Basement Correlation Across the North Atlantic

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T.U. Berlin's longstanding research in Egypt are concise and informative. Hantar's chapter on the North Western Desert, Jenkins' overview of Sinai and Harms and Wray's summary of the Nile Delta are also very useful. Part 4: "Discussion" has highpoints regarding the Mesozoic and Cenozoic evolution of Egypt, which is understandable because so much of the region is covered by sediments of this age. Said's contribution "Cretaceous paleogeographic maps" is an important first step towards reconstructing the ancient landscape of the region. Part 5: "Economic Mineral Deposits" is surprisingly good - usually I find sections on economic geology to be sleep-inducing. Hussein and El Sharkawi's summary of "Mineral Deposits" is comprehensive, with plenty of good maps to aid the uninitiated. E1 Ayouty's summary of "Petroleum Geology" should be a valued overview to those in the hydrocarbon industry. Thorweihe's chapter on the "Nubian Aquifer system" is fascinating - it should be required reading for leaders in the region intent on pumping rivers of water from this fossil aqmfer. Part 6: "Paleontological Notes" contains several very interesting contributions: "'Fossil flora", "Vertebrate Paleontology" and "Paleozoic trace fossils". I had no idea that trilobites could make so many different kinds of scratch marks. Summarizing the book's weaknesses: Balkema should hire a careful proofreader - I was surprised to find about one typographic error per page. Not enough was said about rifting in the Red Sea - this could have easily warranted a chapter of its own. I was left in suspense regarding when the passive margin on the south side of Tethys was formed, and what effect this had on the Mesozoic evolution of the region. Some effort to tie the geology of western desert into the geology of Libya would have been appropriate - indeed, a chart of regional correlations for N. Africa and S.W. Asia would be a wonderful thing. The weakness of the discussion regarding the Precambrian has already been recounted, but it is worth adding that if

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Hume came back from the dead, he would be very displeased to see that so little attention was now being paid to a subject that he held so dear. And the Quaternary of Egypt should be expanded - Said's summary of the evolution of the Nile was fascinating. In this time of global change, the Quaternary geology of Egypt becomes a natural focus. One suspects that future authors or editors of Geology of Egypt will devote a quarter of the book or more to this subject. In conclusion, one must admit the difficulty of comprehensively covering so many aspects of the geology of a region where so much research continues in ever-specializing subdisciplines. It is enough to note that very few of the countries of S.W. Asia or Africa have anything that compares with the tome offered by Said and his host. They are to be congratulated for making the present credible effort, and colleagues in the surrounding regions as well as future Egyptian geologists are challenged to match their determination. Libraries and scientists with interests in any part of the region should invest in this book. Robert J. Stern, Dallas, TX

General Geology J.P. Lefort. Basement Correlation Across the North Atlantic. Springer-Verlag, Heidelberg, F.R.G., 1989. Hardcover, xi + 148 pp. Price D.M. 88.--, ISBN 3-540-18794-4. This is a book so rich in new information and full of background material, and yet so complex, perhaps even convoluted in scope, that it is extremely difficult for me to do justice to it in a short review. Despite my familiarity with the continental elements, and their surface geology, that make up the Paleozoic and older terranes on either side of the North Atlantic and notwithstanding my thorough reading (twice) of the entire book, I am left with a bewildering array of impressions and a sinking feeling that I have understood Jean Pierre Lefort's arguments but cannot

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summarize them succinctly. This statement, made in admiration of his vast knowledge, novel insights and tremendous research effort that form the basis of the well-written text and its extensive 77 illustrations, reveals at the same time the book's drawbacks. As the author himself states in his foreword: "One of the most difficult aspects of the present work is the need to include discussion of all scientific disciplines likely to provide information on the nature of the concealed basement." Indeed, the book is full of geophysical and geological data and information from every imaginable discipline that may have revealed something about continental basement (whether concealed or not), ~ts ages, its structure and its history. The book is organized into eight chapters, the first of which is entitled " T h e search for concealed continental basement beneath the margins and coastal basins of the North Atlantic: Methods and motives." Th,s heavy title - nothing so simple as "Introduction" plunges the reader right away in the thick of the problems, issues, uncertainties and controversies. The title of the last chapter is simpler ("Tectonic mechanism contributing to the structure of Pangaea"), and while appropriate as a concluding chapter, it comes, in my opinion, too late. As I was reading along, I was waiting with increasing impatience for an integrating analysis, a larger framework or context. In between the first and last chapters, an apparently systematic division is made for the partly submerged, but spatially and temporally definable basement complexes: The North American basement as the former western margin of Iapetus; the CaledonianAppalachian mobile belt; Avalon, Iberia and Armorica at the former southern margins of Iapetus; Meguma and the Ligerian (Acadian) features of southern Brittany and Iberia; the basement of Africa and that between Africa and North America; and the Hercynian-A1leghanian mobile belt. However logical this division appears at first glance, it becomes readily apparent that every topic overlaps

