Permanence Of Continents Research Articles

Ophiolites in ocean–continent transitions: From the Steinmann Trinity to sea-floor spreading

Before the theory of plate tectonics took hold, there was no coherent model for ocean–continent transitions that included both extant continental margins and fragmentary ancient examples preserved in orogenic belts. Indeed, during the early 1900, two strands of thought developed, one relying on the antiquity and permanence of continents and oceans, advocated by the mainstream of the scientific community and one following mobilist concepts derived from Wegener's hypothesis (1915) of continental drift. As an illustration of the prevailing North-American view, the different composition and thickness of continental and oceanic crust and the resulting isostatic response showed “how improbable it would be to suppose that a continent could founder or go to oceanic depth or that ocean floor at ± 3000 fathoms could ever have been a stable land area since the birth of the oceans” [H.H. Hess, Trans. R. Soc. London, A 222 (1954) 341–348]. Because of the perceived permanence of oceans and continents, mountain chains were thought to originate from narrow, elongated, unstable belts, the geosynclines, circling the continents or following “zones of crustal weakness” within them, from which geanticlines and finally mountain belts would develop. This teleological concept, whereby a geosyncline would inevitably evolve into a mountain chain, dominated geological interpretations of orogenic belts for several decades in the mid-twentieth century. However, the concept of permanence of oceans and continents and the concept of the geosyncline had already met with the critiques of Suess and others. As early as 1905, Steinmann considered the association of peridotite, “diabase” (basalt/dolerite) and radiolarite (a typical ocean–continent transition assemblage), present in the Alps and Apennines, as characteristic of the deep-ocean floor and Bailey (1936) placed Steinmann's interpretation into the context of continental drift and orogeny. Indeed, in both authors’ writings, the concept of ophiolites as ocean crust is apparent. Between 1920 and 1930, the stage was thus potentially set for modern mobilist concepts that were, however, to prove attractive to only a small circle of Alpine and peri-Gondwanian geologists. After the Second World War, the 1950s saw the rapid progress of the geophysical and geological exploration of oceans and continental margins that provided the data for a reevaluation of the geosynclinal concept. Actualistic models now equated the former preorogenic miogeosyncline of Stille (1940) and Kay (1951) with passive continental margins [C.L. Drake, M. Ewing, G.H. Sutton, Continental margin and geosynclines: the east coast of North America, north of Cape Hatteras, in: L. Ahrens, et al. (Eds.), Physics and Chemistry of the Earth 3, Pergamon Press, London, 1959, pp. 110–189], the (American version of the) eugeosyncline and its igneous rocks with “collapsing continental rises” [R.S. Dietz, J. Geol. 71 (1963) 314–333] and the ophiolites, the Steinmann Trinity, of the (European) eugeosyncline with fragments of oceanic lithosphere [H.H. Hess, History of ocean basins, in: Petrologic Studies: a Volume to Honor A.F. Buddington, Geol. Soc. Am., New York. 1962, pp. 599–620]. The concept of sea-floor spreading [H.H. Hess, History of ocean basins, in: Petrologic Studies: a Volume to Honor A.F. Buddington, Geol. Soc. Am., New York. 1962, pp. 599–620; H.H. Hess, Mid-oceanic ridges and tectonics of the sea-floor, in: W.F. Whittard, R. Bradshaw (Eds), Submarine Geology and Geophysics, Colston Papers 17, Butterworths, London, 1965, pp. 317–333] finally eliminated the weaknesses in Wegener's hypothesis and, with the coming of the “annus mirabilis” of 1968, the concept of the geosyncline could be laid to rest. Ocean–continent transitions of modern oceans, as revealed by seismology and deep-sea drilling, could now be compared with the remnants of their ancient counterparts preserved in the Alps and elsewhere.

