yeti T @?@ShOO0 TOEO OC CM IOHM/1ElN | Daniel Merriman | Crew Member on the maiden voyage of the R/V Atlantis Corporation Member, IS41-79 Trustee, 1944-64 Honorary Trustee & Corporation Member, 1979-84 Oceanographer, Writer, Editor, Fisherman, Educator, Mentor vit ied Lye fy a aie al) We MPA Tar Lil a eed ee ul YALE UNEVERSIPY MRS HEP SAGCELY 2S LEE IMAN MEMORDAL LECTURES Hans Pettersson THE OCEAN FLOOK New Haven: Yale University Press, 1954 London: Geoffrey Cumberlege, Oxford University Press Copyright, 1954, by Yale University Press. Printed in the United States of America by Vail-Ballou Press, Inc., Binghamton, New York. All rights reserved. This book may not be reproduced, in whole or in part, in any form (except by reviewers for the public press), without written permission from the publishers. Library of Congress catalog card number: 54-9521 To My Collaborators on the “Albatross” Mal) The Silliman Foundation In the year 1883 a legacy of eighty thousand dollars was left to the President and Fellows of Yale College in the city of New Haven, to be held in trust, as a gift from her children, in memory of their beloved and hon- ored mother, Mrs. Hepsa Ely Silliman. On this foundation Yale College was requested and directed to establish an annual course of lectures de- signed to illustrate the presence and providence, the wisdom and goodness of God, as manifested in the natural and moral world. These were to be designated as the Mrs. Hepsa Ely Silliman Memorial Lectures. It was the belief of the testator that any orderly presenta- tion of the facts of nature or history contributed to the end of this foundation more effectively than any at- tempt to emphasize the elements of doctrine or of creed; and he therefore provided that lectures on dog- matic or polemical theology should be excluded from the scope of this foundation, and that the subjects should be selected rather from the domains of natural science and history, giving special prominence to astronomy, chemistry, geology, and anatomy. It was further directed that each annual course Vili Vill THE OCEAN > FLOGE# should be made the basis of a volume to form part of a series constituting a memorial to Mrs. Silliman. The memorial fund came into the possession of the Cor- poration of Yale University in the year 1901; and the present work constitutes the thirty-third volume pub- lished on this foundation. Preface By the terms laid down for the lectures given in memory of Mrs. Hepsa Ely Silliman, these are “de- signed to illustrate the presence and providence, the wisdom and goodness of God, as manifested in the natural and moral world.” I believe it is true to say that nowhere on our planet’s surface is there less interference by men with the acts of providence than in great ocean depths, where natu- ral laws have reigned supreme for untold millions of years, in fact since the birth of the ocean itself. It therefore seems to me that the subject discussed in the following pages fits well within the frame of the Act of Foundation. It is for me a great privilege and honor to have been invited to give the Silliman Lectures of 1952 on “The Floor of the Ocean.” The deep ocean has recently come to the foreground of geophysical and geochem- ical investigations, thanks largely to new instruments and new methods of research which were used for the first time by the Swedish Deep-Sea Expedition of 1947— 48. About one-half of the planet’s total surface, con- siderably exceeding in area all the five continents x X THE ,OCEAN EEG@@e taken together, is covered by water masses from one to six miles thick. Only the uppermost surface of this enormous lowland has so far been accessible to in- vestigation, and a relatively small number of sediment samples have been raised from great depths. It seems likely that the new science of submarine geology will be much advanced during the latter half of this cen- tury. Many problems concerning the deep-sea deposits —their structure, their composition, and their origin— will be elucidated through future international efforts in deep-sea research. I owe a debt of gratitude to David H. Horne for clarifying the English of the manuscript, making the index, and helping to see the book through press. HANS PETTERSSON Goteborg, 1954 Table of Contents Preface ks ON LO: The Oceans and Their History 2. Envisaging the Past and Future 3. Exploring the Ocean Floor 4. 5 . Recent Developments in the Investigation of the The Sediment Carpet and the Substratum Deep Ocean Floor . The Deep-Sea Deposits and Their Stratigraphy . Recent Investigations on the Stratigraphy of Deep-Sea Sediments . Deep-Sea Radium and the Geochronology of the Ocean Floor . The Bottom Waters of the Ocean and Their Movements Life in Great Depths Notes Index pal 101 1h 53 fl 167 LW) Illustrations 1. Terra Australis (Mercator, 1587) . The Atlantic Ocean on a half-desiccated earth (Endeavour, 1949) . The Antarctic bottom current in the Atlantic (Wust) . The Pacific and Indian Oceans on a half-desiccated earth (Schott) . Depths in the Indian Ocean (Fairbridge ) . Distribution of ocean and land in Mesozoikum (Gregory ) 7. Map of the Oceans in the Eocene (Von Ihering) 8. Birth of the Atlantic Ocean (Wegener ) 9. Vertical section of a guyot (Hess) 10. er. | Gm 13. 14. Seascape of a half-desiccated earth (by permission of the artist, Chesley Bonestell) Alexander the Great in his diving bell (““Pseudo- Kallisthenes” ) Prince Albert I of Monaco Ocean depths between Madeira, the Canaries, and Gibraltar (Schott) Kullenberg’s piston corer xii 23 26 29 31 35 XIV THE OCEAN FLOOR . Progress in length of sediment cores 36 . The “Albatross” under sail 39 . The course of the “Albatross” 40 . Diatom ooze 49 . Radiolarian ooze (radiolarit ) 50 . Manganese nodule halved (Koczy ) on . Distribution of pelagic sediments (Sverdrup) a . Weibull’s scheme for reflection measurements 56 . Diagram from Weibull’s measurement 57 . Sediment thicknesses found by Weibull 59 . Model from Cloos’ experiment 68 . Corer bent against lava bed (Eriksson) gf" . Ash rain over the Tyrrhenian Sea 78 . Deep-sea core from near Cyprus 80 . Diatoms from the spring flowering 83 . Radiolarians from Pacific depths 84 . Tooth from giant shark (Challenger Reports ) 85 . Vertical circulation near the Equator (Defant) 9] . Sand from the Romanche Deep (Locher ) 95 . Stratified cores from the equatorial Atlantic (Mellis ) 96 . Submarine weathering (Mellis), plagioclase to orthoclase (Mellis) 99 . Abrupt drop in number of radiolarians (Riedel) 107 . Lime and manganese distribution in sediment core from the Romanche Deep (Berrit) 110 . Equipment for radium measurement (Kroll) 117 aD. 40. 4]. 42. 43. 44. 4S. 46. 47. 48. ILLUSTRATIONS Radium distribution in the central Pacific (Oc> Inst: ) Radium distribution in the western Pacific (Kroll) Radium distribution in the Romanche Deep (Kroli) Radium determination in a manganese nodule Water sampling near bottom (Koczy) Turbidity near bottom (Jerlov) Types of turbidity changes near bottom (Jerlov) Changes in water near bottom (Koczy) Deep-sea fish after a square meal (Murray-Hjort) Our largest deep-sea fish (R. Pettersson) XV i) 119 126 128 136 139 £359 141 156 158 1. The Oceans and Their History Bsc thousands of years men have been scanning the ceiling of our universe, the vaults of Heaven. The stars in their courses have stimulated the imagination and fostered belief in ultimate things. Today, thanks to the magnificent resources of modern astronomical observa- tories, especially in America, we are able to probe the remotest spaces of our universe and study galaxies separated from our own small world by hundreds of millions of light-years. Modern physics has shown us how to interpret the faint light signals transmitted to us across enormous gulfs in space. On the other hand, the oceans around us were long neglected. Five centuries ago explorers began to steer their frail ships across the unknown ocean, discovering new continents, but for obvious reasons their interest was limited to the ocean surface, and the great depths beneath remained unknown and unexplored until less than a century ago. True, pioneers of the new science of oceanography had made some earlier attempts to learn how deep the ocean is, the temperature of the water at great depths, and the character of the sediments which carpet the ocean floor, but their tools of research l 2 THE OCEAN. EFLOGS were altogether inadequate for measuring very far below the surface. To our ancestors it was a source of astonishment, not to say dismay, that the Creator in dividing our planet between land and sea should have given an unfairly large share to the barren ocean, as compared to the fruitful continents on which we, his specially favored children, have been allowed to dwell. This apparent dispropor- tion gave rise to hopes of discovering a vast new conti- nent in the southern hemisphere, a Terra Australis (Figure 1), redressing the balance between land and sea. A famous attempt to make this discovery was the expedition to the Pacific Ocean sent out (1768-71) by the British Admiralty under the command of Captain James Cook, the greatest of all marine explorers.’ (In setting Cook first, I pass over that remote countryman of mine who during an inland voyage into North America may have become responsible for the cele- brated Kensington Stone, as well as that still remoter one Erik Raude, who two centuries earlier happened to discover “Vineland the Good.” ) Not even Captain Cook succeeded in finding the vast Terra Australis in the South Seas, for the excellent reason that it is not there; and geographers had to accept the painful fact that the field of work reserved for oceanographers is more than twice as large as their own, occupying over 70 per cent of the planet’s total surface. Viewed through a supertelescope by an extramun- dane astronomer inhabiting, say, one of the outer YOR] Ul PoUT[INO ‘WOO Je ‘sYPAISNP DAdaT “| “BI fee tn zi : at : . es ; i «4 + ¢ bs : Ce ee ‘ P fg Kone ne pees | operas) a ow) ‘ q Y t E ou on 95 in im nh wo. Se ex's , ¥ Bye tpn iets peleiginietalatatadet i tenteles Poe z 7 3 Ca hae é be Rtas: <8 ; acne ‘ “is er ae me , Bee ‘ i : : Rb ie 6, ‘, Be a ep Bes i tec ‘i Roe “4 , em he ; 3 Ma - Es . ie ee ‘ bogey % se oe ae e's ; fs os - % Jue ' wh epee 4) ae 4%" es . i re ee WAY ipprniay i HH ON OHOE SW Ucn) OTN) OP OgrOE AOLae aogedon MuMTE yas oF Sih oon IPT OPE, OU YT MO TEM opy PabL ey Aro py yen gy OO Val dh oS gd SO A: NEBL OS See Ec et bar GN Oe Sey es BE ee in i A ily AOR OOOO RE Rt eee + "i: he ae i eta tnt Sepeampmiinndantesentert tid ence endeiniaaene nan denise medamananane iter eee OL LOOT “ AH ceeaneor emer en aOe “egeenmn acne henennen cage wt cageommrnonmre nie we vasntonee es ier near eeetntinawer rare in cammnemaeerenntnts aeorereneeen pnanirictoreen teonyinmmenan eevee tet ations haecaniee stink nd 4 THE OCEAN FLOOR planets, our earth with its glittering oceans would no doubt be an object of admiration and envy, and would probably be called “the water planet.” It certainly forms a striking contrast to its next neighbors in space. Venus, “the cloud planet,” coyly hides her charms behind an impenetrable veil of dazzling white clouds. (Spectro- scopic analyses indicate these clouds do not contain water but are largely built up from carbon dioxide. ) Her old admirer Mars, “the desert planet,” is also deficient in water. Venus is possibly still in a pre-oceanic stage, but Mars is strongly suspected of having con- sumed his original supply, either drinking it into his crust or perhaps squandering it into interplanetary space. This contrast inevitably suggests that our present oceanic splendor represents a transient stage in the development of earth, which may be on its way toward the Martian state of complete desiccation. According to some pessimists, in another few thousand million years or so oceanographers will have to learn a new profession. Let us, for a moment, anticipate such a future devel- opment of ocean shrinkage and assume our earth to have become half dry, so that the sea surface has fallen below its present level by 4,000 meters, that is, some 13,000 feet. Figure 2 gives an idea of how the Atlantic Ocean will then look. The present continents are gray, the remaining ocean is black, and the parts of the sea bottom uncovered by the retreating ocean are white. One easily recognizes the characteristic S-shape of See ~ oe SS SSS SSS es SS SSS Sas SS Sj Se Fig. 2. The Atlantic Ocean on a half-desiccated earth 6 THE OCEAN FLOOR the Atlantic, but he also notices that a new Atlantean continent has risen out of the sea, dividing the remaining ocean into two parts. This “New Atlantis” is the present gigantic submarine Mid-Atlantic Ridge, with its crest at an average depth of about 10,000 feet. We have special reasons to be grateful that this strange sea change is not likely to occur in our politically unsettled times. One shudders at the international complications which might ensue from the rivalry between East and West for the possession of such a seaborn continent. The remaining black surface on the map is divided between fwo parallel Atlantic Oceans, the present eastern and western Atlantic Valleys, with their low- lands spread 5,000 to 10,000 feet below the level of the ridge between them. Closer inspection shows one, possibly even two, sounds or channels cutting through the Mid-Atlantic continent. The northern one is more hypothetical, whereas there is little doubt regarding the existence of the southern channel, situated just under the Equator. This is the famous Romanche Channel, which runs quite close to the equally famous Romanche Deep, a curious cavity in the sea bottom accidentally discovered in 1883 by the French survey ship “La Romanche.” We further notice a transverse ridge, the Walvish Ridge, which runs northeast from the South Atlantic island of Tristan da Cunha toward Walvish Bay on the west coast of Africa. It acts as a submarine barrier or water divide, holding back the ice-cold DoE AMS: AND FT HETR: Bis TORY / | bottom water from the Antarctic and preventing its entering from the south into the eastern Atlantic Valley. Since there is a corresponding submarine barrier, the Rio Grande Ridge, running westward from the Mid- Atlantic Ridge but broken through by a wide submarine channel, the Antarctic bottom current is free to enter from the south into the western Atlantic Valley, where its cooling effect on the bottom temperature is apparent as far north as the vicinity of the Bermudas. South of the equator a narrow branch from this westerly Antarc- tic bottom current runs toward the northeast, entering the eastern Atlantic Valley through the Romanche Channel. (Figure 3 is a rough representation of the Antarctic bottom current. ) Figure 4 shows what the Pacific and Indian Oceans would look like after the same fall of ocean surface by 13,000 feet. In the Pacific a vast submarine ridge or plateau, laid bare by the retreating ocean water, would stretch northeast and north in a mighty curve from the Antarctic continent, reaching the west coast of Central America. This ridge now supports the very few East Pacific islands. In contrast to these few in the east there is an abun- dance of islands in the central and western parts of the ocean, especially south of the equator. They are mainly of magmatic origin—volcanic cones rising steeply from great depths, a few crowned by lofty peaks towering thousands of feet above the ocean surface. The great 8 THE OCEAN FEOD majority have summits a few hundred feet below the surface but carry above it white diadems of living coral. They are the lovely atolls of the South Seas. In the northern part of the Pacific Ocean we find the vastest lowlands of the earth’s crust, with enormous areas lying at depths of more than 15,000 feet. It is a Fig. 3. The Antarctic bottom current in the Atlantic yyieva poyeoorsap-jjey & UO SUvdDO UvIpPU] pur dyIOeg OL “p ‘sq i ony 2 Pore annem foe i f ffed ~ See. — oom NIAITL QNN YW IZHISIQNI EUR R A) Lag ad Ua ibe 0 a TeLBaes eon Nv3zZO W31711S | Nw bee \ 10 THE OCEAN SEE Gane remarkable fact that the very greatest depths are not found in the central parts of the oceans but are concen- trated within curiously formed furrows or trenches which run close to and parallel with continental coasts or island festoons. In these trenches are found record deeps like the Emden Deep and the Johnson Deep in the Philippine Trench off the west coast of Mindanao, with soundings of very nearly 35,000 feet, and the still greater Challenger Deep southeast of Guam, with a maximum depth of 36,000 feet. This is considerably more than the height above sea level of the world’s highest mountain peak, Mount Everest. Turning to the Indian Ocean, we find in the western part, where most of the banks and islands are located, a great submarine ridge running south to north from the Antarctic Continent. The eastern part of the Indian Ocean is in general of a greater and more uniform depth and has only one deep trench, the great Sunda Double Trench, running along the south coast of Java with a maximum depth of about 25,000 feet. Such are, in brief, the main features of the great cavities in the earth’s crust which are at present filled with ocean water. The question naturally arises whether this has always been so. In other words, what is the history of the oceans in relation to the continents? Here oceanographers must confess their ignorance. What little we believe we know is largely conjecture— theories put forward by students of geophysics, geology, zoogeography, and phytogeography (the last two from ARABIAN BASIN Laccadive. Reheat eed Weiner ee —————ere f ————— —<_ —————— —SSSSSSS=== ae / SSN ees eee Sage ye @ Rodriguez | SS : : Réunion. Mauritius: = | MADAGASCAR ee ee - a ee ye 3S eres Cea fie——— SS 5 pent 5 : / JEFFRIES {New Amsterdam|s55 DEEP | £ 951\Paul ar gone = Crozet s\ ss =| = ire Sa Barco ardis.* ze Jive ea ber ce hen ies Se sae Dd ee “festa Is PESES | |INDIAN-ANTARCTIC BASIN Seren ‘a 2000M/. Ss Compiled by- RW. FAIRBRIDGE University of WA.1948 Fig. 5. Depths in the Indian Ocean 12 THE OCEAN ELOGE the viewpoint of both the present and the remote past. that is, paleontology). Specific hypotheses have been advanced to account for the distribution of plants and animals and their past migrations from continent to continent. It will be necessary to consider these hypotheses briefly, since they have played an important part in discussions of the problem before us, the ocean floor. The evidence is overwhelming that large parts of the present continental surface have in earlier phases of the evolution of our planet been submerged and formed the bottom of relatively shallow epicontinental seas. Thus, the material from which sedimentary rocks such as chalk, shists, and sandstones were built is ancient sediment deposited on the bottom of vanished seas which were laid bare at the regressions of the shore line and gradually hardened into rocks. Our loftiest moun- tains, the Rockies, the Andes, the European Alps, and the Himalayas, are built up largely from such ancient — sea beds, which by enormous horizontal forces have been folded and crinkled into mountain chains. On the other hand, very few if any deposits from great ocean depths are found in the continents. This fact, among others, has led to the theory of the “permanence of the ocean basins,” propounded 90 years ago by the great American geologist James Dwight Dana and his school. The strongest opposition to this view came from the biologists and paleontologists, who claimed to find evidence for “land bridges,” now out of sight below the OCEANS AND” THELR: HISTORY 13 sea surface but which in a remote past afforded roads for the migration of nonaquatic organisms across the wide gulfs separating one continent from another. In general, it has been assumed that the