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Ancient Sedimentary Environments
Sedimentary Geology - Elsevier Publishing Company, Amsterdam - Printed in The Netherlands
Book Reviews Ancient Sedimentary Environments. R. C. SELLEY. Chapman and Hall, London,
1971, 237 pp., £ 2.75 The expressed purpose of R. C. Selley in writing Ancient Sedimentary Environments was to provide an introductory survey that shows how the depositional environments of sedimentary rocks can be recognized. He has succeeded admirably in achieving this and at the same time has provided a work that constitutes a small but useful reference for advanced students of stratigraphic analysis. The introductory chapter of the book presents a general discussion of the classification of sedimentary environments and an evaluation of the methods that can be used to identify their counterparts in the stratigraphic record. The remaining chapters utilize a case history approach in which an ancient rock association is first described and then analyzed in terms of its most probable environment of origin based on current knowledge of modern sedimentary environments. Each case history is accompanied by a general discussion of the problems of identifying the particular sedimentary environment in question and by a brief review of its economic significance. Chapter 2, "River Deposits", begins with an introduction to the morphology of modern high-sinuosity meandering channels and low-sinuosity braided channel complexes. The bulk of the chapter, however, is devoted to a thorough description and environmental interpretation of the Torridon G r o u p (Precambrian) of northwest Scotland and the Devonian non-marine strata of South Wales and the Catskill Mountains, U.S.A. Selley's intimate familiarity with the Torridon G r o u p as a result of his own research shows clearly in his concise treatment of this ancient braided stream system. His account of the Catskill and South Wales fining-upwards cycles outlines the characteristics of rocks that evolved on a coastal plain built by high-sinuosity meandering rivers. The section on economic aspects of ancient alluvial deposits touches briefly on oil and gas deposits, the gold deposits of Witwatersrand in South Africa and the carnotite ores of the Colorado Plateau. U.S.A. A useful approach to reference citation appears for the first time at the end of Chapter 2 where Selley separates the citations into groups with headings such as "The description of the Torridonian sediments was based o n . . . ". "The account of the Devonian d e p o s i t s . . . " , and "Other references quoted in this chapter w e r e . . . ". This format, which is used in l~ke manner at the close of succeeding chapters, gives
154
BOOK REVIEWS
the reader ready access to the literature of the many individual case histories that Selley uses in his introduction to sedimentary environments. In Chapter 3 "Wind-blown Sediments", Selley points out that in order to recognize rocks of eolian origin it is necessary to critically evaluate all available data (to an even greater extent than for other environmental systems) and goes on to use Pennsylvanian through Upper Jurassic sandstones of the Colorado Plateau, western U.S.A. as an example of ancient wind deposition. This chapter seems weaker than the one on river deposits, but this is perhaps expectable due to the difficulty of unequivocally differentiating eolianites from some water-deposited sandstones and also to the relative unimportance of eolianites in economic geology. In Chapter 4, "Lake Deposits", the Green River Formation, one of the largest and best documented examples of ancient lacustrine deposits in the world, is described. The formation is briefly discussed emphasizing lithological diversity, cyclicity and presence of evaporites as being characteristic of both this and other ancient lake deposits. The chapter is concisely presented (less than eight pages). Approximately half of the entire book (Chapters 5-9) deals with sedimentary environments that are transitional between those clearly marine and those clearly non-marine. Inasmuch as rocks of the various transitional facies are so rich in mineral deposits and large in volume within the total sedimentary rock record, this should please both the economic geologist and his more academically oriented colleagues in the universities and surveys. SeUey's general sub-division of depositional shore-lines into lobate (deltas) and linear (barrier island and lagoonal complexes), with the linear type further broken down into clastic, mixed carbonateclastic, and carbonate, forms the basis of the chapter definition for Chapters 5 through 9. Chapter 5, "Deltas", includes a succinct coverage of Recent deltas, a description and interpretation of the Carboniferous Yoredale series and Millstone Grit of northern England, a general discussion of deltaic sedimentation and a brief discussion of the (considerable) economic significance of deltas. The three-page bibliography ending the chapter on deltas is particularly good. In Chapter 6, "Linear Clastic Shorelines", Selley notes the alternation of high-energy versus low-energy zones that is found in the juxtaposed fluviatile coastal plain, lagoon-tidal flat complex, barrier island and offshore marine shelf environments along a linear clastic shoreline. He emphasizes the role played by sediment availability and rate of rise or fall of the land and sea in the development of various types of sedimentary sequences and describes and interprets the economically important Cretaceous shoreline strata of the Rocky Mountains, U.S.A. An excellent discussion is provided in Chapter 7, "Mixed Clastic: Carbonate Shorelines", of the Miocene shoreline sediments of the Sirte Basin, Libya. This discussion is based on Selley's own extensive work as a post-doctoral fellow from Imperial College (London) and Senior Sedimentologist with Oasis Oil Company of Libya. Understandably, this chapter is a highlight of the volume.
