De Graciansky / Roberts / Tricart The Western Alps, from Rift to Passive Margin to Orogenic Belt

An Integrated Geoscience Overview
1. Auflage 2010
ISBN: 978-0-444-53725-6
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 14, 432 Seiten

Reihe: Developments in Earth Surface Processes

The Western Alps, from Rift to Passive Margin to Orogenic Belt addresses the evolution of the Alpine fold belt for the first time in the English language. It builds on classical Alpine geological studies made since the start of the 19th century by combining that research with modern results obtained over the past 50 years using new marine geological and geophysical technologies. The book thus provides an integrated overview of the evolution of the Alps from rift to passive margin to the present fold belt over a significant time span. - An integrated multidisciplinary synthesis of the evolution of the Alps from rift to passive margin to foldbelt - 175 figures, structural maps and cross sections - An index of localities referred to in the fext and figures - A brief summary of the history and development of ideas concerning the evolution of fold belts and passive margins since the 19th century - Provides basis for further enquire and research - Provides wider context relevant to marine and oil industry geoscientists

London, UK

Autoren/Hrsg.

De Graciansky, Pierre-Charles

Roberts, David G.

Tricart, Pierre

Inhaltsverzeichnis

1;Cover;1
2;The Western Alps, from Rift to Passive Margin to Orogenic Belt;2
3;Copyright;5
4;Contents;8
5;Foreword;14
6;Acknowledgements;16
7;List of figures;20
8;Part I: Introduction;32
8.1;1. Geosynclines, Passive Margins, Foreland Basins and Folded Belts: An Introduction;34
8.1.1;1. Prologue;34
8.1.2;2. Orogenesis, Rock Deformation and Development of the Thrust Concept;35
8.1.3;3. Mountain Belts and the Geosynclinal Theory (1859–1965);38
8.1.4;4. Geophysical and Geological Exploration in the Ocean: First Steps and Results;40
8.1.5;5. Continental Drift and Plate Tectonics: Principles;42
8.1.6;6. Sedimentation in Oceanic Basins and Problems in Palaeodepth Reconstruction;54
8.1.7;7. The Wilson Cycle: Mountain Belts, Passive Margins and Foreland Basin-Folded Belts;55
8.2;2. The Alps: Present Day Structure;60
8.2.1;1. The Alps: Main Subdivisions;61
8.2.2;2. The Central and Western Alps: Major Structural Trends;65
8.2.3;3. Alpine Metamorphism;73
8.2.4;4. The Arc of the Western Alps Compared to the Central Alps;75
8.2.5;5. Deep Structure of the Alps From Geophysical Studies;76
8.3;3. On the Origin of the Alps: The Vanished Oceans;86
8.3.1;1. Nappe Stratigraphy and the Existence of the Pre-Alpine Tethyan Oceanic Domain;87
8.3.2;2. Origins of the Tethys;89
8.3.3;3. The Development of the Tethys in the Cretaceous;96
8.3.4;4. Evolution of the Liguro-Piemontais Tethys: Tethyan and Alpine Phases;101
8.3.5;5. Alpine Palaeogeographic Domains in the Context of the Liguro-Piemontais Ocean and Continental Margin;104
8.3.6;6. The Alpine Phase, Late Cretaceous and Tertiary;105
8.4;4. Hercynian Inheritance, Tethyan Rifting and Alpine Nappes;108
8.4.1;1. The Alpine foldbelt incorporates part of the Hercynian foldbelt;109
8.4.2;2. Relations Between Hercynian, Tethyan and Alpine Structural Units;112
8.4.3;3. Conclusions;125
9;Part II: The Tethys Phase;128
9.1;5. The Age of the Onset of Tethyan Rifting in Western Europe;130
9.1.1;1. The pre-rift and syn-rift phases of the Jurassic Tethys;131
9.1.2;2. The Triassic transgressive–regressive cycle of Western Europe: a turning point in the redevelopment of Tethys;132
9.1.3;3. Comparison of the Triassic major transgressive–regressive cycle from the Brianconnais to the Rhone valley;139
9.1.4;4. Relationship of the Middle Triassic and Carnian extensional events to rifting of the Ligurian Tethys;142
9.1.5;5. Triassic palaeogeography and the line of opening of the Ligurian Tethysin the Jurassic;143
9.1.6;6. End of the Triassic (Late Norian and Rhaetian) and onset of rifting inthe Ligurian Tethys;143
9.2;6. The Pre-Ligurian Tethys Rift Phase on the European Margin;146
9.2.1;1. Structures formed by rifting;148
9.2.2;2. Structural framework of the European margin of Tethys in the Alps;162
9.2.3;3. Evidence of extension and pulsed rifting during the Late Triassicand Jurassic;168
9.2.4;4. Modes of subsidence during rifting;173
9.2.5;5. Summary: The future European continental margin in the Westernand Central Alps during the rift phase;175