Pacific Ocean is the most ancient of all the seas, possibly a primary feature of the earth’s crust. Some theoreticians have even gone so far as to suppose its basin to be the “birth scar” left behind when our satellite, the moon, was torn out of the earth’s body by enormous tidal forces. Those who had the privilege of listening to Harold Urey’s masterly exposition of the origin of the planets, and especially of the earth and its moon, in the Silliman Lectures of 1951 will remember on how slight a foundation this hypothe- sis is based.2 Nonetheless, the demand for a reconstruc- tion of the Pacific basin which would satisfy paleontolo- gists and biogeographers has found support among eminent geologists like the late J. W. Gregory. The need to postulate an ancient path of migration from northeast Asia over the Hawaiian Islands to Central America has led to the reconstruction of a hypothetical ancient land bridge called Archigalenis. A similar bridge, called Archinotis, has been suggested as a link between the Antarctic Continent and South America. These and similar tamperings with the map of the Pacific Ocean are not much favored by present-day geologists. However, the evidence for an intercon- tinental land bridge in the far North appears to be much better founded. Behring Strait, which separates north- east Siberia from northwest Alaska, is fairly narrow 14 THE OCEAN FLOOR and has a maximum saddle depth of less than 200 feet. During the great glaciations of Quaternary time, when enormous masses of water were transferred from the oceans to the inland ice, the ocean surface is generally admitted to have sunk about 250 feet, some authorities claiming a still greater lowering. This would imply that unless there was a corresponding sinking of the bottom ; 6 ‘ 7 = Cikiee Gq] 4 PES alee ee es ee a om eee a i ij \ 7 * —™ — d [ i] i 4 4 i SSece H ) rah { a ) | Q a B ka / ia joe A = in ay = oA i eh a = fey =6- 5 = tt ie “a0 TO 180. 6 i i i 400 p (4 “ep p p : p p Da bp ~<“Too 120 Fig. 6. Distribution of ocean and land in Mesozoikum of Behring Strait one might have walked across dryshod a few hundred thousand years ago. It is generally as- sumed that an invasion from Asia into North America, both of animals and of men, took place over this sub- arctic land bridge, so that the ancestors of the Indian population of the New World may have crossed thus from one continent to the other. As for the Indian Ocean, very radical attempts at a HCEANS ANDMPHELIR- AIS TORY 15 reconstruction have been made, one of the most recent being propounded by the Australian geologist Fair- bridge.* In late Paleozoic time a large part of what is now the bottom of the Indian Ocean is assumed to have been above sea level: the famous Gondwana Land, which united Australia and the Antarctic with south- eastern Asia. Lemuria, a last remnant of this ancient continent, hypothetically linked East Africa and Mada- gascar with the Indian Peninsula. Because of a break in the earlier parallelism existing between the paleonto- logical series found on the two continents, the Lemurian land bridge is assumed to have foundered in Mid- Tertiary time. According to Fairbridge the Indian Ocean in its present shape is the youngest of the three oceans. Its northwestern part he assumes to have been formed “only” 10 to 20 million years before our time. However, it is our own ocean, the Atlantic, which has given rise to the most fantastic attempts at reconstruc- tion. Here the paleontologists insist there were three transverse land bridges, separated by the two arms of the ancient sea of Thetys, as shown by Figure 7.* Far to the north the Archiboreis linked northern Europe and the Arctic islands with North America. Farther south, Archatlantis ran across the present Atlantic Ocean from the West Indies to northern Africa. Finally, Archhelenis spanned the southern Atlantic Ocean from Brazil to South Africa. Much fiercer than the discussion over land bridges was that provoked by the famous theory of “continental 16 THES OCEAN FLOOR drift” propounded and worked out in great detail by the Austrian scientist Alfred Wegener,” although the fun- damental idea had been launched a few years earlier by the American Frank B. Taylor.* According to this theory the present continents are mere fragments of the outermost shell of the earth’s crust, supported by being partly immersed in a deeper layer of higher specific Fig. 7. Map of the Oceans in the Eocene weight and greater plasticity. To these continental blocks Wegener ascribed movements in both vertical and horizontal directions. This idea of drifting con- tinents, worked out in great detail by Wegener and his followers, is supposed to explain the striking parallelism between the continental borders on both sides of the Atlantic Ocean, first emphasized by Taylor. Thus, the Atlantic Ocean was taken to be a kind of rift between the OCEANS AND “THEIR HISTORY i, two continental blocks, Europe-Africa and the two Americas, which began to open up in Cretaceous time and is still widening through a progressive westward drift of the two Americas. The Atlantic Ocean would thus have a maximum age in its central parts of less than 100 million years, perhaps only 70 million years. A great variety of arguments geographical, geologi- Fig. 8. Birth of the Atlantic Ocean cal, biological, paleontological, etc. have been brought forward in support of this ingenious theory. Since its vogue in the twenties, adverse criticism has been over- whelming and very few leading scientists of our skeptical age have remained faithful “Wegenerians.” One main objection to the theory is that enormous energy would be required to move the vast continental 18 THE OCEAN FLOODS blocks through a highly resistant substratum, an energy for which no adequate source was suggested, only subcrustal convection currents set up in the substratum at the escape of radioactive heat from the continental blocks through the ocean floor. On the other hand, movements of continents or parts of continents in a vertical direction are generally admitted to have oc- curred. They have been invoked in order to explain the so-called regressions and transgressions of the shore line, and have been attributed to a varying load of inland ice on accumulated sedimentary layers. But horizontal displacements of great magnitude are in general dis- credited. Thus there still remains considerable uncertainty regarding the early history of the ocean basins, and many problems concerning their origin and that of the water masses filling them remain unsolved. Highly interesting contributions to the discussion of these problems have recently been offered by American authorities like Harold Urey and William Rubey. Al- though the theme is too vast to be further dealt with here, certain aspects of it will be considered later. 2. Envisaging the Past and Future Few things are more fascinating than speculation about happenings in the remote future—or in an equally remote past. For instance, what did the earth look like two billion or 500 million or even a paltry 100 million years ago? We have strong reasons to believe that our Tellus really did exist as long ago as two billion years. Assuming that the radioactive transformations known to us proceeded then at the same rate as today, we can ascribe an age of over two billion years to the oldest rocks hitherto submitted to radioactive analysis. However, we know next to nothing about the division between land and sea then prevailing, and whether water in large quantities existed on the primeval earth 1s subject to discussion. Arguments have been advanced to prove that the total volume of ocean water was at the beginning only a fraction of the present total. In a recent brilliant paper William W. Rubey has attempted to show that the water masses of the oceans were derived largely from the earth’s crust rather than, as has been assumed, from a cataclysmic condensation of water vapor present in a very dense primitive atmosphere.' For representatives of the two opposing 19 20 THE OCEAN FLOOR schools of thought on these theories Rubey has coined the expressive terms “the quick soaks,” who prefer to believe that all the water was present from the very beginning, and “the slow soaks,” who think that it increased by small increments over a much longer period of time. The “excess volatiles,” which the slow soaks assume were released gradually from the earth’s crust, are supposed to have been retained within the interior of the earth in quantities amounting to a fraction of 1% of the total weight of the solid matter. Starting from known geochemical data Rubey finds the total quantity of water present in the primitive atmosphere and ocean to have been not more than one- sixth, probably a still smaller fraction, of the present-day total, the rest having been gradually released from the crust during the crystallization of complex silicate melts. A large part of this magmatic water Rubey assumes to have been released as “juvenile water” through hot springs.