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Coarse-grained Deltas
BookReviews Coarse-grained Deltas Albina Colella and David Prior (Eds) International Association of Sedimentologists Special Publication No. 10; IAS; 1990; 357 pp; ISBN 0 632 02894 7 Coarse to gravelly deltas are the theme of this Special Publication of the International Association of Sedimentolgists (IAS). The prime source of the contributions is from the 1st International Workshop on Fan Deltas (1988). The reviewers are an impressive group of international sedimentologists who promise a high quality content. The format of the book and the quality of the plates and illustrations are the same as those found in other publications of the 1AS. Nineteen contributions arc organized into five sections: (l) general considerations, (2) modern alluvial deltas, (3) ancient alluvial deltas - - effects of tectonism, (4) ancient alluvial deltas effects of varying climate and water level and (5) non-alluvial deltas. However, there are only two papers on modern alluvial deltas and only one in the non-alluvial deltas section. The relative lack of modern examples is compensated for by two papers on processes in the opening section, but by far the dominant ingredients of this volume are ancient case studies of one sort or another. The ages of these ancient deltas arc mostly Miocene and younger, with an Oligocene, a Palaeocenc-Eocene and a Cretaceous example. Field locations for both ancient and modern range from Korea, through the Gulf of Suez, Israel, Turkey, Greece, Italy, Spain, Poland, Norway, North America, New Zealand and Antarctica. giving a truly international flavour to the volume. The first three papers by Nemec and Postma tackle the problems of terminok)gy, classification and process and attempt to put into context ~hat follows. There is necessarily in these introductory contributions a summary of a variety of previous work. However, much is new and I feel will be of interest to many working with all types of modern and ancient deltas. Nemec deals with thc problems of an ever increasing choice of classifications and terminology and suggests how each might be used in a hierarchical way, tailored to the data types at hand and the purpose of the delta study, perhaps ranging from basin setting to reservoir geometry. Postma delivers an claborate 12-fold delta classification that is based on types of feeder system and water depth of progradation (shallow v e r s u s deep). This level of detail could be considered overly elaborate for those looking for a simple subdivision of delta types, especially within just coarse-grained varieties. The paper on steep delta slope processes by Nemec is perhaps the most important of the opening papers. This process-orientated review provides an excellent summary of what is presently felt to be known about fan-delta construction, but also allows for the uncertainties to be clearly understood. It also links the observation of modern processes with ancient products and facies sequences. Beyond the introductory papers, my interest was drawn to the Prior and Bornhold contributions on modern and recent fan-deltas in the fjords of British Columbia. Their work in this volume is not entirely new or unpublished, yet is still a fascinating guide to the wide spectrum of subaqueous delta front processes via startling side-scan imagery and detailed bottom profiles. For anyone who has pondered the complex origin of delta front facies sequences in ancient deltas, especially the all too common products of syn-sedimentary deformation and gravity flow processes of all types, these papers are both thought provoking and useful working analogues. The only other paper devoted exclusively to a modern example provides an excellent complement to the British Columbia contributions. Corner e t al. deal much more with the subaerial characteristics and development of a major coarse-grained fjord delta in northern Norway and therefore complete the overall picture of modern deltas of this type. Among the ancient case studies, those dealing with the [inks between tectonics and f:m delta deposition dominate. In 180
