and this review is valuable in summarising modern work and
in drawing together comprehensive bibliographies of published papers. In over 600 pages of A4 double column setting it presents several chapters each of which summarises an aspect of the regional geology. Thus the subjects range from the Archaean basement complex to the Glaciation and Quaternary. The subject matter for each of these chapters is chronologically and geographically determined, and each is accompanied by its bibliography. Additional chapters are concerned with economic resources and potential and include treatment of economic minerals and coal and petroleum geology; there is a brief review of the occurrence of kimberlites. Fossil flora and fauna are described in stratigraphic order in two separate sections. Comprehensive detail of field relationships, petrography and palaeontology are provided in the running text, but in smaller print. Thus, they are immediately available to the reader who is seeking detail, but can be readily skipped by those who want a more general review. There are abundant photographs, many of which have been taken from sea or air and which bring out geological relationships and structures of spectacular scale and clarity. Line drawings and maps which are numbered sequentially (up to Fig. 473) with the photographs are clearly drawn and lettered in consistent style throughout. Most professional geologists will want to read some or all of this book. For those interested in the evolution of early continental crust there is an admirable summary of the Archaean rocks of the west coast, while Caledonian geologists of Europe and North America may find answers to many of their problems in the Caledonian and earlier rocks described from eastern Greenland. The Garder province and the Tertiary complexes provide a wide range of igneous phenomena while the Tertiary and Mesozoic stratigraphy is critical in the chronology of the evolving Atlantic. The discussions and conclusions set out in the various chapters constantly and refreshingly refer back to detailed field relationships and successions, and the text is replete with locally named stratigraphic divisions meticulously assigned to their correct formal status as formations, mem-
293 bets, etc. Such prolific detail might, in a less well edited presentation, cause confusion to the stranger. However, the nature of the rocks is always readily assessed by reference to tables, maps and photographs. This book is not merely a regional geology in which the scale of the geology matches the scale of the region; it is also a text book of geological phenomena and process. A.L. Harris, Liverpool
DIGITAL
FILTERING
IN G E O P H Y S -
ICS O. Kulhanek, 1976. Introduction to Digital Filtering in Geophysics. Elsevier, Amsterdam, 168 pp., Dfl. 60.00, U.S. $ 23.95. This is one of a number of books which has appeared recently on the applications of communication theory to geophysical data processing. The classical aspects of the subject matter have long been available in electrical engineering texts, but the more modern details, particularly applications to digital signals, are closely tied to geophysics. The book is divided into six chapters. The first two chapters cover fundamental transform relationships and design techniques for digital filters. These chapters are well written and fairly complete. The author is very careful to point out pitfalls, as in the case of the two common definitions of the Z transform. Chapter 2 on design of filters follows electrical engineering practice closely. The same is true for Chapter 3 on low, high, and band-pass filters which is straightforward and useful. Chapters 4, 5, and 6 contain the core of the book, as regards applications to geophysics. Chapter 4 introduces the concepts of correlation filter, matched filters and other optimum filters. The material here is clearly presented, but the treatment cannot be considered complete as the subject matter simply constitutes too large a field. Chapter 5 is a brief and oversimplified discussion of deconvolution filters. In the opinion of the reviewer this chapter should be either expanded or deleted. Finally
Chapter 6 deals with multidimensional filters, particularly velocity filtering systems. This chapter is well written, but the coverage is again cursory. References to both earthquake literature and prospecting literature are given, but the author clearly has large array seismology in mind. There is a paucity of examples throughout the book. The bibliography contains approximately two hundred references up through 1974. Each reference is mentioned in the text and the papers cited are fairly representative of the literature. The book also has a useful, but not exhaustive index. In summary, this book would be a useful introductory text for fourth-year students (senior undergraduates in the U.S. system). It supplies the necessary skills for understanding the current literature. Because of its tight organization and reasonable length it also would serve very well as a text for the practicing geophysicist who whishes to acquaint himself with digital methods. Stanley J. Laster, Tulsa, Okla.
TEKTITES J.A. O'Keefe, 1976. Tektites and Their Origin. Elsevier, Amsterdam, 254 pp., Dfl. 95.00, U.S. $ 36.50.
Tektites and Their Origin by John A. O'Keefe is, to my mind the best book that has been written concerning these interesting and puzzling objects. He goes into the earliest known history of man's dealing with these objects and carries the story through to the present time, reviewing the considerable list of theories that have been advanced to account for their presence, distribution, composition, structure, forms and origin. The text consists of 205 pages, richly illustrated, followed by a bibliography of 26 pages, 646 references. After "Definition and Historical Introduction' (Chapter 1 ), the author discusses in Chapter 2 the tektite distribution illustrated by 12 maps. In Chapter 3 ('The Shapes of Tektites')
reported than horizontal movement, but the horizontal studies present some results of great interest. For example, measurements of extension in Iceland, while in general accord with the spreading rate suggested by marine magnetic anomalies, show that, on a short-time scale, the movement is 'jerky' and irregular, with contraction occurring in some years. Other notable examples of horizontal movement measurements are from the highly-instrumented Garm areas in Central Asia and across the San Andreas fault in California. The vertical movement studies include those by the conventional methods of repeated precise levelling and geomorphology, but also some studies by new techniques. As an example, there is, for the Alps, a comparison between the present rate of uplift given by precise levelling and that indicated by fission-track ages, which are reset when rock temperature drops below 120°C, and which therefore give the date at which an uplifted sample was raised above the 120°C isotherm. The conclusion is that uplift proceeded, 6 - 1 0 million years ago, at a rate similar to that of the present day. Other regional studies include the measurement of in-situ stresses, by the methods described in the general papers. In summary, this is a well-produced, well-organized volume, providing a broad view of the place of recent movement studies in modern tectonics. G.D. Garland, Toronto, Ont.
