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Geoscience Canada

The Tooth of Time: Cesare Emiliani Paul F. Hoffman

Volume 39, Number 1, 2012

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Publisher(s) The Geological Association of Canada

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Cite this document Hoffman, P. F. (2012). The Tooth of Time:: Cesare Emiliani. Geoscience Canada, 39(1), 13–16.

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The history behind the development of some of the fundamental concepts in the geosciences is truly fascinating. Some outstanding characters with brilliant insights have laid the foundations of our discipline. This history has a full cast of characters, and major advances have been made by drinking potions laced with ingenuity, serendipity and happenstance. Hypotheses have come and gone, great debates have raged. You all know Paul Hoffman as a researcher of the highest stature, and he has garnered a host of the most prestigious national and international awards for his research. Paul is also a passionate student and disciple of this history, and as is evi- dent from his photograph, he has lived through many of them! He will contribute a column, aptly entitled Tooth of Time, to each issue of Geoscience Canada. His contri- bution to this issue is the first of many fascinating narratives of how major discover- ies are made, the amazing characters to whom we owe so much, and the importance of mentorship as transformative ideas are handed from generation to generation. Photo credit: Francis Macdonald, 2004. Column The Tooth of Time: Cesare all Linnean names an emphatic Bolog- Turekian recently remarked, “Geo- nese accent in his honour. Only decades chemists are often accused of acting Emiliani after the fact did I begin to appreciate like God. There are good reasons for the historic circumstances of Emiliani’s this.” Paul F. Hoffman 1216 Montrose Ave., Victoria, BC talk in Miami. In 1946, Urey had been asked V8T 2K4 Emiliani studied micropaleon- (by Paul Niggli) after a talk at ETH in tology and published on Cretaceous and Zürich whether it might be possible, Pliocene forams in wartime and post- given that rainwater was isotopically It’s funny how a seemingly minor event war northern Italy. He won a Fellowship lighter than seawater, to distinguish in graduate school can take on deeper to in 1948 and marine and continental carbonates by meaning later on. We had a day to kill after a long drive from Baltimore to was recruited by into his isotopic analysis. Urey did some calcula- Miami through the Deep South. It was research group, which was dedicated to tions and discovered that there was a 1967 and we had long hair. Carbonate realizing the dream that “such a tran- measurable temperature effect to con- sedimentologist Bob Ginsburg had sient physical quantity” as the tempera- tend with. “I suddenly found myself come to Johns Hopkins two years earli- ture of seawater could be faithfully with an isotopic thermometer in my er, bringing Paleozoic limestones back recorded in rocks for a hundred million hands.” he said (2). Not quite. The res- to life in Florida Bay, the Florida Keys years or more (1). The group included olution of their mass spectrometer had and Great Bahama Bank. He had to engineer Charles McKinney (who to be improved by a factor of ten. And spend the day bartering with boat oper- supervised the construction of a dupli- they had to figure out how to extract ators but he suggested we attend a talk cate mass spectrometer to the one CO2 gas from carbonate shells without on forams at the Institute of Marine designed by Al Nier in Minneapolis), contamination from the embedded Science (). To be Urey’s graduate student John McCrea organic matter, a problem Epstein honest, I don’t remember much about and Sam Epstein, a postdoctoral solved by a method still used today (3). the substance of the talk, except that chemist with an interest in By 1951, Urey’s group had perfected the the shells of one foram species coil to from Winnipeg by way of McGill. Urey, measurement of paleotemperatures in the left where it is cold and to the right a Nobel laureate in chemistry in 1934 ancient carbonates and were able to where it is warm–just like American (age 41), was the most important Amer- show that a 150-million-year old belem- politics. But I remember the speaker, a ican Earth scientist of the 20th century, nite from the Isle of Skye had lived for fast-talking, high-voltage Italian whose remarkable considering that he devoted four winters and three summers at tem- presentation