BOOK REVIEWS
155
Chapter 8, "Carbonate Shorelines and Shelf Deposits", is based on the general theory of carbonate shelf sedimentation developed by Irwin (1965) in his stratigraphic analysis of the Williston Basin, North America. Selley briefly describes and interprets the environmental significance of the Williston Basin sequence and then goes on to a general discussion of shelf deposits in which he notes the similarity of the carbonates, marls and evaporites (Jurassic-Tertiary) on the northeastern margin of the Arabian Shield to the Williston Basin rocks. He takes the position that it is also possible to extend this concept of high- and lowenergy shelf environments outside the realm of carbonates to clastic sediments and cites as an example the Lower Paleozoic Um Sahm Formation of Jordan.In the closing paragraphs of the chapter Selley emphasizes the great economic significance of rocks and sediments of shelf origin, pointing out that some of the world's major oil fields occur in shelf carbonates of Iraq, Persia, Libya and the Williston Basin and that valuable phosphate deposits occur in Upper Cretaceous shelf carbonates of the Middle East. Chapter 9, "Reefs", begins with a summary of the characteristics of Recent reefs followd by a description and interpretation of the Permian barrier reefs of west Texas, U.S.A. Selley points out the recent questioning (Achaur, 1969; Kendall, 1969) of the true reefal nature of the biolithite facies of the west Texas reefs and notes the current trend to reappraise build-ups of non-wave resistant skeletal debris previously designated as reefs in other parts of the geologic record. He describes and interprets the environmental associations of the Devonian Leduc patch reefs of western Canada and in a general discussion of reefs discusses factors controlling reef geometries and facies (i.e., the interplay of sea-level changes, tectonic setting, biota and oceanography), the reef-evaporite-euxinic shale association and the complexity of reef diagenesis. Under the heading "Economic Geology of Ancient Reefs" he succinctly demonstrates the importance of sedimentology in the location and exploitation of these exceedingly important sites of hydrocarbon accumulation and metallic replacement mineralization. The four and a half page bibliography on reefs should be very useful for the non-specialist who would like a relatively complete introduction to the literature. In Chapter 10, "Flysch and Turbidites", Selley briefly emphasizes the distinctions that should be made when using the terms "flysch", "turbidite" and "greywacke" and notes that the terms are all extremely loosely defined in the literature. The remainder of the chapter includes a summary of the characteristics ofturbidites, a discussion of their origin, a description and environmental interpretation of the origin of the Peira Cava Formation of the Alpine flysch sequence and, finally, a summary of problems related to flysch and turbidites and discussion of the economic geology of flysch sequences. Deposits of the open sea are covered in Chapter 1 I, "Pelagic Deposits". A conventional subdivision of deep-sea deposits into terrigenous sediments, calcareous oozes, siliceous oozes, red clays and manganiferous deposits is used.