* Even if the water which existing hot springs are delivering to the surface consisted of only .8% of juvenile water, in the course of two billion years they could account for the entire volume of present ocean water, without counting contributions of water from volcanic eruptions! * Professor Eugen Wegmann has called my attention to the fact that as defined by E. Suess the term “juvenile” should be used for matter which has not participated in supracrustal cycles, so that the excess volatiles released from the crust should properly be called “juvenile” instead of “magmatic.” PAST AND FUTURE oh A question Rubey does not consider in his exposition concerns the rate at which these contributions from below to the ocean water masses have been delivered. Dividing the total volume of water in the oceans— 1.3 < 10'* cubic meters through two billion years (a conservative estimate for the age of the oceans )—one finds the annual increment to have been on an average .65 x 10° cubic meters, a small fraction of the present annual rainfall over the planet’s surface. There are, however, strong reasons for assuming that this contribu- tion from juvenile water may have varied considerably in the course of geological ages and that it has reached higher values than the average during epochs of in- tensified volcanic and magmatic activity. More recently Roger Revelle, director of Scripps Institution of Oceanography, has taken up the problem of the origin of ocean water.” Revelle believes a large part of the magmatic volatiles—water vapor, carbon dioxide, and mineral acids—has been released from the ocean floor itself through a process of recrystallization of the underlying substratum. In the last 100 million years of earth history a water layer over 3,000 feet deep, according to Revelle, has been produced “from below.” With this release the ocean floor has sunk considerably, so that no very great change in the water level has occurred. Such a subsidence of the ocean floor would explain the gradual sinking of the volcanic islands and the present great depth of the mysterious guyots, the truncated, flat-topped volcanic cones with wave-planed pip} THE OCEAN FEOGR summits which are at present lying in the Pacific Ocean at depths of between 2,500 and 6,000 feet. The carbon dioxide simultaneously released, amounting to about 5% in weight of the water, has given rise to the thick layers of calcareous sediments covering parts of the ocean bed.* It seems reasonable to assume that the effusion of magma over the ocean floor, as well as the release of SLOPING ee Gis — SORRR MIE ) gS LS a y RRR seats Ocean Depths between | Madeira, The Canaries and Gibraltar = km. Depth lines :----200 — 1000 to4000 iM. See ee i Fig. 13. Ocean depths between Madeira, the Canaries, and Gibraltar In our century deep-sea research has taken large strides forward in spite of great technical difficulties. The International Council for Sea Investigations, started by Otto Pettersson in the early years of this century, although limited in scope to seas of moderate depths aD THE OCEAN FPLOGE worked out a number of exact methods of research and analysis, from which deep-sea research has also profited. These new methods were put to practical use in 1910 by the “Michael Sars” Expedition in the North Atlantic, led by Sir John Murray and the Norwegian biologist Johan Hjort.° The methods were also employed by a number of Antarctic expeditions. The culmination was the magni- ficent effort made by the Germans on board the “Meteor.” © This cruise, originally planned by the Austrian oceanographer A. Merz for the Pacific Ocean, for want of a ship with a sufficiently large radius of action had to be limited to the Atlantic. The results gained there were, however, extremely important and revealed unknown features of both the ocean floor and the structure and movements of the ocean water masses. The expedition made excellent use of the technique of acoustic echo soundings then available, but their re- sources for studying the ocean sediments were not adequate and did not show any marked improvement over those of the “Challenger” cruise half a century earlier. The ordinary core-sampler which was used rarely produced cores as much as three feet long, that is, reaching back about 50,000 to 100,000 years in time. Still, even these relatively short cores revealed a signif- icant stratification of the sediment and indicated the possibilities of climatological studies of late Quaternary time, based on an analysis of the surface plankton shells from Foraminifera found in different levels of the core. BX PE ORUNG «: FRoOGEr homogeneous, fine-grained, deep-sea clay. In the lower part several layers of sand were found which mineral- ogical examination showed to be not mafic but of con- Albatross-Starior7 Albarross-StQH/0/7 Depth in Ne SSO Nr 560 centimeters ree s ediment, . ah 100 /00 200 900 1/000 1/00 500 1200 600 7300 600 Joo : 1400 FOO I Mme of red clay mn redclay = blue cloy me sand En/ Dr F Locher Fig. 34. Stratified cores from the equatorial Atlantic tinental origin, that is, derived from a coastal shelf of some continent or large island. Most surprising of all, in the lowest stratum of this sand were found vegetable remains—twigs, nuts, and bark fragments of dicotyle- DEEP-SEA DEPOSITS 97 donous bushes or trees, bespeaking still more empha- tically a continental or island origin. Finally, in the uppermost part of the same core Phleger and his co- workers found a “displaced fauna” consisting of benthonic shallow-water foram shells which apparently had lived in depths of 100 to 200 meters. One is at a loss to explain how these products of a coastal shelf and supramarine vegetation could have been carried to the position of the find at lat. 7° 29’ N., long. 45° 1’ W. The nearest part of the coast of South America is the Amazon Estuary situated at a distance of about 500 nautical miles. F. Locher, a collaborator of Correns who has studied these and other “Albatross” cores from the equatorial Atlantic, has failed to find any Close resemblance between the heavy mineral com- ponents in the deep-sea sand at this locality and the heavy minerals in cores taken by the “Meteor” near the Amazon Estuary.” Moreover, Locher has found similar (although not so thick) sand horizons occurring in cores taken from a stretch of the equatorial Atlantic bottom running northwest to southeast from the posi- tion given above. Altogether, the sand in these cores was neither so profuse nor so coarse grained as in the first, most northwesterly, core mentioned. In the event that a large island harboring vegetation and with a fairly extensive shelf crowned the Mid-Atlantic Ridge north northwest of St. Paul’s Rocks and became sub- merged during a catastrophe of seismic-volcanic char- acter a few hundred thousand years ago, material like 98 THE OCEAN ‘FLOOR that found in the “Albatross” cores might have become distributed over the adjacent sea bottom. However, apart from the general improbability of this explana- tion, the prevailing surface currents at present run from southeast to northwest, that is, in a direction opposite that in which the transportation of sand, foram shells, and vegetable remains might have been supposed to occur. In this dilemma both Locher and Phleger have accepted the explanation of transportation by turbidity currents. This would mean that some very considerable submarine landslides occurring on the shelf off or near the Amazon Estuary produced a sediment-laden bot- tom current of great intensity, extending far enough to transport coarse and unsorted material over a distance of several hundred miles along a slope which cannot on an average have been greater than 1:200, an ex- planation which is difficult to accept. The mystery of the deep-sea sand in this part of the equatorial Atlantic Ocean cannot be considered solved. We may only hope that future expeditions to this region, taking long cores and multiple echogram lines between the locality indicated and the Amazon Estuary, will throw light on this fascinating problem. A most interesting mineralogical study was made by O. Mellis of Stockholm on stones found in a core taken at lat. 29° 21’ N., long. 58° 59’ W., southeast of Ber- muda in a depth of 5,450 meters.* The weathering crust on these stones proved beyond doubt that a trans- PEEPS EA - DEP OSTTS 99 formation of plagioclase into orthoclase has occurred through the substitution of sodium for potassium. An- other find of Mellis and Norin of Uppsala concerns layers of volcanic ash in cores from the eastern Medi- terranean and the Tyrrhenian Sea.* Thus, Mellis found in cores taken southwest of Cyprus and south and southeast of Crete layers of volcanic glass which had Fig. 35. Submarine weathering, plagioclase to ortho- clase probably become deposited after the cataclysmic out- break of the island volcano Santorin in the sixteenth century B.c. Norin, in a core taken in the center of the Tyrrhenian Sea, found a layer of ash which he was able to identify with ash from old Mt. Somma, which 100 THE OCEAN FLOOR erupted probably in the twelfth millennium B.c. The possibility of a dating of similar but more recent vol- canic ash layers, such as those in the Norwegian Sea produced by outbreaks of Mt. Hekla and other Ice- landic volcanoes, seems very promising. 7. Recent Investigations on the Stratigraphy of Deep-Sea Sediments Se April, 1952, when the Silliman Lectures which compose this book were delivered, a highly important contribution to our knowledge of deep-sea sediments and their stratigraphy has been made by Gustaf Ar- rhenius, geologist of the Swedish Deep-Sea Expedition, in his doctoral thesis, Sediment Cores from the East Pacific, published as one of the reports of the Expedi- tion.! It was submitted for official discussion at Stock- holm’s Hogskola on November 15, 1953. The very comprehensive analytical work on which this thesis was based was carried out at Kagghamra, Sweden, by Arrhenius and a staff of collaborators, in- cluding two specialists on microfossils, F. Brotzen and R. Kolbe of Stockholm. Generous grants-in-aid for the work were given by the Swedish Research Council, the Lars Hierta Memorial Foundation, and the Wallenberg Foundation, all of Stockholm. Part 1 of the volume contains the report on the 101 102 THE OCEAN FLOOR general distribution of properties in the sediments, together with an interpretation by the author of the distributions and relationships found. Part 2 gives a detailed description of the different cores examined, with suggested interpretations. Part 3 contains a sum- mary of the late Cenozoic stratigraphy and the geo- logical evolution of the eastern Pacific pelagic area. Part 4 accounts for the methods used in the study of the sediment cores. Fascicle II, which has not yet been published, will contain special contributions to as- sociated problems. Arrhenius deals first with the main components of sediment. 