was so charged with con- only a dozen papers and a tiny fraction peratures ranging from 15 to 21°C, and viction that for years afterwards I gave of his career to Earth science. As Karl that the winters grew progressively 14 colder during its lifetime. Urey hoped to form nor invariant over time. Epstein North Atlantic. He observed that test the idea that climate change was and Toshiko Mayeda had shown that indigenous (not reworked) marine responsible for the extinction of the the subtropical surface waters are heavy, fauna, mainly molluscan, occur sparing- dinosaurs, but the results were inconclu- due to net evaporation, while equatorial ly in the tills and abundantly in the strat- sive. Emiliani would take Urey’s pale- waters, estuaries and the Arctic Ocean ified Drift, up to hundreds of feet othermometer in a new direction. (a large estuary) are light. During an ice above contemporary sea level. He also Emiliani reasoned that younger age, the entire ocean becomes heavier in pointed out that the Drift fauna of carbonate would be better preserved proportion to the volume and degree of Scotland more closely resembled his and that the was a logical isotopic depletion of the ice sheets. Arctic collections than those of the target because of large temperature Emiliani was acutely aware that temper- Clyde (7), an inference subsequently changes associated with the ice ages. He ature and ice volume have complemen- confirmed by Edward Forbes (8). The had studied a Pleistocene foraminiferal tary isotopic consequences for first observation created a major stum- section near and had proposed foraminiferal calcium carbonate, but in bling block for the glacial theory, which a paleoenvironmental proxy based on what proportions? He went to great predicted a large sea-level fall just when foram dimensional variability (prosperi- lengths to show that the saw-tooth the fauna in the lowland Drift indicated ty brings uniformity). In 1951, he sam- changes in the oxygen isotopes of spe- submergence (9). There were no marine pled a Lower Pleistocene section in the cific pelagic forams he observed down- fossils in the Alpine glacial deposits and Palos Verdes Hills of Los Angeles, find- hole correlate with changes in hence the Swiss proponents the glacial ing strong oxygen isotope variations. foraminiferal speciation and size, then theory had no explanation for submer- But correlation with existing the more established proxy for environ- gence, a problem not resolved until long chronology, hopelessly tied to 50-year- mental stress. He studied the depths at after the glacial theory was finally old work on the north slope of the east- which different foraminiferal species accepted (10). Smith’s second observa- ern Alps–Günz, Mindel, Riss, Würm– live as a means of disentangling temper- tion created a problem for climate was impossible. The same year, he ature from ice volume isotopically. He physics. It was then widely assumed that heard a lecture by Hans Pettersson reasoned that temperature change dur- global climate could only get colder describing recent Swedish innovations ing glacial-interglacial cycles was greater over time as the Sun grew dimmer in deep-sea piston coring. Cores from in surface waters than at depth. Deeper- through the loss of radiant heat. the Swedish Deep-Sea Expedition of dwelling species should therefore show Europe was experiencing the last 1947-48 showed quasi-periodic varia- less isotopic change than shallower ones advance of the Little Ice Age, so there tions in calcium carbonate content, if temperature was the main determi- was historical as well as geological (pale- which Gustaf Arrhenius had interpret- nant, but all depths should change in obotanical) evidence for climatic cool- ed in terms of glacial (higher content) lock-step if ice volume was in sole con- ing. The faunal evidence for a geologi- and interglacial (lower content) cycles. trol. He selected four species of plank- cally recent warming implied that cli- Arrhenius numbered the glacial (even tonic forams that live at different depths mate change was bidirectional, a chal- numbers) and interglacial stages (odd and analyzed them independently. Com- lenge to physics that led explicitly to the numbers) counting backward from the paring the down-hole curves, Emiliani experimental demonstration of the so- present interglacial, a scheme later concluded that about 60% of the vari- called greenhouse effect by the Irish- transferred to isotope records. Emiliani ance was temperature and 40% was ice English physicist John Tyndall in 1861 saw his chance and visited