Ancient oceans and continental margins of the Alpine‐Mediterranean Tethys: deciphering clues from Mesozoic pelagic sediments and ophiolites

AbstractIn contrast to Northern Europe where, in the 19th Century, a coherent lithostratigraphy and biostratigraphy was established, many of the ‘odd rocks of mountain belts’ (as christened by Alfred G. Fischer) of the Alpine‐Mediterranean region defied an easy interpretation in terms of the simple English layer‐cake stratigraphy mapped by William Smith. However, as early as 1862, Eduard Suess recognized close affinities between Mesozoic faunas of the Alps and those of the Himalaya. Suess also described many such Alpine sedimentary rocks as pelagic (a term discussed by Antoine Lavoisier in the context of sea‐level change), and the results of theChallengerExpedition (1872 to 1876) convinced the Viennese school of geologists of their deep‐water nature. Based on the composition of Jurassic–Cretaceous faunas, Melchior Neumayr postulated the existence of an equatorial ocean, the ‘Central Mediterranean’ which extended from Central America through the Alpine belt to the Himalaya and beyond, an ocean which Suess subsequently named ‘Tethys’. The question of whether or not deep‐sea sediments could occur on land, as deliberately posed by Gustav Steinmann in 1925, became central to the long‐lasting controversy on the permanency of continents and ocean basins. Indeed, the occurrence of deep‐sea deposits in mountain belts required the disappearance of oceanic areas and a mobilist concept of orogeny that was subsequently applied to the Tethyan region by Emile Argand in the wake of the continental drift hypothesis of Alfred Wegener. Implicit in the views of Wegener and Argand is the concept of an oceanic crust fundamentally different from that of the continents. Although ophiolites had been recognized as a special group of rocks in the early 19th Century, Steinmann was the first to interpret the association of (serpentinized) peridotite, ‘diabase’ (dolerite–basalt) and radiolarite (Steinmann Trinity) in a geodynamic context and to consider it as characteristic of the deep ocean. The comparison of Alpine radiolarites with Recent radiolarian oozes deposited below the calcite compensation depth did not remain unchallenged, because of the local association of these siliceous rocks with coarse clastic deposits. However, after the advent of the turbidity‐current hypothesis, these detrital deposits were reinterpreted as submarine mass‐flow deposits. Consequently, such typical Tethyan facies asRosso Ammonitico,Maiolica/Bianconeand black shales, found in close stratigraphical association with the radiolarites, could be interpreted as deposited on deeply submerged continental and/or oceanic crust where they recorded faithfully a range of interdependent palaeoceanographic phenomena: changes in the relative proportion of siliceous, carbonate and organic‐walled biota, in carbonate saturation of sea water, in oceanic circulation and in the impact of orbital‐climatic cycles. The results of the Deep Sea Drilling Project, with its discovery of typical Jurassic and Cretaceous Tethyan facies in the Atlantic Ocean, dramatically confirmed the early interpretations of European geologists of the 19th and early 20th Centuries.

Are there ancient deep-sea deposits of geologic significance?

Today, when the permanency of continents and of the Pacific is a favorite topic of scientific discussion, with the breakup of an ancient landmass into today’s continents (as proposed by Wegener) high on the agenda and even accepted by some as firmly established, the need for an accurate answer to the above question seems especially urgent — for the answers given are entirely irreconcilable, as is well known. There are researchers who categorically deny the occurrence of deep-sea deposits on today’s landmasses, as do Dacque, Deecke, Scrivenor, Soergel, Walther and others, and on the other hand, there are those who admit a not insignificant dispersion on today’s landmasses of such deposits, and thus a considerable importance for the problems of geogeny, as does this author and, with him, many others such as Andree, Cornelius, the two Heims, Hinde, Kober, Molengraaff, Neumayr, Nicholson, Parona, Suess, Staub, Uhlig, and Wahner.

Biogeography and biogeographical principles

A fundamental problem of biogeography is whether it is an independent, primary discipline with its own methods and principles, or whether it is a secondary discipline dependent on some other branch of science, such as geology. Historically this problem first emerged in the work of Charles Darwin. Darwin in his first “Transmutation of Species” notebook (1837-1838) used biogeographic evidence to erect novel geological hypotheses. These included a continental drift theory in which all the continents were grouped together into the middle of the Pacific Ocean, greatly increasing the width of the Atlantic Ocean (Fig. 1). Subsequently in his “On the Origin of Species” (1859) he rejected that view and argued vehemently in favour of the permanence of continents and oceans (Fig. 2). In his mature work particular geological theories were used as the basis upon which biogeographic narratives were constructed. Alfred Wegener's continental drift theory (1929) differed from Darwin's in that it united the North and South...