156
BOOK REVIEWS
The characteristics of Tethys pelagic deposits of Mesozoic through Early Tertiary age are outlined and a reconstruction of their general environments of deposition offered which features low-energy deposition, absence of photic conditions and slow sedimentation with little influx of land-derived material. The relative unimportance of deep-sea deposits is noted in the closing paragraphs of the chapter. Chapter 12, "Conclusions", is really a statement of Selley's philosophy of stratigraphic analysis, i.e., that there are, and always have been, a number ol sedimentary environments which deposit characteristic facies and that these may be classified into various ideal sedimentary systems or models. Even though the ideal or typical model of a given sedimentary system does not really exist, if one realizes the limitations of the sedimentary model concept it can be useful both in teaching and as a predictive tool in industry. The chapter concludes with "Tables attempting to summarize the diagnostic features of the major sedimentary environments". The book, which is indexed by author and by subject, appears to have a minimal number of typographical errors. Errors of content appear to be few in number and in only a few instances of a serious nature. An example of one of the more serious errors noted is the misplacing of the base of the New York State Devonian System in Figure 2.10, a generalized comparative view of the Catskill and South Wales stratigraphic sections. The small volume is concise, well illustrated and reasonably priced and contains, here and there, refreshing bits of humor. Richard Selley has filled an important need for both those of us who teach and those of us who work in applied aspects of sedimentary geology. K. G. JOHNSON (Saratoga Springs, N.Y,)
Chemical Weathering of the Silicate Minerals. F. C. LOUGHNAN.American Elsevier, New York, N.Y.. 1969, 154 pp., S 10.50. With this new publication, Loughnan (School of Applied Geology, University of New South Wales, Sydney) fulfills the need for a long-desired summary of chemical weathering on a level suitable to graduate students. He warns us in the preface that the present rate of growth in knowledge might make such a book soon obsolete. Although this may be true, a substantial part of the information will remain acceptable for a long time because most of the pertinent fundamental concepts have withstood criticism for several years. In the introduction, Loughnan gives a few necessary definitions and thereby outlines the fields of investigation of his book, Chapter II presents some of the chemical properties and the molecular structural features of the common minerals involved in weathering reactions. "The chemistry of weathering" (chapter III)
Book Reviews Ancient Sedimentary Environments. R. C. SELLEY. Chapman and Hall, London,
1971, 237 pp., £ 2.75 The expressed purpose of R. C. Selley in writing Ancient Sedimentary Environments was to provide an introductory survey that shows how the depositional environments of sedimentary rocks can be recognized. He has succeeded admirably in achieving this and at the same time has provided a work that constitutes a small but useful reference for advanced students of stratigraphic analysis. The introductory chapter of the book presents a general discussion of the classification of sedimentary environments and an evaluation of the methods that can be used to identify their counterparts in the stratigraphic record. The remaining chapters utilize a case history approach in which an ancient rock association is first described and then analyzed in terms of its most probable environment of origin based on current knowledge of modern sedimentary environments. Each case history is accompanied by a general discussion of the problems of identifying the particular sedimentary environment in question and by a brief review of its economic significance. Chapter 2, "River Deposits", begins with an introduction to the morphology of modern high-sinuosity meandering channels and low-sinuosity braided channel complexes. The bulk of the chapter, however, is devoted to a thorough description and environmental interpretation of the Torridon G r o u p (Precambrian) of northwest Scotland and the Devonian non-marine strata of South