the opening section Gawthorpe and Colella provide a comprehensive overview of coarse-grained deltas in rift basins. Their focus is on the large scale architectural contrasts that various supply points (axial v e r s u s marginal and footwall v e r s u s hanging wall) may produce in active extensional regimes. They also provide some useful cautionary comments about delineating tectonic controls from other possibilities. Two other "review" papers by Dabrio and Bardaji et al. examine fan deltas in south-eastern Spain. Both these papers are detailed on [ithofacies and facies sequences and attempt to separate eustatic from tectonic controls within their fan delta successions. In the section specifically dedicated to the effects of tectonics on ancient coarse-grained deltas are five papers. Four of these papers provide very detailed facies descriptions of fan deltas of many types. Marine and lacustrine fan deltas are represented and water depths of progradation range from only a few metres to greater than 150 m. Kazanci and Van der Straaten both provide examples of how extensional tectonics can severely influence the larger scale architecture of fan delta deposits. These two papers also neatly contrast a relatively small scale and marginal lacustrine delta with a much larger and axial marine system. The generation of tectonic sedimentary packets is clearly discussed in both case studies. The following two papers focus much more on the meso scale organization of tim delta facies sequences. Flores examines lacustrine deltas in a transpressional basin and contrasts the facies and facies sequences developed in both marginal and longitudinal (axial) settings. Hwang and Choung describe a marine fan delta deposited in a transtensional basin. Their descriptions of individual sedimentary facies are the most detailed of the entire volume, but the establishment of tectonic controls are perhaps the weakest. Garcia-Mondejar is the final contributor in the tectonic section. This paper is low on facies detail, but instead erects a sequence stratigraphic model for a marine fan delta succession. Erosional unconformities and rapid, almost non-depositional transgressions in the succession are attributed to tectonically driven relative sea level changes and descriptions of the erosionally bounded "sequences' are made in a systems tract framework. The final major section of the volume consists of four contributions dealing with the intluences of climate and water level on coarse-grained deltas. Two of these papers, by Martini and Mastalerz, deal with glacial settings, Bowman describes an example from the arid Dead Sea area, and Massari and Parea describe strongly wave-intluenced, marine fan deltas. All these papers are particularly well illustrated and each deals with unique aspects of fan delta deposition not dealt with elsewhere within the volume. The detailed description of the wave-dominated deltas of Massari and Parea is of particular interest and contrasts with almost all the previous case studies. In this one example the importance of slope instability is relegated, the importance of basin processes heightened and the effects of eustatic changes given a relatively high prominence. An important conclusion that results from an examination of the 'non-tectonic' case studies compared with the preceding sections is that very similar geometries and architectural patterns may result from different allocyclic and autocyclic controls. This led me back to the opening remarks of the editors in which important issues are highlighted. One of these is a realization that the present understanding is insufficient to construct adequate stratigraphic and facies models. I feel this volume has gone a considerable way in increasing our understanding. Many of the papers do have common elements that could be usefully summarized and the
M a r i n e a n d PP.troleum Go.olcmv. 1.q.q2 Vnl 10 A n r i l
Book reviews further development of sequence stratigraphic concepts in coarse-grained deltas will probably lead to more refined and less uncertain stratigraphic models. The volume is completed by a unique contribution by Porebski and Gradzinski. Their lava-fed delta shows many of the classic foreset bedding structures seen in their fluvial-fed counterparts and shares some of the gravity flow processes common on the coarse-grained deltas throughout the other case studies. However, the interpreted eruptive cycles of debris and lava flows create a unique evolution in the delivery mechanisms and grain sizes available for delta construction, which were certainly new and fascinating to this reader. My overall opinion of this publication is that it provides a very useful addition to the growing library of Special
Publications of the IAS. I am especially pleased to report that most of the contributions are well illustrated with good photographs as well as ample drawings and tables. I recommend this book as essential for those working with deltas of any type, modern or ancient. I also expect that it will become a key reference for those joining or continuing the analyses of coarse-grained deltas, which are clearly enjoying a sustained growth interest, as attested by the popularity of the Fan Delta field workshop and the publication of this volume.
