BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA
VOL. 71, PP. 843-908, 14 FIGS.. 2 PLS. JUNE 1960
PALEOTECTONIC EVOLUTION OF THE CENTRAL AND WESTERN ALPS
BY RUDOLF TRUMPY
ABSTRACT This paper deals with the general features of Mesozoic and Tertiary rock sequences and paleogeography in the Alps. It seeks to outline the paleotectonic significance of the rocks and to discuss the structural evolution of the Alpine geosyncline up to the main deformation, with special reference to the sector between the rivers Rhine and Durance. Accent is placed on the relative independence of Alpine structures involving the pre-Triassic basement rocks and of cover nappes consisting only of Mesozoic and Tertiary formations. Normal shallow-water deposits of platform or miogeosynclinal type were laid down over the whole area before eugeosynclinal conditions set in. The typical eugeosynclinal sediments in the central, Penninic belt of the Alps are the Schistes lustres and Bundner- schiefer, with sills and submarine lava flows of basic volcanic rocks (ophiolites). Before metamorphism they consisted mainly of shales and of impure arenaceous and argillaceous limestones. The bathymetric environment of radiolarian cherts and associated rocks is examined, and their deep-water origin is upheld for the Alpine occurrences. Marine polygenic breccias are characteristic of geosynclinal slopes (commonly fault scarps) and not of a particular depth zone. The Alpine Flysch is a particularly significant sediment. Flysch is a thick marine deposit of predominantly detrital rocks, in part turbidites, generally without volcanic rocks, and laid down during compressional deformation of the geosyncline. Of the many different kinds of Flysch some represent transitions to either Bundnerschiefer or Molasse. Essential differences between the early synorogenic Flysch and the later synorogenic to post-orogenic Molasse are listed. Argand's stimulating embryotectonic theory of the evolution of the geosyncline is out- lined and rejected. The Triassic corresponds to a neutral interval, between the Hercynian and Alpine cycles. Early Alpine geosynclinal history was characterized by vertical or ten- sional movements along normal faults that limited narrow platforms and rapidly sub- siding troughs. This tensional deformation weakened in the Late Jurassic, whereupon bottom relief diminished, and "para-oceanic" conditions prevailed over a large part of the Mediterranean realm. New linear welts of compressional origin arose during the Cretaceous and developed into steep island chains limiting the Flysch basins. Gradually the central part of the Alps rose above sea level, and the geosyncline migrated to the north and west. Here it was finally filled and gave way to the foreland trough in which the Molasse was laid down. There is no simple, direct, genetic and space relationship between Hercynian structures, fault-bordered platforms and troughs of the earlier geosynclinal phase, island chains and basins of the Flysch phase, and the later nappe structures. Paleogeographical features are commonly short-lived and migratory.
RESUME Ce travail est consacre aux caracteres gene'raux des dep6ts mesozoiques et nummuli- tiques des Alpes. On a essaye1 d'esquisser la signification paleotectonique des divers types de formations, et de discuter Involution structurale du geosynclinal alpin jusqu'a 1'dpoque des plissements principaux. La plupart des exemples ont dtd choisis dans le secteur entre le Rhin et la Durance. Un bref resume" est destine' a donner les grandes lignes de la tectonique et de 1'histoire gdologique des Alpes. On a insist^ sur I'independance relative des structures affectant le socle pre"-triasique et des nappes de d&ollement. Des depdts neritiques normaux, caracterisant des plateformes ou des miogebsyncli- naux, ont 6t6 forme's partout avant 1'avenement desconditionseugeosynclinales. Less&li- ments caracteristiques de la zone centrale, euge"osynclinale, des Alpes (domaine Pennique s. 1.) sont les Schistes lustres et les Bundnerschiefer, avec des filons-couche et des coulees sous-marines de roches basiques (ophiolites). Avant le me"tamorphisme, ils e'taient surtout formes de schistes argileux et marneux et de calcaires impurs, sableux et marneux. Le 843
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milieu bathyme'lrique des radiolarites et des roches accompagnantes est examine1, et Ton conclut a leur origine en mer profonde. Des breches sous-marines polygfoiques sont ca- racteristiques des talus gebsynclinaux, souvent dus a des failles, mais non pas d'une zone bathyme'trique dfterminee. Enfin, il est essaye1 de donner les caracteres essentiels des flyschs des Alpes. Ce sont des formations epaisses, marines, a predominance de'lritique, et renfermant des depots de courants de turbidite'. II n'y a ge'ne'ralement pas de roches volcaniques. Le flysch s'est depose1 pendant que les efforts de compression tangentielle affectaient dejil le gebsynclinal. II y a de nombreuses especes de flysch, ainsi que des termes de transition soit vers les Bundnerschiefer, soil vers la molasse. Les principales diffe- rences entre flysch et molasse sont indiquees. La seconde partie du travail tralte de 1'dvolution du gebsynclinal. La thebrie d'Argand sur la tectonique embryonnaire est exposee; elle doit probablement etre abandonee. Le Trias correspond a une period neutre, entre les cycles Hercynien et Alpin. Pendant une premiere phase de 1'histoire gebsynclinale, il y avail surtout des mouvements verticaux ou d'extension, le long de failles normales limitant des sillons subsidents et des plateformes assez etroites. Les deformations de ce type devinrent plus faibles au Jurassique superieur. Pendant un certain temps, le relief sous-marin fut peu prononcd, et des conditions "para- oceaniques" regnerent sur une grande partie des pays me'diterrane'ens. De nouvelles rides, dues aux forces tangentielles naquirent pendant le Cretace', et devinrent les "cordilleres", des guirlandes d'tles au relief Ires accentue, limitant les bassins ou se deposait le flysch. Peu a peu, la partie centrale des Alpes s'eleva hors des eaux; le gebsynclinal fut deplace vers le nord et 1'ouest, ou il fut enfin comble' et passa a 1'avant-fosse molassique. II n'y a pas de relation simple et directe, de nature topographique et ge'ne'tique, entre les structures hercyniennes, les plateformes et les sillons de la premiere phase gebsyncli- nale, les "cordilleres" et les bassins de la phase du flysch, et les nappes actuelles. Les ele1- ments palebgebgraphiques sont souvent assez ephemeres, et sujets a des migrations re'pe'- tees.
ZUSAMMENFASSUNG Diese Arbeit behandelt die wichtigsten Ztige der mesozoischen und alttertiaren Sedi- mentbildungen in den Alpen. Es wird versucht, die palaeotektonische Bedeutung der verschiedenen Gesteinsgruppen zu umreissen und die strukturelle Entwicklung der alpi- nen Geosynklinale bis zu den Hauptfaltungsphasen zu verfolgen. Die meisten Beispiele sind dem Abschnitt zwischen dem Rhein und der Durance entnommen. Uber die Tektonik und die geologische Geschichte der Alpen orientiert ein kurzer tiber- blick. Besonders betont wird die relative Unabhangigkeit der Strukturen, in welche das vortriadische Grundgebirge einbezogen ist, und der nur aus mesozoischen und alttertiaren Gesteinen bestehenden Abscheerungsdecken. Normale Seichtwasserablagerungen von Plattform- oder miogeosynklinalem Charakter wurden uberall gebildet, bevor die eigentliche eugeosynklinale Entwicklung einsetzte. Die charakteristischen eugeosynklinalen Sedimente des zentralen, penninischen Faziesbe- reichs sind die Schistes lustre's und BUndnerschiefer, mit Lagergangen und Ergussen basischer Gesteine (Ophiolithe). Vor der Metamorphose bestanden sie grossenteils aus Schiefermergeln und Schiefertonen, sowie aus sandigen und mergeligen Kalken. Die Ab- lagerungstiefe der Radiolarite und der mit ihnen verkniipften Gesteine wird diskutiert, wobei die tiefmeerische Entstehung dieser Bildungen fur wahrscheinlich angesehen wird. Marine Breccien sind bezeichnend filr steile, oft durch Verwerfungen bedingte Geosyn- klinalrander, nicht aber fur eine bestimmte Meerestiefe. Schliesslich wird eine Charak- terisierung der alpinen Flyschbildungen versucht. Es sind dies machtige, ausschliesslich marine, vorwiegend detritische Ablagerungen. z. T. Turbidite. Sie fiihren gewohnlich keine vulkanischen Einschaltungen. Sie wurden wahrend des beginnenden Zusammenschubes der Geosynklinale gebildet. Es gibt viele verschiedene Arlen von Flysch, sowie Ubergangstypen zu Bundnerschiefer und zu Molasse. Die wesentlichen Unterschiede zwischen Flysch und Molasse werden kurz aufgeftihrt. Der zweite Teil der Arbeit gilt der Entwicklung der alpinen Geosynklinale. Argand's Theorie der Embryonalfaltung wird dargelegl, im wesentlichen aber abgelehnt. Die Trias entspricht einer "neutralen Periode" zwischen dem herzynischen und dem alpinen Zyklus. Wahrend einer ersten Phase der Geosynklinalgeschichte herrschten Vertikalbewegungen, wahrscheinlich auch Dehnung, entlang normalen Verwerfungen vor. Diese Bewegungen wurden im Oberjura und in der untersten Kreide schwacher; es herrschte eine Zeitlang geringes Relief des Meeresbodens, bei "para-ozeanischen" Ablagerungsbedingungen in einem weiten Bereich des Mittelmeerraumes. Neue, langgestreckte Hochzonen, die ihre
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Entstehung dem beginnenden Zusammenschub verdanken, entstanden wahrend der Kreide; sie entwickelten sich zu den sogenannten "Kordilleren," steilen Inselrticken, welche die einzelnen Flyschbecken voneinander trennten. Der zentrale Teil der Alpen hob sich allmahlich Uber den Meeresspiegel, die Geosynklinale wurde nach N und W abge- drangt und wurde schlussendlich zum Vorlandtrog des Molassebeckens. Es besteht keine einfache, unmittelbare, raumlich-genetische Beziehung zwischen her- zynischen Strukturen, Trogen und horstartigen Schwellen der ersten Geosynklinalphase, Becken und Kordilleren der "Flyschzeit," und der spateren Deckentektonik. Die palaeo- geographischen Einheiten sind oft recht kurzlebig und verlagern sich im Lauf der geosyn- klinalen Vorgeschichte. IIAJIEOTEKTOHHqECKAH 9BOJIK)I],Hfl ITEHTPAJItHHX H 3AnA#HfcIX AJIfcll
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CONTENTS
TEXT Page Page Mesozoic tensional structures in other Introduction 847 parts of the Alps 886 Opening remarks 847 Remarks on the ophiolite problem 887 Acknowledgments and limitations 847 Paleogeographic pattern during the "Flysch Outlines of tectonic structure 848 phase" 887 Nappe structure and the amount of crustal Early folding movements 887 shortening 848 Structural characteristics of Flysch Alpine structures involving the basement.. 849 Cordilleras 888 D&ollement nappes 850 Tarine and Arvinche Cordilleras of Savoy.. 891 Outlines of stratigraphy 852 Evolution of paleogeographic pattern 891 Facies belts 852 Ephemeral nature of facies belts 891 Helvetic and Dauphine realm 854 Relationship of late Hercynian structures Valais fades belt 854 to Mesozoic facies belts 892 Brianconnais belt in the large sense 855 Relationship of Flysch Cordilleras to Piemont belt 855 Mesozoic platforms 894 Austroalpine realm 855 Obliquity of paleogeographic units 895 Realm of the southern Alps 855 General statement 895 Genetic sequences of Alpine sedimentary Crossing over of facies belts 895 rocks 856 Nonparallelism of paleogeographical and Platform and miogeosynclinal sediments.... 856 structural units 896 Gross characteristics 856 Conclusions 897 Triassic of the southern Alps 856 Five epochs of Alpine history 897 Lower Cretaceous of the Helvetic nappes.. 857 Remarks on geosynclinal nomenclature 898 Jurassic of the Median Prealps 858 Peculiar characteristics of the Alpine geo- Bundnerschiefer, Schistes lustres 860 syncline 899 General statement; metamorphism 860 References cited 900 Lithology and environment 860 Schistes lustre's of the Cottic Alps 861 Bundnerschiefer of central and western ILLUSTRATIONS Graubunden 862 "Pre-Flysch" of Pratigau 864 Figure Page "Leptogeosynclinal" formations 864 1. Palinspastic sketch map (A) and paleogeo- Meaning of the term 865 graphical sketches (B-D) of part of the Radiolarian cherts 866 western Alps 853 Pelagic limestones and azoic shales 866 2. Palinspastic cross section through the Jurassic and Cretaceous of Arosa zone... 867 Mesozoic formations of the Meclianes Jurassic and Cretaceous of the southern nappe in western Switzerland 859 Alps 868 3. Section at Mount Gondran, east of Marine breccia formations 869 Briancon 862 Characteristics and environment 869 4. Section of part of the Bundnerschiefer in Jurassic of the Breccia nappe 870 the TomUl sheet of western Graubunden. 863 Breccias of Sonnwend Mountains, Tyrol.. 872 5. Section of part of the Jurassic and Flysch 873 Cretaceous in southern Ticino 868 General statement 873 6. Jurassic and Cretaceous sequence of the Lithologic and biotal characteristics of Breccia nappe in Abondance Valley Alpine Flysch successions 873 (Chablais) 871 Formational and bedding characteristics 7. Cross section through the border zone of of Flysch. 874 the Alps west of Lake Lucerne 877 Bathymetric setting of Flysch sediments.. 874 8. Age relationship of Flysch formations in Tectonic setting of Flysch sediments 875 the Helvetic belt of eastern ^Switzerland. 879 Relationship of Flysch to other facies 9. "Embryonic geanticlines" in Mesozoic groups 875 time 881 Niesen Flysch (transitional to "pre- 10. Palinspastic section through the Middle Flysch") 876 and Upper Jurassic formations in the Schlieren and Gurnigel Flysch sequences Wildhorn nappe of the Bernese Oberland, of central Switzerland 877 showing the Mesozoic faults 883 Wildflysch of central Switzerland 878 11. Palinspastic cross section through the Flysch of the northern Helvetic belt and Triassic to Middle Cretaceous formations passage to Molasse 878 in the Glarnisch Mountains (Helvetic Molasse 880 nappes of Glarus Alps) 884 Structural evolution during the geosynclinal 12. Very hypothetical cross section through phase 881 some Prealpine nappes at the end of the Argand's theory of embryotectonics 881 Middle Jurassic 885 Importance of Mesozoic faulting 882 13. Time of Flysch sedimentation in different Mesozoic faults in the Helvetic realm.... 882 units of the Swiss Alps 889 "Horst" characteristics of the Brianconnais 14. Cross sections through the frontal part of realm 884 the Penninic nappes in Savoy 890
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Plate Facing page TABLE 1. Tectonic sketch map of the Alps 848 2. Cross sections through the Prealps east of Table Page the Rhone Valley 860 1. Mesozoic stage names. 854
INTRODUCTION works in English (Collet, 1927; Bailey, 1935) are somewhat outdated, although the latter Opening Remarks still makes delightful reading. The remarkable chapters devoted to the Alps in Gignoux's There was a time when the Alps were con- 1 textbook give a very clear picture for the sidered, especially by European geologists, French part of the chain, but progress in this a model for all mountain chains. This was part has been so rapid these last years that during the first quarter of the century, after some major corrections of this picture are the discovery of the Alpine nappe structure. needed. In German, there are two excellent For a while, nappes were found all over the treatises, on the Swiss Alps by Cadisch (1953) world, even in places where they certainly and one on the Austrian Alps by Spengler and did not exist. Ultranappism brought forth by Heritsch (in Schaffer and others, 1951); antinappism—which is only now losing some but both are essentially meant as reference of its exaggerated violence—and the Alpine books. For all details concerning structure nappes were looked at as something quite and stratigraphic sequence the reader can be exceptional. Their very existence was even directed to these two standard works and to questioned. At best, the Alps were a freak, the great monograph by Albert Heim (1919; not worth the trouble of trying to understand 1921), which contains a wealth of significant their history and structure. data. The Alps, however, are neither the paradigm Finally, inasmuch as they figure prominently of all mountain chains nor a regrettable accident in any discussion of Alpine geology, it seems of the Earth's surface. They represent an appropriate to comment briefly here on some extremely complicated but not a unique type Alpine rock terms that have come to be used of tectonic structure. Many tectonic phenomena all over the world. Swiss geologists should be can better be studied in different, less disturbed proud that their little country has given birth fold belts, but for others the outstanding known to terms like Flysch, Molasse, and Biindner- examples are in the Alps, with their deep valleys schiefer, which are recognized, or thought to and their long history of investigation. be recognized, in almost any folded mountain The classic era of Alpine geology lasted chain. In fact, they are not as happy about it from about 1890 (Marcel Bertrand's discovery as they ought to be. These words have a of the Glarus nappes, Schardt in the Prealps) perfectly sound household meaning in the to about 1925 (Staub's Bau der Alpen, 1924). Swiss Alps, but everybody is reluctant to give Since then, a great amount of sometimes a categorical definition, and they were not excellent local work has been done, but the meant for export. If "Flysch" and "Molasse" day of the great synthetic views seems past, are to be used outside the Alps, these terms at least momentarily. During the last 15 should at least designate rock groups showing years, the French geologists have made the some resemblance to the type Flysch and the most significant advances in the study of the type Molasse, and not merely as synonyms of Alps. The outlines of the structure are by now pre-orogenic and post-orogenic deposits. fairly well established, and detailed maps, mostly on scales between 1:25,000 and 1:75,000, cover almost the entire chain. Today, two Acknowledgments and Limitations problems are foremost: one concerns metamor- This paper was written at the suggestion of phism and rock deformation, the other the Preston Cloud. For his unfailing patience and sedimentary pre-history of the fold belt and the pains he has taken in preparing the copy for its relationship with the later structures. This print, the author is deeply indebted. paper aims to indicate our state of knowledge Marcel Lemoine, Walther Nabholz, and on the second point. Alpine geological writings of the last 2 1 The English translation was not available to decades, indeed, are not very encouraging to the author; references are to the last French edition the extra-Alpine reader. The only general of 1950.
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John Rodgers have read the manuscript and Austrian geologist who maintains a local have given invaluable help by their pertinent origin for the northern calcareous Alps east and constructive criticism. Augusto Gansser of the Rhine would develop different views on and my father, Daniel Triimpy, have also the early history of the Alps from the ones proffered very useful suggestions. sketched here. It is inevitable that one should Two of my students have been very helpful take a personal stand on these questions, from in preparing the paper: Sibylle Dollfus for the best of one's knowledge, even in a would-be checking and compiling references, Kimon dispassionate review article. Karagounis for drawing most of the figures. Widely differing estimates have been reached A paper of this kind is necessarily based on for the amount of crustal shortening in the the work of a great number of contemporaries Alps. Cadisch (1953, p. 287) gives a pre- and predecessors in the field reviewed. Because folding breadth of 630 km for the Swiss Alps, much of this, however, is so well known as to which now measure only 150 km across. This amount to common knowledge in the case of figure, obtained by straightening out one the Alps, it is unnecessary as well as impracticable folded stratigraphic datum along a cross sec- to cite specifically all works which contain tion, is open to criticism on two points: relevant contributions to Alpine geology. It (1) It neglects the stretching of Alpine rocks, would also be unrealistic to enter into long which may attain proportions of five to one discussions on all points of disagreement. The or more in certain zones, especially in the author is painfully aware that this paper con- deeper-seated parts of the chain. This stretch- tains some rather unequivocal statements on ing is probably not quite compensated by questions which are in fact still disputed; microfolding. but a certain amount of this is unavoidable when (2) Structural and paleogeographic analysis a large field is compressed into small scope, shows that several important units have dis- and one can only hope that time will vindicate appeared. Many have been removed by erosion; his choice of subjects to slight. the volume of the detrital Oligocene-Miocene A major shortcoming of the present paper Molasse alone is as great as that of the present is its unequal treatment of the different parts Alps. Other structural elements have been of the Alps. Most examples are taken from the drawn downward, into the inaccessible (and northern miogeosyncline (Helvetic-Dauphin^ presumably granitized) depths of the sub- realm) and from the central, Penninic, eugo- stratum. syncline. The author is less familiar with the The two sources of error work in opposite highest, Austroalpine, nappes of Austria and directions, so that Cadisch's figure of 630 Germany and fears to misjudge the significance km for the initial breadth of the Alps may be of local facts, in spite of all the important taken as a fair approximation (±200 km). papers written on this part of the chain. This, A 50 per cent shortening, from 300 to 150 km, again, is a risk which is inherent in the prepara- probably represents an absolute minimum. tion of such a summary paper, and the author (See also Sonder, 1940.) can only ask forebearance on the part of Nappes are generally ascribed to overthrusting colleagues who may know better. (rather than overfolding) from the south, or from the east in the French part of the chain. Outlines of Tectonic Structure Underthrusting from the north, however, seems to provide a more satisfactory cause for many Nappe structure and the amount of crustal phenomena, although most structures can be shortening.—The nappe structure of the Alps explained in either way. In discussing this and can no longer be questioned, but the mechanism, other matters it is convenient to refer to the correlation, and the amplitude of the units belonging originally to a more southerly nappes are still controversial. Uncertainties in or easterly belt as internal and, conversely, correlation fundamentally affect our views on to consider the northerly or westerly zones as paleogeography and render the construction of external. palinspastic maps and sections through the For the structural pattern of the Alps, the whole fold belt difficult and problematical. A reader is directed to the standard works men- French geologist with a tendency to ignore the tioned above. Only a few generalities are given existence of the Valais facies belt and to claim here as the minimum essential background for Piemont origin for all Schistes Iustr6s, a the discussions to follow. Plate 1 shows the Swiss geologist who regards most Prealpine broad areal distribution of the principal tectonic nappes as lower Austroalpine units, and an units.
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Structurally, Alpine rocks can be grouped into part of Montblanc to the south-southwest. The two major classes. One contains the pre- smaller Grandes Rousses massif lies to the Pennsylvanian basement, which was metamor- interior. phosed and folded long before the Alpine (4) The Pelvoux (or Haute Dauphine) massif orogeny; the other comprises the Triassic and differs from the others in its more nearly younger sedimentary and volcanic rocks. The circular outline and its situation farther to the Pennsylvanian and Permian (mainly con- east. tinental) formations play an intermediate role; (5) The amygdaloidal Argentera (or Mercan- sometimes they moved with the basement and tour) massif is isolated in the southernmost sometimes with the cover. In a number of part of the arch. instances the Mesozoic and lower Tertiary (6) Southeast of the Aar massif lies the small sediments were stripped off the basement on Tavetsch and then the larger Gotthard massif. which they were laid down to form decollement They are more strongly marked by Alpine nappes (strip sheets) of their own. Their metamorphism and are not strictly autoch- relationship with the much thicker nappes of thonous; they have moved laterally with the central zone of the Alps, in which the regard to the Aar massif. They have even been basement itself is involved, is often contro- interpreted as nappes. The structure of the versial. Much of our knowledge of the stratig- Gotthard massif can be compared to the raphy of the internal belts of the chain is "composite wedges" of the Apennines (Mig- derived from the study of such cover nappes, liorini, 1948). which have escaped Tertiary metamorphism. BASEMENT NAPPES OF THE PENNINIC BELT: Anhydrite-bearing members in the Triassic2 The lower Penninic nappes appear in the are most important as incompetent layers, transversal uplift of the Ticino and Toce along which the higher formations were sheared valleys. This is the deepest exposed part of off; and presence or absence of anhydrite beds the Alps, with high-grade Tertiary metamor- in the stratigraphic column may determine phism and a distinctive structural style. The whether the Mesozoic cover stayed with the steep-standing roots of higher nappes lie south basement or wandered. of these gneiss mountains. In the ensuing brief summary of structural In Valais, Argand's classical area, the Pen- units those involving the basement rocks are ninic nappes can be examined, thanks to their distinguished from those formed by strip sheets. descent westward into a transversal depression, the axis of which runs from Rawil pass to the central Pennine Alps. Above the lower Penninic Alpine structures involving the basement.— Ticino and Simplon nappes lies the enormous AUTOCHTHONOUS MASSIFS: These are large body of the Grand St. Bernard nappe, of basement slices which rise out of the Mesozoic very complex internal structure and very cover in the external zone of the Alps. irregular strike of tectonic axes. This mass of (1) The largest is the Aar massif of the Berne pre-Triassic, largely upper Paleozoic, rocks and Uri Alps, in central Switzerland. The continues down to the Mediterranean, but small, cylindrical Gastern massif to the north because its base is not exposed many geologists is only locally separated from the main body doubt its nappe character in the western Alps. of the Aar massif by a narrow wedge of Mesozoic A broad belt of cover nappes, however, has sediments. been thrust out between the autochthonous (2) West of a transversal depression, Alpine massifs and the Grand St. Bernard, so that equivalents of the Aar massif rise again in the these two basement units must have been Montblanc massif. The Aiguilles Rouges massif, laterally displaced toward each other. beyond the Chamonix "syndine" to the north- To the Inside and apparently above the Grand west, occupies the structural site of the Gastern St. Bernard lies the Monte Rosa nappe, with massif. a plunging front. The base of the similar (3) The long and bifid Belledonne massif gneiss cupolas of the Gran Paradiso and of the prolongs both Aiguilles Rouges and the external Dora-Maira is not exposed. In Graubunden, pitch toward the east again 2 Represented at the surface by cornieules shows a natural cross section through all the (cargneules, Rauhwacken), very porous and brecci- Penninic nappes. Correlation of units on the ated rocks consisting mainly of calcite, instead of the original anhydrite dolomites. Regarding the two sides of the Ticino uplift is often difficult, genesis of cornieules, see Briickner (1941). and most geologists now working in the Ticino
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tend to discard the possibility. There is, Austroalpine units; but to the south, the limit however, a kind of broad correspondence of the certainly autochthonous basement of between basement nappes of the Valais and the southern Alps can be drawn only with Graubiinden. The Adula gneiss nappe is the difficulty. This seemingly paradoxical relation- main unit of the lower Penninic. Two thick, ship of the greatest thrust sheet of the Alps superposed nappes, Tambo and Suretta, Staub with an autochthonous belt is more easily correlates with the Grand St. Bernard and understood if one takes underthrusting from Monte Rosa nappes of Valais, although the the north as the main movement of the Alpine structures are very different on the eastern orogeny. The upper Austroalpine basement and western sides of the Ticino uplift. The nappes did not extend much farther west Margna nappe (Ma on PL 1), severely sliced up than their present erosion edge in central under the Austroalpine thrust plane, is the Graubiinden. most important basement nappe of the upper Penninic units. Decollement nappes.'— The Penninic nappes then disappear to the east under the great Austroalpine thrust mass. HELVETIC NAPPES AND SUBALPINE CHAINS OF Their Mesozoic cover is again exposed in the FRANCE: In the Swiss Alps, the cover of the window of the Lower Engadine, and both Aiguilles Rouges and Gastern massifs is strictly cover and basement reappear in the window of autochthonous, except for some independent the Hohe Tauern, in the center of the eastern sliding of the Flysch group. The Mesozoic Alps. To any geologist acquainted with the and Eocene cover of the Montblanc and of the whole chain, the Penninic nature of the ele- western Aar massif is stripped off and forms a ments inside the Tauern window is beyond large recumbent fold, the Morcles or Dolden- doubt, even if the Penninic zone may have horn nappe. In eastern Switzerland, where "gone autochthonous" and lost some of its there are no anhydrite members in the Triassic, nappe structure this far east. Clar (1953) the cover of the Aar massif forms only parau- gives an excellent short review on the im- tochthonous slices, little displaced with respect portance of the Tauern window for the structure to their substratum. The Helvetic nappes of the eastern Alps. proper are derived, in the east, from the former BASEMENT NAPPES OF THE AUSTROALPINE covering beds of the Tavetsch massif and, BELT: The lower Austroalpine basement units perhaps, from the northern part of the larger of Graubiinden, which contain much Hercynian Gotthard massif (Fig. IA; PI. 1). They are granite and granodiorite, are represented mainly formed by a number of very spectacular by the Err and Bernina nappes. In the Valais although rather small nappes (e.g., Axen and Alps, the large thrust mass of the Dentblanche, Drusberg on Lake Lucerne, Diablerets and which rests everywhere on Penninic Mesozoic Wildhorn in western Switzerland); but their rocks, can very probably be reckoned as an correlation is hazardous, as the location of approximate equivalent. It is not preserved thrust planes is controlled largely by sed- southwest of the Aosta Valley but must once imentary facies. The Ultrahelvetic nappes, have overlain most of the western Alps. probably derived from atop the Gotthard The "Central Alps" of Austrian geologists, massif and its buried western equivalents, slid east of the Rhine, are formed of crystalline onto the back of the future Helvetic nappes in basement rocks, upon which Paleozoic forma- Oligocene times. When the Helvetic nappes were tions are preserved in large tracts, especially formed, in the Miocene, the Ultrahelvetic on the northern, eastern, and southeastern nappes became pinched into the recumbent border. They constitute the basement core of synclines between and below the Helvetic the upper Austroalpine nappes (including the elements, and their internal structure is now ill-defined "middle Austroalpine" of Grau- hopelessly chaotic. biinden), partly split up into the Campo, On the river Rhine the Helvetic nappes and Silvretta, and Oetztal nappes; the separations the Aar massif pitch very steeply east, below between these units cannot be followed over a Penninic and Austroalpine units; but a narrow long distance. Wedges of Triassic rocks are strip of Helvetic and Ultrahelvetic elements also found in Tyrol and Styria. At their western continues along the northern border of the termination, and along the "frame" of the eastern Alps, below the Penninic Flysch zone. Tauern window, the upper Austroalpine base- In the French Alps of Savoy and Dauphine, ment rocks rest upon the Mesozoic to lower the Helvetic nappes have lost their individ- Eocene sediments of Penninic and lower uality. Southeast of lake Geneva, the Morcles
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fold also merges with the Subalpine chains, Alps, between the river Arve and Lake Thun. of which the main body is a continuation of the Erosion has spared other outliers of Prealpine autochthonous zone of Switzerland extending nappes to the south, in the klippen of Savoy, finally under the Molasse basin. These Sub- and to the northeast around Lake Lucerne. alpine chains form a broad, folded belt of A cross section through the Prealps is given in Appalachian style. The Mesozoic formations Plate 2. are probably sheared off the basement along From the lowest to the highest, the following the lubricating anhydrite layers of the Triassic, units are represented in the Prealpine pile and the outermost of these folds join the of cover nappes: southern end of the Jura Mountains. In south- (1) Ultrahelvetic nappes, which crop out eastern France, Eocene ("Pyrenean") east- along the inner margin northwest of the west folds complexly interfere with the Alpine Helvetic high calcareous Alps (Prealpes in- folds of Miocene age, and the Triassic anhydrite ternes) and along the border of the Molasse rises in diapiric plugs. basin (Prealpes externes) The Ultradauphinois slices, behind the (2) Isolated slices, like the Chamossaire Belledonne and Pelvoux massifs, are more or nappe, and (Penninic?) Schlieren Flysch nappe less in the prolongation of the Ultrahelvetic of central Switzerland root zone of the Valais Rhone valley. (3) Niesen nappe, of unknown, presumably PENNINIC COVER NAPPES OF THE FRENCH lower Penninic, origin ALPS: In the depression between the Pelvoux (4) The nappe of the Prealpes M6dianes or and Argentera massifs, Penninic decollement Klippen nappe, derived from the cover of the nappes rest upon the Jurassic shales of the middle Penninic Grand St. Bernard mass.3 Subalpine Dauphin6 belt. This is the type area The northwestern part (Medianes plastiques) of the Subbrianconnais, with the two main has Subbrianconnais facies; the more internal digitations of Piolit and Morgon. Above is a Medianes rigides belong to the Brianconnais strip sheet showing Brianconnais facies (Es- proper coureous), and this in turn is overlain by the (5) Breccia nappe, which is discussed under great mass of the upper Cretaceous Helminthoid Marine Breccia Formations Flysch, also present in the Maritime Alps to (6) An ophiolite-bearing unit, preserved only the southeast, and of still more internal (Pie- locally, may be correlated with the high montese or Austroalpine?) origin. Penninic Platta nappe and the Arosa zone of Farther east, the Mesozoic of the type Graubunden Brianconnais, in the upper Durance Valley, (7) Simme nappe (Austroalpine?), consisting is less markedly separated from its original mainly of Cretaceous Flysch. This unit formerly substratum, the Pennsylvanian formations of had a great extent and furnished most pebbles the Zone houillere along the front on the to the Oligocene conglomerates of the Molasse Grand St. Bernard mass. Nevertheless, it (8) Erosion remnants of an upper Austro- forms several small nappes and is overridden alpine nappe exist northeast of Lake Lucerne by the Schistes lustres from the Piemont The order of movement can be described as realm. All through the western Alps, these follows: Schistes lustres have moved as one or several (1) Sliding of Simme and Ophiolite nappes cover nappes, independently of their former onto future Breccia and Medianes nappes; basement, which may have been the Dora- sliding of Ultrahelvetic nappes (at the same Maira and Gran Paradiso gneiss domes or time?) onto future Helvetic nappes and onto even more internal elements. the Autochthone. Gravity seems to have been To the north, in the Arc and Isere valleys of an essential factor in this early (Oligocene) Savoy, the Subbrianconnais units are mainly phase represented by the Pas du Roc nappe, and (2) Main thrusting of the Medianes nappe other nappes not visible in the Durance valley (3) Arrival of the Breccia nappe on top of the lie west of it. The Mesozoic cover is gone from Medianes, and (at the same time?) formation the Zone houillere, probably stripped off to of the Helvetic nappes. The Morcles fold form part of the Prealps; but it is preserved on developed before the Helvetic nappes proper. a more internal digitation of the Grand St. 3 Thanks to Ellenberger's (1949; 1958) discoveries Bernard mass, in the Vanoise Mountains and of the typical Medianes rigides formations in the around Mont Cenis. Vanoise, the long-disputed question of the origin of this unit is now probably settled, in spite of PREALPINE NAPPES: The Prealps consist of Staub's (1958) impressive defense of its lower two semicircular areas along the front of the Austroalpine character.