Wales and the Catskill Mountains, U.S.A. Selley's intimate familiarity with the Torridon G r o u p as a result of his own research shows clearly in his concise treatment of this ancient braided stream system. His account of the Catskill and South Wales fining-upwards cycles outlines the characteristics of rocks that evolved on a coastal plain built by high-sinuosity meandering rivers. The section on economic aspects of ancient alluvial deposits touches briefly on oil and gas deposits, the gold deposits of Witwatersrand in South Africa and the carnotite ores of the Colorado Plateau. U.S.A. A useful approach to reference citation appears for the first time at the end of Chapter 2 where Selley separates the citations into groups with headings such as "The description of the Torridonian sediments was based o n . . . ". "The account of the Devonian d e p o s i t s . . . " , and "Other references quoted in this chapter w e r e . . . ". This format, which is used in l~ke manner at the close of succeeding chapters, gives
154
BOOK REVIEWS
the reader ready access to the literature of the many individual case histories that Selley uses in his introduction to sedimentary environments. In Chapter 3 "Wind-blown Sediments", Selley points out that in order to recognize rocks of eolian origin it is necessary to critically evaluate all available data (to an even greater extent than for other environmental systems) and goes on to use Pennsylvanian through Upper Jurassic sandstones of the Colorado Plateau, western U.S.A. as an example of ancient wind deposition. This chapter seems weaker than the one on river deposits, but this is perhaps expectable due to the difficulty of unequivocally differentiating eolianites from some water-deposited sandstones and also to the relative unimportance of eolianites in economic geology. In Chapter 4, "Lake Deposits", the Green River Formation, one of the largest and best documented examples of ancient lacustrine deposits in the world, is described. The formation is briefly discussed emphasizing lithological diversity, cyclicity and presence of evaporites as being characteristic of both this and other ancient lake deposits. The chapter is concisely presented (less than eight pages). Approximately half of the entire book (Chapters 5-9) deals with sedimentary environments that are transitional between those clearly marine and those clearly non-marine. Inasmuch as rocks of the various transitional facies are so rich in mineral deposits and large in volume within the total sedimentary rock record, this should please both the economic geologist and his more academically oriented colleagues in the universities and surveys. SeUey's general sub-division of depositional shore-lines into lobate (deltas) and linear (barrier island and lagoonal complexes), with the linear type further broken down into clastic, mixed carbonateclastic, and carbonate, forms the basis of the chapter definition for Chapters 5 through 9. Chapter 5, "Deltas", includes a succinct coverage of Recent deltas, a description and interpretation of the Carboniferous Yoredale series and Millstone Grit of northern England, a general discussion of deltaic sedimentation and a brief discussion of the (considerable) economic significance of deltas. The three-page bibliography ending the chapter on deltas is particularly good. In Chapter 6, "Linear Clastic Shorelines", Selley notes the alternation of high-energy versus low-energy zones that is found in the juxtaposed fluviatile coastal plain, lagoon-tidal flat complex, barrier island and offshore marine shelf environments along a linear clastic shoreline. He emphasizes the role played by sediment availability and rate of rise or fall of the land and sea in the development of various types of sedimentary sequences and describes and interprets the economically important Cretaceous shoreline strata of the Rocky Mountains, U.S.A. An excellent discussion is provided in Chapter 7, "Mixed Clastic: Carbonate Shorelines", of the Miocene shoreline sediments of the Sirte Basin, Libya. This discussion is based on Selley's own extensive work as a post-doctoral fellow from Imperial College (London) and Senior Sedimentologist with Oasis Oil Company of Libya. Understandably, this chapter is a highlight of the volume.