Andy Pulham
BP Exploration, Houston, TX, USA
A Glossary of Salt Tectonics M. P. A. Jackson and C. T. Talbot Geological Circular 91.4. Bureau of Economic Geology, University of Texas, Austin, Texas; 1991. Price $2.50 This comprehensive and inexpensive glossary is essential for any geoscientist concerned with salt diapirism in industry or academe. The glossary has been compiled by Martin Jackson and Chris Talbot from the Bureau of Economic Geology, who are themselves recognized leaders and innovators in modern kinematic and experimental analysis of salt tectonism. Since the early work of Trusheim and the simultaneous publication in 1968 of memoirs on salt and salt diapirism by the Geological Society of America and the American Association of Petroleum Geologists, considerable advances have been made in the study of salt tectonics as shown in the special issue of Marine and Petroleum Geology (August 1992) on this topic. These advances in understanding have been facilitated by the continuous improvement in the quality of two dimensional and latterly three dimensional seismic that have allowed for better imaging of the complexity of salt structures and their influence on sediment deposition. Perhaps the greatest single advance has been the recognition that much of the slope of the Gulf of Mexico is underlain by a huge salt nappe expressed by the Sigsbee escarpment. Again, studies of exposed diapirs in areas such as the Great Kavir of Iran have emphasized the complexity of internal (and flanking) structure. Latterly, quantitative analysis of salt diapirism using rock and fluid mechanics backed up by experimental modelling has given further insight into salt diapirism and thereby into the interpretation of salt structures on seismic
data. Presentation of these new concepts and analytical techniques in the form of a glossary is thus both welcome and timely. Unusually, the 136 terms in the glossary are not listed in alphabetical order. The ideas and nomenclative are listed sequentially following a logical progression rather than the illogical order of the alphabet. Simple terms related to basic concepts thus come first with more complex terms following as salt tectonism is treated with greater depth. Each term is clearly defined and backed up by figures. The glossary is divided into eight sections: components of salt tectonics, the shape of salt structures, internal structures, the sedimentary record of salt tectonics, basic processes of salt tectonics, allochthonous growth during regional extension, allochthonous growth during regional shortening and, lastly, allochthonous growth. The latter section refers to salt nappe development as observed in the Gulf of Mexico where it has an important impact on hydrocarbon exploration. Three appendices provide definition of key formulae and terms used in rock and fluid mechanics. A short but pertinent bibliography cites key references of modern salt tectonics. This useful and well illustrated glossary is essential for any geoscientist concerned with salt tectonics in industry and academe. Many of the figures can be used as teaching aids.
D. G. Roberts
BP Exploration
Salt Diapirs of the Great Kavir, Central Iran M. P. Jackson et aL Geological Society of America Memoir 177; 1990; 139 pp. Price: $36.25 This Memoir describes the geology of the little known diapir province of the Great Kavir, Central Iran. The Great Kavir basin contains more than 50 spectacularly exposed diapirs formed from two salt sequences deposited in the Eocene through Miocene. Jackson et al. have used field data collected by H. Huber and by co-authors Gansser and Stocklin, together with spectacular aerial photographs, satellite data, scaled centrifuge modelling and analytical modelling to compile a comprehensive book on this unique diapir province. The majority of the Memoir is devoted to a detailed description of the geology of the Tertiary to present day Kavir basin in which the diapirs are formed. The diapirs occur about 220 miles ESE of Teheran in the remote and largely inaccessible
salt desert of the Great Kavir. Numerous closely spaced diapirs of Eocene - Oligocene salt occur in Miocene country rocks. Detailed descriptions and analysis of the stratigraphy of the Kav'ir Basin are combined with an in-depth structural analysis of the diapir structures to derive field based evidence for the mushroom model of diapir formation. Surface geology is extrapolated to depth to construct cross-sections. The various levels of exposure of the diapirs allows a threedimensional analysis of their structure. Variations on the mushroom model involving symmetric, asymmetric and vortex geometries can account for the variability of diapir structures observed in the field. The ultimate product of diapir evolution is the fusion of spreading diapir bulbs into a
