The Anatomy of Mountain Ranges

by Jean-Paul Schaer (Editor), John Rodgers (Editor)

Overview

Focusing on mountain ranges that are relatively unfamiliar to most geologists, this work expands our view of tectonics beyond a standardized textbook approach and illustrates both the extraordinary variety of mountain ranges over the world through time and many of the basic similarities they display.

Originally published in 1987.

The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

Product Details

ISBN-13:	9781400858644
Publisher:	Princeton University Press
Publication date:	07/14/2014
Series:	Princeton Series in Geology and Paleontology , #788
Sold by:	Barnes & Noble
Format:	eBook
Pages:	308
File size:	24 MB
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The Anatomy of Mountain Ranges

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By Jean-Paul Schaer, John Rodgers

PRINCETON UNIVERSITY PRESS

Copyright © 1987 Princeton University Press
All rights reserved.
ISBN: 978-0-691-08452-7

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CHAPTER 1

INTRODUCTION: COMPARATIVE ANATOMY IN GEOLOGY

JEAN-PAUL SCHAER

Université de Neuchâtel

Students working in small universities are more and more absorbed by multiple teaching tasks to which are added burdensome management duties. This situation generates a relative isolation that keeps them away from the dynamic impulses of modern research. To enable them to remain in contact with the most active research groups, the French-speaking universities of Switzerland and the University of Bern have joined together to provide postgraduate courses in Earth Science. Every year a set of lectures is organized, taking stock of one modern and important topic.

During the first months of 1982, the University of Neuchâtel was responsible for setting up a series of lectures on the theme "Comparative Anatomy of Mountain Ranges." Guest speakers from Switzerland and abroad presented for the benefit of an attentive audience the results of their research, which covered orogenic belts on almost all parts of the earth (excluding Australia) and of all ages. The course brought out the great complexity of structures, reflecting the diversity of materials involved and the specifics of structural evolution.

Mountain ranges such as the Alps, and even more the Andes, Appalachians, and Himalayas, cover such vast areas that it is almost impossible for a single person to be familiar with all their specific details. The problems of enormous space and limited time thus prevent most researchers from acquiring a firsthand knowledge that extends over many mountain ranges. Because of this limitation, few authors in Earth Science venture into the field of comparative anatomy. Thanks to his relatively broad knowledge of our globe, John Rodgers, who acted as coordinator for the lecture series, could embark in that direction. His comments in the next article must be read with this in mind. To him and to all those who took part in our efforts, we extend our deep gratitude.

Part of the material expounded at Neuchâtel was elaborate enough for publication, and it is gathered here. We regret not being able to include other contributions that brought out specifics of other ranges but also analogies. We hope the material published will prove useful to a wide audience and pave the way for future papers in comparative anatomy in Earth Science.

It may be a cause for wonder that the course on anatomy of mountain ranges was given in Neuchâtel. One must not forget, however, that this small academic town benefits from a strong tradition in the field. Louis Agassiz taught biology here during the past century. More recently, Emile Argand first and then his student C. E. Wegmann contributed much to impregnating Earth Science with this line of thought.

We felt it would be interesting and instructive to sketch some aspects of the lives and thoughts of these researchers in order to highlight the richness and strength of this method of investigation. From this standpoint, our aim would remain unfulfilled if we did not first recall the man who founded the discipline, the great Georges Cuvier (1769–1832), who was born in Montbeliard, a French city (at that time attached to the Duchy of Württemberg) not far from the Swiss border.

As soon as he had given its lettres de noblesse to comparative anatomy using anatomical structure and its evolution as a basic principle, Cuvier set about to make it the foundation for all animal classification. By systematic comparison of the architecture of living organisms and their fossil remains, he demonstrated that the past must be considered when one is studying the organization of the entire animal world. From the beginning of his research he insisted on the importance of the connections that must exist between the various organs in order to make of them a living unit. He understood that certain functions have such a determining influence on the organism that they can easily be used as a general guide to classification; thus, for him, the nervous system gave the phyla, the respiratory and circulatory organs gave the classes.