BOOK REVIEWS
155
Chapter 8, "Carbonate Shorelines and Shelf Deposits", is based on the general theory of carbonate shelf sedimentation developed by Irwin (1965) in his stratigraphic analysis of the Williston Basin, North America. Selley briefly describes and interprets the environmental significance of the Williston Basin sequence and then goes on to a general discussion of shelf deposits in which he notes the similarity of the carbonates, marls and evaporites (Jurassic-Tertiary) on the northeastern margin of the Arabian Shield to the Williston Basin rocks. He takes the position that it is also possible to extend this concept of high- and lowenergy shelf environments outside the realm of carbonates to clastic sediments and cites as an example the Lower Paleozoic Um Sahm Formation of Jordan.In the closing paragraphs of the chapter Selley emphasizes the great economic significance of rocks and sediments of shelf origin, pointing out that some of the world's major oil fields occur in shelf carbonates of Iraq, Persia, Libya and the Williston Basin and that valuable phosphate deposits occur in Upper Cretaceous shelf carbonates of the Middle East. Chapter 9, "Reefs", begins with a summary of the characteristics of Recent reefs followd by a description and interpretation of the Permian barrier reefs of west Texas, U.S.A. Selley points out the recent questioning (Achaur, 1969; Kendall, 1969) of the true reefal nature of the biolithite facies of the west Texas reefs and notes the current trend to reappraise build-ups of non-wave resistant skeletal debris previously designated as reefs in other parts of the geologic record. He describes and interprets the environmental associations of the Devonian Leduc patch reefs of western Canada and in a general discussion of reefs discusses factors controlling reef geometries and facies (i.e., the interplay of sea-level changes, tectonic setting, biota and oceanography), the reef-evaporite-euxinic shale association and the complexity of reef diagenesis. Under the heading "Economic Geology of Ancient Reefs" he succinctly demonstrates the importance of sedimentology in the location and exploitation of these exceedingly important sites of hydrocarbon accumulation and metallic replacement mineralization. The four and a half page bibliography on reefs should be very useful for the non-specialist who would like a relatively complete introduction to the literature. In Chapter 10, "Flysch and Turbidites", Selley briefly emphasizes the distinctions that should be made when using the terms "flysch", "turbidite" and "greywacke" and notes that the terms are all extremely loosely defined in the literature. The remainder of the chapter includes a summary of the characteristics ofturbidites, a discussion of their origin, a description and environmental interpretation of the origin of the Peira Cava Formation of the Alpine flysch sequence and, finally, a summary of problems related to flysch and turbidites and discussion of the economic geology of flysch sequences. Deposits of the open sea are covered in Chapter 1 I, "Pelagic Deposits". A conventional subdivision of deep-sea deposits into terrigenous sediments, calcareous oozes, siliceous oozes, red clays and manganiferous deposits is used.
156
BOOK REVIEWS
The characteristics of Tethys pelagic deposits of Mesozoic through Early Tertiary age are outlined and a reconstruction of their general environments of deposition offered which features low-energy deposition, absence of photic conditions and slow sedimentation with little influx of land-derived material. The relative unimportance of deep-sea deposits is noted in the closing paragraphs of the chapter. Chapter 12, "Conclusions", is really a statement of Selley's philosophy of stratigraphic analysis, i.e., that there are, and always have been, a number ol sedimentary environments which deposit characteristic facies and that these may be classified into various ideal sedimentary systems or models. Even though the ideal or typical model of a given sedimentary system does not really exist, if one realizes the limitations of the sedimentary model concept it can be useful both in teaching and as a predictive tool in industry. The chapter concludes with "Tables attempting to summarize the diagnostic features of the major sedimentary environments". The book, which is indexed by author and by subject, appears to have a minimal number of typographical errors. Errors of content appear to be few in number and in only a few instances of a serious nature. An example of one of the more serious errors noted is the misplacing of the base of the New York State Devonian System in Figure 2.10, a generalized comparative view of the Catskill and South Wales stratigraphic sections. The small volume is concise, well illustrated and reasonably priced and contains, here and there, refreshing bits of humor. Richard Selley has filled an important need for both those of us who teach and those of us who work in applied aspects of sedimentary geology. K. G. JOHNSON (Saratoga Springs, N.Y,)
Chemical Weathering of the Silicate Minerals. F. C. LOUGHNAN.American Elsevier, New York, N.Y.. 1969, 154 pp., S 10.50. With this new publication, Loughnan (School of Applied Geology, University of New South Wales, Sydney) fulfills the need for a long-desired summary of chemical weathering on a level suitable to graduate students. He warns us in the preface that the present rate of growth in knowledge might make such a book soon obsolete. Although this may be true, a substantial part of the information will remain acceptable for a long time because most of the pertinent fundamental concepts have withstood criticism for several years. In the introduction, Loughnan gives a few necessary definitions and thereby outlines the fields of investigation of his book, Chapter II presents some of the chemical properties and the molecular structural features of the common minerals involved in weathering reactions. "The chemistry of weathering" (chapter III)