Northwest European micropalaeontology and palynology

Northwest European micropalaeontology and palynology

BOOK REVIEWS ogy and petrography of terrestrial materials, planetary structure and plate tectonics (including temporal evolution) and the dynamics of...

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BOOK REVIEWS

ogy and petrography of terrestrial materials, planetary structure and plate tectonics (including temporal evolution) and the dynamics of the oceans and sedimentation. Because of the scope and complexity of these subjects, the treatment is somewhat sketchy and selective. Author's philosophy and preferences guided the drift of the argument and the selection of topics. The last section of the book discusses the modern and past states of life supporting systems, with particular emphasis on air and water. It also deals with the origin and evolution of life, up to and including Homo sapiens. The section describes the dynamics of these systems (e.g. El Nifio, Sahel desertification, geochemical cycles, climate change) and the consequences caused by anthropogenic impact. It is well written and the topics are discussed in considerable detail. This section is a labour of love, dealing with matters that were particularly dear to the author in the last two decades of his life. What is sketched is not a standard recapitulation of a paleontological tree of life and its life forms, but rather an outline of such topics as what constitutes the basis of life, how a cell functions or what is biomineralization. The book closes, fittingly, with the advent of a "big brain" (Homo sapiens) and with his Chernobyl. This is unmistakably Egon's book, tailored to his perception of our planet and its life. It reflects his concern about the dangers arising from human negligence. Although it will not replace Press and Siever and Skinner and Potter as the standard textbooks for introductory geoscience courses, it may serve as an excellent complementary reading and reference book for lower level undergraduate courses and seminars in geology, geography and perhaps biology.

Jfin Veizer, Bochum

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Micropaleontology and palynology D.J. Batten and M.C. Keen (Editors), 1990.

Northwest European Micropalaeontology and Palynology. Ellis Horwood, Ltd. Chichester, U.K. Hardcover. x + 298 pp. Price: £69.95. ISBN 0-745804985. This hardbound volume in the British Micropalaeontological Society Series contains 12 papers on various aspects of the micropalaeontology and palynology of northwest Europe, with emphasis on the North Sea Basin and surrounding areas. The volume is the result of a meeting on 2-3 april 1987 at the Aberdeen University, under the joint auspices of the British Micropalaeontological Society and the Petroleum Group of the Geological Society, London. The main points of ten of the papers in the volume were presented orally at this meeting, the other two were slightly later offerings on the same theme and were thus included in the volume. The papers are arranged in stratigraphic order - from the oldest (Upper Triassic) to modern times, with a concentration in the Jurassic period. Ainsworth et al. (p. 1-44) propose a detailed biostratigraphy of the Upper Triassic and Jurassic of the North Celtic Sea and Fastnet Basins, offshore southwest Ireland. They recognize 25 associations: one in the Upper Triassic, nine in the Lower Jurassic, nine in the Middle Jurassic and six in the Upper Jurassic. All stages can be recognized by microfaunas a n d / o r microfloras (ostracods, foraminifera, dinoflagellate cysts and miospores); however, the precise dating of the Callovian-Oxfordian interval proved to be difficult due to poor microfossil recovery. The Jurassic-Cretaceous boundary can be distinguished throughout both basins; the Triassic-Jurassic boundary is more difficult to locate and is subject of the next paper. Rutherford and Ainsworth (p. 45-69) discuss the micropalaeontological and strati-

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graphical recognition of the Triassic-Jurassic boundary in the same beds in more detail. The difficulty in the recognition lies in the poor recovery of short-ranging palynomorphs and ostracods taxa, and in the absence of lithological breaks coinciding with the system boundary. The analysis of ditch-cutting samples from ten wells has allowed a workable biostratigraphy based on range tops and abundances of selected taxa. Four associations have been identified and have been used to recognize Hettangian and Rhaetian stages. Correlation of the proposed succession with Triassic-Jurassic stages of onshore Britain and Europe is discussed. Guy-Ohlson (p. 70-91) describes the spore and pollen assemblage zonation of Swedish Bajocian and Bathonian sediments. Four zones have been proposed, dated as Early Bajocian, Middle Bajocian, Late BajocianEarly Bathonian and Early Bathonian. Correlation of the zones is made with those in northwest Scania and more in general with other northwest European spore and pollendominated palynofloras. In the fourth chapter, MacLennan and Trewin (p. 92-117) discuss the palaeoenvironments of the Late Bathonian-Mid Callovian in the Inner Moray Firth (N.E. Scotland). They come to the conclusion that combined palynofacies, macropalaeontologicai and sedimentological data provide strong evidence for lagoonal conditions with intermittent marine influence in strata below the Brora Coal at Brora (on the Scottish Coast) and elsewhere but that lagoonal sediments are absent at Beatrice (offshore, in the Moray Firth). The lagoonal embayment, 100 km long and 30 km broad, lays between the Scottish landmass and the Central Ridge of the Moray Firth. Marine waters probably entered from the northeast. An altogether different subject has been described by Nohr-Hansen in his visual and chemical kerogen analyses of the Lower Kimmeridge Clay, Westbury, England (p. 118-134). Visual and chemical kerogen analyses of 50 samples from a clay pit have been