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(4) Passage of the Niesen nappe through nappe is of more southerly origin than the the transversal depression between the Mont- Dachstein—which would result in the most blanc and Aar massif plausible picture of facies distribution—or (5) Late en-bloc deformation of the Prealps whether it is more northerly is still being COVER NAPPES OF GRAUB0NDEN: In Grau- disputed. Fallot (1954) gives the clearest biinden (Grisons), there is a great mass of lower account of the structural problems of the Penninic Biindnerschiefer and Flysch, which eastern Alps. reappears in the windows of the Lower Engadine STRUCTURE OF THE COVER IN THE SOUTHERN and of the Tauern, as well as in the Flysch ALPS: The structural style of this area is much belt along the northern border of the Bavarian simpler than that of the other Alpine regions, and Austrian Alps. These Mesozoic to Eocene, and the apparent sense of movement is reversed partly metamorphosed formations are overlain (slight overthrusting from the north or under- by other cover nappes—those of the Schams thrusting from the south, along steeply in- in the south and the three units of Falknis, clined planes). Oblique faults, in part slip Sulzfluh, and Arosa in the north and east. faults, are prominent. Especially the youngest, The Sulzfluh nappe is probably the M6dianes post-Triassic formations are locally affected by nappe of the Prealps. The author regards the gravity sliding southward. ophiolite-bearing Arosa zone as identical with the high Penninic Platta nappe, and all three nappes as Penninic, but this view is not shared Outlines of Stratigraphy by many geologists who still attach these units to the lower Austroalpine nappes. In the Facies belts.—In the Alps, we can distinguish present interpretation the Mesozoic cover of five major facies belts, each with a different the Err and Bernina nappes has not moved geological history (Fig. IA; PI. 1). They are, far from its pre-Triassic basement in the from the northwest to the southeast: Upper Engadine. (1) Helvetic realm of Switzerland and Dau- AUSTROALPINE COVER NAPPES OF THE NORTH- phine realm of southeastern France: external ERN CALCAREOUS ALPS: These nappes form a miogeosyncline. Its appendage, the Ultra- broad, continuous belt between the Rhine and helvetic and Ultradauphinois belt, leads over to the Danube. On their southern border, they (2) Valais facies belt: external eugeosyncline. lie upon or butt against the great mass of pre- It is relatively narrow in the Valais itself. In Triassic rocks of the upper Austroalpine' the east (Graubiinden) this facies realm be- thrust sheet, from the cover of which they comes much broader and more complex, have probably been stripped along incompetent whereas it may have disappeared to the south- layers in the Paleozoic and Lower Triassic west, in the Durance basin. formations. The sedimentary facies of all (3) Brianconnais belt in the large sense: these nappes is very similar (except the Hallstatt subdivided into the external Subbrianconnais nappe), and the distinction and correlation of and the internal Brianconnais in the strict the individual sheets are hazardous. In the sense. west, however, there are three well-defined (4) Piemont belt of northwestern Italy: units: Allgau, Lechtal, and Inntal. Lechtal is internal eugeosyncline, narrowing toward the the most important and more or less continues northeast. This and belts (2) and (3) constitute eastward into the Stauffen-Hollengebirge nappe the Penninic realm. of the Salzburg Mountains. East of the river (5) Austroalpine and south Alpine realms: Enns, beyond the border of Plate 1, three relatively stable, but at times deeply sub- separate thrust sheets replace it. merged area beyond the Penninic eugeosyncline. In the central segment of the northern The transitional zone between this and the calcareous Alps, especially in the Salzkam- Piemont belt is formed by the Grisonide mergut, the highest cover nappes are preserved. (Graubiinden) belt of the lower Austroalpine The most voluminous of these is the Dachstein nappes. ("high-Alpine") nappe. Two units not shown The stratigraphic composition of these belts on Plate 1, the Hallstatte nappe (reduced to is outlined for the benefit of the extra-Alpine isolated slices), remarkable for its aberrant reader and with apologies to the Alpine reader facies of the Triassic, and the overlying for the gross simplifications. As a convenience Reiteralm nappe, have moved during the to those who might otherwise have to look Cretaceous pre-Gosau phase, but the main them up the European stage names for the disturbance is Tertiary. Whether the Hallstatt Mesozoic are given in Table 1.
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FIGURE 1.—PALINSPASTIC SKETCH MAP (A) AND PALEOGEOGRAPHICAL SKETCHES (B-D) OF PART OF THE WESTERN ALPS (See Plate 1 for orientation). From R. Trumpy (1958, p. 342) and very hypothetical A. Original disposition of facies belts. The more or less autochthonous basement massifs are marked by a pattern of plusses: AM Argentera or Mercantour B2 internal branch of A1 Gastern and P Pelvoux Belledonne A2 main part of Aar B1 external and AR Aiguilles Rouges T Tavetsch M Montblanc G Gotthard Only B1, AR, and A1 are shown in their present position; the other units have been displaced to account for the Tertiary deformations. The probable area of deposition of the sediments of the Meaianes and Breccia nappes is also indicated. B. Early Jurassic (Lias) paleogeography C. Early Cretaceous paleogeography D. Late Cretaceous paleogeography 853
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TABLE 1.—MESOZOIC STAGE NAMES shales, sandstones, and arenaceous limestones. In the French Alps (Dauphine miogeosyncline) Danian comprises very thick argillaceous limestones Maestrichtian followed by dark shales Campanian Middle Jurassic: in the Helvetic belt consists Santonian • Upper Cretaceous of black pyritic shales of lower Aalenian, fol- Coniacian lowed by ironshot sandstones and crinoidal Turonian limestones. Upper Bajocian, Bathonian, and Cenomanian >Middle Cretaceous Callovian beds are condensed in the east. A shaly facies invades the whole thickness in the Albian Dauphin!, where great masses of dark shales Aptian represent the Bathonian, Callovian, and lower Barremian • Lower Cretaceous Oxfordian. Hauterivian Upper Jurassic: dark limestones overlain by Valanginian coral limestones in the north, pelagic limestones to the south. Tithonian Lower Cretaceous: in the Helvetic and north- Kimmeridgian I Upper Jurassic ern Dauphine realm includes 100 to 1500 m of Argovian (upper Oxfordian) I (Malm) shallow-water limestones and shales with thin Oxfordian (restricted) glauconitic members. Represented farther south by pelagic limestones and shales. Gives way to Callovian 2000 m of marl shales in the Vocontian trough Bathonian I Middle Jurassic of southeastern France. Bajocian (restricted) | (Dogger) Upper Cretaceous: mainly pelagic shales and Aalenian (lower Bajocian) limestones in the Swiss Alps. In the Dauphine, the facies of the limestones indicates shallower Toarcian water. Commonly missing or incomplete by Domerian (upper Pliensba- pre-Eocene erosion. chian) Lower Jurassic Paleocene, Eocene, and lower Oligocene: lime- Pliensbachian (restricted) (Lias) stones with large Foraminifera, followed by Sinemurian pelagic shales and by up to 1500 m of Flysch. Hettangian Formations are heterochronous, becoming younger toward the northwest. Rhaetian Norian > Upper Triassic Valais facies belt.— Carnian Pre-Pennsylvanian basement: locally Pennsyl- Ladinian vanian and Permian middle Triassic Anisian Triassic: very much reduced, save for passage zone to the following belt Scythian Lower Triassic Jurassic: thin Liassic limestones. Middle and Upper Jurassic commonly absent (or represented in the lower unfossliferous part of Helvetic and Dauphin^ realm.— the Bundnerschiefer?). Upper Jurassic lime- Pre-Pennsylvanian: folded and metamorphic stones with granite boulders in the Falknis basement group; granites nappe (southeastern margin of the belt) Pennsylvanian: up to 1400 m of continental, Lower Cretaceous: main mass of north- coal-bearing beds in narrow late Hercynian Penninic Bundnerschiefer (2000-3000 m?), with synclines; granites ophiolitic volcanic rocks in the lower part. In Permian: in localized troughs, up to 1800 m the upper part, Flysch characteristics appear of red beds with volcanic rocks gradually ("pre-Flysch"). Typical members Triassic: thin, comprising quartzites, do- are Aptian limestones with dolomite debris lomites, and variegated shales. Includes an- (Tristel and Aroley limestones, often un- hydrite beds in the south and west; spilites at conformable on older rocks), and the green the top in part of the Dauphine belt quartzites and black shales of the so-called Lias: missing in the north; in the Helvetic "Gault." nappes it is represented by up to SOO m of Upper Cretaceous, Paleocene, and Eocene:
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Flysch several kilometers thick, belonging to discussed under Marine Breccia Formations. different basins The Grisonide facies belt of the lower Austro- alpine nappes shows on the whole the same BrianQonnais belt in the large sense.-—Pre- stratigraphic succession as the Piemont eugeo- Pennsylvanian basement syncline, but no volcanic rocks, much thinner Pennsylvanian and Permian: continental for- Lower Jurassic, and a great development of mations with volcanic rocks in the French Jurassic and Cretaceous breccias. Cenomanian Alps, several kilometers thick Flysch is the youngest unit. Lower Triassic: quartzites Middle Triassic: algal limestones and dolo- Austroalpine realm.-—Pre-Ordovician base- mites, up to 1000 m. ment Upper Triassic: anhydrite, shale, and dolo- Ordovician to Mississippian: fairly thick mite; missing in part of the Brianconnais proper marine formations, especially developed in Lias: about 500 m of cherty, silty, and the east (Graz, Carnic Alps). The age of many crinoidal limestones and calcareous shales in slate-graywacke formations is still uncertain. the Subbrianconnais belt. Missing in Brian- Pennsylvanian and Permian: not present connais proper, except in the eastern part of everywhere; continental in the western and the Vanoise. central zone, partly marine in the southeast Middle Jurassic: Zoophycos Dogger of the Lower Triassic: shales and sandstones in Subbriangonnais belt, thick formation of shales the east (with rock salt of the Salzkammergut), and silty limestones, in places oolitic and coral red beds in the west limestones. In the Brianconnais proper, Mytilus Middle Triassic: up to 1200 m algal lime- beds (Bathonian-Callovian), with coal stones and dolomites; siliceous shales with Upper Jurassic: mainly neritic limestones in volcanic tuffs in the west the Prealps, transgressive upon granite in Upper Triassic: Carnian shales, sandstones, Graubiinden. Pelagic limestones predominate dolomites, and plant beds, followed by Norian in the French Alps. limestones or dolomites (up to 1000 m). In the Lower Cretaceous: pelagic limestones with Hallstatt nappe, much thinner pink limestones chert bands, absent from most of Brianconnais with ammonites. Rhaetian shales and lime- proper stones. Upper Cretaceous and Paleocene: marly lime- Lias: facies widely varying (calcareous shales, stones with pelagic Foraminifera (Couches cherty limestone, crinoidal limestone, pelagic Rouges) limestone with ammonites) Lower Eocene: Flysch, but only locally Middle Jurassic: shales, limestones, chert beds Upper Jurassic: radiolarian cherts, followed Piemont belt.—Pennsylvanian and Permian: by fine-grained pelagic limestones with chert. found locally, but commonly difficult to separate The overall thickness of the Jurassic is generally from the basement quite modest. Lower and Middle Triassic: as in the Brian- Lower Cretaceous: pelagic shales and lime- connais, but much thinner stones Upper Triassic: variegated shales and dolo- Upper Cretaceous: Cenomanian Flysch-like mites, thicker than in the Brianconnais beds in the west. The Upper Cretaceous Simme Lias to Bajocian: main body of Schistes and Helminthoid Flysch facies of the western lustres in the western Alps (but note reserva- Alps may belong to this realm. In the east are tions as to their age). Lower Lias in part the Senonian Gosau beds, up to 2000 m of limestones, with benthonic fauna. Microbreccias sandstones, conglomerates, shales, and shallow- along the margins of the trough. Thickness water limestones, locally with workable coal around 2000 m? deposits, unconformable on older, folded rocks Bathonian? to Lower Cretaceous?: thin radio- Eocene and lower Oligocene: locally uncon- larian cherts and fine-grained limestones. formable detrital formations Locally Lower Cretaceous schists and breccias. Intrusion and outflow of basic and ultrabasic Realm of the southern Alps.-—In general ophiolites during the Early Cretaceous. similar to that of the northern calcareous Alps. Upper Cretaceous and Paleocene: Couches The Permian is mainly marine in the east and rouges facies on the external margin, Flysch continental in the west; it contains much farther inward. volcanic rock and also some granites (Baveno). The stratigraphic succession of the Breccia Besides dolomites and algal limestones, the nappe (external margin of Piemont belt) is Middle Triassic also shows volcanic rocks and
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euxenic limestones. The composite thickness characteristically follows an interval of normal of the Triassic may reach 3500 m. The Upper shallow-water sedimentation, which may or Cretaceous consists of pelagic marl shales, may not show an abnormally high rate of sub- followed by Flysch. sidence. During evolution of the geosyncline, eugeosynclinal conditions tend to spread out GENETIC SEQUENCES OF ALPINE from the central troughs, where they originated SEDIMENTARY ROCKS in the Early Jurassic, and to encroach upon the adjoining platforms as well as over parts of the Platform and Miogeosyndinal Sediments bordering miogeosyncline. This shifting is par- ticularly pronounced during the later (Flysch) Gross characteristics.—In the Alps, large areas phases. On the other hand, no instances of a of shelf and miogeosynclinal deposits have been restoration of miogeosynclinal or platform con- affected by the nappe-building processes, and ditions are known (in the Alps) once a eugeo- some of them by metamorphism of epizonal to synclinal belt has been established. mesozonal grade. (See especially Ellenberger, Triassic of the southern Alps.—The famous 1958, p. 353-405.) In these miogeosynclinal Triassic section of the southern Alps may serve belts, the rate of subsidence and of sedimenta- as an example for the type of sedimentation tion may be greater than in the eugeosynclines,4 that prevailed during the neutral phase between but the sediments as a rule are of normal, shal- the Hercynian and Alpine erogenic cycles. low-water origin. Changes in fades and thick- Comprehensive summaries have been published ness are commonly rather abrupt as compared by Leonard! (1955) on the Dolomites, and by de to conditions in the "stable-shelf" areas out- Sitter and de Sitter (1949) on the Bergamask side the Alps, such as the Jura Mountains or Alps. Among the monographic descriptions Swabia. may be mentioned Ogilvie-Gordon (1927), Pia The space-time relationship of miogeosyn- (1937), E. Triimpy (1930), and Wirz (1945). clinal and eugeosynclinal sequences in the Alps The facies development of the Permian and can be summarized as follows: lowest Triassic indicates that geosynclinal evo- (1) Up to the Triassic or to the early Lias, lution was in advance in the eastern area, in miogeosynclinal or platform conditions pre- the Dolomite Mountains. With the early vailed over the whole area of the future Alps. Middle Triassic Anisian stage, carbonate sedi- The Triassic miogeosynclines, in the Briancon- mentation becomes the rule. The thickness of nais belt of the western Alps and in the Austro- Anisian limestones, dolomites, and (rare) bi- alpine to south Alpine realm, are in part in- tuminous shales, however, is still moderate herited from late Paleozoic post-orogenic basins (50-250 m). ("epieugeosynclines"). In any given section, The upper Middle Triassic or Ladinian, on eugeosynclinal sediments are underlain by the other hand, may exceed 1000 m and ex- platform or miogeosynclinal deposits. hibits some striking facies changes. Three (2) A broad, miogeosynclinal belt extends facies types can be distinguished: between the central eugeosyncline and the (1) The so-called "normal" facies, consisting European foreland to the north and west. This of shales with thin limestone bands and chert, belt covers essentially the Helvetic realm of the tuffaceous sandstones, and, in the Dolomite Swiss Alps and the Subalpine chains of France. Mountains, great masses of basic to inter- It was invaded by the Flysch facies, which mediate volcanic rocks. Most of these are sub- possibly should be classed as eugeosynclinal, marine lava flows or tuffs, but some may be during Late Cretaceous and early Tertiary near-surface sills. Even in Lombardy and in time. the western part of the northern calcareous (3) Inside the eugeosyncline and south of it Alps, thin turfite members mark distant man- are unstable platforms, some of which are mio- ifestations of these eruptions. In the Dolomites, geosynclinal: the Brianconnais facies belt the sea may have been fairly deep during depo- (broad sense) of the western Alps and parts of sition of the lower Ladinian, which contains the Austroalpine nappes and southern Alps. an almost exclusively pelagic fauna dominated In other words the eugeosynclinal stage by radiolarians and the floating lamellibranch Daonella. The frequency of land plants in the middle Ladinian indicates that some volcanic 4 The palinspastic cross section given by Cadisch (1946, p. 11) is very impressive in this regard, but cones rose above sea level. (A particular forma- the thickness of the eugeosynclinal Bundnerschiefer tion, the siliceous "splinter shale" of the Val formations has certainly been underestimated. di Scalve, in the Bergamask Alps (de Sitter,
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1949, p. 146), is important as it provides a link again more nearly uniform, although the with the Partnach shales of the northern cal- Carnian still shows a variety of facies types. careous Alps.) The term "normal fades" for Thick dolomites and limestones of shallow- the shales with volcanic rocks is, of course, water origin are of Norian age. quite misleading, for the Middle Triassic out- The overall thickness of the Triassic forma- side of South Tyrol is generally represented by tions reaches 3500 m in some areas of the south- dolomites and limestones. ern Alps, the Triassic of the northern calcareous (2) Poorly bedded dolomites and limestones Alps attains 2000 m, and the Lower and Middle of the "reef" fades, the most famous of which Triassic of the Penninic Brianconnais belt are the Schlern (Sciliar) dolomites and the reaches 1000 to 1500 m. These formations may Marmolata limestones of the Dolomite Moun- well be regarded as miogeosyndinal. Whether tains, and the Esino limestones on Lake Como. the Ladinian of the Dolomites, with its vol- Calcareous algae play a large part in the con- canic rocks and locally greater depth of the struction of these carbonate masses. Why some sea, marks a first abortive attempt toward the of them were dolomitized and others not is an realization of eugeosynclinal conditions re- unsolved problem. mains conjectural. There is some evidence for (3) A euxenic facies of black, bituminous very slight tectonic disturbance between the limestones with dolomite bands occurs in the Ladinian and Carnian stages, and we shall see upper Anisian and Ladinian on Lake Como and that this very moment marks a turning point Lake Lugano. It contains some turfite members in Alpine history. as well as the fossil beds of Monte San Giorgio, Lower Cretaceous of the Helvetic nappes.— with a rich and very well preserved fauna of Miogeosyndinal subsidence started in the marine reptiles but almost no bottom-dwelling Lias of the more southerly part of the Helvetic organisms. facies belt in the Swiss Alps and shifted to the The limestone and dolomite areas show very site of the autochthonous Aar massif in the Late sharp borders against those of the coeval shales Jurassic. Most of the mountains in the domain and volcanic rocks, although the contact has of the Helvetic nappes are carved out of the in many instances been disturbed by later thick and well-stratified, mainly calcareous for- tectonic movements along these zones of me- mations of the Lower Cretaceous. Still the most chanical discontinuity. Stratification in the comprehensive study of the rocks is Arnold carbonate rocks tends to slope outward near Heim's classical monograph (1916); good gen- the borders, and tongues as well as isolated eral accounts are given by Albert Heim (1921) blocks of limestone penetrate the surrounding and Cadisch (1953). shale areas. During Ladinian time, the "reef" In the cover of the Aar massif in eastern facies migrated outward into the hitherto vol- Switzerland, the Lower Cretaceous is only canic basins. The limestone and dolomite about 100 m thick, except where pre-Eocene masses are arranged in strips with a west-north- erosion has removed it. It thickens rapidly west to east-southeast trend. The contrast be- southward and attains 1500 m in the higher tween the stupendous dolomite cliffs and the Helvetic nappes; one stage alone, the Hauteri- lush pasture lands on the volcanic rocks—both vian, thickens from 20 to 600 m over a dis- cut out of rocks of the same age—gives its tance of 40 km across the strike. The predomi- unique character to the landscape of the Dolo- nant rocks are shallow-water limestones, such as mite Mountains. M. Ogilvie-Gordon (1927, p. rudist, crinoidal, bryozoan, oolitic, calcarenitic, 122) proposed a very plausible explanation for and pellet limestones,6 siliceous limestones, fine- these abrupt facies changes. She believes that grained limestones, calcareous shales, and the volcanic rocks were erupted from fissures glauconite beds with phosphatic fossil casts. in deeper-lying compartments, while carbonate Toward the south, most of these shallow-water deposition went on unhampered on the in- limestones pass laterally into shales or into tervening platforms. The lime-secreting algae fine-grained pelagic limestones. (See palm- and corals could not thrive in the volcanic spastic cross-section in Arnold Heim, 1916, troughs because of the greater depth and the p. 480.) This denotes a slope of the sea floor scarcity of oxygen. (See also Cornelius, 1925, p. from the foreland margin toward the geosyn- 375.) It is probably not quite correct, however, cline. Still farther inward, in the Ultrahelvetic to call the dolomite and limestone masses of the southern Alps bioherms, in spite of their great 6 Most "onkoids" (Arnold Heim, 1916, p. 566) or thickness and limited lateral extent. "false eoliths" are faecal pellets (Bruckner, 1951, During the Late Triassic, conditions were p. 198).
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realm, the Lower Cretaceous thins again and is This seems rather improbable, as the regular almost entirely of pelagic facies ("N6ocomien a cyclothems cannot be detected in the structur- Cephalopodes"). This announces the passage ally more active belts of the geosyncline, to conditions where subsidence exceeds sedi- whereas they are common far outside the Alps. mentation. Quite clearly, the cyclothems register some Rhythmic sedimentation is characteristic of widely effective (world-wide?) pulsating mecha- the Helvetic Cretaceous (Arbenz, 1919; nism, not directly related to the preparatory Fichter, 1934; Bruckner, 1937). A typical disturbances in the Alpine geosyncline.6 cyclothem starts with a thin, condensed bed, Jurassic of the Median Prealps.—Yet another generally rich in glauconite and pyrite, followed tectonic environment of more or less miogeo- by shales, which grade upward into limestones. synclinal characteristics is that of unstable The top of the limestone members is sharp platforms inside the eugeosynclinal belt, or and represents a break in sedimentation. between the central eugeosyncline and adjacent Diameter of detrital quartz grains is smallest ordinary miogeosynclines. Sedimentation in n the shales, increases in the limestones, and this type of environment is exemplified by the reaches its maximum in the thin glauconite Jurassic and Cretaceous series of the Median beds, whereafter it drops sharply. This type of Prealps nappe (Fig. 2; PI. 2). A summary of sedimentary rhythm starts with the upper the stratigraphy of the Median Prealps has Sinemurian and has its most characteristic been given by Tercier (1952), and a very development in the Lower Cretaceous. The thorough review of older publications by middle Cretaceous cyclothems are "degene- Jeannet (in Albert Heim, 1922). The stratig- rated;" several of them are crowded into a few raphy of the Subbrianconnais and Briancon- meters. They disappear in the Upper Creta- nais belts of the French Alps, which continue ceous, which is of pelagic facies. (See Bolli, the same facies zones southward, has been 1944.) Such cyclothems are common in the summarized by Gignoux (1950) and Moret shelf formation of the foreland, but they dis- (1954). appear toward the axis of the geosyncline, During the Early Jurassic, the belt of the where sedimentation was more continuous. Medianes plastiques (Peterhans, 1926) and of A convincing interpretation of these rhythms the analogous Subbrianconnais proper (Schnee- yet remains to be found. Most authors agree gans, 1938; Debelmas, 1955), which was only that the gradation from shales to limestones about 30 km broad, was divided into two or indicates a gradual shallowing of the sea, be it three minor troughs and submarine swells. by filling with sediment or by depression of Sedimentation in the former was fairly continu- the sea level. The glauconite beds were laid ous and produced impure, cherty limestones, down under persistent conditions of inhibited followed by silty, calcareous shales. Along the sedimentation; in some instances ammonites of swells, crinoidal limestones predominate, and two or more zones are found in the same bed. the ancient substrate was commonly indurated Erosion is certainly submarine in most cases ("hardground") and pierced with annelid (Arnold Heim, 1925). It is hard to understand borings, where sedimentation was interrupted why sedimentation was slowed down during for the duration of a stage or longer. The this phase, which should coincide with sub- southeasterly part of the Prealpes Medianes sidence of the sea bottom. The role of compac- (Medianes rigides) and the Brianconnais tion is certainly not to be neglected. Bruckner (1951; 1953) has advanced an alternative 6 A possible mechanism was suggested to the hypothesis, relating the cyclothems to hydro- author by Preston Cloud while this paper was in climatic fluctuations. This gives a plausible preparation. Cloud asks: "Is it possible that cyclo- themic sedimentation on the shelves is related to answer to some questions and raises others. episodic large-scale dumping by gravity mass Carozzi has published a great number of notes movement of sediments from the trough-margins (summarized in his paper of 1951) showing (or heads) onto trough-bottoms? Isostatic ad- that the rhythms were not so regular as often justment to such abrupt transfer of load would logically result in local upwarping of the shelves, supposed; he has done very valuable work concurrently with local acceleration of trough subsi- measuring the size and frequency of all the dence. Repeated small upward movements in a components in the sediments, and has shown shelf area undergoing regional subsidence could give enviable optimism in plotting these measure- rise to a succession of cyclothemic deposits; and the mechanism is consistent with, if not a necessary ments in "curves," finally resulting in a "bathy- corollary of, the observed redeposited coarse elastics metrical curve." For Carozzi, the rhythms of that are interbedded with the predominating subsidence are related to tectonic movements. pelagic shales of adjacent flysch basins."
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proper lack Liassic rocks, although some In the Upper Jurassic, limestones are formed Rhaetic and lower Lias was laid down and all over the Medianes area (for detailed analysis, later eroded (before Bathonian time). see Weiss, 1949). The Lower Cretaceous pelagic, The fades distribution of the Middle Jurassic thin-bedded limestones with chert are again is often mentioned. To the northwest, we find found only in the northwestern part, whereas
NW Medianes plastiques Medianes rigides SE
Iz^rj Upper Cretaceous (Couches rouges) Mytilus Dogger (Is., coal) f*^\ Morion ? (dolomite)
If-Lj Lower Cretaceous (Pelagic Is.) Upper Lias I Aalenian (shale its.) p^%| Carnion (shale,anhydrite)
Q j Upper Jurassic Is. Middle Lias (crinoidal I cherty Is.) Pr-H Middle Trios. (Is. I dolomite)
f'^vO'j Argovion (nodular Is.) Lower Lias (crin.,cherty lool.ls.) FQ^ Lower Anhydrite member
[H;!! Zoophycos Dogger (shale I Is., Rhoetic (shale,shelly Is. etc.) [T-XT Lower Trios.quartzites oolites in the SJ FIGURE 2.—PALINSPASTIC CROSS SECTION THROUGH THE MESOZOIC FORMATIONS or THE METJIANES NAPPE IN WESTERN SWITZERLAND Vertical scale exaggerated X 4. After Gagnebin, Jeannet, Lugeon, etc. (references cited) The Triassic formations shown below the basal thrust plane of the nappe have not been stripped from their Paleozoic basement and are now found on the front of the Grand St. Bernard nappe, in Valais.
