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Carbonate mud-mounds: Their origin and evolution
Book Review/Sedimentary Geology 105 (1996) 105-113
coincide with third order sea-level highstands and are obscured during times of lowstand. Thus, it is evident for several reasons that the 'applications of cyciostratigraphy to geochronology still are in their beginnings' (Fischer) and become increasingly uncertain in the Palaeozoic and Proterozoic. Some new timescales spanning several million years could be anchored to the Present, but most timescales based on Milankovitch cyclities so far are isolated 'floating' scales. Therefore I fully agree with the title of Fischer's final chapter: cyclostratigraphy, quo vadis? G. EINSELE(Tfibingen) SSDI 0037-0738(95)00136-0
Carbonate Mud-Mounds: Their Origin and Evolution. C.L.V. Monty, D.W.J. Bosence, P.H. Bridges and B.R. Pratt (Editors). International Association of Sedimentologists, Spec. Pub. 23, Blackwell, Oxford, 1995, 537 pp. Carbonate mud-mounds have been of interest to many geologists because of their strange relationships to the surrounding strata; i.e., mounds of mud commonly formed below wave base which are surrounded by sedimentary rocks of a different composition. Thus, the basic questions arise: How did they form? Where did the carbonate mud come from? How did it get to the site? This book goes a long way toward providing answers and ways of looking at the questions pertaining to carbonate mud-mounds. In addition, it contributes some interesting insights into topics of concern to other aspects of carbonate sedimentation and diagenesis. Carbonate Mud-Mounds is a fairly comprehensive book (17 papers, 537 pages) which grew out of a symposium in 1990. The subject matter ranges from mounds of Prepaleozoic age up to modem mounds of Florida Bay. The book is divided into four sections: Overviews, Paleozoic, Mesozoic, and Cenozoic Mud-Mounds. Although a few of the papers present generalized overview discussions of mounds of a particular age, most present detailed studies of specific deposits. A wide gamut of mound types are described, with the focus on those that are predominantly composed of micrite, although also
109
included are fossil-rich mounds. The mounds described range in depositional environment from deep-water to tidal flat, and their extent ranges from small 'outcrop' size to those over a kilometer thick. In addition, papers discuss many other topics which are present in a wide variety of carbonate strata, which gives the book a much broader appeal than solely for those interested in mud-mounds, e.g., origin of the carbonate mud comprising the mounds, origin of peloids, carbonate cements, dolomitization, ecological relationships, and the origin of the ever enigmatic stromatactis. As defined in this volume, carbonate mud-mounds are " a buildup having depositional relief and being composed dominantly of carbonate mud, peloidal mud, or micrite" (Bosence and Bridges, p. 4). Although not all mounds are of a similar origin, I was impressed by the number of studies in which the author(s) presented evidence that the carbonate mud and peloids are produced in situ by microbial action. Evidence in support of this significant conclusion is included in the description of a number of the mounds studied, such as the: (1) abundance of micrite within the mound and its paucity in the underlying and laterally adjacent strata; (2) differences in the mineralogy and constituents comprising the mounds as compared to the adjacent strata; (3) lack of indications of transportation of sediment comprising the mounds; and (4) common association between micrite and micritic constituents and the microbes capable of inducing the precipitation of micrite. These attributes are more commonly described for older and deeper-water mounds. Although the interpretation of an in situ origin for carbonate mud has been in the literature for some time, the number of studies referring to this origin in this state-of-the-art book appears to signify an evolution in the understanding of the origin of mud-mounds. The overview articles by Monty (The rise and nature of carbonate mud-mounds: an introductory actualistic approach) and Pratt (The origin, biota and evolution of deep-water mud-mounds) were particularly valuable to me. They provided sufficient details yet good overview perspectives of carbonate mudmounds. Lees and Miller (Waulsortian banks) did a similarly commendable job with regard to the classic Waulsortian mounds. As an example of the variety of mud-mounds discussed, Calvert and Tucker
110
Book Reoiew / Sedimentary Geology 105 (1996) 105-113
(Mud-mounds with reefal caps in the upper Muschelkalk (Triassic), eastern Spain) described some interesting dolomitized mounds which initially were composed of up to 60% aragonite botyroids. Another interesting variety of carbonate mud(?)-mounds was described by Wanless et al. (Origin and growth of carbonate banks in south Florida). They described examples of modern shallow water mounds in which the original mud component was significantly reduced by repeated burrowing and infill of the burrows by skeletal debris, an early modification which results in coarse debris-mounds in the place of mudmounds. The main weakness of the book resides with the reproduction of the figures, particularly with the photomicrographs. All too often, photomicrographs are reproduced too small to be of any use to the carbonate petrologist attempting to see the primary data. Additionally, photographic reproduction could, in some cases, have benefited from an increase in contrast. Also, legends on a few of the maps are not legible because the size reduction has resulted in obliteration of the patterns. To its credit, the book is remarkably free of typo's. The minor problems with the figures not withstanding, the book is definitely a worthwhile purchase. This is a must read book for anyone interested in carbonate mud-mound deposits, good for the neophyte and the expert alike, and of interest to most other carbonate geologists as well. HENRY S. CHA~TZ (Houston, Texas) SSDI 0037-0738(95)00142-5