1. Of special interest is the hypothetical explanation of the distribution of calcium carbonate and its relation to present and earlier atmospheric and oceanic circula- tion, notably the formation of calcium carbonate in upwelling water masses rich in nutrient salts, and its dissolution during and after deposition on the ocean floor. From this discussion Arrhenius concludes that the ice ages were characterized by a greatly increased intensity of trade winds, a phenomenon which was not, however, reflected by any marked shift in the latitudes of the equatorial current system. 2. The establishment of a correlation of presumably isochronous strata between the different cores made it possible for Arrhenius to compare regional variations in the amounts of different elements, minerals, and fossils accumulated per unit area between the correlated DEVE SELGATIONS OF STRATIGRAPHY 103 time levels. He was especially interested in titanium.* Between localities within the eastern part of the area investigated he found perceptible variations of titanium accumulation, whereas in the Pleistocene strata of the open, topographically regular part of the ocean only a small fraction of the accumulation showed regional variations. The deviations from uniformity in space were given quantitative expression, and from the re- gional uniformity a corresponding uniformity in time within the area and the time interval in question was inferred. The Pleistocene strata display a marked homogeneity, on which Arrhenius has based a tentative chronology on the assumption of a uniform rate of minerogenous accumulation during the Pleistocene within the east eupelagic area. Arrhenius checked these data against a radiocarbon dating on one core, using the method developed by Libby. To the view of a constant rate of accumulation of minerogenous matter within the area in question eX- ception has been taken by Kullenberg. For the discus- sion of these and other aspects of Arrhenius’ work the reader may be referred to his rejoinder to various criticisms in Tellus (1954). 3. The amount of biogenetic silica in the eupelagic sediments of the eastern Pacific has also been cal- culated by Arrhenius. He finds the maximum rate of * That titanium is less likely to undergo postdepositional changes than other chemical elements has been urged by vari- Ous earlier authors such as Correns, Wiseman, and Koczy. 104 THE OCEAN FLOOR accumulation below the equatorial divergence, where at a certain substage of the Pleistocene glaciation it should have reached 860 milligrams of SiO, per square centimeter in 1,000 years. However, a microscopic examination of the cores proves that many siliceous remains are strongly corroded, which makes it probable that a great part of the biogenetic silica is present in colloidal form. 4. Similar analyses deal with the distribution of organic matter (marine humus), with phosphorus, with the carbon-nitrogen relationship, and with the presence of peroxide of manganese, both in dispersed form and as nodules and micronodules. A great number of excellent diagrams make clear the main relationships found; these relationships en- able Arrhenius to establish correlations among the different cores he has examined and to define the limits between the Pleistocene and Pliocene parts of the cores. These conclusions he supports by similar distribution studies of forams, diatoms, and radiolarians in the cores. Special attention has been given to the reworking of sediments by mud-eating organisms and to recrystal- lization and chemical redistribution after deposition. Studies of thin sections of carefully washed Foramini- fera revealed the fact that planktonic forams which are not recrystallized are more easily attacked than are recrystallized shells and benthonic forams, which ap- pear to be remarkably resistant to dissolution. INVESTIGATIONS OF STRATIGRAPHY 105 Arrhenius states that his studies of the East Pacific sediments have not yielded any quantitative results concerning the influence of the weight of the overlying strata on the water content of an underlying stratum. He assumes that the effect is so small—insofar as the uppermost ten meters are concerned—that it is usually masked by other variations in the composition of the sediment. In calcareous facies of the east eupelagic area even the longest core (15 meters) does not give any unquestionable evidence of expulsion of water by com- paction. It is of interest to compare Arrhenius’ interpretation of changes in calcareous sedimentation—that they are due to a strong upwelling in equatorial divergences with a consequently improved nutrition of the surface plankton—with the earlier interpretation by Schott, who assumes that during glacial epochs surface water in the tropics was cooled by as much as 10° centigrade, so that the extraction of calcium carbonate was much reduced. If this were true, the glacial stages ought to be characterized by a /Jow lime content in the sediments, whereas according to Arrhenius the reverse is the case. As Revelle has recently pointed out, there is not necessarily any contradiction between the two views.” In some regions the cooling of the surface water may have had a predominant effect on tropical pelagic sediments during the glacial periods, whereas in others the increased productivity brought about by intensified atmospheric and oceanic circulation may have been 106 THE OCEAN FLOOR the primary factor. An important remark made by Revelle in the shipboard report of the “Capricorn” Expedition concerns the deposition on the deep-sea floor of sediments high in calcium: If the deposition throughout the geologic past had been like that at the present time it would be impossible to arrive at a geochemical balance, because both the deep-sea and con- tinental sediments would be higher in calcium than the igneous rocks from which they are derived. Thus we arrive at another most important conclusion, namely that the char- acter of the deposition on the deep-sea floor has changed radically with time; throughout most of geologic history, deep-sea sediments must have been lower in calcium than the average igneous rocks, whereas the present deposits have an excess of calcium. Some important contributions toward the knowledge of deep-sea sediments from other workers on the “Albatross” material should also be mentioned. W.R. Riedel of Adelaide, who worked for two years in Goteborg with the radiolarians from our Pacific and Indian cores, found them useful for dating various sediments.* This fact is especially important when calcareous components (the foram tests) are missing. Thanks to Riedel’s work it is now possible to date with a certain degree of accuracy sediments from the Upper Cretaceous and various Tertiary periods. The radiolarians have also proved to be good in- dicators of the transportation and erosion of sediments in the deep sea. Because the tests are more easily kept ENVESTIGATIONS OF STRATIGRAPHY ~107 in suspension than other microfossils such as Foramini- fera, they can be carried along even by bottom currents of low velocity and turbulence. Also, they are less liable to undergo solution during erosion and transportation to different environments than are the forams. By ex- amining mixed faunas of radiolarians in deep-sea cores it has been possible to form a general hypothesis con- C72. > oS co) e C) Total Radiolaria Zygacircus, =) a= —S= NM Boe Cee a8 i=) S No. of Radiolaria per Gram of Sediment. 8 oO oO oO 0" | 500 1000 i) SOO Depth in the core (cm) Fig. 36. Abrupt drop in number of radiolarians cerning erosion by slow bottom currents of small topo- graphical features in the deep ocean. Long deep-sea cores taken in areas with a low rate of sedimentation have enabled Riedel to trace the evolu- tion of certain of the groups of Radiolaria from the Recent back to at least the Lower Miocene. These evolutionary trends are being checked in Tertiary 108 THE OCEAN’? FLOOR deposits on land. It appears that a general evolutionary trend can be demonstrated as having occurred simul- taneously in all parts of the world within, say, the latitudes of 40° N. and 40° S. Recent work by Brotzén and Dinesen on forams from cores taken in the central Pacific Ocean has proved that an abrupt change in the fauna occurred in a core at a depth of 4% meters below the sediment surface. Work by Kolbe has shown the occurrence of an equally abrupt change of the diatom flora in another long core from the same region.’? Research directed toward finding similar unconformities in cores from the other two oceans is now proceeding. A re- markable find by Kolbe in two cores from the equatorial Atlantic is the occurrence of typical fresh-water dia- toms in considerable numbers. Since this find was made in localities several hundred miles from the coast of northwest Africa, the origin of these fresh-water dia- toms is puzzling. Research of considerable interest pursued for some years in Goteborg by Rotschi and Berrit has been devoted to the ferrides present in cores, from both the central Pacific and the equatorial Atlantic, notably the elements Fe, Mn, Ni, and to a certain extent Ti.