the "Zoophycos Dogger," several hundred the pelagic Globotruncana and Globorotalia meters of calcareous shales alternating with limestones of the Couches Rouges (Cenomanian argillaceous and silty limestones. The fauna to Paleocene) spread out uniformly over the consists mainly of cephalopods and of the whole hitherto differentiated facies belt and brushlike dwellings called Zoophycos or Cancel- neighboring realms. lophycus. As one approaches the southeastern Characteristic of this kind of facies belt is border of this trough, oolitic and sandy lime- the abrupt vertical and horizontal change of stones with drifted plant remains make their environment. The thickness of the Middle appearance; they lead to the much thinner Jurassic, for instance, jumps from nothing to "Intermediate Dogger," made up of oolitic and 700m within 4km across the strike. Sediments of calcarenitic limestones. Still farther southeast, the same age, laid down a few kilometers apart, the Middle Jurassic is lacking, and finally one may show coal beds in one place, deep-water enters the domain of the "Mytilus beds," with mud facies in another. Bathymetric interpre- brown, bituminous limestones and coal beds, tation is of course commonly hazardous, but it containing a bottom-dwelling fauna with many seems highly probable that the monotonous endemic species but no cephalopods. At the sequence of the Zoophycos beds was formed base of the Mytilus beds, a laterite band has under several hundred meters of water. In been found (Ellenberger, 1958, p. 293; Badoux spite of this, the facies belt as a whole generally and de Weisse, 1959), proving that the Brian- rose above the adjoining eugeosynclinal realms connais proper was emergent before the Batho- and was not invaded by volcanic material. (This statement is made with some reservation
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as far as the relation between the Subbriangon- sediments of the Brianconnais belt are just as nais and Valais belts during the early and metamorphic as the Schistes lustres, and in middle Jurassic is concerned.) the northern Ticino mesozonal metamorphism has transformed the miogeosynclinal Liassic Bundnerschiefer, Schistes Lustres formations in the cover of the Gotthard massif (± Ultrahelvetic) to about the same extent as General statement; metamorphism.-—The usual the eugeosynclinal Schistes Iustr6s of the lower Mesozoic rocks of the eugeosynclinal troughs Penninic nappes. Breaks in Alpine metamorphic of the Penninic realm are the Bundnerschiefer, zones are found only where the latest Miocene or Schistes lustres, or Calcescisti. These three and Pliocene movements have brought tectonic terms are in part synonymous; Bundnerschiefer elements with different (Oligocene) meta- covers a wider range of formations than do the morphic antecedents into contact. Incidentally, other two. Part of the misunderstanding comes grade of metamorphism conforms very well from the fact that the Schistes lustres or with the classical tectonic reconstructions, and Calcescisti of the French and Italian Alps isometamorphic surfaces are very nearly parallel belong to the more internal Piemont trough, to the top of the Alpine pile of nappes as drawn south and east of the Brianconnais swell, on the much-criticized cross sections by Argand, whereas most Bundnerschiefer of eastern Staub, and others. Switzerland were laid down in a eugeosyncline Lithology and environment.—In the most to the north of the Brianconnais belt, which common epimetamorphic grade, Schistes lustres persisted into Late Cretaceous and even early consist mainly of calcareous sericite schists. Eocene time. Nabholz (in Bolli and Nabholz, Noncalcareous slate, sericite schist, micaceous 1959, p. 238) has given an excellent summary marble, and micaceous quartzite are also on this nomenclatorial question, as well as on abundant. The original lithology is best studied the problem of the Schistes Iustr6s in general. in areas of little tectonic overburden, or in (See also dal Piaz, 1943.) d6collement nappes, which contain nonmeta- The term Schistes lustre's7 itself refers to a morphic equivalents of Schistes Iustr6s. (This conspicuous characteristic of these rocks, their raises an awkward nomenclatorial problem: metamorphism, which ranges from the sericite- nonmetamorphic "Schistes lustres" are neither chlorite zone down to staurotide, kyanite, schists, in the English sense, nor lustrous.) It is, garnet, and biotite. It was long held that this of course, always difficult to prove that a metamorphism was of primary, geosynclinal formation really can be regarded as nonmeta- nature and inherent to the Schistes lustres morphic Schistes lustres as long as the relation- facies. Recent research (e.g., Ellenberger, 1958; ship of the cover nappe with the central part E. Niggli, in Cadisch 1953; Wenk, 1956) has of the Alps is controversial. It seems likely, discredited this view, which was already op- however, that the Liassic "Schistes inferieurs" posed by Cornelius (1930). Alpine metamorph- of the Breccia nappe, the Jurassic of the Grande ism is now proved to have occurred late in the Moenda digitation in the Pas du Roc nappe history of the mountain chain, not before the (Barbier, 1948, p. 49), or the Jurassic and end of the Eocene (Ellenberger, 1952a). This Cretaceous shales of the Arosa zone may give leaves only the Oligocene and part of the a fair idea of what Schistes lustres looked like Miocene for the development of metamorphism. before sedimentary structure was obscured by In a given area, it has affected the (essentially metamorphism. noncalcareous) pre-Triassic basement in the Thin-bedded, argillaceous, silty or more same degree as the Mesozoic rocks. In the rarely sandy limestones, alternating with cal- Vanoise Mountains of Savoy, the platform careous shales, presumably were the predomi- nant rocks of the original Schistes lustres. 7 Stratigraphical analysis of the Schistes lustre's Marly, argillaceous or silty shales form the in the broad sense is still in its beginning. Working major part of some formations. Sandstones are in these areas is like trying to solve one equation fine-grained (diameter of most quartz grains with two variables, stratigraphy and structure (W. Leupold, orally); a solution is possible only by 0.02 to 0.2 mm), commonly argillaceous or making a reasonable assumption for one of them, calcareous, and do not contain much feldspar. say that a certain sequence of formations represents Many of the limestones are calcarenitic. Micro- a normal stratigraphic column. The author recog- breccias, mainly with angular fragments of nizes from bitter experience that a new fact, such as an "unlucky" fossil or some graded beds snowing Triassic limestones and dolomites, occur in inversion, can bring the most beautiful working several areas; they generally show graded hypothesis tumbling down. bedding, whereas most of the sandstones do
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not. Carbonate, quartz sand, and argillaceous Ophiolites (Roches vertes, Pietre verdi) are matter are intimately mixed. Pyrite is abun- commonly associated with Schistes lustres, dant, but euxenic bottom conditions do not although there are otherwise quite normal appear to have been the rule. Schistes lustres formations without volcanic The individual formations of the Schistes rocks. The term has an extremely broad lustres group are ill-defined and grade into meaning, covering ultrabasic and basic, extru- one another. Nothing is left of the regular sive and intrusive rocks: peridotites, gabbros, cyclothems, which render the lithostratigraphic porphyrites, spilites, tuffs, and their various subdivision of the miogeosynclinal sediments metamorphic derivates such as serpentines, in the Helvetic belt so clear cut. Lateral facies amphibolites, prasinites, ovardites, and other changes are common, but research has not "greenstones" (Burri and Niggli, 1945). The progressed far enough to allow detailed analysis. extrusive nature of these magmatic rocks is in The fauna (Bolli and Nabholz, 1959) is many cases attested by pillow lavas and tuffitic extremely poor. This sterility seems to be an beds. The lava outflows seem to have been original feature, although metamorphism may entirely submarine; there is nothing to prove have destroyed many fossils. (See discussion in the existence of a belt of volcanic islands in the Bucher, 1953.) Radiolarians are most frequently Mesozoic history of the Alpine geosyncline. It encountered, but tiny mollusca, bryozoan and is possible, but not certain, that andesitic crinoid fragments, and rare, mainly arenaceous volcanoes existed at a much later time, at the Foraminifera also occur. The few larger shallow- end of the Eocene. Other sheets are probably water organisms, such as the Liassic oysters sills and laccolites. All authors seem to agree described by Nabholz (1945, p. 43), were found that most ophiolites are of Cretaceous, espe- in beds near the base of the group, which do cially Early and middle Cretaceous, age, but not yet show the characteristics of the real some peridotites may be older. The hypothesis Schistes lustres. of synorogenic intrusion along early thrust We may assume that most of the Schistes planes seems to be constantly losing ground in Iustr6s were laid down in fairly deep water, favor of pre-orogenic submarine flows and intru- because of both lack of typical shallow-water sions into unconsolidated, horizontal sediments. sediments and fauna. The environment suggests Schistes lustrfs of the Cottic Alps.—The Cottic only moderately steep submarine slopes, save Alps, in southwestern Piemont and adjoining for the belts in which breccias were formed. areas of the French Durance basin, are the Turbidity currents still are rather exceptional. region where stratigraphic analysis of the The supply of detrital matter, derived chiefly Schistes lustres in the internal, Piemont eugeo- from Triassic and Liassic rocks, was sufficient syncline has the greatest chance of success. to allow the deposition of the thick Schistes Metamorphism is much less pronounced than lustres group, during a time span which seems farther north, probably because the great to have covered a few tens of millions of years overburden of the Dentblanche nappe was no in each eugeosynclinal belt. The Schistes longer present, and the structure is easier to lustres of the Piemont belt reach about 1500 or work out. Even here, however, many questions 2000 m, but the later "pre-Flysch" formations are still moot. The most important older works of the Valais belt may be much thicker. Evalua- are numerous papers by Franchi, between tion of original thickness is, of course, very 1898 and 1929. Recent work by Conti (1953; problematic in the central zone of the Alps. 1955) and Lemoine (1951; 1954; 1955; 1957; Many geologists believe graywackes are the 1959) has greatly advanced our knowledge. typical rock of eugeosynclinal facies assem- The most significant section is the one studied blages. The author has never seen a bed of by Lemoine (1951) on Mount Gondran, east of graywacke in the Alpine Schistes lustres. It is Briancon (Fig. 3). Subsidence in this part of the rather an essentially calcareous (but nowhere Piemont trough started in the Carnian, but dolomitic) rock group. This is a major difference normal shallow-water deposits with benthonic from many older, Paleozoic and Precambrian fossils were laid down well up into the Hettan- eugeosynclines, in which graywackes and non- gian. Dark, cherty limestones form a transition calcareous shales are predominant. This may from these neritic sediments to typical, although be due to the generally warm hydroclimate of only slightly metamorphic, Schistes lustres, the Mesozoic Tethys seas, or it may simply with thin, graded beds of microbreccia. The indicate the difference in geological age, as upper part of this formation, the Gondran there was no calcareous microplankton in the "Flysch," contains some sandstones. It is Paleozoic. overlain by thin ("leptogeosynclinal") beds of
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radiolarian chert and fine-grained, maiolica- lustres of the Val Grana, on the Italian side, type limestones which elsewhere in the Alps and are also separated from the fossiliferous Triassic in the Apennines represent the upper part of and lower Lias in their substratum, by a of the Middle Jurassic, the Upper Jurassic, and thrust plane marked by a thin seam of Triassic the base of the Cretaceous. The ophiolites, cornieule. Lemoine thinks it possible that the ophiolites in "synclinal" position on the Schistes lustres, together with the accompanying cherts Mt. Gendron and limestones, might be relics of a higher W "Ophiolitic nappe," unrelated to the Schistes lustres proper, like the upper part of the Gon- dran section (Nos. 6 and 7 of Fig. 3). In this hypothesis, there is no more direct proof that the Schistes lustre's are really pre-radiolaritic, and they might even be of Cretaceous age. This would make them coeval with the mainly Ophiolites Cretaceous Biindnerschiefer of the external 6 Marbles and rodiclarion chert Valais eugeosyncline; Lemoine rightly holds 5 Gendron "flysch" that a comparison between the stratigraphic 4 calcareous schists with microbreccia evolution of these two basins is premature 3 dark limestones, with chert on top (personal communication). 2 block, fossil if erous limestones, shales I Publication of Lemoine's new results is dolomites (Rhoetion- Hettongion) awaited eagerly, but the author admits that Triassic limestones & dolomites he found the earlier hypothesis rather satisfying. According to Franchi and Conti, Schistes lustres sedimentation started as early as the FIGURE 3.—SECTION AT MOUNT GONDRAN, EAST Late Triassic in the central part of the south- OF BRIANfON ern Piemont geosyncline. Below limestones, After Leraoine (1951; 1955) which are thought to be of Rhaetian and Liassic age, there is a thick formation of phyllitic which appear on top, are submarine lava flows, schists with beds of calcite and dolomite mar- almost certainly of early Cretaceous age. bles and sodic volcanic rocks which Conti Mount Gondran belongs to an external regards as a time equivalent of the Norian digitation of the Schistes lustres nappe, which Hauptdolomite formation farther east. But overrides the Brianconnais zone; but quite the tectonic and stratigraphic relationship of similar sections are reported by Lemoine him- this "Montenotte formation" to the Schistes self and by Conti from farther east. There, the lustres is rather obscure. At any rate, no Schistes lustres proper are much thicker than Triassic Schistes lustres are known from other the Gondran "Flysch" (about 2000 m?) and regions of the Alps. contain less microbreccia. Below them, Norian Biindnerschiefer of GraubUnden.—Large tracts to Sinemurian formations are dated by fossils. in western, central, and northern Graubiinden A part of the ophiolites, commonly associated consist of the monotonous Biindnerschiefer with cherts and maiolica limestones, seem to group. These sedimentary rocks belong to the form synclines on the mass of Schistes lustres, so sheared-off Mesozoic cover of the lower Pen- that it is probable, if not certain, that the ninic nappes, especially the Adula gneiss Schistes lustres of the Cottic Alps are of pre- nappe. An excellent description of them was radiolaritic age, and that they were formed given long ago by Albert Heim (1891). Strati- during the middle and late Lias and the earlier graphic subdivision was attempted by Staub Middle Jurassic. and especially by his pupils H. Jackli (1941) Recently, however, and in the light of new and W. Nabholz (1945; 1951). field observations, Lemoine (1959, and personal The most detailed section is that of the communication) has come to doubt his original highest (Tomul) strip sheet, roughly sum- interpretation, as here reported. He now sus- marized in Figure 4. One observes at first pects that the Gondran "Flysch" does not at glance the difference between these Biindner- all belong to the same unit as the overlying schiefer of the external Valais eugeosyncline cherts, limestones, and ophiolites, and that it and the Piemont Schistes lustres. The only may be much younger than the undoubtedly significant Biindnerschiefer fossils so far found Liassic strata on which it rests. The Schistes are lower Liassic oysters (Gryphaea). They
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Unit ^ Lithology " Fly sch" metamorphosed sss. & shs. Hauptkonglo- coarse conglomerate merat Saf ien quortzites^—'.'—.—.— I quartzites and quartz-bearing schists and fi't T ' • % -*t ' Safien breccia calcareous breccia
Safien limestone cryst. limestone
500m calcareous schists Nolla (orig.argillaceous limestones) Kalkschiefer 200
100 black schists and quartzites 0 Nolla Tonschiefer black, lime-free schists with a few calcareous bands
r 1000 ft
calciferous quartz-sericite Bdrenhorn schist, with marble bands Schist 100 0 albite-bearing quartzite "Schistes lustres limestone with lower Liassic ss" Gryphaea (Jackli) sericite-calcite schist, marble, quartzite 1 marble, dolomite,. Triassic cornieule, quartzite
FIGURE 4,—SECTION or PART or THE BUNDNERSCHIE:FER IN THE TOMUL SHEET or WESTERN GRAUBUNDKN After Jackli (1941) and Nabholz (1945). Ophiolites (mainly sills) are shown in black
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occur in sandy limestones, probably of shallow- sequence between Bundnerschiefer and Flysch. water origin, and not far above the top of the The gradation between these two rock groups Triassic. Dating of the rest of the group is can better be studied farther north, in the based only on lithologic analogies and is Pratigau, where Alpine metamorphism was extremely uncertain. Staub (1937), Jackli less effective. (1941), and Nabholz (1945) considered the "Pre-Flysck" of PrStigau.—The Pratigau black, pyritic slates of the Nolla Tonschiefer valley in northern Graubiinden is cut into a formation equivalent to the black, pyritic great mass of upper Mesozoic and Tertiary Aalenian shales of the Helvetic and Ultra- sediments, the Pratigau schists. They belong helvetic realm. Jackli (1944), however, followed to a more northerly part of the tectonic unit, these beds northeastward and proved that they which contains the Bundnerschiefer section correlate with the probably Lower Cretaceous just described, and correspond to the younger Valzeina formation in the Pratigau. Nabholz formations of that section. P. Nanny (1948) has (1951) and Staub (1958) proposed ingenious studied these formations very thoroughly and solutions to reconcile this fact with the hypoth- has established a well-founded scale. esis of a "comprehensive series" in the Biindner- The apparent thickness of the Pratigau schiefer, encompassing the entire Jurassic and schists is about 6000 m—probably the thickest Cretaceous. The present author (1958) sus- post-Triassic sequence known in the Alps, and pects that most of the Bundnerschiefer in the base is not exposed. Nanny's figure of about northwestern Graubiinden are of Cretaceous 4000 m (1948, p. 59) is too low compared with age, but he was quite rightly rebuked by his his cross sections. The Pratigau sequence is but friend Nabholz (in Bolli and Nabholz, 1959, p. slightly metamorphic; grade increases toward 241) for jumping to conclusions and for adding the south and also vertically, from the summits yet another unverified hypothesis. Cretaceous to the valley bottom 2000 m below (Nanny, age is nevertheless fairly certain for the rather 1948, p. 46). There are no ophiolites. Approxi- similar Ferret schist group in Valais (Triimpy, mately the upper half of the Pratigau group is 1954). If earlier assumptions, also based on reliably dated by Foraminifera as Turonian to very meager evidence, prove correct, the lower Eocene. Below, there is about 2500 or Piemont Schistes lustres as a whole are older 3000 m of Pratigau schists, which has not than the Bundnerschiefer of the North-Pen- furnished diagnostic fossils. This lower half is ninic Valais trough. divided into three formations; the middle one The cross sections published by Nabholz is the already mentioned Valzeina slates. (1945, PL 5; see also present Fig. 4) show the Each formation grades lithologically into the remarkable fact that ophiolites occur only in next higher one, and the youngest one grades the lower part of the Bundnerschiefer group into the overlying Pfavigrat formation, dated (Jackli's "Schistes lustres s.s."). Nabholz con- as Turonian by its Globotruncana assemblage. cluded that the ophiolites intruded during early Nanny assumes that the unfossiliferous lower folding and thrusting and commonly moved part of the Pratigau group is of Early to middle along thrust planes. They did not reach the Cretaceous age, and this is indeed the most sea bottom, which explains their absence from logical working hypothesis. Here again, a very the younger formations of the Bundnerschiefer thick sequence does not represent the entire group. Schoenenberg (1956) has questioned time span (Jurassic and Cretaceous) generally Nabholz's interpretation, but it is difficult to allotted to the Bundnerschiefer-Schistes lustres obtain a decision on the intrusion mechanism group. of the ophiolites in the metamorphic regions of From the sedimentological point of view, southwestern Graubiinden. If it could be proved three subunits can be distinguished in the that the ophiolites in the Valais eugeosyncline Pratigau schists: are derived from submarine lava flows and (1) The lower unit, comprising the three near-surface sills, like those of the Piemont unfossiliferous formations (Lower and middle belt, this would imply that the majority of the Cretaceous?), may without hesitation be—and type Bundnerschiefer are post-ophiolitic, indeed is—called Bundnerschiefer. The main whereas the type Schistes lustres of Piemont rock types are impure, rather thin-bedded are essentially pre-ophiolitic. limestones with small quartz grains (partly The youngest formations in the Tomiil detrital, partly recrystallized cherty matter), sheet, from the Safien limestone upward, to calcareous shales, and argillaceous shales which all authors now assign a Cretaceous age, (or rather slates) with some fine-grained show the characteristics of an intermediate calcareous sandstones. Thin layers of micro-
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breccia are common but not prominent. The correspond more nearly to the Schistes lustres sequence is very monotonous, and rhythmic of the Alps, there being only very rare and sedimentation, if present, is of the symmetric generally dubious occurrences of volcanic shale-limestone-shale type. Graded bedding is rocks in typical Flysch. not recorded from the Pratigau, but some In their typical development, Biindner- graded sandstones and microbreccias have schiefer (including Schistes lustres) and Flysch been observed at equivalent levels of the Ferret are quite distinct rock groups, but there are schists, in Valais (P. Fricker, doctorate thesis, many transitions between the two. The in press). Biindnerschiefer are restricted to the eugeo- (2) In the second subgroup, of Late Creta- synclinal troughs, where they are commonly ceous age, sedimentation is much more varied. associated with ophiolitic volcanic rocks. Their It is essentially calcareous; sandy, more or sedimentation precedes the folding movements. less calcarenitic, limestones pass into calcareous The Flysch facies, which will be discussed sandstones, argillaceous and silty limestones, more fully, marks the "filling-up" of the geosyn- and marl slates. Breccias and conglomerates cline and its encroachment onto areas that had with poorly rounded pebbles are conspicuous, hitherto shown platform or miogeosynclinal and the breccias in the older formations contain characteristics, concurrently with folding and a greater proportion of elements from the base- thrust faulting. ment than do the younger ones. The detrital matter is derived from the north. The breccias and microbreccias show graded bedding, but "Leptogeosynclinal" Formations the grading of the finer-grained sandstones is generally poor. Cyclothems a few meters thick, Meaning of the term.—The term "leptogeo- comparable to those described by Lombard synclinal" (from leptos, thin) was proposed by (1949) from the Niesen Flysch, are common. Triimpy (19S5, p. 220) for thin deep-sea The various bedding phenomena characteristic deposits representing a long time span. This of Flysch are incompletely developed. On the distinction was believed necessary as long as whole the sea appears to have been rather many geologists held that geosynclines were shallower than during deposition of the typical always characterized by abnormally great Biindnerschiefer, submarine slopes steeper, thickness of their sedimentary filling, as indeed and tectonic activity stronger. implied by Dana's original definition. Alpine (3) The Paleocene and lower Eocene forma- geologists, in the wake of Haug (1900), believe tions constitute the third unit. It is a typical that sedimentation in true eugeosynclines Flysch, with argillaceous shales, quartzitic could also be "starved," as long as, for one sandstones, and coarse, graded, feldspathic reason or another, little detrital matter is sandstones, poor in carbonate. furnished and the growth of shell- or skeleton- The Pratigau schist group is especially bearing bottom organisms is hampered. The important, as it shows the vertical gradation deep sea is the most common, but by no means from the Biindnerschiefer type of sedimenta- the only, environment which can cause extreme tion to that of Flysch. This gradation is also slowing down of sedimentation. (See also lateral; proceeding southward the Upper Sonder, 1939.) Today, many workers agree Cretaceous "pre-Flysch" formations become that eugeosynclines are not necessarily the finer in grain, more uniform in character, and sites of abnormally rapid sedimentation. indistinguishable from Biindnerschiefer. It is (Compare Kiindig, 1959.) If this agreement quite impossible to draw a sharp boundary were to become general, the term "leptogeo- line between the two groups of sedimentary syncline" could easily be spared; it was half rocks. Nanny (1948, p. 64) proposes to lump seriously introduced to stress the difference everything together under the common denom- between Dana's and Haug's conceptions of inator of Biindnerschiefer. This is certainly geosynclines, which might have been called, going too far. In other mountain chains (e.g., 10 years ago, the "American" and "European" the Carpathians) the opposite solution is concepts. adopted, and everything is called Flysch. Recognition of the leptogeosyndinal nature of Bertrand (1897) distinguished the "fades a formation depends, of course, on the evidence Flysch shisteux" (Schistes lustres etc.) and the that permits the inference that a certain kind "fades Flysch grossier" (Flysch in the present of sedimentary rock has been formed at bathyal Alpine sense). The "Flysch with ophiolites", or greater depths. Much of the evidence relat- observed in many fold belts, would generally ing to this question is negative, and none of it,
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taken alone, suffices to prove the deep-sea surprising, if one considers the enormous origin of a formation. But the concurrence of vertical movements during short time spans several of the proposed criteria lends a reason- brought to light by modern oceanography. able probability to the idea that many Alpine Silicified driftwood, found in some places, has sediments have indeed been laid down several no bathymetric significance. kilometers below sea level, and under conditions The frequent association of radiolarian approaching those in the present oceans. cherts with ophiolites has been noted by all Radiolarian cherts.—Red, or more rarely observers since Steinmann. For Wenk (1949) green or black, thin-bedded cherts with Radio- and others, this association is significant, and laria are found in the upper Middle Jurassic the proliferation of Radiolaria is supposed to be and lower Upper Jurassic of the Penninic due to the freeing of silica on the sea floor Piemont eugeosyncline and in all the units of during the spilite reaction. But there are many equivalent age south and east of it, down to occurrences of radiolarian cherts far from any the southern Alps. They occur all over the manifestations of submarine volcanism. In Mediterranean, in Greece, in Italy, in southern other cases, the ophiolites can be proved to be Spain, and in northwestern Africa. Manganese younger than the radiolarites, and hence fail as compounds, as coatings or more rarely as a source of silica. At any rate, it will not do to nodules, are common. Grunau (1957) found assume a volcanic supply of silica for the cherts minute particles of ultrabasic rock in certain in the Arosa zone, associated with ophiolites, green radiolarites. The cherts themselves, and another (unknown) source of silica for which in some instances contain but few radio- those in the southern Alps (Grunau, 1947; larians, are generally free of carbonate, but 1959), as the same radiolarite formation they may be interbedded with very fine-grained extends, practically unbroken, over the whole limestones. Grunau (1959) has just published a intervening Austroalpine realm and far beyond. thorough review on the problems of the radio- Taking into account the absence of benthonic larian cherts of the Alps and associated rock fauna from radiolarian cherts, the presence of types, and Cornelius (1951) has also discussed manganese nodules, the very slow rate of the question in a very clear and unbiased sedimentation-10 to 40 m of radiolarite can manner. represent the time span from Bajocian to The bathymetric significance of the radio- early Tithonian, without any evidence of larian cherts has been the object of many gaps—, and the vast horizontal extent of the discussions since Steinmann (1905; 1925, radiolarites of equivalent age, there seems little foreshadowed by Wahner, 1903) in his brilliant reason to reject Steinmann's views on the papers compared them to recent radiolarian deep-sea origin of radiolarian cherts in the Alps. oozes and interpreted them as abyssal sedi- Pelagic limestones and azoic shales.—The ments. In the 1930's and 1940's, European limestones, which accompany the radiolarian geologists tended to consider practically all cherts and overlie them in most sections, are visible sedimentary rocks as having been formed extremely fine-grained, commonly cherty, and in shallow water, and the radiolarites suffered show stylolitic partings, which can crowd the same fate (see especially Grunau, 1947, p. together to give a nodular structure to the 37-53) even though Tercier (1939, p. 77) rock. They contain pelagic microfossils only, opposed these too schematic views. Criticism of such as tintinnids, small globigerinids, and the Steinmann's concept was based mainly on the problematical Nannoconus. Ammonites are association of radiolarian cherts with supposed found locally, but in most places they are shallow-water formations, such as breccias and represented only by their calcitic aptychi; sandstones. The origin of the marine breccias their aragonitic shells have been dissolved. in the Alps will be examined later. The sand- These limestones (Maiolica, Biancone, Apty- stones apparently all are turbidites, character- chenkalk, Hyanenmarmor, etc.) have appar- istic of deep rather than shallow water. Other ently been laid down under conditions where arguments concern the chemical composition of calcite was stable, but no aragonite. Actual the cherts, much richer in silica than are the precipitation of the calcite, inasmuch as it present-day radiolarian oozes. But there has does not belong to pelagic microfossils, may certainly been much diagenetic transfer of have taken place near the water surface. The silica, explaining perhaps also the segregation thickness of these limestones is generally into pure cherts on one hand and limestones, modest, although rather higher than that of the with calcified radiolarian skeletons, on the cherts. It appears that deposition was fre- other. The fact that some radiolarites conform- quently interrupted. ably overlie shallow-water formations is not The argillaceous or siliceous shales which
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occur with the radiolarites and the maiolica so-called "Simme nappe" of the Iberg klippen limestones are always devoid of benthonic on Lake Lucerne (Jeannet, 1941), and with the fossils, except for fucoids. This absence of ophiolite-bearing nappe in the Prealps (Jaffe, remains of shell-bearing, bottom-dwelling 1955). Many authors, however, still consider animals not only in the cherts but also in the the Arosa zone as a lower Austroalpine unit, in other rock types of the radiolarite association spite of its close relationship with the undoubt- is certainly significant. edly Penninic Platta nappe. The correlation G. Colom (1957), who probably knows the here proposed does ;;,way with the highly pelagic formations of the Mesozoic and their anomalous occurrence of ophiolites in an "Aus- microfauna better than anybody else, comes troalpine" unit, and ophiolites become an to the startling but well-founded conclusion "index" to the eugeosynclinal Penninic realm. that almost oceanic conditions prevailed over a Up to the Rhaetic or to the early Lias, the large part of the country surrounding the west- sea remained shallow, as attested by dolomites ern Mediterranean, during the Middle and Late and limestones with benthonic fossils. These Jurassic and the Early Cretaceous. This formations are followed by dark azoic shales concept will certainly call for a thorough with thin bands and lenses of finer-grained, revision of current paleogeographical views. dull-gray limestone. They show a curious The Tethys Sea of middle Mesozoic time, often resemblance to the (presumably younger) considered a narrow and comparatively shallow Argille Scagliose shales and Palombino lime- stretch of sea between two continents, probably stones of the Liguride slide sheets in the is to be likened to a broad expanse of deep northern Apennines. Any geologist would call sea, with localized abyssal troughs—something, this shale sequence Schistes lustres, if it were perhaps, like the existing Carribbean. metamorphic. Sedimentary breccias occur As far as the Alps are concerned the evidence especially in its upper part, which is also richer may be interpreted as suggesting the existence in limestones. Five to 20 m of thin-bedded, red of a broad expanse of deep sea, covering the and green radiolarian cherts comes next. (For Piemont, Austroalpine, and south Alpine their detailed description, see Grunau, 1959, realms during Middle Jurassic to Early Creta- p. 79.) The overlying Aptychus limestone is ceous time. A few islands or swells bearing dated as latest Jurassic and earliest Cretaceous shallow-water sediments (such as the Upper by its pelagic microfauna. The Early Cretaceous Jurassic Plassen limestone of the Hallstatt is represented by shales with some graded beds nappe) rose above the surrounding, para- of sandstone and breccia. The much-disputed oceanic bottoms. If the Pr£alpes Medianes- Maran breccia, with angular fragments of Sulzfluh nappe is of Penninic, Brianconnais dolomite, siliceous shale, and chert, is consid- origin, as the present author believes, the ered as syn-radiolaritic by Cadisch and Richter, Upper Jurassic shallow-water limestones of as post-radiolaritic by Grunau and Gees. this unit were laid down outside (north and Locally, there are Barremian-Aptian limestones west of) this deep-water realm. If, on the with dolomite fragments, overlain by Middle contrary, this nappe belonged to the lower Cretaceous shales and greenish sandstones, Austroalpine units, the limestones necessarily which are quite similar to the Tristelkalk and formed on a broad rise surrounded by deep "Gault" formations of the more external sea. The Upper Jurassic formations unequivo- Falknis nappe. cally assigned to the lower Austroalpine nappes The entire sequence between the lower Lias of the Upper Engadine are entirely in a lepto- and the topmost Cretaceous contains essentially geosynclinal fades of radiolarian cherts and no benthonic fossils, although a few Middle maiolica limestones ("hyena marbles"). Jurassic brachiopods have been found in one Jurassic and Cretaceous of Arosa zone.—The locality (D. Richter, 1957, p. 328) in a kind of Arosa Schuppenzone of the Rhaetic Alps, one rock which is highly unusual for the Arosa zone. of the most interesting although very much The facies of the Jurassic and Cretaceous sliced-up cover nappes of the Alps, lies im- deposits can probably be attributed to deep- mediately below the great Austroalpine thrust water origin of the sediments. The composite mass and above the Sulzfluh (M6dianes) nappe. thickness rarely exceeds 150 m, most of which Several detailed studies have been devoted to is taken up by the "nonmetamorphic Schistes it (Cadisch, 1921; Grunau, 1947; 1959; Gees, lustres" at the base. 1955; D. Richter, 1957). In this paper it is In addition to the sediments there are regarded as the highest Penninic unit; it can large masses of ophiolites which predominate probably be correlated with the Platta nappe in the southern prolongation of the Arosa zone, of southern Graubiinden, with the wrongly the Platta nappe. Grunau (1957) advances
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3km w Arzo ~2mi. Breggicr gorge E Scoglio Mid^^p^erJJj^taceous Scaglia (marl shale)
Lower Cretaceous t . i Maiolico or Bioncone and Biancone: Upper Tithonion white ,f ine -grained limestone
Rodiolorite fm. Lower Tithonion to Radiolorion chert "-•^._ Bothonion and siliceous shales Ammonitico rosso
Domeriano
Transgress! ve fm. \ \ \ \ Bojocion Thin - bedded (L-M Lias) limestones, Norton chert bands, IHouptdolomitfm.) \ \ shales
m \\\\ Slumped beds 200-1 Triossic I \ \ \ Aalenion ft \ V \ v 500 Limestones & shales ^Porphyry boulder 150- Ammonitico rosso 400 (red,nodular Is.) \ \ Dome- ri Gray limestones 300 \ \ °" 100- \ ^^. 200 \ Pliensbachian Siliceous limestones, i \ to with chert nodules; some crinoidol Is. 100 \ Hettangian 50- \ I lUptolZOOnTl 20- L O resting on Rhaetic 10- 0J
FIGURE 5.—SECTION or PART or THE JURASSIC AND CRETACEOUS IN SOUTHERN TICINO After Frauenfelder (1916), Grunau (1959), Renz (1920), Senn (1924), and Vonderschmitt (1940). The two sections are only about 3 km apart; between them runs the Lugano fault.