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the opening section Gawthorpe and Colella provide a comprehensive overview of coarse-grained deltas in rift basins. Their focus is on the large scale architectural contrasts that various supply points (axial v e r s u s marginal and footwall v e r s u s hanging wall) may produce in active extensional regimes. They also provide some useful cautionary comments about delineating tectonic controls from other possibilities. Two other "review" papers by Dabrio and Bardaji et al. examine fan deltas in south-eastern Spain. Both these papers are detailed on [ithofacies and facies sequences and attempt to separate eustatic from tectonic controls within their fan delta successions. In the section specifically dedicated to the effects of tectonics on ancient coarse-grained deltas are five papers. Four of these papers provide very detailed facies descriptions of fan deltas of many types. Marine and lacustrine fan deltas are represented and water depths of progradation range from only a few metres to greater than 150 m. Kazanci and Van der Straaten both provide examples of how extensional tectonics can severely influence the larger scale architecture of fan delta deposits. These two papers also neatly contrast a relatively small scale and marginal lacustrine delta with a much larger and axial marine system. The generation of tectonic sedimentary packets is clearly discussed in both case studies. The following two papers focus much more on the meso scale organization of tim delta facies sequences. Flores examines lacustrine deltas in a transpressional basin and contrasts the facies and facies sequences developed in both marginal and longitudinal (axial) settings. Hwang and Choung describe a marine fan delta deposited in a transtensional basin. Their descriptions of individual sedimentary facies are the most detailed of the entire volume, but the establishment of tectonic controls are perhaps the weakest. Garcia-Mondejar is the final contributor in the tectonic section. This paper is low on facies detail, but instead erects a sequence stratigraphic model for a marine fan delta succession. Erosional unconformities and rapid, almost non-depositional transgressions in the succession are attributed to tectonically driven relative sea level changes and descriptions of the erosionally bounded "sequences' are made in a systems tract framework. The final major section of the volume consists of four contributions dealing with the intluences of climate and water level on coarse-grained deltas. Two of these papers, by Martini and Mastalerz, deal with glacial settings, Bowman describes an example from the arid Dead Sea area, and Massari and Parea describe strongly wave-intluenced, marine fan deltas. All these papers are particularly well illustrated and each deals with unique aspects of fan delta deposition not dealt with elsewhere within the volume. The detailed description of the wave-dominated deltas of Massari and Parea is of particular interest and contrasts with almost all the previous case studies. In this one example the importance of slope instability is relegated, the importance of basin processes heightened and the effects of eustatic changes given a relatively high prominence. An important conclusion that results from an examination of the 'non-tectonic' case studies compared with the preceding sections is that very similar geometries and architectural patterns may result from different allocyclic and autocyclic controls. This led me back to the opening remarks of the editors in which important issues are highlighted. One of these is a realization that the present understanding is insufficient to construct adequate stratigraphic and facies models. I feel this volume has gone a considerable way in increasing our understanding. Many of the papers do have common elements that could be usefully summarized and the
M a r i n e a n d PP.troleum Go.olcmv. 1.q.q2 Vnl 10 A n r i l
Book reviews further development of sequence stratigraphic concepts in coarse-grained deltas will probably lead to more refined and less uncertain stratigraphic models. The volume is completed by a unique contribution by Porebski and Gradzinski. Their lava-fed delta shows many of the classic foreset bedding structures seen in their fluvial-fed counterparts and shares some of the gravity flow processes common on the coarse-grained deltas throughout the other case studies. However, the interpreted eruptive cycles of debris and lava flows create a unique evolution in the delivery mechanisms and grain sizes available for delta construction, which were certainly new and fascinating to this reader. My overall opinion of this publication is that it provides a very useful addition to the growing library of Special
Publications of the IAS. I am especially pleased to report that most of the contributions are well illustrated with good photographs as well as ample drawings and tables. I recommend this book as essential for those working with deltas of any type, modern or ancient. I also expect that it will become a key reference for those joining or continuing the analyses of coarse-grained deltas, which are clearly enjoying a sustained growth interest, as attested by the popularity of the Fan Delta field workshop and the publication of this volume.