* The origin of iron and manganese in deep-sea sediments is not completely cleared up. Arrhenius and others are inclined to distinguish between “halmyrogenic” man- ganese and manganese of minerolytic origin, the latter largely derived from submarine volcanic debris which INVESTIGATIONS OF STRATIGRAPHY 109 has undergone solution and a subsequent vertical migration in the sediment. The manganese in the shave of its peroxide, braunstein, is known to absorb radium, a subject which will be more fully treated in Chapter 8. Also, the iron precipitated from the ocean water is assumed to play a part witix regard to the co-precipita- tion of the mother element of radium, namely ionium. Again, part of the abyssal iron may be assumed to have a magmatic origin and to have become extruded on the deep ocean floor at great submarine eruptions. The nickel content of certain deep-sea sediments, especially those characterized by an excessively slow rate of ac- cumulation, may in part be of cosmic origin, derived from meteors or micrometeors entering the earth’s at- mosphere from without. The curve reproduced here in Figure 37 shows the distribution of manganese along a core from the Romanche Deep, taken from a forth- coming paper by Berrit. The isolated high peaks in the manganese curve are to be interpreted, I believe, as products of great submarine eruptions, since they occur also in other cores from the equatorial Atlantic. The importance of titanium for submarine geochron- ology emphasized by Arrhenius has already been re- ferred to earlier in this chapter. To study this problem of the geochronology of the deep ocean sediments has been one of the main ob- jectives of our work. Of the methods so far applied to solve this very fundamental problem three appear promising: (1) analysis of the composition of the 110 THE OCEAN FLOOR foram tests, (2) measurements of radioactive elements present in different sediment layers, and (3) the study, within certain regions like the Mediterranean and In- donesian Seas, of volcanic ash layers. Apart from the work on the “Albatross” cores here referred to, hardly any systematic investigations of Q MnOor% S S Core 238 % : ho Wi \ A> AY \ A | - Wad Vv V7 \/ S O Oo = - cm deep 250 500 750 1000 1230 Fig. 37. Lime and manganese distribution in sediment core from the Romanche Deep long sediment cores have been published. It is indeed unfortunate that these rare abstracts from the records of the deep should—perhaps because of preconceived ideas on the process of deep-sea sedimentation—be allowed to lie fallow and deteriorate for want of suitable storage. It may sincerely be hoped that the increasing amount of international cooperation in deep-sea re- search will lead to a more respectful treatment of the PNMES PIGATTONS OF "STRATIGRAPHY ‘11 long cores collected at great costs from future deep-sea expeditions than has hitherto been the case. Arrhenius’ pioneer work on the cores from the eastern Pacific Ocean may in many respects serve as a model. 8. Deep-Sea Radium and the Geochronology of the Ocean Floor Ans very long sediment cores which the Swedish Deep-Sea Expedition first managed to raise from great depths have appropriately been called “records of the deep.” Every historian or archaeologist knows how annoying it is to come across reliable but undated records from the past. Hence the problem arises of how these unique records of the deep can be dated, so as to afford the basis of an exact geochronology for past hap- penings on the ocean floor, including the climatic, tectonic, and volcanic catastrophes which have left indelible markings there. It is well known that geologists studying continental rocks and sediments have labored with the same dif- ficulty, that of dating the “records of the rocks.” Thanks to the sequence of different layers or strata in con- tinental sediments, a framework of geological dating was worked out. In this work study of the fossils en- closed in the strata and knowledge of their evolutionary 112 DEEP-SEA RADIUM 145 background were very useful. Paleontology helped geologists to order the protocols of rocks and distin- guish between different periods of geological evolution. Nevertheless, an exact framework was not found until half a century ago, when it was recognized that radio- active elements, each characterized by its own rate of disintegration, are immutable time-keepers. By using the slow transmutation into lead and helium of the two most long-lived ancestral elements, uranium and thorium, the age of rocks can now be determined. The very oldest among them, in which transmutation has proceeded farthest, have ages up to two billion years. Thanks to this discovery of radioactive time-keepers, definite ages can now be ascribed to many different kinds of rocks. Another discovery, made in the first decade of the present century, was the relatively high radium content in abyssal sediments like red clay and radiolarian ooze. Using the ordinary measure of radium content, namely units of the twelfth decimal place or one million- millionth part of the weight, J. Joly of Dublin found samples of red clay from the “Challenger” collection to hold as many as forty such units. This is nearly fifty times more than the average content of radium in sedi- mentary rocks from the continents. The question naturally arose: how does this abyssal radium get down to the deep ocean floor and how can it be utilized for age determinations on different sediment layers? 114 THE’ OCEAN. FROG Forty years ago when I was a young student working under Sir William Ramsay in University College, Lon- don, I was taken on a short cruise in the North Sea with Sir John Murray, who there invited me to come over to the “Challenger” office in Edinburgh and work up his deep-sea sediment samples for radium. Pressure of other projects prevented me from taking advantage of this offer. Ten years later Sir John had passed away, but another leader in oceanography, Prince Albert I of Monaco, invited me to his Musée Océanographique in Monaco to work on the collections of deep-sea sedi- ments kept there. Several years of work, first in Monaco, then in the Institut fiir Radiumforschung in Vienna, and finally in Goteborg, enabled me to confirm several cases of out- standingly high percentages of radium, like those found by Joly. Joly’s first explanation for the origin of deep- sea radium. namely a chemical precipitation of that element as sulphate from ocean water, I could not, however, endorse. A second explanation, also pro- pounded by Joly, that deep-sea radium is “uranium supported” and due to a relatively high concentration of uranium in abyssal depths, has also proved er- roneous. | It took several years of teamwork with specialists from Austria and Scandinavia before a satisfactory explanation of the mysterious occurrence of deep-sea radium could be evolved. First, we proved that sea water is relatively poor in radium but instead contains DEEP-SEA RADIUM (le a fair and nearly constant amount of dissolved uranium—according to measurements by Berta Kar- lik and others ' about 1.3 10° gram of uranium per liter of ocean water of normal salinity, 35% .* Ac- cording to the “equilibrium ratio” + between uranium and radium found in undisturbed rock samples, Ra — 3,000,000: I, there should be .6 «x 10°" gram of uranium-supported radium present in each liter of sea water. According to our measurements, the average radium content of ocean water, which is more variable with locality and depth than is the uranium content, is only a fraction, on an average one-eighth of the equilibrium value. In order to explain the relative scarcity of radium in ocean water and its abundance in deep-sea deposits the author in 1937 suggested that an intervening element in the uranium-radium dynasty— namely ionium, the immediate parent substance of radium—is being removed from solution in sea water through precipitation together with iron. From this assumption it would follow that the precipitated ionium will at its disintegration breed its offspring radium. * The usual abbreviation for expressing small fractions is used here, viz. 1 x 10~—® for units of the 6th decimal place, or millionths, 1 x 10~—12 for millionths of millionths, etc. The notation 35%, may also be written 3.5%. t Radioactive equilibrium between succeeding members of the same dynasty of radioactive elements is attained in the course of time and is characterized by an equal number of atoms from each element being born and disintegrated in a unit of time. 116 THE OCEAN FLOG® This obviously opens a road to radioactive age deter- minations in the deposit, since the two elements will decrease together downward in the sediment with the disintegration of the more long-lived component ionium, i. e. to 50°. in 80,000 years, 25> in 160,000 years, etc. Two American scientists, C. S. Piggot and William D. Urry, were the first to attempt to utilize the hypothe- sis of ionium precipitation for radioactive age deter- minations in long sediment cores, obtained from ocean depths by means of the Piggot corer.” In a series of papers they very ably discussed the problem of the nonequilibrium system of radioactive elements in deposits, showing how the concentration of radium in the deposit should increase from a low value in the uppermost layer to a near-surface maximum reached after about 10,000 years, when the equilibrium radium:ionium had been attained, and from then on downward present the exponential decline with in- creasing depth (and age) characteristic of ionium dis- integration." Their first results appeared very promising by yielding smooth curves of the expected exponential type, but their later results produced more complicated curves. Those the authors explained as due to changes in the rate of sedimentation, notably through a dilution of more radioactive clay components with less active calcareous deposit. It is obvious that even under the most favorable conditions of undisturbed sedimentation and ionium DEEP-SEA RADIUM 117 precipitation at a constant rate, the time span over which this radioactive age-determination method can be used must be limited to a maximum of 300,000 to Fig. 38. Equipment for radium measurement 400,000 years, after which the residual radium-ionium content becomes too far reduced for accurate radium determinations. Unfortunately, later experiments have proved that such favorable conditions are rarely met with in nature. The time span within which the method 118 THE OCEAN FLOOR can be used is therefore much more limited than Pig- got’s and Urry’s pioneer work led them to anticipate.