n o o k REVIEWS

described and compared. The kerogen indicates a marine depositional environment. Three kerogen facies and two subfacies have been distinguished on the basis of visual kerogen analysis. Comparison between the chemical pyrolysis data and the visual data shows that the total organic carbon content, hydrocarbon potential and relative amorphous kerogen content fluctuate in a similar way throughout the sequence. The results suggest that it is possible to predict the relative quantity and quality of kerogen from the composition of a palynological slide. Tyson (p. 135-172) discusses Late Jurassic palynofacies trends in Piper and Kimmeridge Clay formations, both UK onshore and northern North Sea. Most of the investigations were based on unoxidized kerogen preparations, and many of the examined facies exhibited low palynomorph contents even after oxidation treatment. A major strength of the quantitative palynofacies approach as used in this paper is the ability to identify significant differences in what are, from the sedimentological viewpoint, indistinguishable mudrocks. Palaeoenvironmental interpretation and distribution of the lower Kimmeridgian foraminifera from the Helmsdale-Brora Outlier, northeast Scotland is the subject of chapter 7 (p. 173-192), a short paper by Gregory. Only 24 species are illustrated and briefly described. Very probably the assemblages have been transported. Originally, two environments were present separated by marine faulting, with the foraminifera inhabiting the upthrown shallow-water block. Owing to seismic activity or climatic changes, the foraminifera were subsequently transported into the downfaulted anoxic basin during the lower Kimmeridgian. The next chapter by Barron (p. 193-213) is discussing the dinoflagellate cyst biostratigraphy and palaeoenvironments of the same region during the Upper Jurassic. Palynomorph assemblages from the Upper Jurassic fault-controlled submarine slope deposits of east Scotland have yielded miospores and

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BOOK REVIEWS

microplankton in varying abundances. An increase in the ratio of mieroplankton to miospores in the upper Kimmeridgian and lower Portlandian is interpreted as indicating increasing distance from the terrestrial source due to fault-controlled widening of the submarine shelf. Dyer and Copestake (p. 214-235) give a review of Late Jurassic to earliest Cretaceous radiolaria and their biostratigraphic potential to petroleum exploration in the North Sea. Their role for age dating, zonation and correlation of the Kimmeridgian Clay Formation of the northern North Sea is discussed. Thirteen radiolarian "events" are recognized. The suggestion is made that the group can provide an important contribution to the stratigraphic evaluation of the formation in offshore exploration wells. A jump in time to the Upper Cretaceous has been made in the microbiostratigraphy of Bornhoim, Denmark by Packer et al. (p. 236-247). The Upper Cretaceous succession of Bornholm has been investigated as part of a larger study of northwest European Cretaceous microbiostratigraphy. The Bornholm succession is all of marine origin and contains rich assemblages of dinoflagellate cysts, benthonic and planktonic foraminifera. The foraminifera have been used for correlation and indicate a mid-Cenomanian to ? late Turonian-early Coniacian hiatus in the succession. The Tertiary is represented in Keen's paper (p. 248-264) on Oligocene ostracod biofacies from onshore areas of the North Sea Basin. Six benthonic ostracod biofacies have been recognized. Biofacies 1 represents a fauna from a coastal complex; biofacies 2 is recognized from shallow coastal waters above wave base, while biofacies 3 is from a more protected lower-energy environment (depth 0-25 m). Biofacies 4, 5 and 6 represent intergrading low-energy muddy environments of successively deeper water (25-75 m; 75-150 m and deeper than 150 m). The last chapter deals with modern times: Palynomorph and palynodebris distributions

in modern British and Irish estuarine sediments by Farr (p. 265-285). Intertidal sediments of modern British and Irish estuaries and tidally influenced embayments have been analyzed to investigate the degree to which their deposits are characterized by their palynomorph assemblages. The observations made provide criteria for distinguishing estuarine from fully marine or freshwater facies in Quaternary and perhaps older sediments. The volume is concluded with an elaborate general and a taxonomic index, making it very easy to find detailed subjects. The volume is relevant to current petroleum exploration activities in the Northwest European region and has a sound basis for comparison with studies on sediments of similar ages and environments of deposition in many other parts of the world. Especially in the field of palaeoenvironmental research this volume is of outstanding quality. J.H.A. van Konijnenburg-van Cittert, Utrecht

Geostatistics

Edward H. Isaaks and R. Mohan Srivastava, 1990. An Introduction to Applied Geostatistics, Oxford University Press, New York, N.Y., 1989, xix + 561 pp., Price: U.S.$35.00 paperback, U.S.$55.00 cloth. ISBN 0-19505013-4. This is a very useful book for those wishing to learn geostatistics. As the authors point out in the introduction, most classical statistical methods make no use of the spatial information in earth science data sets. Geostatistics was developed to remedy this situation. Geostatistical problems first arose in the field of ore reserve valuation where it is necessary to outline future mining blocks. The following example may illustrate this. Suppose that a map showing element concentration values is available for a stratiform ore deposit; only a minority of these values are above cut-off grade which is determined