9.3;7. Late Jurassic and Early Cretaceous Development of the European Margin Spreading of the Liguro- Piemontais Ocean;178
9.3.1;1. The age of the onset of the post-rift phase and spreading of the Liguro-piemontais Ocean;179
9.3.2;2. Organization of the European margin of the Tethys in the Late Jurassic and Early Cretaceous;179
9.3.3;3. Interpretation of the Valais zone: an oceanic basin of Early Cretaceousage or a failed rift superimposed on the Tethyan margin?;181
9.3.4;4. The behaviour of the Saint Bernard–Monte Rosa (‘SBR’) block during the Late Jurassic–Early Cretaceous rift phase;193
9.3.5;5. Rifting of Late Jurassic–Early Cretaceous age in the Western Alps;194
9.3.6;6. Summary and Conclusions: Deformation of the European Margin During Spreading of the Tethys;197
9.4;8. The Late Cretaceous Phase and the Onset of the Alpine Shortening;200
9.4.1;1. Evolution of the European margin of the Tethys in the Late Cretaceous:early Alpine deformation;200
9.4.2;2. The Pelagic ‘Globigerinid-bearing muds’ of the Western and Central Alps and associated clastic sediments: demonstration of extensional tectonics;206
9.4.3;3. Evolution of the deformation field in the Central and Western Alps during the Late Cretaceous;210
9.4.4;4. Comparison with the Pyrenees and Provence domains 1795. Kinematics and uplift during the Late Cretaceous;210
9.4.5;5. Kinematics and uplift during the Late Cretaceous;213
9.5;9. The Tethyan Margin in Corsica;214
9.5.1;1. Hercynian and Alpine Corsica;214
9.5.2;2. The Initial Position of Corsica During the Mesozoic;216
9.5.3;3. The Transition from the Corsica–Provence Platform to the Liguro-Piemontais Ocean;217
9.5.4;4. Summary: Characteristics of the Tethyan Margin in Corsica;219
9.6;10. The Apulia-African Margin of the Liguro-piemontais Ocean:The Transition from Continent to Ocean;220
9.6.1;1. Southern Alps Transect: Northern Italy to Southern Switzerland;221
9.6.2;2. The Grisons (= Graubu¨nden) transect in eastern Switzerland;227
9.6.3;3. Summary and Conclusion;234
9.7;11. Liguro-piemontais Ophiolites and the Alpine Palaeo-Ocean;236
9.7.1;1. Ophiolites;237
9.7.2;2. Oceanic Sediments;266
9.7.3;3. Summary and Conclusions;270
9.8;12. Recapitulation and Comparisons: Oceans and Continental Margins in the Alps, an Overview;274
9.8.1;1. A short palaeogeographic reminder;275
9.8.2;2. Rifting: comparisons and reflections;276
9.8.3;3. Continental rupture and exhumation of the upper mantle;285
9.8.4;4. The notion of the breakup unconformity: discussion;286
9.8.5;5. Oceanic accretion in the Liguro-piemontais Ocean;289
9.8.6;6. Branches of the Tethys in the future Alpine domain;290
9.8.7;7. Segmentation of the oceanic lithosphere and adjoining continental margins;294
10;Part III: From the Tethys to the Alpine Fold Belt;298
10.1;13. Birth of the Western and Central Alps: Structural Inversionand the Onset of Orogenesis;300
10.1.1;1. The concept of structural inversion;301
10.1.2;2. Increasing intensity of Alpine deformation from W to E in the Western Alps;302
10.1.3;3. Multiphase inversion in the Sub-alpine domain;304
10.1.4;4. Reactivation of extensional faults during inversion;306
10.1.5;5. The role and attitude of decollement surfaces during inversion;313
10.1.6;6. Conclusion: the role of the earlier fault fabric of the passive margin during inversion;317
10.2;14. The Birth of the Western and Central Alps: Subduction,Obduction, Collision;320
10.2.1;1. Subduction, obduction;321
10.2.2;2. The collision;324
10.2.3;3. Chronological constraints;333
10.2.4;4. Modes of orogenesis in the Central Alps along the Matterhorn (Cervin) transect;337
10.2.5;5. Some singularities of Western Alps structure;342
10.3;15. The Alps – Neotectonics;348
10.3.1;1. Seismicity;349
10.3.2;2. Direct measurement of present-day, active deformation of rocks;354
10.3.3;3. Vertical movements;354
10.3.4;4. Horizontal movements;358
10.3.5;5. Study of ‘late’ faults in the Field;360
10.3.6;6. Conclusion;363
10.4;16. Summary, Discussion and Conclusion;368
10.4.1;1. The major events that characterize Tethyan history;370
10.4.2;2. Inheritance: Hercynian, Tethyan and Alpine Structure;371
10.4.3;3. From Tethyan extension to Alpine compression;374
10.4.4;4. Development of the Ligurian Tethys and Transgressive–Regressive cycles at the European scale;378
10.4.5;5. Conclusion: Neotectonics and Alpine Peaks: a common history;385
11;References;392
12;Geographical Index;408
13;Subject Index;422