In geology to this day, the classifications of mountain ranges are based mostly on positional criteria (ocean-continent, continent-continent collision ranges; intracratonic chains; and so forth). One may ask whether there are other parameters with enough influence to impose some structural specificities while excluding others (presence of large granitic batholiths, evolution of sedimentary basins, deformation style, and metamorphic regimes, for example). For Cuvier, the anatomical characteristics that distinguish groups of animals are the proof that different species have not altered since their creation. Can the structural analogies that have been described between young ranges and old ones be taken as proof that our earth and its continents have been evolving for 2,000 or 3,000 Ma (Ma = million years) in an at least similar if not identical fashion? It took Darwin and those who followed him to integrate into comparative anatomy all the riches of ontogeny, embryology, and, above all, phylogeny, which, because it encompasses lines of descent, spreads into the field of paleontology. At this level of research, both the zoologist and the paleontologist know that their documentation is incomplete, because the softer parts of animals very rarely leave any fossil traces and because it is virtually impossible to know all the elementary mutations which, when accumulated along an evolutionary line, can produce perhaps the modifications leading to new species. The geologist studying mountain ranges is put into an even more difficult position since he can only contemplate a very thin slice of the crust (15 km in favorable zones). It is true that, for the past few years, modern geophysics has been bringing forth new information about the specifics of deep zones; this information holds the promise of fruitful comparisons. Although the task is complex, it is important to remain optimistic and to follow Cuvier who stated, in the preface to his work "Recherches sur les ossements fossiles des quadrupèdes," "As antiquarian of a new species, I had to learn how to decipher and restore these monuments, how to recognize and bring together in their primitive order the scattered and mutilated fragments of which they are composed" (Cuvier 1812). This is precisely the object of our study when we set out to classify, analyze, and understand mountain ranges by using the mutilated fragments left to us by successive erosion periods.

Jean Louis Rodolphe Agassiz (1807–1873), born at Môtier in the Swiss canton of Fribourg, was the son of a clergyman whose family originated from the villages of Orbe and Bavois in the canton of Vaud. Agassiz was educated first at Bienne and then for two years at Lausanne Academy. He was a student at the Universities of Zurich, Heidelberg, and Munich, and he finished his studies with a Doctor of Philosophy degree at Erlangen and a degree in medicine at Munich (1830). At the age of 22 he had already published an important paper about fish brought back from Brazil by a German expedition. He dedicated this work to Cuvier, and in his accompanying letter to Cuvier the young author expressed both his admiration for the great teacher and his ambition to study natural sciences even in the face of his precarious financial situation.

Agassiz received a very encouraging reply from Cuvier, informing him that the results described in his publication would be incorporated into the second edition of "Le Règne animal." Agassiz returned to Switzerland for a few months and then left for Paris, passing through Germany where, with the help of his draftsman Dinkel, he studied fossil fish in a number of museums. In Paris he met Cuvier, who was at first somewhat reserved toward him but was soon won over by the young naturalist's enthusiasm and knowledge and by the quality of his work. The friendship between the two men soon became so close that Cuvier gave Agassiz all the documents he had collected concerning fossil fish. With this gift the teacher indicated clearly that he was abandoning his own research on the subject.

Agassiz was scientifically more active than ever, yet he found time to make contact with such interesting people as Alexander von Humboldt, who was in Paris at the time as the personal representative of his king, Frederick William III of Prussia, to Louis Philippe of France. Humboldt loved to encourage young talent and was generous with his time and money. He made Agassiz his protégé and passed on to him his own scientific conception of the world, also impressing upon his young disciple the importance of public relations for someone who is going to make a career in science. Humboldt's example and teaching played a decisive part in Agassiz's education, for it proved to be the basis of his success in America, where his career depended as much on charm and public relations as on scientific knowledge.

In the last phase of his training in Paris, Agassiz was profoundly influenced by Cuvier, so much so that for the rest of his life he considered him his only teacher, the one who enlarged his scientific concepts by explaining to him that precise analysis and patience with facts must always take precedence over theoretical ideas, interpretations, and synthesis. Unfortunately, this period of training was very short, less than six months, because Cuvier died in May 1832. Agassiz thus found himself alone with his enormous projects and as always without financial help. Thanks to the generosity of some citizens of Neuchâtel, enough money was gathered to offer him the position of Professor of Natural Science in their town. Because it gave him the opportunity to live near his family again in a country that he knew and loved, he accepted the offer, arrived in Neuchâtel in September 1832, and wasted no time in getting down to work. In addition to his teaching, he took in the same year a leading role in the founding of the local Society of Natural Science, which immediately impressed the scientific world by the high quality of its publications. Agassiz also became Director of the Museum of Natural History, and an extraordinary scientific activity inflamed the little provincial town, where the population at that time was no more than 5,000. In those days Neuchâtel, as a principality of the King of Prussia, was still dependent on Berlin. For Agassiz this was most fortunate, since it was again possible for him to benefit from Humboldt's generous protection.

During the period Agassiz lived in Neuchâtel, his scientific activity was superlative in both quality and quantity. The spiritual inheritance from Cuvier is present throughout Agassiz's work. For him, meticulous observation remained the basis of sound research, but not carried out blindly, in view of the intensity and diversity of the living world. Major efforts were to be directed toward subjects that offered the best opportunity to improve knowledge. Certain classes of fossils, like the extremely well-preserved echinoids, were ideal material for a better understanding of the past world and its organization (Agassiz et al. 1838–1842). A sum of characteristics was often a more reliable criterion for classifying organisms than was any specific function, however well-defined. But Agassiz also insisted that study of a part, or a function, when carried out in all its detail, would always promote discoveries relating to the entire system. When one has a good knowledge of some important organs, it becomes possible to imagine or even to describe elements that should coordinate them even if they have not been preserved. The constraint of organized life offers a better approach to truth than does an uncontrolled imagination (Agassiz 1833–1843).