Geomorphology and Sedimentology of Estuaries. G.M.E. Perillo (Editor). Developments in Sedimentology 53, Elsevier Science B.V., 1995, Amsterdam, 471 pp., ISBN 0-444-88170-0. The estuaries and tidal embayments of the world have a particular significance for people especially of modern times. These beautiful, fruitful and complex natural environments provide secure shipping harbours, access to hinterlands through the rivers that support them and, on the extensive wetlands on their margins, the unencumbered space in which great manufacturing and trading cities and towns can be
built. What has simultaneously been created, however, are grave problems of flood control and of environmental contamination, pollution and general degradation, which challenge our limited understanding, in holistic terms, of the fundamental science of the lowland coastal zone. Gerardo Perillo's Geomorphology and Sedimentology of Estuaries is a worthy, if a little patchy, contribution to the process of enhancing and disseminating knowledge of these particular coastal systems. The book he has edited consists of 14 chapters each supported by a bibliography - - essentially invited review papers, but not presented at a meeting - - contributed by 20 authors, of whom just four are based outside the Americas; it is interesting to see evidence in the list of authors of a growing South American concern for estuaries. The emphasis in the papers is overwhelmingly physical. Perillo gives in the first two chapters an introduction to the geomorphology and sedimentology of estuaries, together with a review and discussion of the concept and definitions of an estuary. Regarding the latter, it would be surprising if his unusually broad conclusions did not give rise to debate. Chapter 3 is a brief review by Bokuniewicz of the character and global distribution of estuaries in coastal-plain settings. He points to the difficulties of reconciling hydrographic (salinity-based) classifications of estuaries with schemes based on geomorphological and sedimentological features. Castaing and Guilcher in Chapter 4 contribute a review of the geomorphoiogy and sedimentology of rias, drawing on examples from the British Isles, France, Iberia, the Middle and Far East, and Argentina. The paper points to the geological antiquity of many rias - - they are non-glacial in origin - - and their relationship to sea-level changes. Rias need more study. Fjords are the product of the advance and retreat of glacial ice and relative sea-level changes during the Quaternary. Syvitski and Shaw, in Chapter 5, point to the importance and variety of this type of highly changeable estuary characteristic of high latitudes. Their review is detailed and comprehensive, drawing attention to the great diversity of processes operating in fjords and the rapid advances in understanding that have been made in recent years. Tide-dominated estuaries and tidal rivers are im-
coincide with third order sea-level highstands and are obscured during times of lowstand. Thus, it is evident for several reasons that the 'applications of cyciostratigraphy to geochronology still are in their beginnings' (Fischer) and become increasingly uncertain in the Palaeozoic and Proterozoic. Some new timescales spanning several million years could be anchored to the Present, but most timescales based on Milankovitch cyclities so far are isolated 'floating' scales. Therefore I fully agree with the title of Fischer's final chapter: cyclostratigraphy, quo vadis? G. EINSELE(Tfibingen) SSDI 0037-0738(95)00136-0
Carbonate Mud-Mounds: Their Origin and Evolution. C.L.V. Monty, D.W.J. Bosence, P.H. Bridges and B.R. Pratt (Editors). International Association of Sedimentologists, Spec. Pub. 23, Blackwell, Oxford, 1995, 537 pp. Carbonate mud-mounds have been of interest to many geologists because of their strange relationships to the surrounding strata; i.e., mounds of mud commonly formed below wave base which are surrounded by sedimentary rocks of a different composition. Thus, the basic questions arise: How did they form? Where did the carbonate mud come from? How did it get to the site? This book goes a long way toward providing answers and ways of looking at the questions pertaining to carbonate mud-mounds. In addition, it contributes some interesting insights into topics of concern to other aspects of carbonate sedimentation and diagenesis. Carbonate Mud-Mounds is a fairly comprehensive book (17 papers, 537 pages) which grew out of a symposium in 1990. The subject matter ranges from mounds of Prepaleozoic age up to modem mounds of Florida Bay. The book is divided into four sections: Overviews, Paleozoic, Mesozoic, and Cenozoic Mud-Mounds. Although a few of the papers present generalized overview discussions of mounds of a particular age, most present detailed studies of specific deposits. A wide gamut of mound types are described, with the focus on those that are predominantly composed of micrite, although also
109