Leseproben

Chapter One Geosynclines, Passive Margins, Foreland Basins and Folded Belts
An Introduction
Pierre-Charles De Graciansky; David G. Roberts; Pierre Tricart    Ecole Nationale Supérieure des Mines de Paris (France)
University of London, Egham, Surrey (United Kingdom)
University of Grenoble (France) Publisher Summary
This chapter discusses geosynclines, passive margins, foreland basins, and folded belts. Application of the geosynclinal model provided guidelines for geological exploration and thinking in different fold belts worldwide and particularly those surrounding the Mediterranean. The shallow Moho under rifts and passive margins shows stretching of the crust and lithosphere. Foreland basins are associated with continental collision and formed by flexure of the lithosphere. They are elongated basins that thicken toward the adjoining contemporaneous fold or orogenic belt. The deflection of the lithosphere that forms the accommodation space infilled by foreland basin sediments is determined by the flexural rigidity of the lithosphere and the magnitude of the load imposed by the orogenic belt or wedge. The chapter also describes the Wilson cycle from the mountain belts, passive margins, and foreland basin-folded belts. 1 Prologue
Although geological sampling of surficial sediments in shallow and deep water dates back to the Challenger expedition in the 19th century, detailed studies of continental margins did not begin until after World War II. While early gravity expeditions led by Meinesz (1941) among others had yielded some insights into the deeper structure of the margins of the Pacific and Atlantic Oceans, the use of sonar and other techniques developed during the war allowed for rapid mapping of the sea floor and also investigation of the deeper structure beneath the shelf continental slope and abyssal plains. It had long been recognized that pelagic sediments identified by the Challenger expedition (Murray and Renard 1891) had their equivalents in folded belts. However, the range of possible interpretations remained large especially in view of the then established view of the permanence of the ocean basins. Simplicity versus complexity were the two bywords that differentiated the community of marine geoscientists from those concerned with terrestrial geology and geoscience. Suess in his seminal global geology summary (1885) noted that ‘the possibility was recognised of deducing from the uniform strike of the folds of a mountain chain, a mean general direction or trend line: such trend lines were seldom seen to be straight but consisted of arcs or curves, often violently bent curves of accommodation; the trend lines of central Europe were observed to possess a certain regular arrangement and to be traceable in part as far as Asia. It was further recognised that the ocean from the mouth of the Ganges to Alaska and to Cape Horn is bordered by folded mountain chains while in the other hemisphere this is not the case so thatPacific and Atlantic types may be recognised.’ Suess thus recognized, over a hundred years ago, the fundamental differences between the active (Pacific) and passive (Atlantic) continental margins. He noted the continuity of the circum Pacific and Alpine–Himalayan fold belts whose association with calc alkaline volcanism and deep earthquakes is now very well known and understood. Suess was also well aware of the problems of major marine transgressions especially that of the Late Cretaceous. However, Suess thought that the ocean crust was similar to that of the continents and that the oceans owed their origins to ‘subsidence and collapse’. However, the technological hurdles that had to be overcome to determine the geology of continental margins were matched by the problems imposed by the complex and intense deformation of folded belts exposed on land. 2 Orogenesis, Rock Deformation and Development of the Thrust Concept