* The most extensive investigations of this kind so far undertaken have been made in the Oceanographic Institute of Goteborg on cores taken from great depths during the Swedish Deep-Sea Expedition with the “Albatross.” ®> Out of cores from the central Pacific Ocean, consisting largely of red clay or radiolarian ooze, a considerable number of samples have been measured for radium by the standard method of radon determinations, most of the work being done by Kroll.° Two of his curves showing radium distribution at.vary- ing depths in Pacific sediment cores are here reproduced as Figures 39 and 40. It is seen that instead of a simple exponential curve, falling off downward below the near-surface maximum expected (see Figure 39), there are two, four, or even more maxima which are separated by equally sharp minima. Moreover, in certain cores there were found relatively high values of radium content at such great depths below the sediment surface that, considering the slow rate of sedimentation, most of the precipitated ionium from the surface layer ought to have had time to become disintegrated. 7 In spite of the fact that these findings are at variance with theory, Kroll, calculating the total amount of radium in a core down to levels where the ionium- supported radium becomes insignificant, has been able to approximate values of the rate of sedimentation on CORE 698 Q 40 20 JO 40 SOcm Fig. 39. Radium distribution in the central Pacific Core 86B wg Ra/g be “« t) 10 20 30 40 50 cm. Fig. 40. Radium distribution in the western Pacific L210 LHE OCEAN-FLOGE the order of | to 2 millimeters of red clay per 1,000 years.‘ How shall the irregularities found by Kroll in the vertical distribution of radium on cores from the equatorial Pacific Ocean be explained? Variations in the rate of total sedimentation or in the rate of ionium precipitation is an explanation which meets with dif- ficulties when the variations in radium content are very abrupt and the character of the deposit is apparently homogeneous. An alternative explanation—that the variations may be due to a migration of radium to lower levels, leaving its mother element ionium behind —depends on present determinations of ionium by a photographic method. This method has been evolved at the Institut des Recherches Nucléaires in Brussels by Picciotto and his co-workers, in collaboration with and with some support from the Oceanographic Institute in Géteborg.* In nuclear photographic plates exposed to the radiation from a sediment sample from which all radioactive elements except thorium and ionium have been eliminated, the short tracks produced by their alpha particles are counted. The results of this impor- tant work indicate that there exists radioactive equilib- rium between radium and ionium in the maxima of the radium curves, except in the uppermost surface layer, where there is an excess of ionium. That the superficial radium maxima near the sedi- ment surface cannot well be uranium supported seems obvious, since a concentration of radium as high as 50 DEEP-SEA RADIUM tox units of the twelfth decimal place, 1. e. 50 x 10” er Ra/ gr sediment,* would require a concentration of uranium 3,000,000 times higher, or 150 x 10° er U/ gr sediment! Nevertheless it appeared desirable to find out by dependable measurements how much uranium is actually present in sediment cores, especially in layers where there is a high concentration of radium. The fluorescence method worked out for measuring uranium in sea water is excellent, but in sediment sam- ples the presence of certain other chemical elements like magnesium and manganese, difficult to separate completely from the uranium, interferes with the fluorescence in ultraviolet light of the latter element. In earlier attempts to apply the fluorescence method to uranium determinations of deep-sea sediments these difficulties were not completely overcome, and the results were accordingly inaccurate. Thanks to helpful cooperation from Hecht, who devoted two months in Goteborg to collaboration with Kroll, the difficulties were finally surmounted, so that accurate uranium measurements could be carried out on a number of sediment samples. Some of the results obtained by Hecht and Kroll on samples from cores raised by the “Albatross” are set out in the following table. The first column gives the number of the core, the second the depth below its upper end from which the samples analyzed were taken, the third the uranium content in millionths of the weight, the fourth the corresponding “Gram of radium per gram of sediment. ee THE OCEAN FLOR CORE CENTIMETERS 10-6 £0=2 10-12 NUMBER FROM Top GR U/GR GRRA/GR GR RA/GR SED. 76 1.5—3.0 0.76 0.27 14.4 76 40—41.5 11.4 4.0 Ws) 76 200—201.5 ANG pay 0.6 76 300—301.5 De 0.95 0.1 76 400-—401.5 1.8 0.63 0.0 76 $00—5S01.5 1.46 0.51 — 76 600—601.5 fet, 0.38 Opt 76 710-711.5 1.18 0.41 0.2 76 801.5—803 0.96 0.33 0.2 76 910—911.5 2.64 0.92 0.3 76 931.5—933 2.40 0.84 0.3 76 1,030—1,031.5 £42 0.5(?) 0.4 76 1,130-1,131.5 2.10 O73 0 76 1,230—1,231.5 225 0.78 0 76 1,351.5—1,354 2.26 0:79 0.1 69B * 4.1—5.2 4.4 125 Sie 83 4.5—6.5 0.7 0:25 219 83 12.5—14.5 ie 0.42 0.4 86B 6.6—7.7 3.64 127 41.0 86B 14.3-15.4 5535 1.16 45.1 86B 18.2—19.3 2.40 0.84 S22 86B 30.8—31.9 2.66 0.93 30:2 86B 44.5-45.6 2.4 0.84 Qe S77 Bam 3.0-3:3 4.0 1.4 2hes 87B 40.6—41.7 31.05 10.8 12.4 238 4849.5 3250 iene 3.2 238 128—129.5 191 . 0.66 67.6 238 158—159.5 2 0.78 28.0 238 248—249.5 1.91 0.66 8.3 238 418.5—420 1.40 0.49 moe! 238 688—689.5 bees 0.61 3.4 238 758—759.5 2.43 0.85 6.9 238 968—969.5 1.14 0.40 _- 238 1,248-1,249.5 2.94 1.03 1.32 DSN 447.5—449.5 21 0.73 0.88 pray | 501.5—503.5 2235 0.82 2:08. * “B” indicates cores of shorter length, taken by means of a gravity corer. DEEP-SEA RADIUM $23 equilibrium value of uranium-supported radium in 10 '? or Ra / gr, and the fifth the radium concentration actually found. The cores numbered 69 to 87 are from the equatorial region of the Pacific Ocean, core 238 was raised from the Romanche Deep in the equatorial Atlantic Ocean, and core 251 was taken near the equator in the same ocean but farther west. With the exception of two outstandingly high amounts of uranium in core 76 at depths of 40 centi- meters and 200 centimeters respectively below surface, and one in core 87B at 41 centimeters, all the uranium amounts found are moderate, ranging from .76 to 4.0 of the sixth decimal place. The corresponding equilib- . rium values for radium range from .27 to 1.4 units of the twelfth decimal place, whereas in the case of the three outstanding uranium values before mentioned, the figures for uranium-supported radium are 2.5, 4.0, and 10.8 units of the twelfth decimal place. Comparing these latter radium values with those actually found near the surface with maxima of up to 50 units, we may say that at least in the upper levels of the cores and especially in the central Pacific Ocean uranium- supported radium accounts for only a small fraction of the radium actually present. These results definitely contradict Joly’s second ex- planation for the high radium values found in the upper levels of the red clay: that they are due to an accumula- tion of uranium in great depths. Obviously the high radium values found near the sediment surface must 124 THE OCEAN FLOOR have another origin. The only acceptable explanation so far advanced is that they are ionium supported. However, no definite proof of this hypothesis had been produced until in the summer of 1952 Picciotto and his co-workers in Brussels developed the photographic method already mentioned for direct measurements of the ionium present in sediment samples. It is of interest to note that the amount of ionium- supported radium in the upper levels of a core is of the same order as the quantity of potential radium to be expected from the disintegration of the uranium present in the superposed column of sea water, although some- what in excess of the latter quantity by a factor varying, according to Kroll’s measurements, from 1.3 to 2.8. From this fact he infers that the content of uranium and/or ionium in ocean water has been higher during the latter half of the Pleistocene than it is at present, a conclusion supported also by calculations made by Koczy.* Reverting to the question about the cause of the complicated shape of the curves showing radium dis- tribution in the sediment cores studied by Kroll, one may note that he has calculated the variations in the rate of sedimentation required to explain their shape * Recent measurements by Nakanishi, Smith-Grimaldis, and others indicate a higher uranium value, although at present the most plausible average would seem to be 2+ 1 X 10~° ger U L. With this higher value, Ilvoll’s factor is reduced to an average value near unity. DEEPSEA RADIUM E25 and arrived at the conclusion that in the central and western region of the equatorial Pacific Ocean, from which most of the cores he has studied were raised, a general increase in the rate of sedimentation probably occurred about 100,000 years ago, possibly as the re- sult of an increase in submarine volcanic activity. Such an increase is likely to have given rise to a locally in- creased intensity of bottom currents, which in turn brought about a horizontal transportation of sediment. That other postdepositional changes in the sediment stratification could have been operative in causing a redistribution of radioactive layers appears to be borne out by the remarkable curve showing the radium dis- tribution in the upper eight meters of core 238, raised from the great depth of 7,500 meters in the Romanche Deep. This being a long core raised by means of the excellent Kullenberg piston-corer, its uppermost part is likely to be missing, which may explain the absence of a superficial layer rich in radium. The surprisingly high radium content of 69 to 58 units of the twelfth decimal place (the highest ever found in any core from the open ocean) occurs at a depth of between 128 and 139 