Geologic History of Oceans: Introduction: ABSTRACT

Only a few years have passed since the concepts of the permanence of continents and ocean basins and the stability of the oceans were widely accepted, and the notion of continental drift was regarded as heresy. Since inception of the programs of deep ocean coring, however, a major new body of data has appeared. Many of the new observations are in conflict with traditional ideas. It has become evident that the oceans have a fascinating and complex history, and the history of ocean chemistry appears to be inextricably interwoven with the development of oceanic organisms. It had been tacitly assumed by many geologists that the oceans constituted a massive buffer system, stabilizing climate and affecting geochemical processes on the surface of the earth and in its atmosphere. Now deep-sea sediments are known to bear a record of dramatic changes, some local, some of worldwide significance. It is the purpose of this symposium to explore new ideas which are being generated, and to provide a synthesis of the present state of knowledge concerning the history of the oceans. End_of_Article - Last_Page 341------------

Permanency of Continents and Ocean Basin Lineations

CARR1 recently proposed that the close correspondence between lineations on continents and the ocean floor and a theoretical shear net calculated by Vening Meinesz2 militates against the hypothesis that the continents have drifted since Pre-Cambrian time. The long linear sea floor fracture zones, all discovered since Vening Meinesz drew his net, are admirably suited for testing such a correspondence. Some appear on the charts used in Carr's investigation, but many newly discovered ones do not. The whole pattern of fracture zones does not show a significant correlation with the shear net.

Deep-Sea Deposits in But Not on the Continents

The early principle of geology that deep-sea deposits do not occur on continents has been seriously challenged by both paleontologists and marine geologists. So, in turn, has the dependent Doctrine of Vertical Permanency, according to which elevator tectonics with relative changes between ocean basin and continental levels do not take place. (Other aspects of permanency, such as permanency of continents in position as opposed to drift, or of their areal plan as opposed to accretion, are independent questions.) The writers agree with those who ascribe a deep-sea (>2,000 meters) environment to radiolarian cherts, graptolite shales, and graywackes. Recognition of the role of turbidity-current emplacement has altered the interpretation of much of the evidence for these lithofacies being shallow-water beds, e.g., sandstone layers, current ripples, neritic faunal remains, and plants. From a world-wide review of the well-known localities, the writers find, however, that such hemipelagic deep-water deposits are confined uniquely to the eugeosynclinal facies. It is suggested that this facies is deposited originally at the base of the continental slope as a continental-rise prism; hence, it is ensimatic rather than ensialic as are other marine deposits found on continents. Subsequently, landward t rusting causes continental accretion and orogeny. The collapsed eugeosynclinal prism thus becomes a part of the deep continental fabric. The incorporated deep-sea sediment may be considered conveniently as being in the continent. By this proposed process, the Doctrine of Vertical Permanency is sustained even though deep-sea deposits do bulk large in eugeosynclinal flysch.

West African Fold Belt

A belt of folded early and middle Paleozoic rocks extends along the Atlantic coast of Africa from Morocco at least as far south as Senegal. East of the belt is a flat-lying section of chiefly clastic rocks which overlaps the Precambrian African Shield. The belt comprises a bordering folded zone and an inner zone exhibiting strong deformation, dynamic metamorphism, and possible igneous intrusions. There is evidence of an erosional hiatus associated with the Caledonian, but the main fold movements were post-Devonian (Hercynian). After uplift and erosion, portions of this orogenic belt were obscured by the deposition of Mesozoic and Tertiary sediments along the downwarped coastal zone. The author proposes the name Mauritanides for the Paleozoic orogenic belt of West Africa. This feature should be considered in future speculations regarding continental drift and the permanence of continents.

XIII.—The Evolution of Continents: A Possible Reconciliation of Conflicting Evidence

In a letter to Nature published in 1881, J. D. Dana recapitulated his reasons for suggesting, first in 1846 and on frequent occasions afterwards, that “the continents have always been continents … and have never changed places with the oceans.” This view of the permanency of continents and oceans became generally adopted by Sir Charles Lyell (1868) and other leading naturalists during the middle of the last century: it became recognised as what might be called the orthodox doctrine.