H.B. de Saussure (1740–1799), the Swiss naturalist from Geneva, was one of the first to express the idea that the torsion of beds observed on the flanks of Alpine valleys might be caused by ‘forcing back’ of rock material. His classic interpretation of the fold of the Arpenaz waterfall (Fig. 1.1) which dominates the Arve valley near the small town of Sallanches (between Chamonix and Geneva) was made, however, without any of the present knowledge of the rheological properties of rocks. Figure 1.1 Fold of the Arpenaz waterfall, Haute Savoie (France). H.B. de Saussure (1740–1799), probably the first or among the first Alpine geologists, described the fold of the Arpenaz waterfall between Geneva and Chamonix in the Arve valley. To explain the observed deformation, he proposed that the Jurassic and Cretaceous limestones were soft muds at the time of deformation. Today, one of the interesting aspects of this fold is that it shows the divergence of structure towards the external part of the fold belt, here to the NW. Horace Benedict de Saussure (1790). The permanence of continents and oceans was considered a basic truth by authors of the first three quarters of the 19th century. In consequence, they found difficulty in conceiving that the rocks forming the mountains had been subjected to horizontal displacements greater than those observed in associated folded beds. Not until the 1880s would the existence of thrusts be demonstrated clearly. A comparison of concurrent structural interpretations of the Glarus area (Switzerland) classically exemplifies the debate at the end of the 19th century on this issue (Fig. 1.2). Figure 1.2 Two structural interpretations of the Glarus Alps. (A) Albert Heim sketched two large facing recumbent folds. A fan fold is required to explain the Churfisten structure on the left of section. The interpretation resolves the problem of abnormal superposition with respect to the normal way up succession at the same time minimizing the magnitude of the sub-horizontal tectonic transport of thrust material. The illustration provided by Heim in his 1878 paper is superb. It adopts and recaptures the earlier conclusions of Arnold Escher (1866). M: Molasse; f: Flysch; c: Cretaceous; J: Jurassic.; t Trias; p: Permian. From A. Heim 1878. (B) Marcel Bertrand introduced the notion of tectonic ‘covering’ originating the concept of the thrust nappe. He had not visited the field from the time of 1884 publication on the subject. He used structural results related to the coal basin of northern France to reinterpret the conclusions of A. Heim without contesting the validity of the observations. His sketch illustrates the concept according to which thrust nappes are derived by rupture of the inverse flank of a recumbent fold. From Marcel Bertrand (1883–1884), reproduced after Bailey (1935), Fig. 10, p. 40. The interpretation of Heim (1891) which portrays two facing folded beds adroitly resolved the problem of abnormal superposition with respect to the normal bed succession while reconciling the intellectual requirement to minimize the amplitude of sub-horizontal displacements of rocks (Fig. 1.2A). The 1884 interpretation of Bertrand in the same area subsequently gained the support of the community from the end of the 19th century. This described one of the first Alpine thrusts using modern extant ideas (Fig. 1.2B). From then on, classic thrust interpretations were made by great authors such as Schardt (1893) for the Prealps (Fig. 2.8), Lugeon (1902) for the Helvetic nappes, Termier (1903) for the Western Alps and for the Eastern Alps (Fig. 2.6A). 3 Mountain Belts and the Geosynclinal Theory (1859–1965)
The enormous thicknesses of sediments documented in fold belts and their adjacent basins caused major difficulties reconciled in the ‘geosynclinal’ theory (Fig. 1.3A) of Hall (1859) and Dana (1873). These thicknesses far exceeded the depths of the modern oceans and the sediments typically consisted of shallow marine deposits. Obviously subsidence had to have taken place to allow the accumulation of such thicknesses. Dana used the term ‘geosynclinal’ with reference to a subsiding and infilling basin resulting from his concept of crustal contraction due to a cooling earth. Figure 1.3 (A) Interpretation of the Appalachian system in Middle Ordovician time. This reconstruction derives from the Hall and Dana’s geosynclinal model. It has been the starting point for the interpretation of mountains for about a century (1858–1965). From Drake et al. (1959), Fig. 7, p. 7(B) Interpretation of the Alpine Geosynclinal, after Gignoux (1950). The Alpine geosynclinal model was taught from the 1930s to the end of the 1950s. It described a ‘geanticline’ for the Brianconnais cordillera characterized by littoral sediments (figured here by dotted lines) separating two troughs with thick sedimentation. This cordillera was identified as an ‘embryonic nappe’. Ophiolites were supposed to have been injected at the base of the...