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with the preceding and later ones, and that each area plays a role more than once in the successive tectonic events that occurred in the North Atlantic domain. All major orogenies in the region are reviewed: Grenvillian, Pan A f r i c a n / C a d o m i a n / A v a l o n i a n , Taconian, Caledonian, Acad,an, Hercynian/Alleghenian, and these overlap in time just as much as the spatial definitions happen to intertwine in wide and fuzzy boundary zones. As noted by Jean Pierre: "Even though small-scale correlations remain incomplete, it is nevertheless possible to go beyond regional studies in order to begin answering some important questions on why Caledonian effects are detectable within the Hercynian domain and why Hercynian deformation is locally overprinted onto Taconian or Acadian structures." But what a daunting task it is to unravel these effects rapidly becomes clear as one reads along. And yet, a demonstration of the convolutedness of the temporal and spatial definition is precisely one of Lefort's goals with this study. I was most impressed by the extensive maps, many occurring as two-page foldouts. They are detailed, well-explained with good legends and well integrated with the text discussions. The text itself has benefitted from the editorial talents of M.S.N. Carpenter, and reads well. Another most valuable asset of the book is its multihngual and extensive bibliography. I cannot think of any important references that appear to have been missed. It is clear then that this book is a "strong" piece of "carpentry," a complexly constructed monument, and a text not for the faint-of-heart. It is a research monograph and a rich resource. No one investigating the pre-Pangea tectonics of Iapetus, similar Paleozoic oceans, and the formerly adjacent continental pieces, will be able to resist the purchase of this book, although impoverished graduate students should place their hope on finding it in a nearby institutional research library. Because I've worked on some of the book's subjects, I have considerable appreciation for this book; perhaps if I

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BOOK REVIEWS

read it at least three more times, I will be able to make optimum use of this valuable resource in my own work. For others who are not directly involved in basement studies, this book may be skipped. Rob Van der Voo. Ann Arbor, MI Natural Hazards

E. Bryant. N a t u r a l Hazards. Cambridge University Press, 1991 xviii+ 294 pp. Price: £40.00/U.S.$79.50 (Hardcover) ISBN 0-52137295-x £14.95 (US$29.95 (Paperback) The book by Bryant concerns an extremely timely topic: with the exponential increase of the human population, more and more marginal areas are being settled that are threatened by all kinds of natural hazards. The latter are of climatic and geological origin; often (as e.g. in landslides) there is an interconnection between the two. Thus, the book is divided from the start into two sections, viz. a climatic section and a geological section. A p p e n d e d to this is a third section on socml impacts, inasmuch as the severity of a particular disaster is often conditioned not only by the actual natural event, but also by the human response to it. In the main part of the book (on the nature of hazards), the individual types of hazards are first described in appropriate chapters in general terms, then several specific examples are given and finally probabilistic/predictive possibilities are mentioned. In this fashion, large scale storms, strong winds (tornadoes), oceanographic problems (sea ice, beach erosion, eustatic rises), droughts/floods and natural fires are discussed in the "climatic" part, and earthquakes, volcanic eruptions (and attendant effects like lahars) and land instabilities are described in the "geologic" part. The "social" part of the book describes the response of people and authorities first to warnings, and second to the aftermath of

an event. The lack of foresight described is simply appalling ("go home and be calm"); after the event, people are usually left to their own devices, at least at first, rising with incredible stamina to the occasion. However, resulting emotional problems are severe. Quaint at this juncture is the repeated reference to the responses of "Marxist society"; these sections must have been written before the recent demise of the "socialist" countries. As the author writes himself in his "Introduction" (p. 8), the book has been written "assuming little knowledge in Earth Science at the university level". This reviewer can also testify that the book does not go deeply into physical science or probability theory: nobody will be able to glean a true understanding of the physics of natural disasters, nor will he be able to construct risk-charts or hydrographs from available data sets, based on information given in the book. Thus, the book is evidently not intended for professionals, but rather for interested laymen who have a general education corresponding to a European "matura" or an American "high school matriculation". It may also be useful for first year university students who take the study of natural hazards as a minor. In effect, for such audiences the book makes easy and fascinating reading. Thus, the whole course of the current (February 1992) "El Nifio" conditions (warming of the coast of Peril, flooding in California, mild winter around the North Atlantic margin) follows exactly the scenario described in the book. One could only hope that politicians and public authorities would take the warnings contained in it to heart. The blanket statement that "natural hazards are predictable" (p. 273), though, is certainly overoptimistic. The general risk level is predictable, and s o m e hazards can be predicted - but nobody could have predicted the Tang Shan earthquake in 1976. The present state of the art is such that in many cases, there are precursors that unequivocally predict an impending disaster (such as an earthquake) - but that the