A CONTRIBUTION TO THE GEOLOGICAL HISTORY OF THE NORTH ATLANTIC REGION

There may be said to be two main branches of geological investigations the physical and the biological—not, of course, that these can be regarded as independent or divorced from each other, but to a certain point they can make their contributions independently. For a full history, the physical and the biological changes must be known and their mutual relationship understood. It seems possible, however, that the physical history of the earth is likely to be known in much greater detail than that of the fauna and flora, for the “dry lands,” tenanted as they undoubtedly were by various forms of life, have left behind a record which can be fairly well traced on the physical side but will always refuse to yield up all its secrets on the biological side, since only rarely have the land animals and plants been preserved by a lucky chance in the rocks accumulating at the time of their existence. The permanence of continents and ocean-basins has long been a subject of controversy. Lyell, in his “Principles of Geology,” makes reference to the early ideas of the Mediterranean peoples on this subject, while Lyell himself was of opinion that continents and ocean-basins do change places in the course of ages. This idea was early challenged by both physicists and biologists. The physicists, led by Lord Kelvin, regarded the general framework of the earth as having been fixed in very early times, and Kelvin considered that the oceans and continents may have been mapped out ...

The Permanence of Continents and Oceans

I CAN find no flaw in the reasoning on the dynamical question of the permanence of continents and oceans, in Mr. Starkie Gardner's letter in NATURE of December 5 (p. 103), by which he endeavours to show the universal “tendency for deep oceans to become deeper, and for mountain chains to grow into higher peaks.” But when he says it is opposed to no known facts, I wish to ask how it is to be reconciled with the fact of the general distribution of marine deposits over the face of the earth, so that every part of what is now land appears to have once been ocean?

Permanence of Continents & Ocean-Basins, with Special Reference to the Formation and Development of the North American Continent

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

I.—On the Permanence of Continents and Ocean-Basins, with Special Reference to the Formation and Development of the North American Continent

Under the influence, perhaps, of the prevailing idea of evolution in all things, the conviction has been growing in the minds of geologists in recent times that the larger features of the earth's surface have grown from the earliest times, and therefore that the places of the continents and ocean-basins have been substantially permanent. Prof. Dana is largely the originator and expounder of this view, and he has applied it with great skill to the American continent. But while I believe the view is substantially true, I cannot but think that it may be, and has been, pushed too far. It is true indeed that the opponents of the view have attributed to its advocates a strictness in the use of the term ‘permanent’ which they have never urged. It is true that by permanence is meant only permanence of place, not of outline, and that substantial permanence is not inconsistent with very large changes by oscillation, especially at the end of the great Eras. But, making every allowance for such latitude of meaning, there has been, undoubtedly, some confusion of thought and looseness of statement on this subject. We give a few examples.

Permanence of Continents and Oceans

MANY naturalists are accustomed, in lecturing, to speak of the existing ocean basins as “permanent.” Though this must to a large extent be a true statement, many geologists at all events must be perfectly aware that the former distribution of life requires that nearly all lands, however remote at present, must have been, perhaps more than once, in connection with each other. Tropical South America is perhaps the most isolated continental province now existing. I would ask these naturalists to explain how its species of tropical genera not peculiar to it got there, and how many of them came to be represented in Europe in Tertiary times.

The Permanency of Continents

As a small contribution to this theory, the Cornish beaches may furnish a quota. They are entirely composed of finely comminuted shells, with a small admixture of fragments of Bryozoa, spines of minute Echinoderms, and occasional mica flakes. Such sandy beaches occur in small bays, and if subjected to metamorphic action would form lenticular masses of limestone intercalated between the strata deposited above and below them. Hence such occurrences of limestone might well indicate such a littoral origin as is here displayed.

IV.—The Fallacy of the Theory of the “Permanence of Continents”

It is rather remarkable that the Theory of the Permanence of Continents and Oceans has passed so comparatively unchallenged by geologists. I long since attempted to show that Mr. Wallace's supposition that the Chalk was a shallow and littoral sea deposit was untenable. In comparing analyses of chalk, as he does, with Atlantic ooze, no allowance whatever is made for the loss of iron from the body of the chalk by crystallization, nor for the segregation of silica into flints. The Chalk may have undergone so great a change in addition, since its upheaval vast ages ago, through the removal of some of its constituents by percolating water, that comparative analyses can only be of value when these losses are taken into consideration.