Andy Pulham
BP Exploration, Houston, TX, USA
A Glossary of Salt Tectonics M. P. A. Jackson and C. T. Talbot Geological Circular 91.4. Bureau of Economic Geology, University of Texas, Austin, Texas; 1991. Price $2.50 This comprehensive and inexpensive glossary is essential for any geoscientist concerned with salt diapirism in industry or academe. The glossary has been compiled by Martin Jackson and Chris Talbot from the Bureau of Economic Geology, who are themselves recognized leaders and innovators in modern kinematic and experimental analysis of salt tectonism. Since the early work of Trusheim and the simultaneous publication in 1968 of memoirs on salt and salt diapirism by the Geological Society of America and the American Association of Petroleum Geologists, considerable advances have been made in the study of salt tectonics as shown in the special issue of Marine and Petroleum Geology (August 1992) on this topic. These advances in understanding have been facilitated by the continuous improvement in the quality of two dimensional and latterly three dimensional seismic that have allowed for better imaging of the complexity of salt structures and their influence on sediment deposition. Perhaps the greatest single advance has been the recognition that much of the slope of the Gulf of Mexico is underlain by a huge salt nappe expressed by the Sigsbee escarpment. Again, studies of exposed diapirs in areas such as the Great Kavir of Iran have emphasized the complexity of internal (and flanking) structure. Latterly, quantitative analysis of salt diapirism using rock and fluid mechanics backed up by experimental modelling has given further insight into salt diapirism and thereby into the interpretation of salt structures on seismic
data. Presentation of these new concepts and analytical techniques in the form of a glossary is thus both welcome and timely. Unusually, the 136 terms in the glossary are not listed in alphabetical order. The ideas and nomenclative are listed sequentially following a logical progression rather than the illogical order of the alphabet. Simple terms related to basic concepts thus come first with more complex terms following as salt tectonism is treated with greater depth. Each term is clearly defined and backed up by figures. The glossary is divided into eight sections: components of salt tectonics, the shape of salt structures, internal structures, the sedimentary record of salt tectonics, basic processes of salt tectonics, allochthonous growth during regional extension, allochthonous growth during regional shortening and, lastly, allochthonous growth. The latter section refers to salt nappe development as observed in the Gulf of Mexico where it has an important impact on hydrocarbon exploration. Three appendices provide definition of key formulae and terms used in rock and fluid mechanics. A short but pertinent bibliography cites key references of modern salt tectonics. This useful and well illustrated glossary is essential for any geoscientist concerned with salt tectonics in industry and academe. Many of the figures can be used as teaching aids.
D. G. Roberts
BP Exploration
Salt Diapirs of the Great Kavir, Central Iran M. P. Jackson et aL Geological Society of America Memoir 177; 1990; 139 pp. Price: $36.25 This Memoir describes the geology of the little known diapir province of the Great Kavir, Central Iran. The Great Kavir basin contains more than 50 spectacularly exposed diapirs formed from two salt sequences deposited in the Eocene through Miocene. Jackson et al. have used field data collected by H. Huber and by co-authors Gansser and Stocklin, together with spectacular aerial photographs, satellite data, scaled centrifuge modelling and analytical modelling to compile a comprehensive book on this unique diapir province. The majority of the Memoir is devoted to a detailed description of the geology of the Tertiary to present day Kavir basin in which the diapirs are formed. The diapirs occur about 220 miles ESE of Teheran in the remote and largely inaccessible
salt desert of the Great Kavir. Numerous closely spaced diapirs of Eocene - Oligocene salt occur in Miocene country rocks. Detailed descriptions and analysis of the stratigraphy of the Kav'ir Basin are combined with an in-depth structural analysis of the diapir structures to derive field based evidence for the mushroom model of diapir formation. Surface geology is extrapolated to depth to construct cross-sections. The various levels of exposure of the diapirs allows a threedimensional analysis of their structure. Variations on the mushroom model involving symmetric, asymmetric and vortex geometries can account for the variability of diapir structures observed in the field. The ultimate product of diapir evolution is the fusion of spreading diapir bulbs into a
Marine and Petroleum Geology, 1993, Vol 10, April
181