good arguments for assigning these ophiolites Jurassic and Cretaceous of the southern to two phases: intrusive peridotites of Late Alps.—The "leptogeosynclinal" deep-sea facies Jurassic age and extrusive spilites, which is not restricted to the eugeosynclinal belt but flowed out in the middle and Late Cretaceous. also occurs over a very wide area south and The Mesozoic series of the Arosa zone affords east of the Penninic realm. The well-known a fair example of a "lepto-eugeosynclinal" section in the Breggia gorge, in southern Ticino facies group. But the study of similar rock (Fig. 5, right-hand column) may serve as an assemblages is much easier in other mountain example for the facies of the Jurassic in the chains, where the structural complications in southern Alps. From the middle Lias onward, the eugeosynclinal belt are not so enormous. the facies is uniform all over the southern
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Alps, except for the existence of another forma- time, with downthrow to the east. The western tion of red nodular limestones, the Ammonitico block was tilted westward, as the Liassic rosso superiore, of Kimmeridgian age, in the erosion is strongest just west of the fault. eastern part. The fault had almost no influence on the Above Norian dolomites and Rhaetic shales facies of the formations from the Domerian and limestones, the Jurassic starts with a great upward, except that thicknesses are somewhat thickness (up to 1200 m) of regularly bedded greater in the downthrown block. This can limestones, with layers and nodules of chert, mean either that the displacement diminished and some intercalations of crinoidal limes tones. in the middle Lias, or that the whole area be- The fauna is poor, but sufficient to show the came deeply submerged. A submarine difference presence of all stages of the lower Lias and of of level of, say, 300 m would change the facies the Pliensbachian (lower middle Lias). The of the sediments on either side if the sea were Domerian, Toarcian, and Aalenian limestones, shallow, whereas at depths of, say, 2000 m such a on the contrary, are very rich in ammonites, change would presumably have little effect on especially of the two pelagic groups of Phyllo- sedimentation, or might at most give rise to ceratacea and Lytoceratacea, to the near ex- some slumping. clusion of other fossils, except for planktonic or pseudoplanktonic lamellibranchs of the genus Marine Breccia Formations Posidonia. A slumped bed 12 m thick occurs in the upper Aalenian of the Breggia gorge, and Characteristics and environment.—Schistes several features in the Jurassic sediments of Iustr6s and leptogeosynclinal deep-sea deposits the surrounding area can probably be ascribed are not the only formations characteristic of to syngenetic slumping. (See Grunau, 1959, the eugeosynclinal belt of the Alps, dating from Figs. 37, 39). From the Bajocian onward, the the times preceding the early synorogenic macrofauna almost disappears, apparently be- Flysch phase. Polygenic marine breccias are cause of dissolution of aragonitic remains on perhaps just as significant for the understand- the bottom; aptychi of ammonites are the only ing of the structural history of the geosyncline megafossils. The whole sequence clearly denotes (Arbenz, 1919, p. 261). a gradual deepening of the sea, which reached These breccias are of varied origin. Intra- its maximum in the late Middle and early formational breccias are common in many Late Jurassic when the radiolarian cherts were Triassic limestones and dolomites (Helvetic: laid down. As long as the sea remained shallow, Widmer, 1949; Brianconnais belt: Debelmas, up to the middle Lias, sedimentation kept up 1952; 1955; Genge, 1958; Austroalpine nappes: with subsidence (miogeosynclinal conditions); Cadisch et al, 1919; Kappeler, 1938; Sander, after this, "starvation" set in, and the rate of 1936). For most such breccias, break of thixo- sedimentation dropped sharply ("leptogeo- tropy provides a satisfying explanation (Genge, synclinal" conditions). 1958, p. 190); they can develop vertically and West of the Breggia outcrops is a broad laterally out of normal strata and commonly valley, filled with Pleistocene deposits. The also show evidence of slumping. There was important Lugano fault runs north-south apparently a considerable amount of seismic along this valley. On the western side of the activity during the Triassic, culminating toward valley, only a few kilometers from the Breggia the end of the Ladinian. Other monogenic gorge, the Jurassic is again exposed, but in a limestone-dolomite breccias may be due to very different facies (Fig. 5, left-hand column). diagenetic replacement (Gignoux and Avnime- Instead of the lower Liassic cherty limestones lech, 1937), and certain Triassic breccias are which attain 1000 m or more, there are only certainly terrestrial. thin lower Liassic and Pliensbachian deposits, We are here, however, concerned with marine filling karstic cavities in the deeply eroded polygenic breccias of Jurassic and Cretaceous Norian dolomites. (The very complex stratig- age. These again show very different char- raphy and lithology of these karst fillings is acteristics. The matrix consists of shales, being studied in detail by F. Wiedenmayer of limestones, or even cherts; there is little detrital Basle.) This very sudden change of facies can quartz, and the breccias are not associated hardly be explained otherwise than by assum- with sandstones. Among the detrital compo- ing that the Lugano fault is a very ancient fea- nents, Triassic carbonate rocks are often ture and was already active during Liassic preponderant; basement rocks may play a
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large part in some Cretaceous breccias. These of the Alps as reliable indicators for shallow- elements are commonly very closely packed, water environment. They have interpreted and the matrix in most instances seems second- these breccias as coastal-abrasion products, as ary. The rounding of the components is deltaic deposits, or as having formed by wave imperfect or nonexistent, the sorting poor to action on shallow platforms (e.g., Tercier, 1952). very good. Graded bedding is common. These The association of breccias with radiolarian marine breccias make up isolated beds or cherts was in turn held to be a convincing lenses, whole formations, or thick, poorly argument against deep-water origin of the stratified and narrowly localized bodies. latter. In fact, most Alpine breccias lack the Breccias of this type occur in almost every characteristics of shallow-water psephites, tectonic unit of the Alps, and they range in age notably the inevitable rounding of the com- from Rhaetic to Late Cretaceous. Nevertheless, ponents. R. Triimpy (1955a) and Allemann there are certain zones in which Mesozoic (1956, p. 108) have insisted on the notion that breccias are very abundant and make up a large polygenic marine breccias could form at any part of the rock sequence. Three belts are thus depth, provided there was a sufficient slope characterized: and contemporaneous tectonic and seismic (1) The outer margin of the complex Brian- activity. Interbedding of breccias with radio- connais platform in the broad sense—that is, larian cherts, maiolica limestones, and shales the inner margin of the Valais trough: Oxfordian without bottom fauna denotes deep-water Breche du Tel6graphe in the Subbrianconnais environment for the former rather than shallow- of Savoy (Barbier, 1948; Schoeller, 1929), Upper water environment for the latter, especially Jurassic and Lower Cretaceous of the Falknis where these breccias show coarse graded nappe in Graubiinden (Allemann, 1956; D. bedding. Triimpy, 1916). Jurassic of the Breccia nappe.—The Breccia (2) The inner margin of the Brianconnais nappe is one of the higher units of the Prealps. platform and outer margin of the Piemont It is preserved mainly in the Chablais arch trough: breccias of the "Quatrieme Ecaille" south of Lake Geneva and in a smaller area in near Briancon (Lemoine, 1951), Cretaceous the Bernese Oberland south of Lake Thun. Tsanteleina breccia of the Vanoise (Ellenberger, Very good accounts of its stratigraphy have 1958, p. 327), Jurassic breccias of the Breccia been given by K. Arbenz (1947), Chessex nappe in the Prealps, discussed below. (1959), Lugeon (1896), and Schroeder (1939). (3) The border zone between the eugeosyn- The exact provenience of the Breccia nappe is clinal Piemont trough and the Austroalpine still unknown, but there is good circumstantial realm: Dolin breccias in the Dentblanche evidence for deriving it from the most westerly nappe of Valais (Hagen, 1948), Maran breccia part of the Piemont eugeosyncline, adjoining of Arosa zone, and numerous breccias of the Brianjonnais platform. different age in the lower Austroalpine nappes The post-Triassic formations of this remark- of the Upper Engadine. able structural unit are listed in Figure 6. Shal- Even in the comparatively tranquil, miogeo- low-water sediments with benthonic fossils were synclinal Helvetic realm, breccias, mainly of formed up to the Sinemurian (early Lias). The Early and Middle Jurassic age, occur in the "Schistes inferieurs" are probably a good vicinity of ancient fault scarps, and some of example of nonmetamorphic Schistes lustres the microbreccias are turbidity-current deposits (although without ophiolites). Crinoidal and (Carozzi, 1957). The same is true for the upper bryozoan fragments in calcarenitic limestones Austroalpine nappes. are the only fossil remains. The localization of pre-orogenic marine The same kind of rocks constitute the layers breccias along the limits between platforms between the breccia beds and the matrix of the and deeper-lying troughs certainly provides a breccias in the "Breche inferieure." The lower clue to their genesis. It is linked to the existence limit of this formation is certainly diachronous. of tectonic scarps, in most instances contempo- The breccia members consist mainly of angular raneous normal faults and flexures. Some of the fragments of Triassic dolomite and of Liassic breccia bodies are simply submarine scree limestone; only boulders derived from pene- deposits, and they share the absence of medium- contemporaneous, poorly consolidated rocks sized detritus with subaerial scree. Others may show some rounding. The thickness of individ- be due to shattering and mixing of consolidated ual beds changes abruptly. Some coarse and or semiconsolidated rocks by earthquakes. irregular graded bedding is common but not Many geologists have considered the breccias general; medium-grained breccia passes upward
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Unit Age Lithology
Flvsch Poleocene ^ ' '. F « ' '•*• shale sandstones Couches Upper ^-"^ I — 1~1,;;JL red, argillaceous Is. rouges Senonion * &-J ' ] ',,',!,'„' f '• fine-grained Is. with chert 1 nwpr r.rpt X^-»gnr V"- V
Brectie iifhomon* ( 5l° Breche Vi °i-j» t breccias, mainly dolomite >~' "> '' N -•• Inferieure (o°o°O°o fragments; of ten graded ? i - i • 1 - i r o ooo 'lO O O 0 0 ('' \<\ x-HrV ... ) ] 0 L t. ] 0 | n \ \ f ^ .^ \ ,' ^> or argillaceous Is. j| — 1 — 1 — I O v_ "?• ~ <^ calcareous shales O >ft C* J> !!• • - S Co Qooo > 3 S\ — l-ri, —},- *~ ^* \o Oo o O o e ir T—O cy «- .« .» -^^T »~ »«T~j •n \-. — "-'-— - Schistes •- vj-^-J " 1 •» j 2 £[-\~\—\- silty shaly Is often crinoidal infpneurs YT ~\— — — calcarenites >-^— —. — V^ ' - i - -M A : r- /~7— i — ^ . 'a— > ' f "• cherty i crinoidal Is. ,, . f' ' ' il— - — ^ mfeneurs Lios V_ < / • i . i o)» -•—oolitic Is. Knoenc " v- >• ~ie8'-_ shales, dolomites, shelly Is. (. II ll II dolomites Upper Triassic J ~\\ \\ FIGURE 6.—JURASSIC AND CRETACEOUS SEQUENCE OE THE BRECCIA NAPPE IN ABONDANCE VALLEY (CHABLAIS) Mainly after Chessex (1959) Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 872 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS into fine breccia, and this in turn into cal- ents, essentially different carbonate rocks, are carenite. No cross-bedding has been recorded, rather well sorted. From east to west, the although load casts and ripple marks are thickness of the breccia and the size of the developed locally (Kuenen and Carozzi, 1953). fragments decrease, while the proportion of Most breccias are polygenic, but limestone dolomite components increases. Large blocks beds can break up, apparently by slumping, to and slabs of older rocks, and even of Upper form mtraformational breccias (K. Arbenz, Jurassic cherty limestones occur in several 1947, p. IS). Transport of the components was places. Graded bedding is observed locally. from west to east, a fact already noted by The breccia has undergone considerable Lugeon and in accord with the presumed diagenetic change, mainly silicification and origin of the Breccia nappe on the steep eastern partial dissolution of limestone elements. flank of the Brianconnais rise (Compare Figure Wahner (1903, p. 118), to whom we are 12). Probably this steep slope was of tectonic indebted for an admirable monograph on these origin and was the seat of repeated earthquakes. mountains, regarded the Hornsteinbreccia as a These may have provoked a preliminary shat- tectonic breccia, attributable to the Cretaceous tering of the Triassic and Liassic rocks. Trans- orogenic movements. At the time he wrote, port of the fragments apparently took place by many sedimentary breccias in the Alps were slumping and sliding movements, rather than interpreted as "mylonites" by Termier and by true turbidity currents (Kuenen and Carozzi, others. A thorough account of the historical 1953). Evidence on the depth of the water in development of thought on this subject was which the breccias came to rest is contradictory. given by Spengler in the second part of Crinoidal fragments are so abundant in certain Warmer's work (1935, p. 118-153). One reason limestone beds that it is logical to suppose Wahner would not accept a sedimentary that the animals lived not far away. On the origin of the breccia was its association with other hand, the existence of a submarine slope deep-sea sediments. Ampferer (1908), on the that permitted coarse detritus to travel over a contrary, insisted on the sedimentary nature of minimum distance of 12 km implies considerable the Sonnwend breccias. Further and more depth at the bottom of the slope. decisive proof of a sedimentary origin was In any event, the siliceous shales and radio- brought forth by Sander (1941) and by his larian cherts of the next higher formation, the pupil Weynschenk (1949),8 who noted resed- Schistes ardoisiers, may well be deep-sea imentation phenomena, but who also stressed deposits. By this time, the conditions on the the strong post-depositional deformation of sea bottom were unfavorable for calcium-carbo- the breccias. nate deposition, so that limestone elements in These post-depositional movements are not the breccia members are commonly corroded. necessarily due to Cretaceous (pre-Gosau) As in most parts of the Alpine geosyncline, orogeny. Heritsch (1915) suggested slumping as carbonate sedimentation was resumed during an important factor in the genesis of these the Late Jurassic. breccias. Tectonic and seismic activity, followed Breccias ofSonnwend Mountains, Tyrol.—The by slumping and slow mass-gliding movements, Jurassic "Hornsteinbreccien" of the Sonnwend really seems to provide the most satisfying or Rofan Mountains above Lake Achen, north- explanation. The complicated structures in the east of Innsbruck, have been the object of leptogeosynclinal Jurassic formations of the passionate controversy. In this part of the more easterly Kammerkar and Osterhorn upper Austroalpine nappes, Rhaetic and lower mountains discovered by Vortisch (1927, and Liassic formations are of normal shallow-water abstract in Schaffer et al., 1951, p. 354-357) are origin. They are followed by thin red limestones much more easily understood as being caused with manganese nodules, containing cephalopod by gravitational sliding during the geosynclinal faunas of the middle and upper Lias. These in stage than by compressional thrusting. This is turn are overlain by red and brown siliceous a further indication for the deep-sea origin of shales and radiolarian cherts. The Hornstein- radiolarian cherts and associated rocks. If the breccias, the thickness of which ranges from slopes were sufficiently steep and long for 10 to 150 m, are interbedded with these cherty large-scale gliding, and if the facies remained rocks. Above it are thick limestones with chert bands, of Late Jurassic age. "The rather curious criteria invoked by Weyn- As a rule, the breccias are poorly bedded, schenk for proving shallow-water origin of all for- except for their lower part, where they alternate mations in the Sonnwend Mountains were severely with radiolarian cherts. The angular compon- criticized by Grunau (1959). 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(1) Flysch corresponds essentially to detrital or terrigenous deposits, quite subordinately Flysch biogenic ones, deposited in a more or less regu- lar alternation of sandstones and micaceous General statement.—To the inhabitants of the shales, with, sometimes, intercalations of con- Bernese Oberland and of Obwalden (south- glomerates or of limestones. east of Lake Lucerne), Flysch means a more or (2) On the whole, it always represents a less shaly rock, producing moist acid soils and rather thick formation (group), the lithological given to superficial slumping and flowing8". units (formations) of which are poorly individ- This dialect term was introduced into geological ualized. publication by Studer in 1853 and has since (3) It is made up exclusively of marine sedi- been used in variable connotations (the his- ments, in part neritic, butin partalsoof bathyal torical development will be treated by W. origin. Leupold in the Lexique stratigraphique inter- (4) From the paleogeographical point of national). There is now a kind of general view, Flysch must be considered a deposit agreement among Alpine geologists on the proper to basins broken by steep and discontin- definition of the term, although this definition uous Cordilleras. cannot be laid down in a few words. Some We shall follow Tercier by examining these misuses persist, however; thus normal neritic points. or pelagic formations of Tertiary age are some- Lithological and biotal characteristics of Alpine times still called Flysch (e.g., south-Helvetic Flysch successions.—Sandstones and shales, al- Einsiedeln and Blattengrat "Flysch," consisting ternating regularly over, in some instances, of pelagic marl shales and a thick limestone thousands of meters, are the typical Flysch member with large Foraminifera), and of rocks. The sandstones are generally micaceous, course many geologists have applied the term commonly feldspathic, and some varieties con- to formations outside the Alps which show tain a large proportion of detrital carbonate no resemblance whatever to Alpine Flysch (e.g., grains. Rounding is generally poor, except for the Purbeckian of the Jura, brackish and the largest grains, and sorting is characteristi- subsaline carbonate rocks with intraformational cally poor (Rech-Frollo, 1953; 1954). The ce- breccias). ment is commonly calcitic, but may be argilla- More than any other Alpine term, the facies ceous or silty. Most sandstones are associated name Flysch has been applied to formations of with finer-grained detrital rocks, such as cal- other fold belts. A good "universal" definition careous mudstones (commonly designated by of Flysch has recently been advanced by Kue- the misleading term "Kieselkalk"). Typical nen(1958, p. 329): graywackes are rather exceptional. Flysch shales are invariably silty, commonly sandy, "A thick sequence of pre-paroxysmal marine and generally show mica flakes on the bedding geosynclinal sediments, consisting of an alternation of evenly stratified shale and muddy sandstone planes. They may or may not contain a large (graywacke, etc.) and showing at least a moderate proportion of calcium carbonate. The shale- amount of graded bedding. The maximum grain sandstone ratio is very variable (from about size in the graded beds is 5 to 10 cm diameter. 10:1 to 1:5). Coarser material is not graded and subordinate in amount. Transitions to or alternations with cal- The coarse detrital members of Flysch se- careous types also occur. Geological age is ignored." quences generally show a very wide range of nature and size of components, among which In this paper, we are concerned only with the basement rocks are commonly conspicuous. Flysch of the Alps. As Kuenen himself re- The elements are poorly rounded, and primary matrix is generally abundant. 8a Flysch never was a quarryman's term as Flysch limestones are generally of the "Al- suggested by Eardley and White (1947, p. 981). berese" type, thinly bedded and of exceedingly Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 874 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS fine grain. Genesis of these limestones is very and the subdivision of the Flysch facies is almost enigmatic, particularly as they have as yet as difficult as that of the Schistes lustres yielded no fossils, not even a pelagic micro- (although less haphazard because of the fossils biota. which diligent search will always reveal in the Ophiolites occur only quite exceptionally in Flysch). No cyclothemic units of larger order typical Flysch formations; they are character- can be observed; the normal pulsatory move- istic of the older Biindnerschiefer group. Debris ments were obscured by the contemporary tec- of intermediate to basic volcanic rocks, on the tonic activity. other hand, is very prominent in some Tertiary Owing to the tectonic complications and to Flysch formations. the bad state of the outcrops, which are the bane An important feature of Flysch sediments is of the geologist's life in Flysch country, it is dif- the lack of an autochthonous, shell-bearing, ficult to follow a given unit or bed of a Flysch bottom-dwelling fauna. Fossils of the Flysch be- sequence very far. Nevertheless, at the scale of long to three categories: a quarry or even of a hillside, the individual (1) Tracks and burrows of bottom-dwelling beds show little change in composition and animals, such as fucoids and helminthoids. thickness. This characteristic contrasts strongly Seilacher (1955) has shown that this type of with the more limited lateral extent of most organic trace indicates deep water, beyond the beds in the Molasse successions. The beds are penetration of light. rather thin—a few centimeters or decimeters— (2) Shells of benthonic animals, mainly larger and fairly regular; sandstone members several Foraminifera (Siderolites, Nummulites, etc.) and meters thick are found only occasionally. fragments of calcareous algae (e.g. Lithotham- Graded bedding and the different sole mark- nium) and of bryozoans. These fossils occur in ings caused by turbidity currents and bottom graded sandstones, and the mass of the remains creep are common in most Flysch sequences (rather than their size) is of the same order as (Allemann, 1956, p. 93-144; Crowell, 1955; that of the sand grains (generally a few milli- Hsu, 1959; Kuenen, 1953; 1957a; Kuenen and meters in diameter). Clearly, these neritic fossils Carozzi, 1953), but these features are not at all were redeposited with the detrital matter, by regularly developed, and the grading of Alpine turbidity currents and slumps. The scarcity of Flysch sandstones is generally much less well molluscan debris is noteworthy. developed than that of many Paleozoic gray- (3) Pelagic and characteristically microscopic wackes. In many instances, only the topmost fossils (Radiolaria, planktonic Foraminifera), part of sandstone beds is graded. Erosional dis- some of which occur in graded sandstones and continuities at the base of sandstone layers are may be resedimented. Plant fragments are not quite exceptional, and current ripple marks are rare in some Flysch formations and can be rare; small-scale current-bedding is of some classed with category (1) (in coarse, basal layers importance in the youngest Flysch formations. of sandstones) or (2) (on bedding planes). Evidence of slumping is not infrequent in the Formational and bedding characteristics of transitional facies to both Biindnerschiefer and Flysch.—The thickness of Flysch sequences is Molasse; on the other hand, it seems to be generally considerable, greater than that of the absent from the more "flyschy," typical Flysch earlier Schistes lustres group. Flysch deposits of formations, in which the sandstones are in large any tectonic unit measure between a few hun- proportion turbidites. dred and some thousands of meters, frequently Bathymetric setting of Flysch sediments.—All 1000 to 2000 m. This great thickness ordinarily Flysch sediments are of marine origin, and none corresponds to a relatively short time span, shows evidence of abnormal salinity, except in covering a few stages (in rough figures, 5 to 20 zones of transition to Molasse, where the greatly million years). It is only where Flysch follows narrowed Flysch sea became brackish. The bot- Biindnerschiefer without a break, as in the Pra- tom waters were generally well aerated, but in tigau, that a veritable "comprehensive series", this respect, again, the youngest Flysch forma- representing, for instance, the whole Cretaceous tions are abnormal and show lack of oxygen. epoch, is found. Flysch sedimentation is thus Up to the 1940's, Flysch formations were very rapid, by Alpine standards. generally regarded as neritic shallow-water de- Flysch sequences are characterized not only posits. Tercier (1947, p. 179) was among the by rapid, but also by more or less continuous, first to oppose these views, with very sound sedimentation. No major breaks are recorded arguments. In his opinion Flysch sedimentation by paleontological evidence. The different litho- was not restricted to any particular depth zone stratigraphic units are linked by passage beds, but could take place along steep slopes, from Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 GENETIC SEQUENCES OF ALPINE SEDIMENTARY ROCKS 875 coastal environments down to great depth. With sediments show the influence of contempora- the extremely fruitful notion of turbidity cur- neous tectonic movements much more clearly. rents taking its triumphal course, the pendulum The marine breccias of Jurassic and Early Cre- has swung to the opposite extreme, and prac- taceous age discussed earlier also related to tec- tically all graded sandstones of Flysch type are tonic activity, but these breccias were restricted being considered as deep-sea sediments. This to certain belts in the vicinity of ancient fault also is probably exaggerated. scarps. During the time of Flysch sedimenta- As a general rule, Flysch sediments can be tion (Cenomanian to early Oligocene) the sub- said to have formed below the reach of wave marine relief was much stronger, and tectonic action. One important (although negative) piece movements affected the whole of the Alpine of bathymetric evidence is the lack of an au- belt, although not all of its parts at the same tochthonous shell-bearing fauna. In addition, time. The swells and platforms of pre-Ceno- turbidity-current deposits of great horizontal manian time were submarine, or at best rose extent presuppose the existence of long slopes above the sea as low islands. When the Flysch and imply great depths at the far end of these was formed, large tracts of the original basin slopes. However, the abundance of resedi- were emerged and undergoing active elevation mented larger Foraminifera and calcareous and erosion. Flysch sedimentation immediately algae in some Flysch sandstones, and of well- precedes in time the major structural revolution rounded pebbles (among a majority of poorly of each paleogeographic unit. rounded ones) in some Flysch conglomerates A very puzzling problem concerns the source indicates that shallow-sea, perhaps even coastal, of the sand in the Flysch sediments. Rising cor- environments were not far from those where dilleras would of course furnish a great amount these Flysch sediments were laid down. The of detrital matter, but it is hard to explain why abundance of floated vegetal remains may also and how most of this was reduced to compara- point in this direction, although it is by no tively small grain size before being resedimented means decisive. The author knows of no con- by turbidity currents and slower mass-redepo- clusive evidence of lime leaching in Flysch de- sitional processes. Possibly much of the frag- posits, whereas such evidence abounds in the mentation of rocks took place in shallow waters older, leptogeosynclinal formations; this, how- surrounding the emerged island belts, and some ever, may be due to the accelerated rate of dep- of it by river transport. Some authors (espe- osition. The author estimates that most Flysch cially Bruckner, 1952) have considered a deltaic rocks have formed at depths exceeding 200 m, origin for Flysch materials. This idea was re- but not more than a few kilometers. Flysch cently taken up by Kuenen (1957b; 1958), who sedimentation marks the filling of the geosyn- has given much thought to the problem in con- cline. nection with the proved longitudinal filling of Some shallow-water sediments do occur lo- many Flysch troughs by turbidity currents. cally in Flysch formations. The Cretaceous Reconstruction of the paleogeographical config- Simme Flysch contains beds of polygenic con- uration during "Flysch times," however, leaves glomerates (the Mocausa conglomerates), with little or no space for the existence of larger river well-rounded pebbles, and layers with a rich systems inside or outside the present Alps. In bottom fauna of Cenomanian age (Campana, many instances (e.g., Niesen Flysch, Pratigau 1943; Jeannet, 1912-1913). These deposits Flysch, part of Gurnigel Flysch), it can be might even be regarded as approaching the shown that the detrital matter is derived later- Molasse type of facies, related, of course, not ally from the Cordilleras, even if it may have to the principal, Tertiary folding phases of the been redistributed along the axis of the basins western Alps, but to the mid-Cretaceous by turbidity (or other) currents. Much of this orogeny of the Austroalpine nappes, to which material was furnished by granites and other the Simme nappe perhaps should be attributed. rocks of the pre-Triassic basement. Also, the northern Penninic or Ultrahelvetic Relationship of Flysch to other facies groups.— Sardona flysch of the Glarus Alps—not a very No gradation of Flysch into normal, miogeo- typical Flysch in some respects—has one mem- synclinal or platform deposits is known. Where ber, the Paleocene Sardona quartzite, consist- the two types of formations enter into strati- ing of clean, occasionally cross-bedded quartz graphical contact, the Flysch rests unconform- sandstones (Leupold, 1937; 1942; Riiefli, 1959). ably on the older rocks, down to the pre-Trias- Tectcmic setting of Flysch sediments.—Com- sic basement. pared with the older miogeosynclinal and eu- We have already seen, however, that the geosynclinal formations of the Alps, the Flysch Btindnerschiefer group of sediments may pass Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 876 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS upward and laterally into Flysch, and that it is Lombard (1942; 1949; 1956, p. 638) is still un- quite impossible to draw a sharp boundary be- published, save for a few preliminary notes. tween the two. The stratigraphic sequence of the nappe be- The relationships of Flysch to pelagic forma- gins with isolated slices of crystalline basement tions, such as radiolarian cherts, maiolica lime- rocks and a very unimpressive development of stones, and especially calcareous shales or Triassic. It is followed by Liassic crinoidal argillaceous limestones with planktonic Forami- limestones and nonfossiliferous, slightly meta- nifera, are of prime importance. Sediments of morphic argillaceous slates, apparently of Ju- this type in many places underlie Flysch forma- rassic and perhaps Early Cretaceous age. In tions. The boundaries are commonly sharp, or some sections, these slates grade upward into there may be lateral transitions and gradation the Niesen Flysch proper, which in other places by interbedding. Much of what is called "Flysch rests unconformably upon the older formations. calcaire" in the western Alps consists of shale- The Flysch itself ranges up to 2000 m thick. It limestone alternations, which may represent a differs widely in composition from the north- transitional facies between pelagic sediments or eastern to the southwestern end of the chain, Blindnerschiefer to typical Flysch. Where and correlation between the two areas has yet Flysch sedimentation took place over formerly to be established. Most of it is of Late Creta- miogeosynclinal or nongeosynclinal belts, there ceous (especially Maestrichtian) age; the top- are pelagic sediments between the neritic forma- most part reaches into the Paleocene or early tions and the Flysch (e.g., Eocene Stad shales Eocene. Cenomanian Orbitolina has also been in the Helvetic Alps, Cretaceous to Paleocene found (Lombard, 1942), but it is still difficult to Couches Rouges in the Prealps). This implies judge how much of the group is older than that the downbuckling of a particular belt pre- Campanian. ceded its filling by Flysch sediments. Studer, in 1853, did not consider the "Niesen Just as Biindnerschiefer pass upward and breccia" as Flysch, and the Niesen Flysch dif- outward (north or west) into "pre-Flysch'1 and fers in many respects from other, more typical Flysch, the Flysch itself grades upward and Flysch sequences. It forms a chain of bold, outward into Molasse. The subsiding belt thus pyramid-shaped mountains (PL 2), contrasting shifted toward the external border of the Alps with the soft hills of other Flysch areas. (The and was more and more filled in by detrital mat- Eocene Aiguilles d'Arves Flysch of Savoy and ter from the rising chain. the Cretaceous to Eocene Arblatsch Flysch of There is nothing like "The Flysch" of the Graubunden give the same morphological effect Alps, but a great many different kinds of as the Niesen Flysch.) Limestones form a large Flysch. Their lithological and bedding features proportion of the Niesen sequence, and most of vary widely, their age from Cenomanian to them are not of the sublithographic Alberese early Oligocene. (Sedimentation of "pre- type; one unit consists essentially of rather Flysch" type set in even earlier, during the thick-bedded limestones with calcified sponge Early Cretaceous.) Some of these formations spicules. Other benthonic shelly fossils, such as are quite unequivocally Flysch; others repre- crinoid fragments and even brachiopods, are sent particular types, and still others are tran- found at some places. Conglomerates are very sitional either to Biindnerschiefer (including prominent, especially at the southwestern end "pre-Flysch") or to Molasse. Four examples il- of the chain. Many of them contain enormous lustrate these differences. boulders of granite and of crystalline schists. Niesen Flysch (transitional to "pre-Flysch"). Many of these conglomerates and breccias are —The Niesen nappe is known only from the reminiscent of the older scarp breccias discussed Prealps between the Rhone and Lake Thun, in a preceding section on the Breccia nappe. over a distance of 60 km along the strike. It lies The coarse material is derived from the west— between the Ultrahelvetic nappes below and that is, from the external margin of the basin. the M6dianes nappe above (PI. 2), but its About 20 km farther east, the lower part of the exact origin is still disputed. However, it can Niesen Flysch is formed by monotonous cal- safely be assumed that the Niesen nappe is de- careous shales with a few beds of graded sand- rived from the lower Penninic Valais facies belt, stone, but no more conglomerates. Grading in probably from the more external part of it. The general is poor; on the other hand, small-scale most important monographs are those by An- cyclothems a few decimeters or centimeters drau (1929), Bornhauser (1928), McConnell thick have been described from the upper part (1951), and de Raaf (1934); recent research by of the Niesen Flysch (Lombard, 1949). When Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 GENETIC SEQUENCES OF ALPINE SEDIMENTARY ROCKS 877 complete, they show the sequence sandstone- The Schlieren Flysch (Fig. 7) fills a large shale-limestone, with many variations. Sole syncline on the Helvetic nappes between Lake markings and load casts are abundant; con- Thun and Lake Lucerne; probable equivalents torted bedding is not uncommon. There is good are also found south and east of Lake Lucerne. evidence of breaking up of beds by penecontem- It rests upon wildflysch of late Eocene age and NW Schofmatt SE 1979m Eocene Schlieren Flysch Lower Cretaceous \EoceneN Molasse \Border Flysch \ (Middle Helvetic nappes) x Upper Eocene Habkern Wildflysch (Oligocene) \ (complex) (Ultrohelvetic) \ i 1 (km < 1 mile FIGURE 7.