GEOLOGY OFGREENLAND A.Escher and W.S. Watt, 1976. Geology of Greenland. Geological Survey of Greenland, Copenhagen, 603 pp., DKr. 195.00. Geology of Greenland is a lavishly produced, comprehensive review. Magnificent exposures and explicit geological relationships available in Greenland have attracted geologists from many universities who have worked, with mutual benefit, with those from the Geological Survey. Results of much of this modern work have become dispersed in the journals and this review is valuable in summarising modern work and
in drawing together comprehensive bibliographies of published papers. In over 600 pages of A4 double column setting it presents several chapters each of which summarises an aspect of the regional geology. Thus the subjects range from the Archaean basement complex to the Glaciation and Quaternary. The subject matter for each of these chapters is chronologically and geographically determined, and each is accompanied by its bibliography. Additional chapters are concerned with economic resources and potential and include treatment of economic minerals and coal and petroleum geology; there is a brief review of the occurrence of kimberlites. Fossil flora and fauna are described in stratigraphic order in two separate sections. Comprehensive detail of field relationships, petrography and palaeontology are provided in the running text, but in smaller print. Thus, they are immediately available to the reader who is seeking detail, but can be readily skipped by those who want a more general review. There are abundant photographs, many of which have been taken from sea or air and which bring out geological relationships and structures of spectacular scale and clarity. Line drawings and maps which are numbered sequentially (up to Fig. 473) with the photographs are clearly drawn and lettered in consistent style throughout. Most professional geologists will want to read some or all of this book. For those interested in the evolution of early continental crust there is an admirable summary of the Archaean rocks of the west coast, while Caledonian geologists of Europe and North America may find answers to many of their problems in the Caledonian and earlier rocks described from eastern Greenland. The Garder province and the Tertiary complexes provide a wide range of igneous phenomena while the Tertiary and Mesozoic stratigraphy is critical in the chronology of the evolving Atlantic. The discussions and conclusions set out in the various chapters constantly and refreshingly refer back to detailed field relationships and successions, and the text is replete with locally named stratigraphic divisions meticulously assigned to their correct formal status as formations, mem-
293 bets, etc. Such prolific detail might, in a less well edited presentation, cause confusion to the stranger. However, the nature of the rocks is always readily assessed by reference to tables, maps and photographs. This book is not merely a regional geology in which the scale of the geology matches the scale of the region; it is also a text book of geological phenomena and process. A.L. Harris, Liverpool
DIGITAL
FILTERING
IN G E O P H Y S -
ICS O. Kulhanek, 1976. Introduction to Digital Filtering in Geophysics. Elsevier, Amsterdam, 168 pp., Dfl. 60.00, U.S. $ 23.95. This is one of a number of books which has appeared recently on the applications of communication theory to geophysical data processing. The classical aspects of the subject matter have long been available in electrical engineering texts, but the more modern details, particularly applications to digital signals, are closely tied to geophysics. The book is divided into six chapters. The first two chapters cover fundamental transform relationships and design techniques for digital filters. These chapters are well written and fairly complete. The author is very careful to point out pitfalls, as in the case of the two common definitions of the Z transform. Chapter 2 on design of filters follows electrical engineering practice closely. The same is true for Chapter 3 on low, high, and band-pass filters which is straightforward and useful. Chapters 4, 5, and 6 contain the core of the book, as regards applications to geophysics. Chapter 4 introduces the concepts of correlation filter, matched filters and other optimum filters. The material here is clearly presented, but the treatment cannot be considered complete as the subject matter simply constitutes too large a field. Chapter 5 is a brief and oversimplified discussion of deconvolution filters. In the opinion of the reviewer this chapter should be either expanded or deleted. Finally
Chapter 6 deals with multidimensional filters, particularly velocity filtering systems. This chapter is well written, but the coverage is again cursory. References to both earthquake literature and prospecting literature are given, but the author clearly has large array seismology in mind. There is a paucity of examples throughout the book. The bibliography contains approximately two hundred references up through 1974. Each reference is mentioned in the text and the papers cited are fairly representative of the literature. The book also has a useful, but not exhaustive index. In summary, this book would be a useful introductory text for fourth-year students (senior undergraduates in the U.S. system). It supplies the necessary skills for understanding the current literature. Because of its tight organization and reasonable length it also would serve very well as a text for the practicing geophysicist who whishes to acquaint himself with digital methods. Stanley J. Laster, Tulsa, Okla.
TEKTITES J.A. O'Keefe, 1976. Tektites and Their Origin. Elsevier, Amsterdam, 254 pp., Dfl. 95.00, U.S. $ 36.50.
Tektites and Their Origin by John A. O'Keefe is, to my mind the best book that has been written concerning these interesting and puzzling objects. He goes into the earliest known history of man's dealing with these objects and carries the story through to the present time, reviewing the considerable list of theories that have been advanced to account for their presence, distribution, composition, structure, forms and origin. The text consists of 205 pages, richly illustrated, followed by a bibliography of 26 pages, 646 references. After "Definition and Historical Introduction' (Chapter 1 ), the author discusses in Chapter 2 the tektite distribution illustrated by 12 maps. In Chapter 3 ('The Shapes of Tektites')