Emile Argand (1874–1940) was born in Geneva. His life and work have been admirably described by his teacher Maurice Lugeon (1940). Here only some striking aspects of the career of this exceptional man can be presented. All those who knew him were impressed by his amazing visual memory; he was able to draw a map of any part of the world from memory with amazing accuracy. Certainly, he had strengthened this gift when, on leaving college, he did his apprenticeship as a draftsman. Before devoting his life to geology, he studied medicine for 2 years, until the age of 23, and it was probably then that he received a solid grounding in anatomy. Throughout his life Argand stressed the importance of geometry and precise drawing, and several of his papers are accompanied by beautiful sections, admirably drawn not just for themselves but to enable the reader to have an exact picture of volumes which, as they are constantly modifying with time, imply permanent work within this supplementary dimension. His geometric analysis is governed by the cylindrical principle, though not as rigidly as once thought, since it is softened and guided by axial variations that show the relative plasticity of materials and the heterogeneity of obstacles. Axial variations in the vertical plane are above all important for deciphering deep structures to a depth of 20 to 40 km. After 1912, probably about 1914, Argand discovered Alfred Wegener's work, and its broad vision reinforced his own enthusiasm from then on. From his research on the topography and geometry of the Central Pennine Alps, he developed a powerful technique that enabled him to understand the architecture, the deformations, and the movements not only of the Alps but also of the continents, which fell into an order that is perfectly coherent both for the time and the future. Already in his paper "Sur l'arc des Alpes occidentales" (Argand 1916), nearly all the "argandian" message is clearly given. The analysis focuses on the core of the alpine structure, showing how the superficial character of the deformation of the Austro-Alpine nappes contrasts with the plastic style of the Pennine folds, which in turn impose their style on deeper zones.

Argand then took a great interest in recent ranges, especially those of East Asia, because they show side by side and simultaneously the successive stages through which more evolved chains have passed. Thus comparative anatomy allowed Argand to go back in time, and it led to a concept of tectonic embryology (Figure 1-1). Even if continental drift is not directly referred to, the whole evolution of the geosynclinal domain is already visualized as the consequence of tangential movements affecting rigid blocks, which as they approach deform plastically the large marine zone separating them.

In 1924 Argand's masterwork, The Tectonics of Asia, appeared. Its message is a direct continuation of Edward Suess's work, "Das Antlitz der Erde," which the teacher from Vienna had finished a few years earlier, and which presents an analytical geological description of the entire earth. Argand admired this work so much that he referred to it in the first line of his text. But for Argand the analysis and the description of structures had to be pushed still further to include studies of different scales, from continents to thin sections. These static images must be used to discover at each instant the evolution of volumes in time, to create an animated picture. It should be possible to place all observations in the framework of the unitary theory of Wegener's continental drift, a theory full of force, flexibility, and possibilities of invention. All the structures should fall into place as functions of displacement and of the relative plasticity of the deformed materials and preexisting structures. Anatomy, the geometry of structures, was the basic science that permitted one to control imagination. In 1927 the Academy of Science in Paris awarded the Prix Cuvier to Argand for the whole of his work, without underlining, as might have been expected, the spiritual line of descent that joins the zoologist to the geologist, and the essential contribution of the latter to this new form of comparative anatomy.

(Continues...)

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Table of Contents

• FrontMatter, pg. i
• Contents, pg. v
• Contributors, pg. vii
• Chapter 1. Introduction: Comparative Anatomy in Geology, pg. 3
• Chapter 2. Differences between Mountain Ranges, pg. 11
• Chapter 3. Tectonic Framework of Precambrian Belts, pg. 19
• Chapter 4. A Tectonic Model for the Crustal Evolution of the Baltic Shield, pg. 31
• Chapter 5. The Lower Allochthon in Southern Norway: An Exhumed Analog of the Southern Appalachians Deep Detachment?, pg. 59
• Chapter 6. The Structure and Evolution of the Hercynian Fold Belt in the Iberian Peninsula, pg. 65
• Chapter 7. Evolution and Structure of the High Atlas of Morocco, pg. 107
• Chapter 8. The Pan-African Belt of West Africa from the Sahara Desert to the Gulf of Benin, pg. 129
• Chapter 9 Tectonic Evolution of the Southern Andes, Tierra del Fuego: A Summary, pg. 173
• Chapter 10. Structure and Evolution of the Peruvian Andes, pg. 179
• Chapter 11. The Kinematic Puzzle of the Neogene Northern Andes, pg. 211
• Chapter 12. The Tectonics of Táchira: A Sample of North Andean Tectonics, pg. 229
• Chapter 13. The Appalachian Geosyncline, pg. 241
• Chapter 14. Comparative Studies on Profiles across the Northwest Himalayas, pg. 261
• Chapter 15. The Active Taiwan Mountain Belt, pg. 277
• INDEX, pg. 295