—CROSS SECTION THROUGH THE BORDER ZONE or THE ALPS WEST or LAKE LUCERNE After Mollet (1921) and Schaub (1951). X indicates thrust fault. poraneous slumping (e.g., McConnell, 1951, p. is in turn overlain by outliers of the Medianes 40). nappe in the Giswiler Stoeke (Vonderschmitt, Turbidity currents, while certainly active, 1923). The Schlieren Flysch, 1500 m thick, thus do not appear to have been the essential agent constitutes a nappe of its own, and its original of transport for the detrital matter in the Nie- substratum is unknown. It may belong either to sen Flysch, except possibly its uppermost parts. the internal part of the Ultrahelvetic or to the For this particular type of Flysch (or "pre- external part of the Penninic realm. Because of Flysch"?) bottom creep, as put forward by its rather simple tectonic structure, some good Lombard in his monumental work (1956), must outcrops, and especially thanks to a monograph certainly be considered as an important factor. by Schaub (1951), its stratigraphic succession is The persistence of calcareous deposition better known than that of most other Flysch through much of the group implies that depth sequences. of the sea was not excessive, at any rate not in The record begins with a Flysch of Late Cre- the western part of the present chain. Lateral taceous age, consisting of shales with helminth- variations of facies are more abrupt than in the oids, sandstones of generally fine grain, and later and more typical "turbidite Flysch" for- siltstones. Peculiar, very fine-grained quartzitic mations. sandstones showing an oily luster on fracture Other Cretaceous Flysch and "pre-Flysch" planes ("Oelquarzit") are found in the basal formations of the Valais facies belt show rather part of the Schlieren group, and also in many similar characteristics: for instance, the middle Cretaceous Flysch formations of eastern Swit- part of the Pratigau schists (discussed earlier), zerland and of Austria. Their origin is very or the Tarentaise breccias of Savoy, Aosta enigmatic. Sole markings are fairly well de- (northern Piemont), and Valais (Schoeller, veloped; some contorted lamination has been 1929; R. Triimpy, 1954), which contains a unit observed, but grading is generally poor and of giant conglomerates having rounded boulders commonly absent. South of Lake Lucerne, up to 35 m across. coarse breccias with elements of basement rocks Schlieren and Gurnigel Flysch sequences of form an important part of this basal unit of the central Switzerland.—The Schlieren and Gurni- Schlieren Flysch (Geiger, 1956). gel sandstone Flysch complexes can serve as The Paleocene is represented by sandstones, examples for typical Flysch formations. commonly arkosic and very well cemented, in Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 878 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS thick beds (up to 10 m), with thin shale parti- higher nappe (Fig. 7). The term was introduced tions. Many of the sandstone beds begin with by Kaufmann in 1870 (Cadisch, 1953, p. 174). microbreccias. The main body of the layer is "Wild" refers to the bedding, which is extremely characteristically of uniform grain size, but at irregular or chaotic. Wildflysch consists mainly the top there is regular grading into finer- of shales, generally poor in carbonate mineral grained, laminated sandstone, commonly with content, with torn and contorted beds and drifted plant fragments, and into shale. lenses of sandstone and of calcareous mudstone. The lower Eocene part of the Schlieren Flysch Its age is late Eocene (Priabonian). It com- forms a very thick and monotonous sandstone- monly contains large boulders of widely differ- shale alternation. The sandstones are feld- ing type, embedded in shaly matrix: crystalline spathic and only moderately calcareous. In this schists, the very peculiar Habkern granite, and portion, graded bedding is constant and very an array of Mesozoic sedimentary rocks, some regular; each sandstone-shale sequence is about of them very rich in nondeformed fossils. In 2 m thick. Individual laminae may also show other places, there are large masses of "Leimern grading. Sole markings and other typical tur- beds", that is, Upper Cretaceous limestones bidite features are conspicuous (Hsu, 1959), and Paleocene marl shales with pelagic Fora- and Hsu (1960) established a southwest-north- minifera. Instructive descriptions of Wildflysch east direction for the currents. The nummulite outcrops are given by Beck (1911), Gigon succession, meticulously worked out by Schaub (1952), Jeannet (1941), Soder (1949), and (1951), shows a remarkably complete record of others. the early Eocene. The Foraminifera are found The general aspect of Wildflysch forcibly in the coarse basal layers of the sandstone beds. suggests submarine slumping and sliding on a The Gurnigel-Voirons Flysch belt of the ex- large scale, on a steep slope adjoining an ternal Prealps (Gagnebin, 1924; Lombard, actively rising ridge. It is not yet certain 1940; Tercier, 1928) consists mainly of a sand- whether this slope faced north or south. One stone Flysch very similar to the Schlieren measured granite boulder is 13,000 m3, and Flysch. There is no Cretaceous Flysch, but on some of the slide masses of Leimern beds are the other hand the succession reaches up into more than 100 m long. The sliding evidently the middle Eocene. As a rule, the polygenic took place during the sedimentation of the sandstones are more calcareous and coarser Wildflysch; Buxtorf (1943) has described a than those in the Schlieren Flysch. Graded beautiful transgression contact between Lei- bedding is irregularly developed, but sole mark- mern limestones and Wildflysch. These con- ings are common. Direction of turbidity cur- temporaneous block slides are reminiscent of rents is mainly northwest-southeast (Crowell, the "olistrostromi" of the Apennines. The main 1955; Hsu, 1960). This led Hsu to assume that thrusting and gravity sliding of the Ultrahel- the Gurnigel and Schlieren Flysch basins lay vetic nappes occurred soon after the deposition on different sides of the same Cordillera, on of the Wildflysch. which, among other rocks, the Habkern granites Wildflysch fades is not limited to the upper cropped out. The Gurnigel Flysch would thus Eocene of the Ultrahelvetic nappes, but it is not become of more internal origin than the Schlie- displayed elsewhere so characteristically. Nor- ren Flysch. For structural and paleogeographi- mal Flysch rich in shales can assume a Wild- cal reasons, the present author favors another flysch-like habit when subjected to slumping or hypothesis: Gurnigel and Schlieren Flysch were to strong and irregular tectonic deformation. laid down in the same basin, the former to the Flysch of the northern Helvetic belt and passage northwest and nearer the "Habkern granite to Molasse.—These Flysch masses (Fig. 8), islands," the latter farther southeast and east, which attain a thickness of nearly 2000 m, are as today, and presumably in deeper water. The the youngest and originally the most external different transport directions might be attrib- (northerly or westerly) of the Alps. Their age is uted to transverse turbidity currents on the latest Eocene to early Oligocene. By this time, northwestern slope of the basin, changing to the the main body of the future chain already was longitudinal southwest-northeast direction in above sea level and had undergone considerable the basin axis. folding and thrusting. The axis of subsidence Wildflysch of central Switzerland.—The type had shifted northward to the site of the present Wildflysch (vildfleesh) belongs to the Ultra- Aar, Montblanc, and Aiguilles Rouges massifs. helvetic nappes of central and western Switzer- The foredeep continued to wander outward land. It is generally overlain by the Schlieren during sedimentation of this Flysch, and it and Gurnigel Flysch sequences; the former con- reached the inner margin of the Molasse basin stituting certainly, and the latter probably, a in the middle Oligocene. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 GENETIC SEQUENCES OF ALPINE SEDIMENTARY ROCKS 879 The Tertiary formations in this region are formation, the Taveyannaz sandstones, con- markedly heterochronous (Fig. 8). They begin sists of thick-bedded, greenish, mottled sand- with normal neritic deposits: limestones and stones with partings of argillaceous and silty glauconitic quartz sandstones with large Foram- shale. Shale fragments, embedded in a semi- Subalpine zone Autochthonous Helvetic nappes Ultrohelvetic eroded, or basin covered up by higher nappes Santonian Coniacian — i —T-=^ i — i — i — i — i ^—^— i — neritic limestones I sandstone pelagic limestones marl-shales with —.-i shales I arenaceous pelagic forams. =i^l Is. (Wang beds) FIGURE 8.—AGE RELATIONSHIP or FLYSCH FORMATIONS IN THE HELVETIC BELT or EASTERN SWITZERLAND The horizontal distance is about 70 km. After Bruckner (1952), much modified (based in part on results of Leupold and his students). inifera (Nummulites, Assilina, Discocydina) consolidated state, are common in the basal and calcareous algae. These are lower Eocene in layers of sandstone. Graded bedding and sole the originally southeastern part of the Helvetic markings are not conspicuous. Many sandstones realm, middle Eocene in a median belt, and of this and the next higher formation are gray- lower upper Eocene in the northwest; lines of wackes, a type of rock elsewhere rare in the invariant facies (isopic lines) cross the struc- post-Paleozoic series of the Alps. The Tavey- tural trend at angles up to 35°. These neritic annaz sandstones are remarkable for being formations are overlain by pelagic marl-shales composed mainly of detritus of andesitic and with Globigerina (Stad shales), equally heter- spilitic lavas, among others pillow lavas (de ochronous, which in turn pass abruptly upward Quervain, 1928; Vuagnat, 1952). Many of and southeastward into sandstone Flysch. the spilitic lavas are strikingly similar to This autochthonous9 and north Helvetic nonmetamorphic ophiolites from the upper Flysch is poor in carbonate minerals. Its lower Penninic nappes. The Taveyannaz sandstones pass upward into the Altdorf or Val d'llliez 9 In eastern Switzerland, tectonic structures of sandstones, where the volcanic material is grad- the Flysch are quite disharmonic with regard to ually replaced by more polygenic detritus, those of the Mesozoic cover of the Aar massif, and among which fragments of radiolarian chert are the Flysch cannot be considered as strictly au- tochthonous (Bruckner, 1943; Styger, thesis in noteworthy. Silty shales without carbonate are press). more abundant here and commonly show regu- Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 880 RUDOLF TRtiMPY—CENTRAL AND WESTERN ALPS lar graded beds of millimeter thickness. The equivocal nomenclature; the same beds are sandstone beds are characteristically graded, called Flysch in the Val d'llliez and Molasse and there is also much slump folding with elsewhere. truncated tops and small-scale current-bedding. Bruckner (1946), Moret (1934), and Vuagnat Molasse (1952) have worked out the lithostratigraphy of this Flysch sequence and have shown that Detailed discussion of the Molasse forma- the older formations lap out toward the north- tions is beyond the scope of this work, which is west, where the base of the Flysch finally be- concerned only with the sediments of the Alpine comes unconformable. Material was derived geosyncline, and not with the synorogenic de- from the inside of the basin, much of it appar- posits outside and on the mountain chain. ently from higher Penninic nappes, but in the In its original sense Molasse designated soft similar gres d'Annot of southeastern France sandstones with argillaceous and calcareous ce- Kuenen et al. (1957) have found south to north ment. In southern France, on the other hand, it —that is, longitudinal—transport. Research on is used for shelly limestones. It is now generally current direction has not yet been undertaken understood as a group term or, outside the Alps in the north Helvetic Flysch of the Swiss and their foreland, as a facies term. Alps. Molasse deposits fill the marginal depressions In eastern Switzerland, the youngest part of ("exogeosynclines") on both sides of the Alps. the Flysch consists of coarse polygenic sand- The Molasse at the northern foot of the Alps is stones, with some layers of roundstone con- itself folded and overridden by the frontal part glomerate. In western Switzerland, especially of the Alpine cover nappes. It reappears in in the Val d'llliez, the passage of Flysch to windows under these nappes, in the Val d'llliez Molasse is exposed (Schroeder and Ducloz, and between Gresten and Scheibs, in Austria 1955; see also present Fig. 8). Here, the sand- (Prey, 1957). Where the base of the molasse is stone beds become thinner and more widely exposed, it follows conformably and without a spaced toward the top, and the Flysch grades major break upon Flysch. At the eastern ex- into a unit consisting mainly of micaceous, tremity of the Alps, Oligocene and Miocene for- marly shales, with fishes, euryhaline lamelli- mations lap over on the older, folded and thrust branchs, and drifted land plants. While the rocks. The facies of these sediments, as well as lower part of this formation was being deposited of those of the Vienna basin, differs in some re- salinity and oxygen content of the water were spects from that of typical Molasse and is not still about normal, but then the sea became considered here. brackish, and bottom conditions became re- The Molasse ranges in age from middle Oligo- ducing. These bituminous shales are overlain cene to latest Miocene. Near the border of the by marine sandstones in regular beds, without Alps, thicknesses are enormous—4500 m for the grading, above which begins the terrestrial, middle and upper Oligocene in eastern Switzer- middle Stampian formation of the Molasse land (Habicht, 1945). Sedimentation and "foot- rouge. by-foot" subsidence were more rapid than in The micaceous shales and overlying sand- any part of the geosyncline proper. Away from stones represent the very last deposits of the the Alps, the Molasse thins abruptly and meas- Alpine geosynclinal sea. All that is left of its ures only 1500-2000 m in the central part of the ancient glory is a narrow strait of brackish and Molasse basin. shallow water, and this last remnant is finally Only the most important differences between filled by the detritus from the rising Alps. But Flysch and Molasse are mentioned here. It is the same formation of Rupelian (lower middle understood that the two group or facies types Oligocene) shales and sandstones that was laid are linked by passage beds, but nobody will down in this expiring Flysch Sea appears in confuse a typical Flysch and a typical Molasse many places in Switzerland and Bavaria along outcrop. the inner margin of the Molasse basin, where it (1) The Flysch sediments formed within the is called "Lower Marine Molasse." The marine Alpine geosyncline; Molasse belongs to the sandstones in its upper part are very consistent, marginal depressions outside the chain or (in in spite of changing names such as gres des the eastern Alps) to basins on the Alps them- Carrieres, gres de Vaulruz, Horwer Flatten, and selves. Bausteinzone. Nothing could better illustrate (2) In consequence of this, Flysch is entirely the fades development of this formation, inter- marine, Molasse mainly continental. The ma- mediate between Flysch and Molasse, than this rine Molasse formations were laid down in Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 GENETIC SEQUENCES OF ALPINE SEDIMENTARY ROCKS 881 shallow, temporarily brackish seas, except for a/., 1953; Rumeau, 1954; Rutsch, 1946; Speck, regions like the Vienna basin. 1953. (3) In a given area, Flysch sedimentation begins with the first folding movements and STRUCTURAL EVOLUTION DURING THE ends before the most important phases of tec- GEOSYNCLINAL PHASE tonic deformation. Molasse was formed during Argand's Theory of Embryotectonics and after these phases. (4) Except for the different degree of indura- Since the end of the nineteenth century, it tion some Molasse sandstones can be strikingly has become clear that the original Alpine geo- FIGURE 9.—"EMBRYONIC GEANTICLINES" IN MESOZOIC TIME Copied from Argand (1916). Northwest to the left. The "geanticline" in the center of the diagram repre- sents the Brian;onnais belt, along the front of the future Grand St. Bernard nappe; the one to the right prefigures the front of the Dentblanche nappe. Ophiolites in black. similar to some Flysch sandstones. Argillaceous synclinal belt included a number of longitudinal and silty sandstones as well as sandy shales are swells and basins. Haug (1900; 1911) was the common in the Molasse; coal beds, some of first to establish a succession of (partial or them workable, are frequent; limestones (shelly intra-) geosyndines and "geanticlines." (This and fresh-water limestones) are negligible. use of "geanticline" for linear welts inside a (5) Conglomerates with well-rounded pebbles geosynclinal belt, of course, does not conform to (Nagelfluhen) are abundant and make up whole Dana's original definition.) Haug considered mountains along the inner margin of the basin. these elements as more or less symmetrical. Most of them are fluviatile, deltaic deposits; Emile Argand (1916; 1920) proposed a coherent others are marine shore-zone conglomerates. theory on the origin and the structural signifi- Both types are absent from typical Flysch. cance of these paleotectonic units (Fig. 9). In (6) Graded bedding, so typical of many his view, the "geanticlines" were nothing more Flysch formations, has not been recorded from than incipient ("embryonic") anticlinal folds the Molasse. Cyclothems of the "Pennsylva- on the bottom of the geosyncline. These folds nian" type, starting with an erosion surface are held to be asymmetric, with a steep external and, if complete, having a coal or fresh-water flank and a more gentle slope toward the south limestone member in their upper part, are com- or east. To him they represented the early mon (Bersier, 1945; 1949; 1950). Washouts, stages of development of the great nappes (es- coarse and irregular cross-bedding, and ripple sentially the Grand St. Bernard and Dent- marks (both current and wave) are well de- blanche nappes). "Neritic" formations are veloped. found along the front (exterior) of these nappes, (7) The bedding of the Molasse formations is "bathyal" ones on the back (interior) and in generally thicker than that typical of the the synclines between nappes. From the first Flysch, and individual sandstone, conglomerate, faint swells of Pennsylvanian time to the last or shale members may reach 50 m. On the other tectonic convulsions in the Miocene or Pliocene hand, the lateral extent of beds is very limited Argand saw a perfectly straightforward line of except for a few marker beds like fresh-water events in which asymmetric folds became exag- limestones or rare volcanic ash beds. gerated into recumbent folds and thrust surfaces For all problems bearing on the sedimenta- developed gradually along the inverted limbs. tion, stratigraphy, and paleogeography of the (Argand considered all nappes as great recum- Molasse group, the reader is referred to the bent folds, a view no longer accepted.) Ophiolite numerous papers on these subjects, from which magma followed these thrust surfaces and only a few recent works of general importance flowed out in the deepest internal part of the are here cited: Abele et al., 1955; Biichi, 1950; individual troughs. During the Tertiary parox- Fuechtbauer, 1954; Hofmann, 1957; Lemcke et ysms, these thrust folds continued to move at an Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 882 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS accelerated rate and finally became the great ics refers to the paleogeographical configuration Penninic nappes with basement cores. Some of of late Triassic, Jurassic, and early Cretaceous these nappes—the Simplon nappes and the time. In Argand's original concept, crustal Monte Rosa nappes—came into being after the shortening by tangential compression had al- others and had no embryonic prefiguration in ready set in during the late Paleozoic. Later Mesozoic times. authors have postponed the onset of embryonic Argand's theory certainly was a stroke of folding to the Triassic or to the early Jurassic. genius and quickly won wide acceptance. It fur- But in the new interpretation of Alpine pre-oro- nished a beautiful means of explaining Alpine genic history, the structural pattern of the geo- paleogeography, imputing all the vicissitudes of syncline in the Jurassic and Cretaceous is Alpine history to one process and to one only, ascribed essentially to radial or tensional the "impact of Africa on Europe."It was enthu- stresses. On the other hand, there is ample evi- siastically taken up by Staub (1917), who ap- dence of genuine folding during the later geo- plied it to Graubiinden and who recognized a synclinal phase, when the Flysch was laid down far greater number of individual geanticlines (Cenomanian to early Oligocene). In discussing and geosynclines than Argand had, each of the the structural evolution of the geosyncline, we swells being now represented in the frontal part must distinguish between these two phases. of a nappe. Embryotectonics came near to being accepted as an established fact and played Importance of Mesozoic Faulting a large part in the brilliant syntheses by Gig- noux (1950), Moret (1954), Staub (1937; 1942), Mesozoic faults in the Helvetic realm.—Giinz- and Tercier (1952). ler-Seiffert (1941; 1952) was the first to draw In the success of this theory, in spite of attention to the importance of Mesozoic fault- Haug's judicious warnings (1925, p. 243), it was ing hi the Alps. His studies of the Helvetic often forgotten that it had been founded on nappes of the Bernese Oberland led him to rec- very scant and controversial stratigraphic evi- ognize three major longitudinal east-northeast dence. Detailed research in different parts of to west-southwest breaks affecting thickness the Alps failed to prove the existence of embry- and facies of the Jurassic and Cretaceous forma- onic folds, such as Argand had visualized. tions (Fig. 10). These faults were reactivated Many submarine or temporarily emergent welts during the Tertiary orogeny when they had a were discovered, but they were not systemati- strong influence on the fold structures. Down- cally asymmetric, did not show anticlinal struc- throw of the faults was originally to the south, ture, were not all persistent, and are not neces- and the individual fault blocks were tilted sarily linked to the fronts of nappes. Many northward. South of each fault, the formations steep scarps were shown to face the wrong way are much thicker and more nearly complete —toward the south or, in the western Alps, than to the north. According to Gunzler the toward the east. In the meanwhile, the study movements along the faults were synchronous, of other mountain chains, presenting a more discontinuous, and coincide with Stille's (1924) easily readable paleogeographic record because orogenic phases: early Cimmeric phase proved of less extreme tectonic complications, produced by the localized development of Upper Bajo- no evidence of crustal shortening during the cian, Bathonian, and Callovian;10 late Cimmeric earlier phases of geosynclinal history (Bucher, phase demonstrated by lack of Tithonian; Aus- 1933). tric phase established by lack of middle Creta- In the Alps, two factors were instrumental in ceous, etc. The tensional effect of the fault the formulation of a new concept of paleotec- movements is clear enough for Jurassic time, tonics: the discovery of Mesozoic normal faults but the later and weaker Cretaceous and Eocene in the Helvetic realm by Giinzler-Seiffert (1941; movements are not so easy to interpret. 1952), and Lemoine's (1953) scale reconstruc- Mesozoic faulting on a large scale has also tion of the Brianconnais "geanticline" (1953), been reported by Baer (1959) from the western which showed a broad, gently undulating sub- end of the Aar massif. marine swell limited by scarps on either side. In the Helvetic nappes of the Glarus Alps, in Almost simultaneously Debelmas (1957), Schoenenberg (1958), and R. Trumpy (1955a; 1957; 1958) concluded that the theory of em- 10 Stille's early Cimmeric phase is supposed to bryonic prefiguration of Alpine nappes should have taken place between the Triassic and the Jurassic. This is just one example, among many, be abandoned, at least as a dogma. showing how far the phase concept will be stretched The criticism of the theory of embryotecton- to fit the observations of its believers. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 STRUCTURAL EVOLUTION DURING THE GEOSYNCLINAL PHASE 883 eastern Switzerland, pre-Alpine faults have platform in the north and the miogeosynclien been described independently from Giinzler's in the south. This flexure scarp was active dur- pioneer work. Stratigraphic knowledge of this ing the Early Jurassic, always with downthrow area is still much indebted to the masterly works to the south; movements were continuous, al- NNW SSE Lower Valonginion (shales) Argovian to Tithonion (limestones) Upper Oxfordian (shales) Upper Bajocian (crinoidal limestone) Lower Bajocian s.str.( = Middle Baj.s.D,shales I sandy Is. Aalenian ( = LowerBaj. s.i.) shales I sandstones FIGURE 10.—PALINSPASTIC SECTION THROUGH THE MIDDLE AND UPPER JURASSIC FORMATIONS IN THE WlLDHORN NAPPE OF THE BERNESE OBERLAND, SHOWING THE MESOZOIC FAULTS After Giinzler-Seiffert (1941) by Arnold Heim (1916) and Oberholzer (1933). though not of uniform intensity. Farther south, In Pennsylvanian and Permian time, part of a pattern of antithetical flexure steps denote the present Glarus Alps was occupied by a late tensional deformation. Hercynian fault trench, which was filled by the The Aalenian transgression covered all the thick continental formations of the Verrucano. region of the Glarus nappes (indeed, almost the Movements along the north-northeast to south- whole of the Helvetic realm) with its black, southwest trending faults which bordered this pyritic shales. Some of the Liassic flexures trench ceased before the Triassic, which is rep- do not appear to have become reactivated. New resented by thin terrestrial and shallow-water faults came into existence in the late Aalenian. marine deposits with evaporites in the south- Detailed mapping and Stratigraphic research eastern part. Liassic formations are absent from by Schindler (1959) in the Glarnisch Mountains the cover of the autochthonous Aar massif and has given remarkable data on these Mesozoic from the lower (originally more northerly) faults (Fig. 11). One fault had a downthrow of Helvetic nappes. In the higher nappes is 450 m more than 100 m in the Middle Jurassic; south of Liassic sandstones, shales, and arenaceous of the fault, the Bajocian is almost ten times limestones, all shallow-water deposits. The Li- thicker than it is immediately north of it. Some assic formations appear very suddenly (R. breccias are found in the downset limb, and Triimpy, 1949). The Lias-free northern area Schindler (1959, p. 22) also records slumping was probably part of a large, low island extend- along the fault scarp, but this second point is ing across much of the future Molasse basin. not quite certain. The fault angle was rather To the southeast, all Liassic formations appear low (20-45°). The fault blocks are tilted to the almost along the same line and thicken north, as in the Bernese Oberland (Fig. 11). abruptly. Maximum thickness is reached only Movement along these faults continued dur- a few kilometers from the margin of the subsid- ing the Late Jurassic, but, as the stratigraphy ing basin. Breccias with elements of Triassic of the limestones of this age is yet imperfectly and (rarely) Permian rocks also occur along the known, it is difficult to establish the direction hinge line between the stable, probably emerged of the movement. Things become clear again in Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 884 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS the Lower Cretaceous formations, most of (1953) really started the revolution of its paleo- which show different thicknesses on the two tectonic interpretation. sides of the fault line and sedimentary breccias The Brianconnais realm encompasses not in the downset limb (Fig. 11). The elements of only the Brianconnais proper but also its north- these breccias were embedded in a semiconsoli- ern prolongation in the Vanoise Mountains of NNW SSE MC Albian-Cenomonion (glauconite beds) Urg Urgonion Is. fbcies of U Barremion -L.Apti<"> Bar Lower Barremion shales Hout Hauterivian cherty limestone U.Val Upper Volonginion, Is. I sh. LVal Lower VWonginion(p.p.Berriosion) Is. ish. U Jur Quinten limestones, Upper Jurassic M Lias Bandy Is. of Middle Lias C-A Collovion(condensed) and L.Argovian Is. L Lias Lower Lias: shale,ss., sandy Is. Boj Bojocion crinoidal Is. U Trias, variegated shale Aal Aolenian shale I ss. L- M Trias, basal quortjite,dolomite (anhydrite-dol. in the S) A^f Breccias --t- FIGURE 11.—PALINSPASTIC CROSS SECTION THROUGH THE TRIASSIC TO MIDDLE CRETACEOUS FORMATIONS IN THE GLARNISCH MOUNTAINS (HELVETIC NAPPES or GLARUS ALPS) After Schindler (1959), slightly modified. Vertical scale exaggerated X 2 dated state. One tectonic offset discovered by Savoy, the internal part of the Prdalpes Medi- Schindler, earlier a normal fault with down- anes, the Barrhorn Mountain group of Valais throw to the south, reversed its action in the (Ellenberger, 1952b), and, very probably, the late Valanginian and became a reverse fault, Schams nappes of central Graubiinden. It sep- with a south-north thrusting effect (right-hand arates the Subbrianconnais realm to the ex- fault in Fig. 11). On the whole the fault move- terior (west or north) from the eugeosynclinal ments during the Early Cretaceous resulted in Piemont realm to the east or south. Its essential a far smaller vertical throw than those of the stratigraphic characteristics were outlined early Middle Jurassic or along the Liassic hinge lines, in this paper. The sedimentary series is much and their tensional nature is much less evident. thinner and less complete than in the adjoining This is, of course, expectable from the general belts, and up to the top of the Middle Jurassic tectonic history of the geosyncline. (or, in the Prealps, to the Lower Cretaceous) it Displacement along the Mesozoic faults of contains only shallow-water sediments. the Glarus nappes apparently took place by Inside the Briangonnais facies belt there are small, commonly repeated steps, and not si- generally no angular unconformities, despite multaneously along the different faults. There great gaps. Over large areas, Bathonian or even is no evidence of the "erogenic phases" invoked Upper Jurassic limestones rest quite regularly by Giinzler. upon Ladinian dolomites. Angular unconformi- "Horst" characteristics of the Brian^onnais ties, at places very sharp, are limited to a very realm.—The Brianconnais "geanticline" is the few localities. Two striking examples have been dominant paleogeographic feature inside the described by Tissot (1955, p. 159) from the Penninic eugeosyncline of the western Alps, vicinity of the Galibier Pass and by Debelmas especially during Jurassic time (Figs. IB, 2, 12). and Lemoine (1957a) from the Peyre-Haute It was long considered a classical example of an Mountains south of Briancon. Near the Gali- asymmetrical embryonic fold (Gignoux, 1950; bier Pass the disturbance can be traced to a Moret, 1954). Staub (1951, p. 102) was prob- normal fault of Cretaceous age, and breccias ably the first to ascribe a horstlike structure to occur in the downset eastern flank. On the the Brianconnais rise, and the paper by Lemoine whole, however, the sea bottom (or during part Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 STRUCTURAL EVOLUTION DURING THE GEOSYNCLINAL PHASE 885 of Early and Middle Jurassic time the land 12; PI. 2). These different facies limits do surface) on the Brianconnais rise was fairly not coincide, and there is much crossing over. level; the general configuration is that of a There are some small pre-Bathonian faults in broad platform. In the type area of the Brian- this transitional zone, but no scarp breccias Prealpes Medianes n. { Breccia n. Simme n. Zoophycos I Intermediate Mytilus Breccias Rodidarion Dogger ' Dogger Dogger cherts nappe NW Middle Jurassic Lower Jurassic m Triassic 4000 A Hypothetical prolongation of internal Brian^onnais and Acceglio zone 2000 5 10 20km miles 10 FIGURE 12.