included are fossil-rich mounds. The mounds described range in depositional environment from deep-water to tidal flat, and their extent ranges from small 'outcrop' size to those over a kilometer thick. In addition, papers discuss many other topics which are present in a wide variety of carbonate strata, which gives the book a much broader appeal than solely for those interested in mud-mounds, e.g., origin of the carbonate mud comprising the mounds, origin of peloids, carbonate cements, dolomitization, ecological relationships, and the origin of the ever enigmatic stromatactis. As defined in this volume, carbonate mud-mounds are " a buildup having depositional relief and being composed dominantly of carbonate mud, peloidal mud, or micrite" (Bosence and Bridges, p. 4). Although not all mounds are of a similar origin, I was impressed by the number of studies in which the author(s) presented evidence that the carbonate mud and peloids are produced in situ by microbial action. Evidence in support of this significant conclusion is included in the description of a number of the mounds studied, such as the: (1) abundance of micrite within the mound and its paucity in the underlying and laterally adjacent strata; (2) differences in the mineralogy and constituents comprising the mounds as compared to the adjacent strata; (3) lack of indications of transportation of sediment comprising the mounds; and (4) common association between micrite and micritic constituents and the microbes capable of inducing the precipitation of micrite. These attributes are more commonly described for older and deeper-water mounds. Although the interpretation of an in situ origin for carbonate mud has been in the literature for some time, the number of studies referring to this origin in this state-of-the-art book appears to signify an evolution in the understanding of the origin of mud-mounds. The overview articles by Monty (The rise and nature of carbonate mud-mounds: an introductory actualistic approach) and Pratt (The origin, biota and evolution of deep-water mud-mounds) were particularly valuable to me. They provided sufficient details yet good overview perspectives of carbonate mudmounds. Lees and Miller (Waulsortian banks) did a similarly commendable job with regard to the classic Waulsortian mounds. As an example of the variety of mud-mounds discussed, Calvert and Tucker
110
Book Reoiew / Sedimentary Geology 105 (1996) 105-113
(Mud-mounds with reefal caps in the upper Muschelkalk (Triassic), eastern Spain) described some interesting dolomitized mounds which initially were composed of up to 60% aragonite botyroids. Another interesting variety of carbonate mud(?)-mounds was described by Wanless et al. (Origin and growth of carbonate banks in south Florida). They described examples of modern shallow water mounds in which the original mud component was significantly reduced by repeated burrowing and infill of the burrows by skeletal debris, an early modification which results in coarse debris-mounds in the place of mudmounds. The main weakness of the book resides with the reproduction of the figures, particularly with the photomicrographs. All too often, photomicrographs are reproduced too small to be of any use to the carbonate petrologist attempting to see the primary data. Additionally, photographic reproduction could, in some cases, have benefited from an increase in contrast. Also, legends on a few of the maps are not legible because the size reduction has resulted in obliteration of the patterns. To its credit, the book is remarkably free of typo's. The minor problems with the figures not withstanding, the book is definitely a worthwhile purchase. This is a must read book for anyone interested in carbonate mud-mound deposits, good for the neophyte and the expert alike, and of interest to most other carbonate geologists as well. HENRY S. CHA~TZ (Houston, Texas) SSDI 0037-0738(95)00142-5
Geomorphology and Sedimentology of Estuaries. G.M.E. Perillo (Editor). Developments in Sedimentology 53, Elsevier Science B.V., 1995, Amsterdam, 471 pp., ISBN 0-444-88170-0. The estuaries and tidal embayments of the world have a particular significance for people especially of modern times. These beautiful, fruitful and complex natural environments provide secure shipping harbours, access to hinterlands through the rivers that support them and, on the extensive wetlands on their margins, the unencumbered space in which great manufacturing and trading cities and towns can be
built. What has simultaneously been created, however, are grave problems of flood control and of environmental contamination, pollution and general degradation, which challenge our limited understanding, in holistic terms, of the fundamental science of the lowland coastal zone. Gerardo Perillo's Geomorphology and Sedimentology of Estuaries is a worthy, if a little patchy, contribution to the process of enhancing and disseminating knowledge of these particular coastal systems. The book he has edited consists of 14 chapters each supported by a bibliography - - essentially invited review papers, but not presented at a meeting - - contributed by 20 authors, of whom just four are based outside the Americas; it is interesting to see evidence in the list of authors of a growing South American concern for estuaries. The emphasis in the papers is overwhelmingly physical. Perillo gives in the first two chapters an introduction to the geomorphology and sedimentology of estuaries, together with a review and discussion of the concept and definitions of an estuary. Regarding the latter, it would be surprising if his unusually broad conclusions did not give rise to debate. Chapter 3 is a brief review by Bokuniewicz of the character and global distribution of estuaries in coastal-plain settings. He points to the difficulties of reconciling hydrographic (salinity-based) classifications of estuaries with schemes based on geomorphological and sedimentological features. Castaing and Guilcher in Chapter 4 contribute a review of the geomorphoiogy and sedimentology of rias, drawing on examples from the British Isles, France, Iberia, the Middle and Far East, and Argentina. The paper points to the geological antiquity of many rias - - they are non-glacial in origin - - and their relationship to sea-level changes. Rias need more study. Fjords are the product of the advance and retreat of glacial ice and relative sea-level changes during the Quaternary. Syvitski and Shaw, in Chapter 5, point to the importance and variety of this type of highly changeable estuary characteristic of high latitudes. Their review is detailed and comprehensive, drawing attention to the great diversity of processes operating in fjords and the rapid advances in understanding that have been made in recent years. Tide-dominated estuaries and tidal rivers are im-