centimeters below the top of the core. Measure- ments of both uranium (marked by crosses below the curve) and ionium prove that this abnormally high concentration of radium is ionium and not uranium ~ supported. The most plausible explanation of this distribution of ionium-supported radium is suggested by a con- 126 THE OCEAN ¥FEOOe sideration of the topography of the Romanche Deep. At a distance of only 10 nautical miles from the great depth out of which the core was obtained the Mid- Atlantic Ridge rises sharply to a level of only 2,600 meters below the water surface, 1. e. a difference in level of nearly 5,000 meters, or an average slope of about Qv 9 kYg Core 238 40 20 x x x x x x (a) — 1 O77 2 4 6 8 Fig. 41. Radium distribution in the Romanche Deep 25:100. The conditions are thus favorable for a sub- marine landslide, technically called a slump. It seems reasonable, therefore, to assume that a relatively short time ago—short compared to the half-value period of ionium—a slump carried sediment down from the slope, covering with more than one meter of in- active sediment the former surface layer of the bottom of the great deep, which had earlier been exposed to DEEP-SEA RADIUM [27 sedimentation and ionium precipitation below a water column 7,500 meters high. Obviously it would be futile to attempt to calculate the average rate of sedimenta- tion from radium measurements in the Romanche eep. It is equally futile to attempt a dating of deep- sea deposits from radium measurements up to one million years back in time, as has recently been at- tempted by J. L. Hough for a core from the south Pacific Ocean, using radium measurements on the same core Urry used to obtain his data. It seems necessary to consider here also another way in which radium may become removed from sea water and concentrated on the bottom: through adsorption by peroxide of manganese. That an affinity exists be- tween the two elements, radium and manganese, is well known, manganese deposits from thermal sources on the continents often being rich in radium. Experiments made in Goteborg several years ago proved that braun- stein powder, i.e. peroxide of manganese, shaken with a highly dilute radium solution is effective in removing the radium even in concentrations as low as those exist- ing in sea water. The so-called manganese nodules afford striking examples of this tendency of radium to become adsorbed with manganese peroxide. Meas- uring the radium present in thin concentric layers removed from manganese concretions, the author proved that the radium content falls off rapidly with increasing depth below the nodule surface and becomes too low for accurate measurements at a depth of one 128 THE OCEAN ‘FLOOR centimeter. If the radium in the nodules is unsupported by its predecessors in the radioactive element series, it should decrease to 50% of its surface value after 1,600 years, to 25% in another 1,600 years, etc. In this way it becomes possible to measure the rate of radial growth of a nodule, the results showing a one-millimeter incre- ment in the course of 1,000 years. This is the first Zone C | Zone b Zone 2 ; ize a (nucleus) Prol ale <—T JE. 127 Institut des Recherches Nu- cléaires, 120 Institut fur Radiumforschung, 88, 114 Institute for Nuclear Studies, 134 LAT International Council for Sea Investigations, 31 International Union of Geod- esy and Geophysics, 46 Java Deep, 159 Jenlove NG. 135138. 140: 154 Johnson Deep, 10 Joint Commission of Ocea- nography, 46 Foly Jeg IS ie h23 Juvenile water. See Ocean water, origin Kalle Ko 438 Karhk?Bertaz7 kbs Kelvin, Lord, 30 Kermadec Trench, 159f. Kjellberg, G., 131 Kozy, BF. 5-E5 2103n;; 1L29f 135 242i, £49 Kolbe, R., 89, 101 Krafft, Captain N., 38 Kroll WViktor.88,-.18.. bot 124 Kuenen, Philipp, 52, 70, 74, LO, TATE. Kullenbers; Bore, 335i... 3-7, Ate Ase (OS. ho. AST, LST 124, Lamont Observatory, 67 Land bridges, 12ff.; Archat- lantis, 15; Archhelenis, 15; 178 Land bridges (continued) Archiboreis, 15; Archiga- lenis, 13; Archinotis, 13; Lemurian, 15 Landergren, S., 88 Lars Hierta Memorial Foun- dation, 101 Laughton, A. S., 70 Lemuria, 15 Libby, W., 103, 131 Life in great depths, 151ff. Locher, s.- 97h: Magellan, 25 Magmatic volatiles. See Ocean water, origin Manganese nodules, 51, 84, 104, 127-8, 162 Marshall Line, 67 Marsigli, Conte Luigi Ferdi- nando, 27n. Mathews, Christine, 130 Mellis, Otto, 76, 88, 98f., 134 Merz,A:, 32 Mid-Atlantic Ridge, 6f., 22, 50,U07 ts, 70> 94) 097 cal 26; 141 Mohorovic, 65 Mohorovicic Discontinuity, 66, 74 Mucd-eaters, 81, 104, 153 Murray, Sir John, 32, 114 Musée Océanographique, 114 THE OCEAN. FLEOGOE Nakanishi, 124n. National Research Council of Sweden, 86 Norin, E., 76, 88, 99 Nybelin, O., 152, 157 Ocean, exploration of. See Exploration of ocean Ocean banks, 29 Ocean basins: “birth-scar,” 13; continental drift, 15ff.; land bridges, 12ff.; origin, 16, 18; permanence, 12ff. Ocean bottom. See Ocean floor Ocean floor: bacteria, 153; 161ff.; configuration, 6, 30, 81-2; construction, 63ff.; earthquake centers, 66; ex- ploration, 2, 25; geochro- nology, 112ff.; life; tsim. light, -152it 14f.; pressure, 154; recent developments from investi- gations, 69ff.; shape, 6ff.; sinking, 14, 21, 24 Ocean sediment. See Sedi- ment Ocean water: origin, 19ff.; proportion of to land, 2, 24; rate of accumulation, 20ff.; volume, 19ff. Oceanographic Institute . of movement, IN DEX Goteborg, 33, 86, 89, 118, 120 Weeans: «ape, 13, °.15,- 17; depit..8, 10; 21, 25, 38, 70; future, 24; main physi- cal features, 6—10 Orogenesis, 78 Ovey, C., 88 Pacific Basin, 67 Parker, Frances, 42 Peirson, Jean, 42 Pettersson, Otto, 31 Philippine Trench, 10, 159f., 63/165 Phipps, Captain (Lord Mul- grave), 27 Phleger, Fred, 42, 88, 97f. Phytoplankton, 90, 93f. Picciotto, -E:, 88; 120, 129 Bievot, ©. S.,33; 116; 118 Planets: Mars, 4; Venus, 4 Plankton: 42, 44. 77f., 89, 124, 104f., 145. See Phyto- plankton, Zooplankton Poele * radiocarbon; - 103; 179 131; radon, 118; thorium, PiSir- 129; uranium, 113 ff. See Radium Radiolanians; 50; 83f., » 921., 10682 E132. ELS. 140 Radwunn ylOOe Zi. 19 manganese nodules, 85, 127—8; measurement, Esthet seawater,” 152 in sediment, 116ff. Ramsey, Sir William, 114 Red clay, 30350,:52,:60L.) 79, 2) San Oe) 96s tls aeh ts: 123, 144f. Revelle; Roger, 21,. 42.574; 105f. Richter, 68 Riedel; Wa AR 712789; 106, 134, 140 Rio Grande Ridge, 7 Romanche Channel, 6, 142 Romanche Deep, 6, 9%4f., LOOT 2S 2 i 127, 141f. Ross, Sir James Clark, 27 Rotschi, H., 71, 88 Royal Society of Goteborg, 33,37; 43 Rubey, William W., 18ff. St. Paul’s Rocks, 74, 97 Sand, deep-sea, 97f., 148 Schott, W., 88, 105 180 Scripps Institution of Ocea- nography, 21, 24, 41, 42n., GAAS ol. LOZ Sea mounts, 72 Sediment: age, 48, 52, 60-1; AST. 5-77, distribution, components, SOff., 102ff.; 53; equipment for measur- ing, 34, 55ff., 85, 87; geo- chronology, 112ff.; methods of measurement, 54, 55ff.; origin, 22, 48; recent in- vestigations, 30, 54ff., 69ff.; stratigraphy, 77ff., 1O1ff.; thickness, SOA 69ff.; transportation of, 74ff.; velocity of sound in, 57-8, 65) 72,04 Sediment cores. See Cores Sedimentation, rate of, SIff., 61 Seismic waves, utilization of, S4ff. Shepard, Francis, 42, 75, 140, 149 “Sial” and “Sima,” 63ff. Siliceous algae. See Diatoms Smith-Grimaldis, 124n. SOFAR layer, 65 Solomon Deep, 159 Stetson, H., 140 Submarine canyons, 7, 75, 147 Submarine erosion, 147 THE OCEAN - EEGGEe Submarine landslides, 80 Submarine volcanism. See Volcanic eruptions, sub- marine Substratum, nature of, 63ff., TZ,014- Suess, Eduard, 20n., 63 Sunda Double Trench, 10 Swallow, J. C., 72 Swedish Deep-Sea Expedition of 1947-48, 38, 40, 42, 46, 69, 73, 76, 79, S6E., Soa. 101,° 118, 135)4145aiees 157; Reports of, 43, 86 Swedish Research Council, 89, 101 Taylor, Frank B., 16 Terra Australis, 2 Thetys Sea, 15 Tolstoy, Ivan, 22, 41, 67ff. Trawling, 156ff. Turbidity currents. See Bot- tom currents Tyrrhenian Sea, 76, 78, 99 Urey, Harold, 13, 18 Urry, William D., 116, 118 Vastage, 78 Volcanic eruptions, — sub- marine, 62, 77, 80-1, 91, 146 Volcanic glass, 99 END EX Volcanoes as contributors to deep-sea deposits, 48, 73, 77-8, 99-100, 109, 110, 138, 146-7 Wallenberg, K. A., 33 Wallenberg Foundation, 101 Walvish Ridge, 6 Water sampling, results, 138ff.; technique, 135ff. Wegener, Alfred, 16, 61, 63 181 Wegmann, Eugen, 20n. Weibull, Waloddi, 34, 38, Sat... 70 Wiseman, -J. DD. -H:2 90, +93; 103n. Woods Hole Oceanographic Institution, 37, 41, 67 Wist, G., 144f. Zero line; 271.,- 3071512065 AoBell, Claude, 1628-165 Zooplankton, 94 Silliman Memorial Lectures Published by Yale University Press meer “Or. PRIN F Electricity and Matter. By Joseph John Thomson Experimental and Theoretical Applications of Thermody- namics to Chemistry. By Walter Nernst Radioactive Transformations. By Ernest Rutherford Theories of Solutions. By Svante Arrhenius Irritability. By Max Verworn Stellar Motions. By William Wallace Campbell Problems of Genetics. By William Bateson The Problem of Volcanism. By Joseph Paxson Iddings Problems of American Geology. Dana Commemorative Lec- tures Organism and Environment as Illustrated by the Physiology of Breathing. By J. S. Haldane A Century of Science in America. By Edward Salisbury Dana and others The Intestinal Flora. By Leo F. 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Baitsell Elementary Particles. By Enrico Fermi Paleontology and Modern Biology. By David M. S. Watson The Planets. Their Origin and Development. By Harold C. Urey ET dial nt ; { ot Pa lien 2 ein ” i Pl Pr - | > VO : Wy Uae a a ‘ , sy Pe ee a Ml od Fa } PTY Werke.) Land it rs Moet Wee j Fae ar ane yy "i , 4 s') D ee aA Ny He a mh | An ihe . ij ‘ i ; ‘ va J a ‘ "th ie ' i ) j 1h, iw Wa | Fn he Ww Tas | ‘ \, : at. ie} é yi \ ’ y 4 ne, | if f t J he | a ‘ \s } J ‘Shah Me, Veiga see . as Neary Mer: ca Le ey my ae ie eth Wu) . Ge ‘Nhs wy WA ra na Bian SM aN we ate) MXit | HUT) a 5 ih aK iM wy 1 th ime ie al 1! zy Beibans Lk See