—VERY HYPOTHETICAL CROSS SECTION THROUGH SOME PRE ALPINE NAPPES, AT THE END OF THE MIDDLE JURASSIC Vertical scale exaggerated X 2.5 connais it measured at least 50 km across the have been reported. At any rate, the external strike (Lemoine, 1953) and was affected by margin of the Brianconnais platform of Jurassic gentle undulations, which are expressed by the and Cretaceous time cannot be regarded as the presence or absence of thin pelagic deposits of front of a mobile embryonic fold or thrust fold. Oxfordian and Early Cretaceous age. Along the The internal margin of the Brianconnais belt, strike this platform extended from the Medi- its limit against the Piemont eugeosyncline, is terranean to the Rhine. much sharper and steeper. From north to south The external (western or northern) margin there are three regions where the passage be- of the Brianconnais belt is not very sharply tween the two facies realms can be studied: defined. It is best exposed in the nappe of the (1) In the Prealps, the Breccia nappe is prob- Prealpes M6dianes, where the Meclianes rigides, ably derived from the most northwesterly part to the southeast, represent the external part of of the Piemont trough. We have seen that the the Brianconnais realm, and the Medianes Jurassic breccias of this unit were probably laid plastiques are characterized by an almost com- down east of a steep, tectonically active fault plete stratigraphic sequence (Upper Triassic to scarp. The components of the breccias are de- Paleocene or lower Eocene). The limit between rived from the eastern marginal zone of the the two belts can be defined by the wedging out Brianconnais platform, mainly from its Triassic toward the southeast of the Upper Triassic,11 formations. the Middle Jurassic in Zoophycos Dogger facies, (2) The Vanoise Mountains of Savoy have the nodular limestones of the Argovian, or the recently become a key area of Alpine geology. Lower Cretaceous cherty limestones (Figs. 2, Brilliant and painstaking work by F. Ellen- berger (1949; 1958) has led to some amazing stratigraphic discoveries. In the western (ex- 11 This definition is the most satisfying one (R. Triimpy, 195Sb), as the presence or absence of the ternal) part of the Vanoise, the sequence is very incompetent Upper Triassic beds has great tectonic similar to that of the Briangonnais proper, and consequences (basal thrust plane of the Medianes still more like that of the M6dianes rigides. plastiques in the Carnian, whereas in the Meclianes rigides, where there is little or no Upper Triassic, Discounting metamorphism, the sequence is it is the Scythian). quartzites of the Lower Triassic, thick lime- Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 886 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS stones and dolomites with gastropods and cal- already mentioned microbreccias which appear careous algae of the Middle Triassic, thin neritic in the upper Lias of the Gondran zone and in formations of the Upper Triassic and lower Lias, the Schistes lustres on the western margin of Sinemurian to Bajocian missing, Mytilus Dog- the Piemont trough. ger, Upper Jurassic limestones, Lower Creta- All these new results indicate a steep and ceous missing, Upper Cretaceous and Paleocene mobile geosynclinal slope, along the internal Couches Rouges limestones, and a little Flysch. margin of the Brianconnais platform. There is Farther east, in the zone called Val d'lsere- no evidence of a gradual passage from the "ne- Ambin (see also Goguel and Lafitte, 1952), the ritic" Brianconnais sequence into the bathyal whole post-Middle Triassic sequence is much comprehensive series of the Schistes Iustr6s—a thinner, incomplete, and includes Jurassic and passage which most authors up to 1949 assumed Cretaceous breccias with boulders mainly of and which would be expected in the light of the Triassic rocks. This zone apparently marks a theory of embryo tectonics. Figure 12 presents hinge line, probably with downthrow to the an impression of the Brianconnais "geanticline" east. Still farther inward, Liassic beds appear as it is now understood. very abruptly. They are somewhat improperly Mesozoic tensional structures in other parts of called Prepiemontese Lias (see Ellenberger and the Alps.—The Helvetic and Brianconnais ex- Lemoine, 1955) and they include Rhaetic and amples discussed above suggest the following lower Liassic fossiliferous limestones, followed conclusions: by about 500 m of argillaceous and siliceous (1) The outer (northern and western) margin limestones, not unlike Schistes lustres without of the Liassic and Middle Jurassic miogeosyn- ophiolites. They are intercalated between the clines is marked by a series of contemporaneous Triassic and the Mytilus Dogger of an otherwise normal faults, dipping south and east at me- quite normal Brianconnais sequence. The rela- dium angles. Fault blocks are tilted to the north tionship of the "Prepiemontese" Lias with the and west. Piemontese Schistes lustres is not yet estab- (2) The Brianconnais facies belt appears, lished. The hypothesis that the Liassic forma- especially during Jurassic time, as a broad, tions of the eastern Vanoise represent a mar- gently undulating platform, limited by a steep, ginal facies of the Piemont Schistes lustres is mobile scarp to the east and south. plausible. If it could be corroborated, this would The internal margin of the Piemont eugeo- prove the pre-radiolaritic (about Pliensbachian syncline can also be interpreted as a steep geo- to Bajocian) age of the Schistes lustres of the synclinal slope. Sediments of this slope should western Alps. be sought in the cover of the lower Austroalpine (3) East and southeast of Briangon, the nappes (Err and Bernina on PI. 1). The works typical Brianconnais zone and the Piemont of Cornelius (1935), Roesli (1927), Staub (1948), Schistes Iustr6s come into direct contact; the and Stocklin (1949) give a good idea of the latter constitutes an independent cover nappe. Mesozoic stratigraphy of this area, in spite of The discovery of the Acceglio zone (Debehnas controversy about the age of certain formations. and Lemoine, 1957b; Lemoine, 1957; Michard, The Mesozoic cover of the Dentblanche nappe, 1959) is of capital importance for understanding preserved at only one place in southern Valais, the paleogeography of the western Alps. This has the same general features (Hagen, 1948). zone forms the eastern prolongation of the The sequence is characterized by small thick- Brianconnais zone, and it appears in windows ness and abundance of sedimentary breccias of below the Schistes lustres nappe in the valleys various ages. These formations were generally on the Italian side of the chain. It is character- interpreted as consisting mainly of shallow- ized by an extremely reduced stratigraphic se- water sediments, laid down on and in front of quence; a few meters of Upper Jurassic and the mobile geanticline at the front of the Aus- Upper Cretaceous limestones rest upon the troalpine nappes. Several Cordilleras and inter- quartzites of the Lower Triassic or even on vening troughs are distinguished by Staub Permian formations. As the Jurassic and Creta- (1917; 1948; 1958). The shallow-water origin of ceous sediments are of pelagic facies, the Ac- some formations in the lower Austroalpine ceglio zone probably does not belong to a "cor- nappes is supposed to be proved mainly by the dillera," but rather to the upper (more westerly) abundance of breccias and by the incomplete part of the steep geosynclinal slope, whence sedimentary record, but it was concluded in the most of the Triassic and Jurassic formations discussion of marine breccia formations that have crumbled off. Their debris may be found breccias of this type are not characteristic of farther east, lower on the same slope, in the any particular depth zone. The Upper Jurassic Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 STRUCTURAL EVOLUTION DURING THE GEOSYNCLINAL PHASE 887 uniformly shows the leptogeosynclinal pelagic movements. Most ophiolites date from the radiolarian chert and aptychus limestone assem- (Early and Middle?) Cretaceous, and they were blage, and no neritic deposits younger than the emplaced perhaps just when stresses in the middle Lias are known with certainty from the geosyncline became reversed and crustal short- Upper Engadine. The realm of the lower Austro- ening first set in. By this time, the granitic alpine nappes might in part correspond to the layer below parts of the eugeosynclinal troughs hinge zone between the Austroalpine platform may have become rather thin, but the gneissic (itself deeply submerged during much of Juras- basement cores of the Penninic nappes are sic and Early Cretaceous time) and the Piemont there to prove that it was not altogether di- trough. It seems not impossible to ascribe the gested by subcrustal erosion. very complex paleogeographic pattern of this area to a system of fault blocks tilted south- Paleogeographic Pattern during the ward, like a symmetrical counterpart to those "Flysch Phase" of the Helvetic realm. This is also the opinion of F. Roesli (personal communication). Early folding movements.—It has been sug- As to the southern Alps, the influence of con- gested that the paleogeographic pattern of the temporary faulting on sedimentation in the Alpine geosyncline during Triassic, Jurassic, and Triassic of the Dolomite Mountains and in the Early Cretaceous time was to a large extent Jurassic of the southern Ticino has already been governed by tensional stresses. Basins and stressed. platforms were bordered by fault- and flexure Remarks on the ophiolite problem.—The preva- scarps. No folding phases have been recorded lence of tensional stresses in the Alpine geosyn- with certainty up to the Early Cretaceous.12 cline up to the Cretaceous affords a much easier During this long time, shallow-water sediments explanation for the rise, intrusion, and outflow were laid down on the platforms and in the of ophiolitic magma than the theory of embryo- bordering miogeosyncline, while Bundner- tectonics, which asked for compressional schiefer and "leptogeosynclinal" deep-sea de- stresses during the whole Mesozoic. Fault and posits characterize the eugeosynclinal troughs, flexure zones along the tectonic scarps separat- and the latter also a wide realm to the south. ing the platform realms (Brianconnais, includ- Breccias are localized along the geosynclinal ing Subbriangonnais, and Austroalpine) from slopes. It is certainly no coincidence that the Valais and Piemont troughs would provide Flysch sedimentation, resulting from much the channels for the ophiolites, which spread more rapid erosional and depositional processes, out in the deeper eugeosynclinal belts but did starts as true orogenic folding movements not reach the platforms. The same phenomenon, begin. on a much smaller scale, was earlier noted in the Some of these premonitory Cretaceous fold Middle Triassic of the Dolomites. movements may be listed here, without any The mechanism of ophiolite intrusion is still attempt at completeness (see also Spengler, somewhat controversial. Peridotite and gabbro 1927): bodies of laccolithic form are presumably (1) Pre-Cenomanian folding, especially in intrusive. On the other hand, many spilites the western part of the higher Austroalpine with pillow structures (and accompanied by nappes. M. Richter (in Kockel et al., 1931, tuffs) certainly represent submarine lava flows. p. 97-104) has given an excellent description But in the metamorphic central part of the of this deformation, which produced rather Alps, where most ophiolites are now localized, gentle folds and normal faults with downthrow it is difficult to arrive at a conclusion for in- to the south. dividual ophiolite sheets. (2) Turonian folding of the Devoluy Moun- Ophiolites are distributed mainly along two tains in southern Dauphin6. This phase gave lines, following the internal margin of both rise to well-defined east-west fold. (See Glan- Valais and Piemont eugeosynclines. Few or no geaud and d'Albissin, 1958). Mercier (1958) volcanic rocks are found on the external margins of these troughs, in spite of the very 12 The field evidence on which Parejas" (1946) pronounced faulting and warping along the middle Liassic "Ferden phase" was founded is not scarp between the Brianconnais and Piemont confirmed by Baer (1959, p. 59). A "Neocimmerian" phase at the end of the Jurassic is mentioned in belts. This systematic asymmetry—which was, many published papers, but, although there was of course, explained very elegantly by Argand's certainly some crustal unrest in various parts of the theory—may give a hint that ophiolite intrusion Alps at this time (Cornelius, 1937), proof of sub- was early influenced by the beginning orogenic stantial folding has not been found. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS gives the age of the disturbance as post- tion went on, the more internal islands coalesced Cenomanian and pre-Late Turonian. and formed a broad welt above sea level, while (3) Pre-Gosau (pre-Coniacian) orogeny of Flysch sedimentation continued, or started, the Austroalpine nappes. The marine Gosau in the more northerly and westerly parts of beds, containing a rich benthonic fauna, the original Alpine basin. transgress thrust planes of the higher (older), There is ample evidence of folding and even dtollement nappes of the northern calcareous thrusting from the Cenomanian onward—that Alps, especially in the Salzkammergut The is, during the time when the different Flysch main thrusting is of Tertiary age, but the formations were laid down. We may certainly existence of Cretaceous strip sheets in this assume that the rise of the "Flysch Cordilleras" (originally very southerly) part of the Alps is was due to these tectonic movements, which proved. The Cenomanian is not known from resulted in crustal shortening. Debelmas (1957) the Salzkammergut, but farther west the un- has very lucidly demonstrated that these conformity between Cenomanian and Gosau cordilleras are quite different from the older is only slight; thus the exact dating of the (especially Jurassic) "geanticlines," which seem pre-Gosau folding and thrusting is not es- to be horstlike structures caused by vertical tablished. In fact it is not even certain whether and tensional movements, and that the com- the pre-Cenomanian and the pre-Gosau dis- pressional Flysch cordilleras did not necessarily turbance are not identical; but tectonical anal- develop on the site of older platforms. ysis proves that there were two phases before Overlap of Flysch formations on folds and deposition of the Gosau beds. minor thrusts beneath is characteristic. The (4) Pre-Maestrichtian folding in the south- very nature of Flysch sandstones and breccias ern part of the Helvetic realm, indicated by the is evidence that the granitic and gneissic pre- angular unconformity between the Wang beds Pennsylvanian basement lay bare and was (Fig. 10) and older formations down to the eroded over large areas. The question whether Upper Jurassic limestones. The folding dies out Flysch transgresses over more important nappe northward. thrusts, however, must be examined in more Important Cretaceous movements have cer- detail. For the lower Senonian Gosau beds of tainly occurred in other parts of the Alps, the eastern Alps, this fact is proved; but the but their exact age is less well established. In Gosau beds, in spite of their comparative youth, particular, the age of the deformation of the do not show the characteristics of Flysch lowermost Penninic nappes (with Alpine granite facies. In fact, they might rather be likened to gneisses) is not known, except that it lasted a sort of older marine "Molasse". until the Miocene. The idea that the detrital matter of most In Tertiary times, there were many erogenic Flysch formations, and especially the exotic phases, which may even overlap in time. blocks in the Wildflysch, was derived from Movements in the late Eocene ("Pyrenean advancing nappe fronts was first advanced by phase") are especially important for Flysch Schardt (1898). This would imply that the sedimentation. The main phase of the western exotic boulders in the upper Eocene Wild- Alps falls about between early and middle flysch of the Ultrahelvetic nappes, for instance, Oligocene and coincides with the change might be of much more internal origin and from Flysch to Molasse sedimentation. The might once have belonged to Penninic or latest folding movements, which represent the Austroalpine nappes. main phase of the Jura Mountains, affected The gradual shifting of Flysch basins toward the uppermost Miocene or lowermost Pliocene the outside of the Alps supports this hypothesis. formations. In the Pleistocene, there was Higher nappes ordinarily have older Flysch considerable uplift and some faulting in the formations than do lower ones, although this Alps. is not an unbreakable rule. The upper limit of Structural characteristics of Flysch cordil- the Flysch in any belt, except the autochthonous leras.—We may picture the Flysch cordilleras one where it passes into Molasse, is fixed today as chains of steep, disconnected islands, com- by the base of a higher nappe. In some instances, monly rising immediately from rather deep cover nappes may have slid by gravity into a troughs, but in places with narrow coastal or more external basin where Flysch was being submerged platforms on which the larger laid down, and may actually have closed this Foraminifera and calcareous algae might pros- basin; but, very commonly, the tops of Flysch per. Basement rocks cropped out in many formations were eroded before a higher unit places on these islands. As time and deforma- overrode them. The folding progressed from Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 STRUCTURAL EVOLUTION DURING THE GEOSYNCLINAL PHASE 889 south to north (east to west in the French Flysch. A source area north and west of many Alps), and the beginning and the end of Flysch Flysch troughs excludes Schardt's hypothesis sedimentation followed it; evolution of the for these Flysch formations at any rate; Western Switzerland Eastern Switzerland c "> oo -, .y , £ 2 c c .2 Santoncan Coniacian Helvetic Turanian ' belt i Helvetic belt Cenom- anian 1 FIGURE 13.—TIME OE FLYSCH SEDIMENTATION IN DIFFERENT UNITS OF THE Swiss ALPS Brianconnais realm in the broad sense lagged the nappes cannot have overridden the basin (Fig. 13). before the Flysch sedimentation, which com- Transgressive overlap of the Pratigau Flysch monly followed deposition of fine-grained pelagic and its more southerly equivalents in Grau- sediments. biinden over most of the Penninic nappes, But it is wrong to state the problem of Flysch from the lower Penninic Adula up to the high provenience as a choice between advancing Penninic Margna, was proposed by Leupold nappes or Cordilleras inside the geosyncline, as (1933) and was accepted by many geologists if the two were mutually exclusive. The material (Nanny, 1948; Staub, 1937; 1958; W. Ziegler, in the older and more internal Flysch formations 1956). The present writer still feels uncertain is certainly derived to a large extent from as to the field evidence for this in the very Cordilleras arising between the individual Flysch complicated and moraine-covered key area basins. The latest, north-Helvetic Flysch, around Tiefencastel, in central Graubunden. however, received its detritus, including a Lugeon (1916) opposed Schardt's hypothesis large amount of volcanic rocks, just as surely on the origin of the exotic boulders in the from much more internal, south-Penninic Wildflysch and invoked a Cordillera in the nappes, which had already moved into prox- Ultrahelvetic realm itself. Most subsequent imity of the Flysch basin. In this respect also, workers have followed this view (e.g., Tercier, conditions during the latest Eocene and early 1928; Leupold, 1942). It is confirmed by recent Oligocene were premonitory to those of the studies on current directions in several Flysch Molasse, where practically all the material is formations, which show for instance that the brought in from the rising Alps in the south. detrital matter in the Ultrahelvetic Gurnigel In connection with the longitudinal rilling of Flysch is derived from the northwest (Crowell, many Flysch troughs, Kuenen (1957b; 1958) 1955; Hsu, 1960). A sand- and boulder-furnish- has suggested a third possibility: an extra- ing Cordillera also lay north of the basin of the Alpine source for the detrital matter, which Pratigau Flysch and west of that of the Niesen would have been brought into the Flysch Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 890 RUDOLF TRttMPY—CENTRAL AND WESTERN ALPS Mt. du Fuz W \ Torentaise i p,^ du Roc \ x, I (Gde.Moendo sub-unit) J Ultrodouphinois Dauphinois * \ post-Eocene thrusts V pre-Eocene thrusts Ultradauphinois Pas du Roc (Perron des Encombres sub -unit! Dauph i Ultradauph. Torentaise (Valois) Pas du Roc(Subbriaa) Brianijonnois ^rrr\ Flysch(Aig.d'Arves)| Eocene Flysch \^z\ Flysch ll Cretaceous f^L'OS Lias |[||||[||[ Cretaceous M | Upper Jurassic Upper Trias. Trios. HH TrTriosi . [~^~| Oxford.-Callov. (gypsum) BTmian Permo-Penns i Pennsylvanton ff3 Middle Juris. Middle Trios.ds.) | Basement Lias I Pennsylvanian i 3km 2 mi les I Trias. —i FIGURE 14.—CROSS SECTIONS THROUGH THE FRONTAL PART or THE PENNINIC NAPPES IN SAVOY After Barbier (1948). The lower section runs just north of the river Arc, the upper one about 11 km farther north. troughs at one of their extremities. As Kuenen synclinal phase is commonly very difficult to remarks, this possibility can probably not be unravel, especially because the exact origin of applied to the Alps because of general paleoge- many flysch sequences that form cover nappes ography during times of Flysch sedimentation. of their own is unknown or controversial. Paleozoic and Precambrian siliceous rocks, Flysch Cordilleras also have a disconcerting which alone could have furnished the great tendency to vanish into thin air; thus, the amount of quartz and feldspar now contained peculiar Habkern granite which furnished great in the Flysch, lay buried under carbonate boulders to the Wildflysch and enormous masses rocks of Mesozoic age all over the country to of its characteristic greenish quartz and pink the north and west of the Alps. Only certain feldspar grains to the Gurnigel and Schlieren areas in the Mediterranean, like the western Flysch sandstones is not known in outcrop. part of Corsica, could be a possible external The works of Kockel et al. (1931), Kraus (1932; source—for instance, part of the Annot sand- 1942), Richter (1957), and Richter and Miiller- stones in southeastern France show a southerly Deile (1940) give a good idea of the complexity source of detritus. of troughs and Cordilleras in the partly Ultra- Alpine paleogeography of the final geo- helvetic but mainly Penninic Flysch zone along Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 STRUCTURAL EVOLUTION DURING THE GEOSYNCLINAL PHASE 891 the foot of the eastern calcareous Alps. These conformity at the base of the Cretaceous Aroley authors distinguish several Cordilleras (especially formation is much less pronounced than that the Rumunic and "Vindelician" ridge), in ad- below the Eocene Flysch, although, to judge dition to the front of the advancing Austro- by their components, the Aroley breccias over- alpine nappes, which all furnished detritus to lay Triassic and basement rocks not far away. the mainly Cretaceous Flysch and "pre-Flysch" Only in the Eocene is there clear sedimentary basins. proof of the existence of a cordillera; but there Tarine and Arvinche Cordilleras of Savoy.— is no doubt that this cordillera arose over a Two Flysch Cordilleras of different type in the belt which had shown great crustal unrest western Alps have been illustrated by Barbier during Mesozoic times. (1948) and Schoeller (1929). As a result of the The more external Ultradauphinois zone, Alpine orogeny the two Cordilleras are now in representing the Arvinche "cordillera," is immediate proximity (Fig. 14). capped by the Aiguilles d'Arves Flysch, which The internal or Tarine Cordillera is repre- is up to 2000 m thick. The age of this Flysch is sented in the Tarentaise nappe (nappe des mainly late Eocene, but the base may be Breches de Tarentaise).13 Its Lower Mesozoic Lutetian. Barbier (1948, p. 120, 246; 1956) has sequence is incomplete: rather thin Triassic beautifully demonstrated that it lies uncon- formations, followed by 50-200 m of Liassic formably on its substratum of Jurassic to limestones and locally some calcareous shales, Paleozoic formations, and on the eastern border which may belong to the Middle Jurassic. In of the Pelvoux massif even on granite. This the north, the Aroley limestones and breccias, substratum possessed an imbricate structure with Orbitolina indicating Barremian or Aptian before the transgression of the Flysch.14 But age, transgress these rocks. The Aroley beds this strong pre-Priabonian or pre-Lutetian are followed by probably still Cretaceous for- deformation affects a Jurassic series of thick, mations of "pre-Flysch" characteristics. South monotonous shales and argillaceous limestones. of the river Isere a thick Flysch succession of Unlike the Tarine cordillera, the Arvinche middle to late Eocene age rests with sharp tectonic ridge had no Jurassic antecedents. We angular unconformity upon the older for- know nothing about the Cretaceous history of mations down to the basement. The Tarentaise the belt; formations of this age are missing and nappe thus has Cretaceous Flysch, or rather were probably eroded before deposition of the pre-flysch, in the north, and Eocene Flysch in Aiguilles d'Arves Flysch. the south (Barbier and Triimpy, 1955). This comparison is intended to show that Thus a Tarine Flysch Cordillera could not Flysch Cordilleras could develop on the sites of have existed in the Triassic. The thin and belts with quite different Mesozoic paleotec- neritic Jurassic formations certainly mark a tonic history. belt of shallower water, if compared with the thick, shaly sediments of the same age in the Evolution of Paleogeographic Pattern adjoining units of Savoy (Ultradauphinois slices to the west, Grande Moenda digitation Ephemeral nature of fades belts.—Believers of the Pas du Roc nappe to the east). In Valais, in embryotectonics long held that the troughs another digitation of the Tarentaise nappe, the and ridges inside the geosyncline persisted Ferret zone, is present between the Ultra- practically throughout the pre-orogenic history helvetic (approximately Ultradauphinois) root of the Alps, and that a straightforward evo- zone and the Tarentaise proper. This unit has lution led from the first faint bulges to the no Jurassic, but many hundreds of meters of final great nappes. Modern stratigraphic re- Bundnerschiefer, probably of Early Cretaceous search brings out a different story, and a age, conformably underlying the Aroley for- bewildering instability of paleotectonic ele- mation. The Tarine "cordillera" of Mesozoic ments in space and time appears (Fig. 1). This time was not stable; subsidence and uplift instability is an essential feature of the Alpine varied abruptly in time and in space. The un- geosyncline, more even than subsidence, and it 13 is perhaps more pronounced here than in any Barbier regards the Tarentaise nappe as an other mountain chain. external unit of the Subbrianconnais belt, but its fades affinities are clearly with the Valais realm. The tectonic position of the unit of the Petit St. 14 The existence of rather violent tectonic move- Bernard, with Schistes lustre's and ophiolites, is ments preceding the deposition of the Aiguilles probably between the Tarentaise nappe and the d'Arves Flysch certainly does not entitle it to be Subbrianfonnais proper. (See Elter and Elter, called "molasse" (Termier and Termier, 1957, p. 1957.) 685). Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 892 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS The thick, monotonous, calcareous shaly the ridges, internal platforms, and scarps. The groups of Schistes lustres type, in particular, minor swells and furrows in mobile belts such were often considered the result of continuous as the Subbrianconnais-Medianes plastiques filling of rather deep, regularly subsiding, facies zone, paleogeographic elements a few permanent troughs. These are the "series kilometers or tens of kilometers broad, show comprehensives" of Tertnier, where sediments repeated and rather irregular shifting of the ranging without gaps from the Triassic or the axes of subsidence and of uplift (or "non- Lias up to the Upper Cretaceous or to the subsidence") during the Mesozoic. The mono- Eocene were of uniform facies, in contrast to graphs of Barbier (1948), Debelmas (1955), the varied and incomplete neritic Mesozoic Jeannet (1912-1913; 1918), Peterhans (1926), sequence on the "geanticlines." The very and Schneegans (1938) describe striking ex- valuable attempts at regional stratigraphic amples. Others can be found in the Austro- synthesis of the Bundnerschiefer by Jackli alpine and in the Helvetic-Dauphine realm. (1941) and Nabholz (1945), for instance, are (See especially Faure-Muret, 1955.) The based on this working hypothesis. mobility of the paleogeographic pattern is also But we have seen that the Schistes lustres of expressed by the repeated penecontemporane- the Cottic Alps probably represent only a ous erosion. comparatively short time span. The Piemont It is difficult to state any general rule about trough came into being in the Late Triassic, direction of displacement of the paleogeographic and, from the middle Lias onward, it subsided features. It is, of course, tempting to think of a and received the Schistes lustres group. The gradual shifting of the axis of subsidence from trough persisted right into the Cretaceous, but south to north during the geosynclinal history about in Bathonian time sedimentation became (Cornelius, 1925; Frank, 1930). One might, for starved ("leptogeosynclinal"), probably by instance, list the belts with the greatest thick- drowning of the surrounding platforms and by ness for each system: Triassic in the southern subsidence of the trough bottom to "oceanic" Alps, Jurassic in the Schistes lustres of the depths.16 On the other hand, evidence shows Piemont trough,16 Cretaceous in the north- that most of the Bundnerschiefer of the ex- Penninic Bundnerschiefer, Eocene in the Ultra- ternal, Valais eugeosyncline are of Cretaceous helvetic Flysch, Oligocene in the Molasse of age, and that this trough was still incompletely the foothills. But a more detailed analysis of developed during the Jurassic. In the Triassic, Alpine stratigraphy reveals so many exceptions at any rate, the "trough" belonged to a rise to this "rule" that skepticism arises as to its that separated the German epicontinental universal validity. Triassic basin, with its southern and very The author has recently summarized the shallow marginal belt in the Helvetic realm, essentials of Alpine pre-orogenic history from the Brianconnais basin. (R. Triimpy, 1958; Fig. 1 of present paper), so These results on the age of the Biindner- it is not necessary here to discuss the vicissi- schiefer and Schistes lustres are, to be sure, tudes of the paleogeographic pattern. It is somewhat provisional. Still, it is fairly certain essential, however, to examine whether the that environment did not stay constant in the geosynclinal evolution is of one mold—as in two eugeosynclinal troughs during all of the Argand's theory—or whether we must dis- Mesozoic era, or even during the whole of the tinguish different epochs, with basically differ- Jurassic and Early Cretaceous. The thick ent paleotectonic structure. sequences of the Biindnerschiefer-Schistes Relationship of late Hercynian structures to lustres type were laid down fairly rapidly during Mesozoic facies belts.—The region from which rather short time, followed or preceded by the Alps arose belonged to the central part of episodes of arrested sedimentation. Many the great late Paleozoic fold belt of central and other, especially Paleozoic, geosynclines ap- southern Europe. The history and structure of parently received much thicker and more the Hercynian chains is extremely complex, homogeneous shale-graywacke deposits. and there is no reason to believe that any part If conditions were unstable in the eugeo- of the future Alps was not affected by these synclinal troughs, they were even more so on movements. Circumstantial evidence seems to 16 The Jurassic formations of the miogeosynclinal 15Lemoine's reservations (1959, and personal Dauphine trough are in fact thicker, but subsidence communication) as to this interpretation were in the Piemont eugeosyncline was stronger (arrest mentioned under discussion of the "Schistes lustres of sedimentation under "leptogeosynclinal" deep-sea of the Cottic Alns." conditions). Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 STRUCTURAL EVOLUTION DURING THE GEOSYNCLINAL PHASE 893 point to an Early Pennsylvanian ("Sudetic") heritance is sometimes difficult to interpret,17 date of the main deformation. as many of the nappes whose sedimentary After this orogeny, and quite probably as a history is well known are strip sheets of post- result of the isostatic disequilibrium created by Triassic formations, and the nature of their it (Hsu, 1958), a number of elongated, fault- pre-Triassic basement cannot be made out bordered basins developed in central Europe, with precision. four or five of them on the site of the future The relationship of late Paleozoic to Mesozoic Alps. These basins were filled by very thick, paleogeography has been especially well worked detrital, mainly continental formations of out by Ellenberger (1958) in the Vanoise Pennsylvanian and Permian age. Marine Mountains. The axial part of the Lower incursions of this age were essentially limited to Pennsylvanian to Middle Triassic "archaic the southeastern Alps. Volcanic activity was Brianconnais geosyncline" became the non- strong, especially during the early Permian, subsiding Brianconnais platform of Mesozoic and furnished great masses of basic and acid time. Upper Triassic and lower Liassic for- lavas, tuffs, and ignimbrites. Fracturing and mations are only locally preserved on this folding occurred at least twice thereafter, during platform, Pliensbachian to Bajocian ones not the Pennsylvanian ("Asturic phase") and at all. (The "Prepiemontese Lias" of the between the early and late Permian ("Saalic eastern Vanoise may mark a temporary en- phase"), but these patterns were not parallel to croachment of the Piemont fades belt onto the later Alpine structures. The divergence is adjoining parts of the Brianconnais.) On the clearly shown by a post-Eopermian and pre- other hand, the Piemont belt to the east, which Triassic syncline in the Aiguilles Rouges massif, had received few sediments of late Paleozoic to which strikes N. 15° E., whereas the neighboring Middle Triassic age, began to subside during Chamonix "syncline," a narrow zone of much- the Late Triassic, notably in the Cottic and aminated Mesozoic rocks separating the, Ligurian Alps. In the Subbriangonnais belt Aiguilles Rouges from the Montblanc massif, to the west, the Upper Triassic formations are runs almost exactly southwest-northeast. In the also thicker than in the Brianconnais, and great basement thrust mass of the Austrian they contain anhydrite beds of Carnian age. All Alps, too, older structures commonly strike at through the western Alps, the Subbrianconnais Iright angles to the Alpine tectonic lines (Metz units, including the M6dianes plastiques, are 1952). stripped off along this incompetent anhydrite- By the beginning of the Triassic, the bearing formation (Figs. 2, 13; PL 2). There are remnants of the Hercynian Mountains were good reasons to believe (R. Triimpy, 1955b) levelled, and the clean, water-laid arkosic or that the complete section of the Subbriancon- quartz sandstones of the Scythian spread nais belt also had Lower and Middle Triassic beyond the limits of the Paleozoic subsiding formations of Brianconnais fades, although areas. In some of the late Hercynian basins, somewhat thinner than in the Brianconnais subsidence continued, resulting in much thicker proper. Lower and Middle Triassic sequences than This is the phenomenon of "Reliefum elsewhere. Most important of these is the kehrung" (Jenny, 1924), of inversion of sub- "archaic Brianconnais geosyncline" (Ellen- sidence. During the Triassic, the subsiding berger, 1949; 1950; 1958), which contains basin became consolidated and developed into several thousands of meters of continental a nonsubsiding platform ("geanticline"), and upper Paleozoic formations, up to 500 m of new geosynclinal basins were born outside the Lower Triassic quartzites, and up to 1000 m of ancient ones. The Piemont eugeosyncline Middle Triassic limestones and dolomites. started to subside in the Carnian, at first as a The question whether or not the Hercynian shallow depression; but it deepened during the infrastructure had a major effect on the Lias to reach oceanic depth during the Middle paleogeography of Mesozoic (or rather post- Jurassic (assuming a pre-radiolaritic age for Mesotriassic) times is difficult to answer. Staub the Schistes Iustr6s). The Ladinian-Carnian (1954; 1956) advocates a very marked influence transition was certainly a crucial moment in the early history of the Alps. It marks the end of these structures, especially of fault lines of the last remnants of Hercynian structures and of the distribution of late Paleozoic granites. Strongly granitized belts would tend 17 As far as the Glarus Alps are concerned, the to behave as ridges during the later history. The writer feels unable to adopt the views of his teacher stratigraphic evidence for this Hercynian in- Staub (1954). Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 894 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS and the birth of the Alpine paleogeographical only by currents and paleogeography. Finally, units. the pelagic, although not necessarily deep- There might be a Hercynian heritage in post- water, limestones of the Cenomanian to Triassic paleogeography, but the corre- Paleocene Couches Rouges formation are spondence of the two structures is inverted, the practically identical in the Brianconnais realm, negative elements of one epoch becoming the in the Subbrianconnais belt, even in the positive ones of the next. The present writer Falknis nappe of Graubtinden, and also in the has reservations about this as a general rule, parts of the Piemont realm which lie next to however. The spatial coincidence of the the Brianconnais (Breccia nappe in particular). "archaic Brianconnais geosyncline" and the While the thin Couches Rouges were being Mesozoic (essentially Upper Triassic to Middle laid down over a Brianconnais platform which Cretaceous) Brianconnais rise in the Vanoise had more than doubled its breadth and whose Mountains may be accidental. The two boundaries with the adjoining facies belts had structures are not parallel; farther north, in the become quite vague, Flysch was already being Valais-Prealps cross section, the post-Carnian formed in more distant belts (Fig. 1). These formations covering the main part of the pre- are (1) the Valais realm to the north Carnian subsiding basin are of Subbrianconnais, (Cretaceous formations of Schlieren Flysch, not of Brianconnais, facies, and in Graubiinden Niesen Flysch, Pratigau Flysch, etc.), (2) the the Upper Jurassic limestones of the Sulzfluh internal parts of the Piemont and probably also nappe, which almost certainly represents the the external parts of the Austroalpine realm to prolongation of the Brianconnais facies belt, the south and east (Simme Flysch, Helminthoid rest directly upon granite. This angular di- Flysch of the southwestern Alps, etc.). Detrital vergence of Hercynian structures and Mesozoic matter was trapped by these troughs on either facies lines excludes, in our opinion, a far- side of the Couches Rouges ("Brianconnais") reaching genetic influence of the former on the platform, and only in the late Paleocene and latter. early Eocene was a little Flysch spread over Relationship of Flysch Cordilleras to Mesozoic it.18 Except at one place (Wegmiiller, 1953, p. platforms.—Emphasis was earlier placed on the 44), no instance is known where Flysch trans- essential paleotectonic difference between the gresses pre-Cenomanian formations of the Jurassic and Early Cretaceous topography on Brianconnais realm proper. This platform, by the one hand and that of "Flysch times" on far the most prominent feature inside the the other. It remains to inquire whether the Penninic geosyncline of the western Alps during two types of structures are interrelated. Jurassic time, became obsolete by degrees, and Again, the fate of the Brianconnais platform no longer played an important role during the is highly significant (Figs. 1, 2). It came into early phases of the Alpine orogeny. This fact being in the Carnian and had its heyday be- is surely quite incompatible with the concept tween the Pliensbachian and the Bathonian of embryotectonic prefiguration of nappes. (Fig. 12), when most of it was dry land, while This picture is a very general one. In the great masses of shales and of argillaceous and Helvetic realm, too, the faults and flexures of silty limestones were laid down on either side "Mesozoic," tensional type were most active (Lias and lower Zoophycos Dogger of the Sub- during the Lias and the earlier Middle Jurassic. brianconnais-Medianes plastiques, Schistes lus- During the Late Jurassic and the Early tres of the Piemont trough). It is still well ex- Cretaceous, displacements along these faults pressed during the later Middle Jurassic, by were much smaller. Flysch sedimentation the shallow-water facies of the Mytilus Dogger. again develops quite independently from the In the Late Jurassic, the difference of facies ancient structures; basins and Cordilleras in the Subbrianconnais belt becomes slighter, wander gradually outward. whereas the deeper, leptogeosynclinal Piemont This does not mean that Flysch Cordilleras belt was still quite distinct. Apparently, the nowhere developed on the sites of former ridges, Brianconnais platform was again better marked during the Early Cretaceous. Sediments of 18 Both the "Plattenflysch" of the Prealps this age are missing on it, whereas there are (Delany, 1948; Klaus, 1953; Twerenbold, 1955) and pelagic limestones with chert layers on either the Helminthoid Flysch of the southwestern Alps side. Lemoine (1953) has shown, however, (Lanteaume, 1957), which were long thought to belong to the same tectonic unit as their substratum that, in the type area of the Brianconnais at of Brianconnais facies type (including Paleocene least, pelagic conditions prevailed over the Couches Rouges), are of Cretaceous age and of more whole belt, and sedimentation was inhibited internal origin. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 STRUCTURAL EVOLUTION DURING THE GEOSYNCLINAL PHASE 895 platforms, or scarps. The previously discussed The question of obliquity and limited extent Eocene Tarentaise cordillera certainly formed of paleogeographic units must be examined on the site of a belt that had been rather from two directions: nonparallelism of facies strongly deformed during the Mesozoic. The zones of different ages, and nonparallelism of eastern margin of the Brianconnais belt, which paleogeographical and structural entities. was active during both the Early Jurassic and Crossing over of facies belts.—The instability the Late Cretaceous, may be another example of Alpine paleogeographic features implies that (Lemoine, 1957). The point to be stressed is facies belts of different ages can run at angles that Flysch Cordilleras—an early expression of to each other. This is notably the case for the the compressional tectonic forces by which the late Hercynian basins and the Mesozoic geo- Alpine nappes were built—could arise wherever synclines. But even during the Alpine prepa- the causal stresses obtained, and that their ratory phase, crossing of the isopic lines (lines location was little influenced by the disposition of equal facies, Arnold Heim, 1908) for different of the Mesozoic troughs and rises, many of formations can be easily demonstrated. which had become indistinct before Flysch Tectonic structures in the Helvetic nappes of sedimentation set in. Switzerland trend in general west-southwest to east-northeast. As already mentioned, Liassic Obliquity of Paleogeographic Units formations are absent from the originally northern part of the Helvetic realm, and they General statement.—The hypothesis of set in very rapidly along a line which is inter- embryotectonics implied that there was a preted as a contemporaneous flexure. This line direct, genetic link between paleogeographic runs about east-west, with some embayments. belts and tectonic units. The great nappes and, It is now seen in the higher Helvetic nappe of concomitantly, the major facies zones were eastern Switzerland, in the cover of the southern considered to have an almost unlimited ex- flank of the Aar massif in central Switzerland, tension along the strike of the chain. This and in the Chamonix "syncline" between geometrical and paleogeographical constancy Aiguilles Rouges and the Montblanc massif in furnished a double handhold for identifying and western Switzerland. The axis of the Liassic comparing individual nappes, often in great Dauphin6 geosyncline, with its thick formations detail, from one end of the chain to the other. of dark shales and shaly limestones, runs The works of the great masters of Alpine about parallel to the marginal scarp and can be tectonics, such as Argand, Lugeon, Kober, followed from the Ultrahelvetic cover of the Staub, and Termier, are full of discussions on Gotthard massif to the Helvetic nappes of the the correlation of nappes observed in the Bernese Oberland, to the Subhelvetic Morcles different transverse sections between Vienna nappe in the Rhone Valley, and finally to the and Genoa, or even beyond to the Carpathians Subalpine chains of Savoy. Isopic lines for the and to Corsica. Middle Jurassic formations have a similar This "cylindrist" dogma was vigorously orientation, whereas those for the Cretaceous attacked by other geologists. To these "fes- run more nearly parallel to the structural trend. toonists," the most remarkable of whom was The Eocene facies belts are arranged quite Gignoux, the Alpine paleogeographic units form otherwise and run about southwest-northeast festoons of limited extent, relieving each other when plotted on a palinspastic map (Boussac, along the strike of the chain and of the geo- 1912; Leupold, 1942). They form angles up to syncline. To adherents of this line of thought, 35° with the tectonic zones and up to 45° with the original basin of the Niesen Flysch, for the Liassic facies belts. The northwestern limit instance, was never much longer than the 60 of the middle Eocene transgression, for instance, km along which the Niesen nappe is now touches the Rawil pass, between Valais and the preserved (Lugeon and Gagnebin, 1941, p. 51). Bernese Oberland (high Helvetic Wildhorn Criticism of the Argandian edifice was certainly nappe), the Pilatus near Lucerne (border chain, necessary, and it is only natural that it overshot belonging either to the front of the Wildhorn- its mark. Considering the Alps as a regular Drusberg or to the back of the lower Axen geometric body and as a chaos are two com- nappe), and the Kistenpass between Glarus and fortable, but not necessarily very productive, working hypotheses.19 nappes and the amount of crustal shortening. The author adheres to the sect of noncylindrist Big- 19 The "festoonists" are often also called "Little- Alpians, which probably includes the majority of Alpians" (Swift, Voyage to Lilliput), meaning that French and Swiss Alpine geologists of the younger they have a tendency to minimize the amplitude of generation among its members. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 896 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS Graubunden, in the autochthonous cover of the Gignoux, 1950, p. 311). North of the river eastern Aar massif. Arc, in Savoy, a new element not represented The limit between the Brianconnais and Sub- in the classical section of the Durance Valley brianconnais belts in the Median Prealps nappe appears between the Ultradauphinois and Sub- of western Switzerland furnishes another ex- brianconnais zones. This, the Tarentaise nappe, ample of crossing over of fades belts. The is the most southwesterly evidence of a facies Brianconnais-M6dianes rigides realm is readily belt for which the author (1955b) reintroduced distinguished from its northwestern neighbor Haug's term of "Valais geosyncline" or, better, by its lack of Upper Triassic, lack of Lias, Valais realm. This belt broadens to the north- absence of Middle Jurassic or representation east and takes in more elements: the Ferret only by Mytilus beds, lack of Argovian nodular zone to the outside and the Schistes lustres of limestones, and lack of Lower Cretaceous the Petit St. Bernard to the inside of the (Fig. 2). The lines marking these different Tarentaise nappe. The most external digitation facies limits cross each other in a complicated of the Subbrianconnais units (Grande Moenda), and unsystematic manner; as a result it is im- with its shaly facies of the Lower and Middle possible to assign the klippen of central Switzer- Jurassic, may mark the transition between the land (tectonic outliers of the M6dianes nappe) Subbrianconnais and the Valais facies belt. to a definite facies belt of the same nappe in The original breadth of the latter in Valais may western Switzerland (Peterhans, 1926; Weiss, have been of the order of 100 km. 1949). The Mithen, east of Lake Lucerne, for Farther east, in Graubunden, the Valais instance, show a very "northerly" facies of the facies belt is much broader, more complex, and Upper Triassic and the Middle Jurassic, but distinctly eugeosynclinal. All the Bundner- also "Brianconnais" characteristics, such as schiefer and Flysch masses of northern and absence of Lower Jurassic and Lower Cre- central Graubunden belong to it. The Sub- taceous formations. brianconnais belt loses its individuality between The review by de Sitter and de Sitter- Ticino and Lake Lucerne. Equivalents of the Koomans (1949) on the Bergamask Alps also Brianconnais facies belt are found only in the contains very suggestive maps showing the Sulzfluh nappe overlying these schist groups obliquity of facies zones in the Permian and and in the Schams nappes (especially the Triassic of the southern Alps. Kalkberg and Marmorzone units) south of NonparalleUsm of paleogeographical and them. These complicated decollement nappes structural units.—The cylindrist working hy- lie near the front of the Suretta basement pothesis that the major Alpine nappes did not nappe, which is believed to correspond to part essentially change their geometrical character- of the Grand St. Bernard nappe of the western istics along the strike of the chain has been Alps. If they belonged to the original cover of challenged on tectonic grounds. The axes of the Suretta nappe there would still be con- microfolding show a very complicated pattern cordance between basement nappes and paleo- in areas like the Vanoise (Ellenberger, 1958) or geographical zones, in spite of the great the gneiss nappes of the Ticino (Wenk, 1956). broadening of the north Penninic Valais realm. The major structural units, although they do But those who have worked on the Schams not in all cases conform to the trend of the nappes (especially Staub, 1937; 1958; Streiff, microfolding, also show strong deviations from 1939; Neher, personal communication) deny normal strike. This makes the detailed this possibility and generally agree on the parallelism of nappes on a purely geometrical derivation of most Schams units from the high- base very problematical, but it seems possible Penninic Margna nappe, which nobody would to give an approximate correlation of units on think of correlating with the Grand St. Bernard either side of the transverse Ticino uplift. nappe. In this case, the discrepancy of facies Paleogeographical evidence, of course, has been belts and major nappes (basement nappes) is widely used for nappe correlation, but the two total, and the comparison of tectonic units by methods should be kept apart, as we cannot paleogeographical evidence becomes impossible. a priori assume the parallelism of structural and Between Savoy and Graubunden, the Brian- paleogeographical units. connais platform would run across almost the In most of the French Alps, the Subbrian- whole breadth of the Penninic geosyncline. In connais realm appears to be directly contiguous the French-Italian Alps, the eugeosynclinal to the Dauphinois-Ultradauphinois miogeo- Piemont trough lies inside (east) of the Brian- syncline, and most workers agree that there connais rise. In Valais and Ticino, there are were no other zones between the two (e.g., two eugeosynclines, of about equal importance, Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 STRUCTURAL EVOLUTION DURING THE GEOSYNCLINAL PHASE 897 on either side of it. In Graubunden the external The basal shear planes of decollement nappes Valais trough is by far the more prominent; are governed largely by the facies of the if the Schams nappes are derived from the Mesozoic formations, especially by the in- Margna, equivalents of the Piemont belt are competent anhydrite members of the Triassic. present only in the Platta (= Arosa) cover Thrusts will follow incompetent formations nappe. If the basement nappes east and west for a long distance and then cut at a larger of the Ticino transverse uplift can be correlated angle through competent ones. Facies changes at all, which many authors doubt, it is only on affecting the competency of the rocks—an- purely geometrical grounds. hydrite to dolomite, or shale to limestone—will We should probably distinguish more rigor- strongly influence the structure of cover nappes ously between the thick nappes with basement (for instance, Fallot, 1953; Helbling, 1938; cores and the thin decollement nappes (strip Lemoine, 1952; de Sitter, 1939; R. Triimpy, sheets) consisting only of Mesozoic and lower 1955a). Because the localization of thrust planes Tertiary formations. There has long been a is determined by facies, cover nappes are in tendency to assign each decollement nappe to a some instances more nearly parallel to the particular basement nappe, and to regard the paleogeographic zones than are the basement former as a kind of frontal prolongation of the nappes. latter. The two phenomena are probably of The two phenomena—the stripping of the different order, however, and came into ex- cover and the formation of "gneiss nappes"— istence at different times. It becomes apparent are not necessarily directly related. Many that in many instances the Mesozoic cover was basement units lost their cover at an early stripped off its basement before the latter stage, either by shearing off or by erosion during became involved in the major nappe-building the "Flysch phase" of geosynclinal history. In processes, at a rather early state of the Alpine some it has been replaced by a "false cover" orogeny. that moved forward from more internal zones This is evident in particular for the Median ("remplacement de couverture" of Ellenberger, Prealps, which originated in an area that was 1958). As far as the large nappes with basement later affected by Alpine metamorphism. They cores are concerned, there is no simple genetic must have left this area and moved north- link between Mesozoic paleogeography and westward, bearing the Simme nappe on their present-day nappe structure. As the author has back, before metamorphism set in, and before already observed (R. Triimpy, 1958), "this the "lid" of the Austroalpine Dentblanche does not make things easier for the Alpine nappe, with its mighty basement core, covered geologist, and still less so for his extra-Alpine the Penninic zone of the western Alps. Meta- reader." morphism is contemporaneous with or slightly later than the main folding and thrusting of the CONCLUSIONS Penninic gneiss nappes. Structural evidence shows that the Breccia Five Epochs of Alpine History nappe and especially the Niesen nappe were the latest units to take their place in the Prealpine The structural history of the Alps can be edifice, the Niesen nappe even after the for- divided into five epochs, each of which has mation of the Helvetic nappes (Badoux, 1945). engendered its own set of sedimentary rocks. These two nappes are the only ones that have First: The Hercynian post-orogenic and any (although small) remnants of pre-Triassic anorogenic phase (would be included in the formations, and the basal beds of the Niesen "pre-orogenic" phase of most authors) started nappe are the only formations of the Prealps with the subsidence of elongated, commonly that bear the stamp of Alpine metamorphism. fracture-bounded basins on the Hercynian For the Austroalpine cover nappes of the chain after its main deformation. During the northern Calcareous Alps, the case is somewhat Pennsylvanian and Permian, these basins were different. Initial stripping off of the cover began filled by detritus from the Hercynian during the Cretaceous pre-Gosau phase, but Mountains. When they were levelled, by the the main movement took the decollement beginning of the Triassic, sedimentation spread nappes, together with their basement of the beyond the "epieugeosynclinal" basins, but Silvretta-Oetztal nappe, over the Penninic they remained the seat of stronger subsidence area. Additional independent gliding of cover than the other areas, especially in the case of nappes occurred during this Tertiary defor- the "archaic Brianconnais geosyncline." An- mation (Fallot, 1954). other belt with rapid subsidence lay in the Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 898 RUDOLF TRUMPY—CENTRAL AND WESTERN ALPS southeast (South Tyrol, highest Austroalpine Brianconnais platform, the Helvetic miogeosyn- nappes); possibly its evolution was advanced cline, and even the nongeosynclinal belt beyond it beyond that of the main part of the future (Fig. 13). In these areas, downbuckling pre- Alps. ceded the arrival of the flood of detrital matter; Second: Alpine pre-orogenic epoch ("Schistes pelagic formations invariably underlie Flysch. lustres times"). In the western Alps, the change Flysch cordilleras show evidence of folding from late Hercynian to early Alpine paleo- and thrusting. While compressional stresses geography can be dated precisely (Ladinian- grew stronger, the outflow of ophiolites ceased. Carnian transition), but the Triassic as a whole All through "Flysch times," erogenic defor- was a transitional period. The Piemont geo- mation went on. The earliest nappes of the syncline commenced in the Late Triassic as a eastern Alps are Late Cretaceous; those of the gently downbuckled basin, but from the middle western Alps are late Eocene. By the time the Lias onward it became a deep and rapidly youngest (early Oligocene) Flysch was laid subsiding furrow. The paleogeography of Early down over the Helvetic realm, most of the and Middle Jurassic time shows a marked Alps already was above sea level. In any contrast between troughs and nonsubsiding but particular Flysch basin, the major thrusting instable platforms. The Piemont Schists lustre's movements put an end to Flysch sedimentation, accumulated in the troughs. Breccias are but in some places Flysch is transgressive on prominent along geosynclinal scarps. The ex- folds and minor thrusts. ternal miogeosyncline received even thicker Fourth: Late synorogenic or epi-orogenic sediments than did the eugeosynclinal belts. In phase ("Molasse times"). The last remnant of the Late Jurassic, very little detrital matter the geosyncline shifted to the external border was brought into the geosyncline; the Piemont of the chain; the narrow remaining arm of the trough entered into its "stage of vacuity" Alpine sea became shallow and brackish and (Aubouin, 1959) and received only thin deep-sea was finally filled by detritus from the rising deposits. Most of the Bundnerschiefer of the Alps. Strong subsidence of the Molasse "exo- Valais trough are of Cretaceous age. The evo- geosyncline" goes along with the upheaval of lution of the Valais and Piemont eugeosynclinal the Alps. The major thrusts are formed, meta- belts was obviously not concordant. morphism and granitization (on a smaller scale The structural pattern of this pre-orogenic than in many similar chains) take place. epoch is governed by vertical movements, Erosion attacks the chain down to several perhaps even tensional stresses resulting from a kilometers below the original structural surface. stretching of the crust. Normal faults and From late Oligocene to middle Miocene, the flexures mark the borders between platforms Alps formed a chain of high mountains, but they and troughs. During the Cretaceous, ophiolites were not more than a hilly tract of country by found their way along these fracture belts, the beginning of the Pliocene. The present perhaps at the very time when compressional morphology, especially of the western Alps, is stresses set in. the product of Pleistocene uplift and erosion. There was probably a period of less con- Post-orogenic volcanic activity started in the trasting submarine topography between the Eocene south of the Alps, in the Miocene to the phase of strong vertical movements (Early and north. Middle Jurassic) and the onset of the tangential Fifth: Compressional deformation has almost movements (Middle Cretaceous to Eocene). ceased (Pliocene and Pleistocene), but vertical Third: Early synorogenic or cata-orogenic movements continue, perhaps with some dis- phase ("Flysch times"). From the Cenomanian placement along strike-slip faults. or, locally, the Early Cretaceous onward new ridges ("cordilleras") arose in the Alpine geo- Remarks on Geosynclinal Nomenclature syncline. Their location shows no simple re- lationship to the platforms and troughs of the The author had intended to devote a section preceding epoch. These cordilleras rose above of this paper to geosynclinal nomenclature, but sea level and furnished great masses of detritus while it was being written Aubouin (1959) to the remaining troughs on either side, which published an excellent and well-documented were rapidly filled by Flysch sediments. Flysch review of the problem. Its treatment also by sedimentation started hi the Austroalpine Dunbar and Rodgers (1957, p. 312) and by realm, in the Piemont and Valais troughs, but King (1959, p. 54) shows that a consensus is moved outward (northward and westward) in imminent. The proposed restriction of the course of time and finally encroached upon the term "geosyncline" to the orthogeosynclines of Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 CONCLUSIONS 899 Stille would certainly clarify things (see also term "leptogeosyncline" becomes useless, and Glaessner and Teichert, 1947) and would be the author will gladly lend a hand to bury his approved by most European geologists, who own brain child. The term is necessary only as for more than half a century have used the long as the historical definition of geosynclines term only in connection with the mio- and is upheld. eugeosynclines from which folded mountain Many geologists—certainly including the belts arose. present author—use the term "geosyncline" in If, for historical reasons, it is necessary to a sloppy way for features of quite different keep Dana's broad definition—any elongated order of size and complexity (Thetys, Alpine, basin which received an abnormally great Penninic, and Piemont geosynclines). The indi- thickness of sedimentary formations, as com- vidual troughs which make up a geosyncline pared to its surroundings—then it becomes should be distinguished under other names, such necessary to distinguish a large number of as secondary geosynclines (Haug) or intrageo- different kinds of "geosynclines" of quite synclines (Tetiaev; see Aubouin, 1959, p. 156). different geotectonic significance, by prefixes or Trying to be unmistakably precise, however, by some other means. Most geologists probably can make geological language heavier and do not favor using the word "geosyncline" for heavier; doubt naturally arises whether it is a shallow basins of almost circular outline ("auto- material advance to science to call the Piemont geosynclines") or for fault-bordered troughs belt in the Upper Jurassic a meso (?)-ortho-eu- that lie outside the fold belts and contain lepto-intrageosyncline. primarily continental deposits ("taphrogeo- synclines"). Nevertheless, one of Dana's original examples of a geosyncline was the Peculiar Characteristics of the Alpine Geosyncline Triassic "taphrogeosyndine" of Connecticut. Classifications of course nearly always pro- The Alpine geosyncline can certainly not vide too rigid a set of boxes for the great serve as a suitable standard specimen of "The number of natural variations observed. Kay Geosyncline"—leaving aside the historical (1947; 1951), who has been criticized for setting "type" specimen in the western Appalachians. up a large number of categories for geosynclines, First of all, reconstruction of Alpine paleo- has done much to show how the different types geography is much too difficult, and over large grade into each other. tracts very doubtful, because of the great Even if one restricts the term to orthogeo- structural complications, metamorphism, and synclines, it is commonly difficult to decide primary lack of fossils in many formations. No what is a geosyncline and what is not. The really secure synthesis can be given until we Molasse foredeep ("exogeosyncline")—not a know more about the stratigraphy of the geosyncline by the author's standards—gradu- Schistes lustres and before settling the contro- ally develops out of the Alpine geosyncline, versial points regarding the origin of several which shifts and is filled. Distinction between important cover nappes—to mention only eugeosynclines and miogeosynclines also may Helminthoid Flysch, Simme, Niesen, Schams, be controversial. Volcanism cannot be used as and the Flysch nappes along the border of the the only criterion: the Triassic of the Dolomite eastern Alps. On the other hand, the Alpine Mountains is a good example of miogeosynclinal geosyncline differs materially in several ways deposition with volcanic material, the Blindner- from many others. schiefer of the Pratigau exemplifies eugeo- Compared with those of many other (es- synclinal sedimentation without volcanism. pecially Paleozoic) mountain chains, sedi- Should Flysch formations be classed as miogeo- mentary rocks of the Alpine geosyncline are synclinal or eugeosynclinal? They develop over very calcareous. This is normal for the miogeo- mio- and eugeosynclines alike; they have no synclinal belts, but even the eugeosynclinal volcanic materials, but conditions of relief and Schistes lustres have a high proportion of of contemporaneous mobility approach those of calcium carbonate. Typical graywackes are true eugeosynclines. absent in the Schistes lustres and not very Another point concerns the thickness of abundant in the Flysch. Pre-orogenic ophiolitic accumulated sediments, considered as the volcanism is relatively modest. essential characteristic of geosynclines by Hall Sediment accumulation in the Alpine basins and Dana. Many otherwise quite typical geo- was less pronounced than in many other geo- synclines received little sediment over long synclines (rates cited in Kay, 1955). During intervals. If this is generally recognized, the long intervals, the eugeosynclinal troughs and Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 900 RUDOLF TRtlMPY—CENTRAL AND WESTERN ALPS areas to their interior received only very thin and strongly subsiding troughs were limited by deposits. This "period of vacuity," still more fault scarps. Movements along these scarps are evident in the Tethyan geosynclines around vertical and denote tensional stresses; they the eastern Mediterranean, in Greece and were strongest during the Lias and the earlier Turkey, may be due to the existence of para- Middle Jurassic. oceanic conditions during the second half of the (3) Deep-sea sediments, especially of Middle Jurassic and the beginning of the Cretaceous. Jurassic to Early Cretaceous age, are wide- Even the Flysch sequence of the Alps looks spread in the eugeosynclinal belts and also modest, compared with that of the Carpathians farther south, in the Austroalpine and south or of the northern Apennines, but this is Alpine realms. At that time the Alps may have perhaps because the Alps are more deeply represented an incipient or threshold ("mono- eroded; in the late Oligocene they may have liminary") erogenic belt (Glangeaud, 1957). resembled the Carpathian and Apennine (4) The Cordilleras of the Flysch stage were "Flysch mountains," to judge from the pebbles steep island arcs, engendered by compressional in the Alpine Molasse conglomerates. Also, stresses and not directly related to the earlier where the deepest parts of the northern platforms. Apennines are exposed, in the Apuanic Marble (5) On the whole, paleogeographical units Mountains, rocks and structure look decidedly are rather ephemeral and subject to repeated "Alpine." shifting. The essential feature of the Alpine geo- (6) There is no simple relationship between syncline is perhaps its instability. Instead of a rises inside the Mesozoic geosyncline and permanent trough, in which great masses of Tertiary (or Late Cretaceous) nappe structures. sediments and volcanic deposits were heaped This last point needs one final comment. up, there is a bewildering succession of troughs The author has insisted that there is no simple, and rises, some of them quite small and quite direct, readily understood relationship between ephemeral. Crustal unrest, rather than sub- paleogeographical elements and major nappes, sidence, is the hallmark of the sedimentary such as was provided by the theory of embryo- history of the Alps. tectonics. Some relationship evidently does Does this very turbulent pre-orogenic history exist, but it is not simple and has yet to be reflect the same deep-seated causes as the worked out. The different structural patterns extraordinary tectonic complications of the which succeeded one another in time and space Alps? It seems that the nappe structure of the during the preparatory and paroxysmal phases Alps is not an isolated, but certainly an extreme, of Alpine history are certainly, in some complex case. This complicated structure severely limits way, all expressions of one great process. The reconstruction of Alpine paleogeography. We nature of this process is, in the main, a geo- have learned a lot of new facts in the last 10 chemical and geophysical problem, to the years, chiefly concerning the western Alps; solution of which the field geologist and stra- but much remains to be done before a coherent tigrapher can contribute mainly by presenting paleogeographical synthesis can be attained. and co-ordinating the facts, and by demanding For this reason, study of simpler mountain that a theory of mountain building accord with chains will perhaps contribute more signifi- and account for them. This the author has cantly to the genesis and the life history of attempted to do in greatly condensed form, geosynclines than will that of the Alps. Never- and from the works of several generations of theless, the Alps are certainly significant in that Alpine geologists. they afford some insight into the very complex past of a very complex chain. Some points now REFERENCES CITED fairly well established are: (1) An interval of only slightly contrasting Abele, G. et al., 1955, Erlauterungen zur Geologi- submarine topography precedes the birth of schen Ubersichtskarte der Stiddeutschen the Alpine geosyncline. Subsidence of the late Molasse 1:300 000: Bayrisches Geologisches Landesamt Munchen, 106 j). Paleozoic "epieugeosynclines" can be ascribed Allemann, Franz, 1956, Geologic des Furstentums to isostatic compensation following Hercynian Liechtenstein (Stidwestlicher Teil), Unter folding, but not so the formation of the Alpine besonderer Beriicksichtigung des Flyschprob- geosyncline itself, which followed the last lems: Histor. Ver. Fiirstentum Liechtenstein Jahrb., v. 56, p. 1-244 (1957) preceding folding by about 30 million years. Andrau, E. W. K., 1929, La geologic du Pic Chaussy (2) During the earlier stages of Alpine geo- et ses abords (Alpes vaudoises): Amsterdam, synclinal history slightly subsiding platforms Centen, 99 p. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 REFERENCES CITED 901 Ampferer, Otto, 1908, Studien iiber die Tektonik der Niesenkette: Mitt. Naturf. Gesell. Bern, des Sonnwendgebirges: Jahrb. k. k. Geol. p. 32-113 (1929) Reichsanst., Bd. 58, Heft 2, p. 281-304 Boussac, Jean, 1912, Etudes stratigraphiques sur Arbenz, Kaspar, 1947, Geologic des Hornfluhge- le Nummulitique Alpin: Mem. carte geol. bietes (Berner Oberland): Beitr. Geol. Karte France, 662 p. Schweiz, Neue Folge, Lief. 89, 91 p. Bruckner, W. D., 1937, Stratigraphie des auto- Arbenz, Paul, 1919, Probleme der Sedimentation chthonen Sedimentmantels und der Griesstock- und ihre Beziehungen zur Gebirgsbildung in decke im oberen Schachental (Kanton Uri): den Alpen: Naturf. Ges. Zurich Viertel- Naturf. Gesell. Basel Verb., Bd. 48, p. 77-182 jahrsschr., Jahrg. 64 , 1941, Ueber die Entstehung der Rauhwacken Argand, fimile, 1916, Sur 1'arc des Alpes Occiden- und Zellendolomite: Eclogae geol. Helv., v. 34, tales: Eclogae geol. Helv., v. 14, no. 1, p. no. 1, p. 117-134 145-191 , 1943, Tektonik des oberen Schachentals , 1920, Plissements precurseurs et plissements (Kanton Uri): Beitr. Geol. Karte Schweiz, tardifs des chaines de montagnes: Soc. Helv. Neue Folge, Lief. 80, 42 p. Sci. Nat. Actes, 101 sess., pt. 2, p. 13-39 , 1946, Bemerkungen liber die nordhelvetischen Aubouin, Jean, 1959, A propos d'un centenaire; Flyschbildungen in der Westschweiz. Naturf les aventures de la notion de geosynclinal: Ges. Basel Verb., Bd. 57, p. 62-74 Geog. phys. et Geol. dynamique Rev., Ser. 2, , 1951, Lithologische Studien und zyklische v. 2, fasc. 3, p. 135-188 Sedimentation in der helvetischen Zone der Badoux, Heli, 1945, La geologic de la Zone des Schweizer Alpen: Geol. Rundschau, Bd. 39, Cols entre la Sarine et le Hahnenmoos: Mat. Heft 1, p. 196^12 Carte Geol. Suisse, Nouv. Se"r., livr. 84, 70 p. , 1952, Globigerinenmergel und Flysch; ein Badoux, Heli, and de Weisse, Godefroy, 1959, Les Beitrag zur Geologic der jtingsten helvetisch- bauxites siliceuses de DreVeneuse: Soc. vaudoise ultrahelvetischen Ablagerungen der Schweizer - Sci. nat. Bull., v. 67, no. 300, p. 169-177 alpen: Naturf. Ges. Basel Verb., Bd. 63, p. Baer, Alec, 1959, L'extremit£ occidentale du Massif 17^0 de 1'Aar (Relations du socle avec la couverture): , 1953, Cyclic calcareous sedimentation as an Soc. neuchateloise sci. nat. bull., v. 82, p. 5-160 index to climatic variations in the past: Jour Bailey, E. B., 1935, Tectonic essays, mainly alpine: Sed. Petrology, v. 23, no. 4, p. 235-237 Oxford, Univ. Press, 200 p. Bucher, W. H., 1933, The deformation of the earth's Barbier, Reynold, 1948, Les zones ultradauphinoise crust: Princeton, N. J., Princeton Univ. Press, et subbrianconnaise entre 1'Arc et 1'Isere: 518 p. Carte geol. France me'm., 291 p. , 1953, Fossils in metamorphic rocks, a review: , 1956, L'importance de la tectonique Geol. Soc. America Bull., v. 64, p. 275-300 "ante'nummulitique" dans la zone ultradau- Biichi, U. P., 1950, Zur Geologie und Palaogeo- phinoise au N du Pelvoux; la Chaine arvinche: graphie der siidlichen mittellandischen Molasse Soc. ge"ol. France Bull., ser. 6, v. 6, p. 355-370 zwischen Toggenburg und Rheintal: Kreuz- Barbier, Reynold, and Triimpy, R., 1955, Sur 1'age lingen, Bodan, 100 p. du Flysch de la zone des Breches de Tarentaise: Burri, C., and Niggli, P., 1945, Die jungen Soc. geol. France Bull., ser. 5, t. 5, fasc. 1-3, Eruptivgesteine des mediterranen Orogens: p. 207-216 Zurich, Guggenbiihl and Huber, 654 p. Beck, Paul, 1911, Geologic der Gebirge nordlich Buxtorf, August, 1943, Ueber Vorkommen von von Interlaken: Beitr. Geol. Karte Schweiz, Leimernschichten in der Unterlage des Neue Folge, Lief. 29, 100 p. Schlierenflyschs: Eclogae geol. Helv., v. 36, Bersier, Arnold, 1945, Sedimentation molassique; no. 2, p. 204-206 Variations lat&ales et horizons continus a Cadisch, Joos, 1921, Geologie der Weissfluhgruppe 1'Oligocene: Eclogae geol. Helv., v. 38, no. 2, zwischen Klosters und Langwies (Graubiinden). p. 452-458 (Geologie von Mittelbunden, Abt. I): Beitr. , 1949, La sedimentation cyclique de type Geol. Karte Schweiz, Neue Folge, Lief. 49,91 p. molassique paralique en fonction de la sub- , 1946, On some problems of Alpine tectonics: sidence continue: Sedimentation et Quater- Experientia, Bd. 2/1, p. 1-16 naire France, 1949, p. 9-15 , 1953, Geologie der Schweizer Alpen: 2d. ed., , 1950, Les sedimentations rythmiques Basel, Wepf, 480 p. synorogeniques dans 1'avant-fosse molassique Cadisch, Joos, Leupold, W., Eugster, H, and Brau- alpine: 18th Internal. Geol. Cong. Rept., pt. chli, R., 1919, Geologische Untersuchungen in 4, p. 83-93 Mittelbunden: Naturf. Gesell. Zurich, Viertel- Bertrand, Marcel, 1897, Structure des Alpes jahrsschr., v. 64, p. 339-416 franchises et recurrence de certains fades Campana, Bruno, 1943, Geologie des nappes preal- sedimentaires: Compte-rendu Cong. geol. pines au Nordest de Chateau-d'Oex: Materiaux internal., pt. 3, p. 163-177 Carte g&>l. Suisse, nouv. ser., livr. 82, 64 p. Bolli, H. M., 1944, Zur Stratigraphie der Oberen Carozzi, Albert, 1951, Rythmes de sedimentation Kreide in den hoheren helvetischen Decken: dans le Cretace helvetique: Geol. Rundschau, Eclogae geol. Helv., v. 37, no. 2, p. 217-328 Bd. 39, Heft 1, p. 177-195 (1945) , 1957, Tracing turbidity current deposits down Bolli, H. M., and Nabholz, W. K., 1959, Biindner the slope of an Alpine basin: Jour. Sed. Petrol schiefer, ahnliche fossilarme Serien und ihr ogy, v. 27, no. 3, p. 271-281 Gehalt an Mikrofossilien: Eclogae geol. Helv., Chessex, Ronald, 1959, La geologic de la haute v. 52, no. 1, p. 237-270 vallee d'Abondance, Haute-Savoie (France): Bornhauser, Max, 1928, Geologische Untersuchung Eclogae geol. Helv., v. 52, no. 1, p. 296-400 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 902 RUDOLF TRtJMPY—CENTRAL AND WESTERN ALPS Clar, Eberhard, 1953, Zur Einfugung der Hohen Prealpes medianes: Eclogae geol. Helv., v. 41, Tauern in den Ostalpenbau: Verb. geol. Bun- no. 1, p. 95-99 desanst., Heft 2, p. 93-115 Dunbar, C. O., and Rodgers, John, 1957, Principles Collet, Leon, 1927, The structure of the Alps: of stratigraphy: New York, Wiley, 356 p. London, Arnold, 289 p. Eardley, A. J., and White, M.G., 1947, Flysch and Colom, G., 1957, Sur les caracteres de la se'dimenta- Molasse: Geol. Soc. America Bull., v. 58, p. tion des Geosynclinaux mesozoiques: Soc. geol. 979-990 France Bull., ser. 6, v. 7, p. 1167-1187 Ellenberger, Francois, 1949, Sur la serie strati- Conti, Sergio, 1953, Studi geologic! sulle Alpi graphique et la structure de la Vanoise: Carte occidental! (2° contribute). Delimitazione geol. France Bull., v. 47 (1950), no. 226, p. areale e cprrelazioni stratigrafiche nella forma- 83-118 zione dei calcescisti l.s. delle Alpi liguri, , 1950, Subsidence et Transgressions dans la marittime e cozie: Serv. Geol. d'ltalia boll., v. Vanoise (Zone du Brianconnais au Nord de 75, fasc. 2, p. 525-539, (1954) 1'Arc): Acad. sci. (Paris) Comptes rendus, t. , 1955, Studi geologic! sulle Alpe occidental! 230, p. 1409-1411 (3° contribute). La formazione dei Calcescisti , 1952a, Sur 1'age du metamorphisme dans la nei suoi rapporti stratigrafici e tettonici con i Vanoise: Soc. geol. France C. R. somm., no. complessi basali e marginali delle Alpi liguri, 15, p. 318-321 marittime e Cozie: Serv. geol. Italia Boll., v. , 1952b, Sur 1'extension des facies brianconnais 77, fasc. 2-3, p. 275-326 en Suisse, dans les Prealpes medianes et les Cornelius, H. P., 1925, Zur Vorgeschichte der Pennides: Eclogae geol. Helv., v. 45, no. 2, p. Alpenfaltung: Geol. Rundschau, Bd. 16, Heft 285-286 5 pi. 350-377, Heft 6, p. 417-434 ——-, 1958, Etude geblogique du pays de Vanoise: , 1930, Zur Frage der Beziehungen von Meta- Carte geol. France me'm., 561 p. morphose und Tektonik in den franzosischen Ellenberger, F., and Lemoine, M., 1955, Les facies Alpen: Mitt. Geol. Gesell. Wien, v. 23, p. 142- prepiemontais et le probleme du passage de la zone du Brianconnais aux Schistes lustre's , 1935, Geologic der Err-Julier-Gruppe; 1. Teil: pi&nontais: Soc. geol. France C. R. somm., no. Das Baumaterial (Stratigraphie und Petro- 7-8, p. 146-148 graphie, excl. Quartar): Beitr. Geol. Karte Elter, Giulio, and Elter, Piero, 1957, SuU'esistenza, Schweiz, Neue Folge, Lief. 70/1, 321 p. nei dintorni del Piccolo S. Bernardo, di un , 1937, Ueber den Oberjurakalk mit klastischen elemento tettonico riferibile al ricoprimento Beimengungen yom Hohen Student (Murztaler del Pas du Roc: Accad. Naz. dei Lincei (Cl. Kalkalpen, Steiermark): Geol. Bundesanst. Sci. fis., mat. e nat.) Rend., ser. 8, v. 22, fasc. (Wien) Verh., pt. 9-10, p. 212-215 2, p. 181-187 ——•, 1951, Zur Frage der Absatzbedingungen der Fallot, Paul, 1953, Du r61e des decollements en Radiolarite: Geol. Rundschau, Bd. 39, Heft 1, Tectonique: "Scientia," 47ieme Annee, 6 p. p. 216-221 , 1954, Les dilemmes tectoniques des Alpes Crowell, J. C., 1955, Directional-current structures orientales: Soc. Geol. Belg. Ann., t. 78, p. from the Prealpine Flysch, Switzerland: Geol. 147-170 Spc. America Bull., v. 66, p. 1351-1384 Faure-Muret, Anne, 1955, Etudes geologiques sur Dal Piaz, Giambattista, 1943, Rapporti e differenze le massif de 1'Agentera-Mercantour et ses fra la formazione pennidica dei calcescisti enveloppes se'dimentaires: Carte geol. France alpini e la formazione argillosa ofiolitifera Me'm. expl., 336 p. dell'Apennino settentrionale: Reale Accad. Sci. Fichter, H. J., 1934, Geologic der Bauen-Brisen- Torino Atti, v. 77 e 78, p. 37-52 Kette am Vierwaldstattersee und die zyklische Debelmas, Jacques, 1952, Les Breches du Trias Gliederung der Kreide und des Malm der superieur dans le massif de Gaulent au Sud de helvetischen Decken: Beitr. geol. Karte Bnancon pres 1'Argentiere (Hautes-Alpes): Schweiz, Neue Folge, Lief. 69, 128 p. Univ. Grenoble lab. gdologie fac. sci. Travaux, Frank, Manfred, 1930, Das Wandern der "Tektoni- tome 30, p. 103-106 schen Vortiefe" in den Alpen: Centralblatt f. , 1955, Les zones subbrianconnaise et brian- Min. Geol. u. Palaont, Abt. B, Jahrg. 1930, p. connaise occidentale entre Vallouise et 9-22 Guillestre (Hautes-Alpes): Carte geol. France Frauenfelder, Albert, 1916, Beitrage zur Geologic me'm., 171 p. der Tessiner Kalkalpen: Eclogae geol. Helv., , 1957, Quelques remarques sur la conception v. 14, p. 247-367 actuelle du terme "Cordillere" dans les Alpes Fuchtbauer, Hans, 1954, Transport und Sedimenta- internes Francaises: Soc. geol. France Bull., tion der westlichen Alpenvorlandsmolasse: ser. 6, v. 7, p. 463-474 Heidelberger Beitr. Min. Petr., v. 4, p. 26-53 Debelmas, J., and Lemoine, M., 1957a, Discordance Gagnebin, Elie, 1924, Description geologique des angulaire du Rhftien sur le Trias dans le massif Pr&lpes bordieres entre Montreux et Semsales: de Peyre-Haute au S de Briancon—Importance Soc. vaudoise Sci. nat. me'm., v. 2, no. 1, p. 1-69 de I'e'rosion ante-rhe'tienne dans la zone brian- Gees, Rudolf, 1955, Geologic von Klosters: Bern, connaise: Soc. geol. France Bull., ser. 6, v. 7, Mader, 24 p. p. 489-493 Geiger, Max, 1956, Die Unterlage der zentral- , 1957b, Calcschistes piernontais et terrains a schweizerischen Klippengruppe Stanserhorn- facies brianconnais dans les hautes vallees de Arvigrat, Buochserhorn-Musenalp und Kle- la Maira et de la Varaita (Alpes Cottiennes, wenalp: Eclogae geol. Helv., v. 49 no. 2, p. Italic): Soc. geol. France C. R. somm., no. 3 407-452 Delany, Frances, 1948, Observations sur les Couches Genge, Erwin, 1958, Ein Beitrag zur Stratigraphie rouges et le Flyscb dans plusieurs regions des der svidlichen Klippendecke im Gebiet Spill- Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 REFERENCES CITED 903 gerten-Seehorn (Berner Oberland): Eclogae Heim, Arnold, 1908, Die Nummuliten- und Flysch- geol. Helv., v. 51, no. 1, p. 151-211 bildungen der Schweizeralpen: Abh. schweiz. Gignoux, Maurice, 1950, Geologic stratigraphique, pal. Gesell., v. 35, 301 p. 4th ed.: Paris, Masson, 735 p. , 1916, Monographic der Churfirsten- Gignoux, Maurice, and Avnimelech, Moses, 1937, Mattstockgruppe. Dritter Teil: Stratigraphie Genese de roches se'dimentaires brechoides par der Unteren Kreide und des Jura; Zur Litho- "intrusion et eclatement": Soc. geol. France snesis: Beitr. geol. Karte Schweiz, Neue Bull., ser. 5, v. 7, p. 27-33 f olge, Lief. 20, p. 369-573 Gigon, Werner, 1952, Geologie des Habkerntales , 1925, Ueber submarine Denudation und und des Quellgebietes der Grossen Emme: chemische Sedimente: Geol. Rundschau, Bd. 15, Naturf. Gesell. Basel Verb., Band 63, no. 1, Heft 1, p. 1-47 p. 49-136 Helbling, Robert, 1938, I. Die Anwendung der Glaessner, M. F. and Teichert, C., 1947, Geosyn- Photogrammetrie bei geologischen Kartierun- clines; a fundamental concept in geology: Am. gen, II. Zur Tektonik des St. Galler Oberlandes Jour. Sci., v. 245, p. 465-482, 571-591 und der Glarneralpen: Beitr. Geol. Karte Glangeaud, Louis, 1957, Essai de classification Schweiz, Neue Folge, Lief. 76, 133 p. gebdynamique des Chalnes et des phenomenes Heritsch, Franz, 1915, Die Oesterreichischen und orogeniques: Geographic phys. et Geologie Deutschen Alpen bis zur Alpino-Dinarischen dynam. Rev., ser. 2, v. 1, fasc. 4, p. 200-220 Grenze (Ostalpen): in Handbuch der regionalen Glangeaud, Louis, and d'Albissin, M., 1958, Les Geologie, Stemmann and Wilckens, Editors, phases tectoniques du NE du DeVoluy et leur v. 2, no. 18, Heidelberg, Winter, 153 p. influence structurologique: Soc. g&l. France Heimann, Franz, 1957, Untersuchungen in der Bull., ser. 6, t. 8, no. 7, p. 675-688 subalpinen und mittellandischen Molasse der Goguel, J., and Lafitte, P., 1952, Observations Ostschweiz: Eclogae geol. Helv., v. 50, no. 2, preliminaires sur le massif d'Ambin: Soc. Geol. p. 289-322 France Bull., ser. 6, v. 2, p. 575-595 Hsu, K. J. (1958), Isostasy and a theory for the Grunau, H. R., 1947, Geologie von Arosa (Grau- origin of geosynclines: Am. Jour. Sci., v. 256, btinden), mit besonderer Berucksichtigung des p. 305-327 Radiolarit-Problems: Zurich, Aschmann and , 1959, Flute- and groove-casts in the Prealpine Scheller, 108 p. flysch: Am. Jour. Sci., v. 257, p. 529-536 ——, 1957, Spurenelemente einiger schweizerischer , 1960, Paleocurrent structures and paleo- Ophiolithe, Radiolarite und Mergel: Experi- geography of the Ultrahelvetic Flysch basins: entia, v. 13/9, p. 347-354 Geol. Soc. America Bull., v. 71, p. 577-610 -, 1959, Mikrofazies und Schichtung ausge- Jackli, Heinrich, 1941, Geologische Untersuchungen wahlter, jungmesozoischer, radiolaritfuhrender im nordlichen Westschams (Graubiinden): Sedimentserien der Zentral-Alpen: Leiden, Eclogae geol. Helv., v. 34, no. 1, p. 17-105 Brill, 179 p. , 1944, Zur Geologie der Statzerhornkette: Giinzler-Seiffert, Hans, 1941, Persistente Briiche Eclogae geol. Helv., v. 39, no. 1, p. 1-30 im Jura der Wildhorn-Decke des Berner Ober- Jaffe, F. C., 1955, Les ophiolites et les roches landes: Eclogae geol. Helv., v. 34, p. 164-172 connexes de la region du Col des Gets (Chablais, , 1952, Alte Briiche im Kreide/Tertiar-Anteil Haute Savoie): Bull. Suisse Mineralog. der Wildhorndecke zwischen Rhone und Rhein: Petrogr., t. 35, fasc. 1, p. 1-150 Geol. Rundschau, v. 40, Heft 2, p. 211-239 Jeannet, Alphonse, 1912-1913, Monographic geolog- Habicht, Konrad, 1945, Geologische Untersuch- ique des Tours d'Al et des regions avoisinantes ungen im siidlichen sanktgallisch-appenzelli- (Prealpes vaudoises); Premiere Partie: Mat. schen Molassegebiet: Beitr. Geol. Karte Carte geol. Suisse, Nouv. Ser., livr. 34, p. 1-466 Schweiz, Neue Folge, Lief. 83, 166 p. , 1918, Monographic geologique des Tours Hagen, Toni, 1948, Geologie des Mont Dolin und d'Ai et des regions avoisinantes (Prealpes des Nordrandes der Dent-Blanche-Decke vaudoises); Deuxieme Partie: Mat. Carte zwischen Mont Blanc de Cheilon und Ferpecle geol. Suisse, Nouv. Ser., livr. 34, p. 467-701 (Wallis): Beitr. Geol. Karte Schweiz, Neue , 1941, Geologie der oberen Sihltaler-Alpen Folge, Lief. 90, 64 p. (Kanton Schwyz): Schwyz. Naturf. Gesell. Haug, Ernile, 1900, Les gebsynclinaux et les aires Ber., Heft 3, 1938/40, 24 p. continentales. Contribution a 1'etude des Jenny, Hans, 1924, Die alpine Faltung; Ihre Anord- regressions et des transgressions marines: Soc. nung in Raum und Zeit: Berlin, Borntraeger, Geol. France Bull., ser. 3, v. 28, p. 617-711 176, p. , 1911, Trait^ de Geologie: Paris, Colin, 4 vols., Kappeler, Ulrich, 1938, Zur Geologie der Ortlerg- 2024 p. ruppe und zur Stratigraphie der Ortlerzpne , 1925, Contribution a une synthese stratigraph- zwischen Sulden und dem Engadin: Zurich, ique des Alpes Occidentales: Soc. Geol. France Fluntern, 124 p. Bull., ser. 4, v. 25, p. 97-244 Kay, Marshall, 1947, Geosynclinal nomenclature Heim, Albert, 1891, Geologie der Hochalpen zwis- and the craton: Arn. Assoc. Petroleum Geolo- chen Reuss und Rhein: Beitr. Geol. Karte gists Bull., v. 31, p. 1289-1293 Schweiz, Lief. 25, 503 p. , 1951, North American geosynclines: Geol. , 1921, Geologie der Schweiz. Band 2: Die Soc. America Mem. 48, 143 p. Schweizer Alpen, erste Halfte: Leipzig, Tauch- , 1955, Sediments and subsidence through nitz, p. 1-476 Time, p. 665-684 in The crust of the Earth: , 1922, Geologie der Schweiz. Band 2: Die Geol. Soc. America Spec. Paper 62, 762 p. Schweizer Alpen, zweite Halfte: Leipzig, King, P. B., 1959, The evolution of North America: Tauchnitz, p. 477-1018 Princeton, Princeton Univ. Press, 190 p. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 904 RUDOLF TRUMPY-CENTRAL AND WESTERN ALPS Klaus, Jean, 1953, Les couches rouges et le flysch , 1959, Remarques a propos de quelques faits au sud-est des Gastlosen (Prealpes romandes): et hypotheses concernant Page des Schistes Soc. Fribourgeoise Sci. nat. Bull., v. 42, p. 5-128 lustres piemontais dans les Alpes cottiennes et Kockel, C. W., Richter, M., and Steinmann, H. G., brianconnaises: Soc. geol. France Bull., ser. 7, 1931, Geologic der Bayrischen Berge zwischen t. 1, no. 1, p. 90-92 Lech und Loisach: Wiss. Veroff. D. u. Oe. Leonard!, Piero, 1955, Breve sintesi geologica delle Alpenver., Bd. 10, 231 p. Dolomiti occidentali: Soc. geol. italiana boll., Kraus, Ernst, 1932, Der nordalpine Kreideflysch: v. 74, pt. 1, p. 3-80 Geol. u. palaont. Abh., Neue Folge, Bd. 19, Leupold, Wolfgang, 1933, Neue mikropalaontologi- Heft 2, 138 p. sche Daten zur Altersfrage der alpinen Flysch- , 1942, Neue Wege der nordalpinen Flysch- bildungen: Eclogae geol. Helv., v. 26, no. 1, p. forschung. Der Nordalpine Kreideflysch: Neues 295-319 Jahrb. Min., Geol., Pal., Abt. B, Heft 1, 2, , 1937, Zur Stratigraphie der Flyschbildungen p. 1-243 zwischen Linth und Rhein: Eclogae geol. Helv., , 1951, Die Baugeschichte der Alpen, Bd. I, v. 30, no. 1, p. 1-23 II: Berlin, Akademie-Verlag, 552 and 489 p. , 1942, Neue Beobachtungen zur Gliederung Kuenen, Ph. H., 1953, Significant features of graded der Flyschbildungen der Alpen zwischen Reuss bedding: Am. Assoc. Petroleum Geologists und Rhein: Eclogae geol. Helv., v. 35, no. 2, Bull., v. 37, p. 1044-1066 p. 247-291 , 1957a, Sole markings of graded graywacke Lombard, Augustin, 1940, Geologie des Voirons: beds: Jour. Geology, v. 65, p. 231-258 Mem. Soc. Helv. Sci. Nat., v. 74, Me'm. 1, , 1957 b, Longitudinal filling of oblong sedi- 112 p. mentary basins: Koninkl. Nederl. Geol.-Miinb. , 1942, Observations sur la nappe du Niesen Genoot. Verb., Geol. Ser. 18, p. 189-195 dans le territoire de la feuille Wildstrubel-Est: , 1958, Problems concerning source and trans- Eclogae geol. Helv., v. 35, no. 2, p. 118-124 portation of Flysch sediments: Geologie en , 1949, Les recurrences lithologiques du sommet Mijnbouw (n. ser.), 20e Jaarg., p. 329-339 du Niesen et leur interpretation: Eclogae geol. Kuenen, Ph. H., and Carpzzi, A., 1953, Turbidity Helv., v. 42, no. 2, p. 426-434 currents and sliding in geosynclinal basins of , 1956, Geologie sedimentaire; Les series the Alps: Jour. Geology, v. 61, p. 363-373 marines: Paris, Masson, 722 p. Kuenen, P. H., Faure-Muret, A., Lanteaume, M., Lugeon, Maurice, 1896, La region de la Breche du and Fallot, P., 1957, Observations sur les Chablais (Haute Savoie): Paris, Libr. Poly- Flyschs des Alpes maritimes francaises et ital- technique, 108 p. iennes: Soc. Geol. France Bull., se'r. 6, t. 7, , 1916, Sur Forigine des blocs exotiques du p. 11-26 Flysch prealpin: Eclogae geol. Helv., v. 14. p. Kiindig, E., 1959, Eu-geosynclines as potential oil 217-246 habitats: 5th World Petroleum Cong. Proc., Lugeon, M., and Gagnebin, E., 1941, Observations sec. 1, paper 25, 13 p. et vues nouvelles sur la geologic des Prealpes Lanteaume, Marcel, 1957, Nouvelles donnees sur le romandes: Soc. vaudoise Sci. nat., no. 47, v. Flysch a Helminthoides de la Ligurie occiden- 7, no. 1, 90 p. tale (Italic): Soc. Geol. France Bull., se'r. 6, t. Me Connell, R. B., 1951, La nappe du Niesen et 6, p. 115-123 ses abords entre les Ormonts et la Sarine: Lemcke, K., von Engelhardt, W., and Fiichtbauer, Materiaux Carte geol. Suisse, nouv. ser., livr. H., 1953, Geologische und sedimentpetro- 95, 94 p. graphische Untersuchungen im Westteil der Mercier, Jacques, 1958, Sur Fage de la phase tecto- ungefalteten Molasse des suddeutschen Alpen- nique "ante-senonienne" a 1'W du Devoluy vorlandes: Beihefte zum Geol. Jahrb., Heft 11, (Dr6me): Soc. geol. France Bull., ser. 6, v. 8, 109 p. no. 7, p. 689-697 Lemoine, Marcel, 1951, Donnees nouvelles sur la Metz, Karl, 1952, Zur Frage voralpidischer geolgie du Brianconnais oriental et sur le Bauelemente in den Alpen: Geol. Rundschau, probleme de la quatrieme ecaille: Soc. Geol. Bd. 40, Heft 2, p. 261-275 France Bull., se'r. 6, t. 1, p. 191-204 Michard, Andre, 1959, Contribution a 1'etude , 1952, Le decollement de la couverture Brian- geologique de la zone d'Acceglio-Longet dans connaise et ses consequences: Acad. sci. (Paris) la haute Varaita (Alpes cottienes, Italie): Soc. Comptes rendus, t. 234, p. 1195-1197 geol. France Bull., ser. 7, t. 1, no. 1, p. 52-61 , 1953, Remarques sur les caracteres et 1'evplu- Migliorini, C. I., 1948, I cunei composti nell'oro- tion de la paleogeographie de la zone brian- genesi: Soc. geol. Italia Boll., v. 67, p. 29 (1949) connaise au Secondaire et au Tertiaire: Soc. Mollet, Hans, 1921, Geologie der Schafmatt-Schim- Geol. France Bull, se'r. 6, v. 3, p. 105-120 bergkette und ihrer Umgebung (Kt. Luzern): , 1954, Documents nouveaux et hypotheses sur Beitr. Geol. Karte Schweiz, Neue Folge, Lief. la stratigraphie des "Schistes lustres" du 3, 66 p. Queyras (Hautes-Alpes): Acad. Sci. Comptes Moret, Leon, 1934, Geologie du massif des Bornes rendus, v. 238, p. 496-498 , 1955, Observations nouvelles sur la strati- et des Klippes Prealpines des Annes et de graphie de la Zone Piemontaise (Schistes Sulens (Haute-Savoie): Soc. geol. France, lustres du Queyras): Carte geol. France Bull., Nouv. Ser., mem. 22, 162 p. v. 52, no. 241 (1954), p. 273-282 , 1954, Problemes de stratigraphie et de tecto- , 1957, Calcschistes pidmontais et terrains a nique dans les Alpes francaises: Univ. Grenoble fades brianconnais dans la haute vallee de lab. geologic fac. sci. Travaux, v. 31, p. 1-38 1'Ubaye (Basses-Alpes): Soc. geol. France C. Nabholz, W. K., 1945, Geologie der Bundner- R. somm., no. 3, p. 41-45 schiefergebirge zwischen Rheinwald, Valser- Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 REFERENCES CITED 905 und Safiental: Eclogae geol. Helv., v. 38, no. 1, Rutsch, Rolf, 1946, Neue Auffassungen fiber die p. 1-119 Entstehung der Molasse-Sedimente: Eclogae , 1951, Beziehungen zwischen Fazies und Zeit: geol. Helv., v. 38, no. 2, p. 407-411 Eclogae geol. Helv., v. 44, no. 1, p. 131-158 Sander, Bruno, 1936, Beitrage zur Kenntnis der Nanny, Paul, 1948, Zur Geologic der Pratigau- Anlagerungsgefuge (Rhythmische Kalke und schiefer zwischen Rhatikon und Plessur: Dolomite aus der Trias): Mineralog. u. Petrog. Zurich, Fretz, 127 p. Mitt., v. 48, p. 27-209 Oberholzer, Jakob, 1933, Geologic der Glarneralpen: , 1941, Zum Gesteinscharakter der Horn- Beitr. Geol. Karte Schweiz, Neue Folge, Lief. steinbreccien des Sonnwendjochgebirges: 28, 626 p. Reichsstelle f. Bodenforsch. Ber., Jahrg. 1941, Ogilvie-Gordon, Maria M., 1927, Das Grodener-, p. 81-89 Fassa- und Enneberggebiet in den Sudtiroler Schaffer, F. X., editor, 1951, Geologie von Dolomiten: Geol. Bundesanstalt (Wien) Abh., Oesterreich, 2d. ed.: Wien, Deuticke, 805 p. v. 24, pt. 1, 376 p. Schardt, Hans, 1898, Les regions exotiques du Parejas, Edouard, 1946, Indices d'une orogenese versant Nord des Alpes Suisses (Prdalpes du dans le Lias moyen du Ferdenrothorn (Loet- Chablais et du Stockhorn et les Klippes): schental) et autres observations: Soc. Phys. Soc. vaudoise Sci. nat. Bull., v. 34, no. 128, p. Hist. nat. Geneve Comptes rendus, v. 63, no. 113-219 1, p. 53-54 Schaub, Hans, 1951, Stratigraphie und Palaon- Peterhans, Emil, 1926, Etude du Lias et des tologie des Schlierenflysches mit besonderer GsSanticlinaux de la nappe des "Prealpes Beriicksichtigung der paleocaenen und untere- medianes" entre la vallee du Rhone et le Lac ocaenen Nummuliten und Assilinen: Schweiz. d'Annecy: Soc. Helv. Sci. Nat. Mem., vol. 62, palaont. Abh., Bd. 68, 222 p. mem. 2, 343 p. Schindler, C. M., 1959, Zur Geologie des Glarnischs: Pia, Julius, 1937, Stratigraphie und Tektonik der Beitr. Geol. Karte Schweiz, Neue Folge, Lief. Pragser Dolomiten in Sudtirol: Vienna, Bres- 107, 136 p. sanpne, Weger, 248 p. Schneegans, Daniel, 1938, La geologic des nappes Prey, Siegmund, 1957, Ergebnisse der bisherigen de 1'Ubaye-Embrunais entre la Durance et Forschungen Uber das Molassefenster von PUbaye: Carte geol. France me'm., 339 p. Rogatsboden (NO.): Jahrb. geol. Bundesanst., Schoeller, Henri, 1929, La nappe de 1'Embrunais au v. 100, p. 299-358 Nord de PIsere: Serv. Carte geol. France Bull., de Quervain, Francis, 1928, Zur Petrographie und no. 175, t. 33, 422 p. Geologic der Taveyannaz-Gesteine: Zurich, Schonenberg, Reinhard, 1956, Ueber das Alters- Leemann, 86 p. verhaltnis von Ophiolithmagmatismus und de Raaf, M., 1934, La Geologic de la nappe du Orogenese im Penninikum der Schweizer Alpen: Niesen entre la Sarine et la Simme: Materiaux Neues Jahrb. Geol. u. Palaont. Monatsh., no. Carte geol. Suisse, Nouv. ser., livr. 68, 105 p. 9, p. 401-410 Rech-Frollo, Marguerite, 1953, Recherche de , 1958, Neue Untersuchungen fiberembryonal e criteres petrographiques de la notion de Flysch: Tektonik: Geologie, Jahrg. 7, Heft 3-6, p. Soc. Geol. France Bull., t. 3, fasc. 7-8, p. 342-352 537-542 Schroeder, J. W., 1939, La Breche du Chablais , 1954, Les gres du Flysch ultrahelvetique des entre Giffre et Drance et les roches eruptives environs de Fribourg (Suisse): Soc. Geol. des Gets: Geneva, Kundig, 138 p. France, C. R. somm., 8th nov., p. 282-284 Schroeder, J. W., and Ducloz, Ch., 1955, Geologie Renz, Carl, 1920, Beitrage zur Kenntnis der Jura- de la Molasse du Val d'llliez (Bas-Valais): formation im Gebiet des Monte Generoso, Materiaux Carte Geol. Suisse, nouv. sen, livr. Kanton Tessin. Eclogae geol. Helv., v. 15, 100, 43 p. no. 2, p. 523-588 Seilacher, Adolf, 1955, Die geologische Bedeutung Richter, D., 1957, Beitrage zur Geologic der Arosa- fossiler Lebensspuren: Deutsche geol. Gesell. Zone zwischen Mittelbiinden und dem Allgau: Zeitschr., Bd. 105, p. 214-227 Neues Jahrb. Geol. u. Palaont. Abh., v. 105, Senn, Alfred, 1924, Beitrage zur Geologie des Heft 3, p. 285-372 Alpensiidrandes zwischen Mendrisio und Richter, Max, 1957, Die Allgau-Vorarlberger Flysch- Varese: Eclogae geol. Helv., v. 18, no. 4, p. zone und ihre Fortsetzung nach W. und E.: 552-632 Deutsche Geol. Gesell. Zeitschr. v. 108, no. 2, de Sitter, L. U., 1939, The principle of concentric p. 156-174 folding and the dependence of tectonical struc- Richter, Max, and Mfiller-Deile, G., 1940, Zur ture on original sedimentary structure: Geologic der ostlichen Flyschzone zwischen Koninkl. Nederlandse Akad. Wetensch. Proc., Bergen (Obb.), und der Enns (Oberdonau): v. 42, no. 5, p. 413-430 Deutsche geol. Gesell. Zeitschr., Bd. 92, Heft de Sitter, L. U., and de Sitter-Koomans, C. M., 1, p. 416-430 1949, The geology of the Bergamasc Alps, Roesli, Franz, 1927, Zus Geologic der Murtirolgruppe Lombardia, Italy: Leidse geol. mededel., pt. bei Zuoz (Engadin): Jahrb. Philosoph. Fakultat 14 B, p. 1-257 II Univ. Bern, Bd. 7, p. 140-156 Soder, P. A., 1949, Geologische Untersuchung der Ruefli, W. H., 1959, Stratigraphie und Tektonik des Schrattenfluh und des sudlich anschliessenden eingeschlossenen Glarner Flysches im Weisstan- Teiles der Habkern-Mulde (Kt. Luzern): nental (St. Galler Oberland): Zurich, Eclogae geol. Helv., v. 42, p. 35-109 Schmidberger and Muller, 194 p. Sonder, R. A., 1939, Meerestiefe und lithologische Rumeau, J.-L., 1954, Gfologie de la region de Fazies: Eclogae Geol. Helv., v. 39, 260-263 Payerne: Paris, Crepin-Leblond, 108 p. , 1940, Uber das Ausmass des alpinen Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 906 RUDOLF TRtiMPY—CENTRAL AND WESTERN ALPS Krustenzusammenschubs: Eclogae geol. Helv., la Lithosphere. II: Orogenese: Paris, Masson, v. 33, no. 2, p. 353-362 940 p. Speck, Josef, 1953, Gerollstudien in der subalpinen Tissot, Bernard, 1955, Etude geblogique des massifs Molasse am Zugersee: Zug, Kalt-Zehnder, du Grand Galibier et des Cerces (Zone brian- 175 p. connaise, Hautes-Alpes et Savoie): Univ. Spengler, Erich, 1927, Ueber die von H. Stille in Grenoble lab. geologic fac. sci. Travaux, v. 32 der nordlichen Kalkzone der Ostalpen unter- (1956), p. 111-193 schiedenen Gebirgsbildungsphasen: Centralbl. Triimpy, Daniel, 1916, Geologische Untersuchungen Min., Geol. Palaont., Abt. B, no. 4, p. 138-148 im westlichen Rhatikon: Beitr. Geol. Karte Staub, Rudolf, 1917, Ueber Faciesverteilung und Schweiz, Neue Folge, Lief. 46, Abt. 2, 163 p. Orogenese in den Schweizeralpen: Beitr. Geol. Triimpy, Eduard, 1930, Beitrag zur Geologie der Karte Schweiz, Neue Folge, Lief. 46, Abt. 3, Grignagruppe am Comersee (Lombardei): 198 p. Eclogae geol. Helv., v. 23, no. 2, p. 379-487 , 1924, Der Bau der Alpen: Beitr. Geol. Karte Trumpy, Rudolf, 1949, Der Lias der Glarner Alpen: Schweiz, Neue Folge, Lief. 52, 272 p. Denkschr. Schweiz. Naturf. Gesell., Bd. 79, , 1937, Gedanken zum Bau der Westalpen Abh. 1, 192 p. zwischen Bernina und Mittelmeer, I. Teil: , 1954, La zone de Sion-Courmayeur dans la Vierteljahrsschr. Naturf. Gesell. Zurich, v. 82, haut Val Ferret valaisan: Eclogae geol. Helv., 140 p. v. 47, no. 2, p. 315-359 (1955) , 1942, Gedanken zum Bau der Westalpen —-, 1955a, Wechselbeziehungen zwischen Palaeo- zwischen Bernina und Mittelmeer, II. Teil: geographie und Deckenbau: Vierteljahrsschr. Vierteljahrsschr. Naturf. Gesell. Zurich, v. Naturf. Gesell. Zurich, v. 100, p. 217-231 87, 138 p. , 1955b, Remarques sur la correlation des , 1948, Ueber den Bau der Gebirge zwischen unites penniques externes entre la Svoie et le Samaden und Julierpass und seine Bezie- Valais et sur 1'origine des nappes prealpines: hungen zum Falknis- und Bernina-Raum: Soc. geol. France Bull., ser. 6, t. 5, p. 217-231 Beitr. geol. Karte Schweiz, Neue Folge, Lief. , 1957, Quelques problemes de palebgebgraphie 93, 57 p. Alpine: Soc. geol. France Bull., s&. 6, t. 7, , 1951, Ueber die Beziehungen zwischen Alpen p. 443-461 und Apennin und die Gestaltung der alpinen , 1958, Remarks on the pre-orogenic history of Leitlimen Europas: Eclogae geol. Helv., v. 44, the Alps: Geologie en Mijnbouw, no. 10, Nw., no. 2, p. 29-130 Ser., Jahrg. 20, p. 340-352 , 1954, Der Bau der Glarneralpen: Glarus, Twerenbold, Eugene, 1955, Les Prealpes entre la Tschudi, 182 p. Sarine et les Tours d'AI. Region des Monts , 1956, Grundlagen und Konsequenzen der Chevreuils: Fribourg, St. Paul, 116 p. Verteilung der spathercynischen Massive im Vonderschmitt, Louis, 1923, Die Giswiler Klippen alpinen Raum: Eclogae geol. Helv., v. 49, no. und ihre Unterlage: Beitr. Geol. Karte 2, 291-311 Schweiz, Neue Folge, Lief. 50, Abt. 1, 37 p. , 1958, Klippendecke und Zentralalpenbau; , 1940, Bericht Uber die Exkursion der Schweiz- Beziehungen und Probleme: Beitr. geol. Karte erischen Geologischen Gesellschaft in den Stid- Schweiz, Neue Folge, Lief. 103, 184 p. Tessin, 30. September-2. Oktober 1940: Eclogae Steinmann, Gustav, 1905, Geologische Beobach- geol. Helv., v. 33, no. 2, p. 205-219 tungen in den Alpen. II: Die Schardt'sche Vortisch, Wilhelm, 1927, Oberrhatischer Riffkalk Ueberfaltungstheone und die geologische und Lias in den nordostlichen Alpen. II. Teil: Bedeutung der Tiefseeabsatze und der ophioli- Jahrb. Geol. Bundesanst, Bd. 77, Heft 1-2, thischen Massengesteine: Ber. Naturf. Gesell. p. 93-122 Freiburg, v. 16, p. 18-67 Vuagnat, Marc, 1952, Pe'trographie, repartition et , 1925, Gibt es fossile Tiefseeablagerungen von prigine des microbreches du Flysch nordhelve't- erdgeschichtlicher Bedeutung?: Geol. Rund- ique: MateViaux Carte geol. Suisse, nouv. ser., schau, Bd. 16, p. 435-468 livr. 97, 103 p. Stille, Hans, 1924, Grundfragen der vergleichenden Wahner, Franz, 1903, Das Sonnwendgebirge im Tektonik: Berlin, Borntraeger, 443 p. Unterinnthal, ein Typus alpinen Gebirgsbaues, Stocklin, Jovan, 1949, Zur Geologie der nordlichen pt. 1: Leipzig and Wien, Deuticke, 356 p. Errgruppe zwischen Val d'Err und Weissenstein Wahner, Franz (and Spengler, Erich, Editor), 1935, (Graubunden): Thesis, Zurich; Innsbruck, Das Sonnwendgebirge im Unterinntal, ein Wagner, 105 p. Typus alpinen Gebirgsbaues, pt. 2: Leipzig Streiff, Victor, 1939, Geologische Untersuchungen and Wien, Deuticke, 200 p. im Ostschams (Graubunden): Zurich, Fluntern, Wegmuller, Walter, 1953, Geologie des Niederhorn- 235 p. Kummigalm-Gebietes (nordostlich Zweisim- Tercier, Jean, 1928, Geologic de la Serra: Materiaux men, Berner Oberland): Wimmis, Ilg, 127 p. Carte geol. Suisse, nouv. ser., livr. 60, 111 p. Weiss, Hans, 1949, Stratigraphie und Mikrofauna , 1939, Depots marins actuels et series geolog- des Klippenmalm: Affoltern, Weiss, 306 p. iques: Eclogae geol. Helv., v. 32, p. 47-100 , 1947, Le Flyscn dans la sedimentation alpine: Wenk, Eduard, 1949, Die Assoziation von Radio- Eclogae geol. Helv., v. 40, no. 2 (1948), p. larienhornsteinen mit ophiolithischen Erstar- 164-198 rungsgesteinen als petrogenetisches Problem: ——, 1952, Problemes de sedimentation et de Experientia, v. 5, no. 6, p. 226-232 tectonique dans les Prealpes: Rev. Questions , 1956, Die lepontinische Gneissregion und die sci. (Louvain), 44 p. jungen Granite der Valle della Mera: Eclogae Termier, H., and Termier, G., 1957, L'Evolution de geol. Helv., v. 49, no. 2, p. 251-265 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021 REFERENCES CITED 907 Weynschenk, Robert, 1949, Beitrage zur Geologic Schweiz. palaont. Abh., Bd. 65, No. 2, p. 1-84, und Petrographie des Sonnwendgebirges pi. 74-76 (Tirol), besonders der Hornsteinbreccien: Inns- Ziegler, W. H., 1956, Geologische Studien in den bruck, Wagner, 66 p. Flyschgebieten des Oberhalbsteins (Graubiin- Widmer, Hans, 1949, Zur Geologic der Todigruppe: den): Eclogae geol. Helv., v. 49, no. 1, 78 p. Wetzikon and Riiti, Buchdruckerei, 97 p. GEOL. i^^ Eroc. TECHN. HOCHSCHULE, Wirz, Albert, 1945, Beitrage zur Kenntnis des SOKNEGGSTEASSE 5, ZURICH 6, SWITZERLAND Ladinikums im Gebiete des Monte San Giorgio: MANUSCRIPT RECEIVED DECEMBER 11, 1959 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/71/6/843/3416896/i0016-7606-71-6-843.pdf by guest on 02 October 2021