Göteborg, volume (5). (11). Never underestimate the power of obtaining samples from a number of This was not the first time humble mollusca. Atlantic and Pacific deep-sea cores. invertebrate paleontology played a piv- Fast forward 100 years to 1961. These were supplemented by samples otal role in the struggle to understand Teddy Bullard, head of Geodesy and Urey obtained from Maurice Ewing at the ice ages. In 1836, the celebrated Geophysics at Cambridge University Lamont from the Atlantic and Scottish yachtsman, conchologist and was now convinced that Emiliani’s Caribbean. In two of the Swedish cores, Biblical scholar James Smith application of Urey’s paleothermometer much sediment was missing and the (1782–1867) of Glasgow–not to be held great promise, and a new stable core tops, the first samples to be ana- confused with the English map- isotope lab dedicated to paleotempera- lyzed, turned out to be Miocene and maker–first used the term “till” in a tures was established in the Quaternary Oligocene in age, based on their benth- geological sense, for a “stiff unstratified Research unit at Cambridge. The lab ic forams. Isotopic analysis of these clay, confusedly mixed with boulders” would reflect nearly 15 years of techni- same forams showed that deep-ocean (6). Together with overlying stratified cal improvements since Urey’s mass bottom water temperature was 7°C in clays and gravels, till forms what was spectrometer was installed at Chicago. the Miocene and 10°C in the Oligocene, then called the Diluvium, or Drift, of Setting up the new lab would be the compared with 2°C today. Emiliani had Newer Pliocene age. (The name Pleis- PhD project(!) for a recent Cambridge found a first-order climate change in tocene was introduced by Lyell in 1839 physics graduate and son of the East deep time in spite of himself (4). but he disavowed it. The name was not Africa field geologist Robert Shackle- Not everything would come so used during the great controversy over ton. Nick Shackleton was up to the task easily. The problem for Pleistocene the glacial theory of 1837–1865.) Smith and by 1967, the year of his PhD (and paleotemperature is that the isotopic sailed extensively and dredged for shells my trip to Miami), the Cambridge lab composition of seawater is neither uni- in the Clyde Estuary and the Arctic was producing data more precise than GEOSCIENCE CANADA Volume 39 2012 15 the Chicago lab (12). But the crux of change in lock-step, as they should do if of Pacific Core V28-238 from the the problem wasn’t precision, it was the the composition of seawater, not its Solomon Plateau, which yielded a beau- same uncertainty plaguing Emiliani, temperature, was in control. Recalling tiful isotope record of 22 stages, tied for now at the University of Miami: the an argument put forward by oceanogra- the first time to the Brunhes–Matuyama effect of seawater temperature versus pher Wally Broecker, Shackleton sug- geomagnetic reversal (0.78 Ma) in stage global ice volume on oxygen isotopes in gested that because the glacial ocean 19 (16). The isotope record from V28- carbonate. Both Emiliani and Shackle- was saltier, planktonic forams had risen 238 could be correlated stage by stage ton did mass-balance calculations, based into warmer waters due to buoyancy. with Emiliani’s records from the oppo- on estimated volumes and isotopic Emiliani appears to have neglected this site side of the globe (17). CLIMAP compositions for peak glacial and inter- factor and it must have galled the foram also spawned Shackleton’s collaboration glacial ice sheets: Emiliani’s estimate of specialist to be caught out by a newly- with Jim Hays (Lamont) and John the mean isotopic depletion of the Lau- minted PhD geochemist. But then Imbrie (Brown), resulting in the spectral rentide ice sheet was –15‰ PDB, less Shackleton showed his class. In conclu- analysis of deep-sea records that resur- than half the value calculated by Eric sion, he wrote, Emiliani’s curves rected the Milankovitch theory as the Olausson in Göteborg (based on Wili become even more valuable because pacemaker of the ice ages (18). This Dansgaard’s data from Greenland), sub- they constitute a direct record of the ice turn of events brought joy to Emiliani, sequently confirmed by Shackleton (13). ages, not an indirect record through sea- who had been an outspoken supporter The result was that Emiliani’s calcula- water temperature (14). of the Milankovitch theory during its tion underestimated the ice-volume The ice-volume only paradigm eclipse (19). effect by a factor of two. prevailed for twenty years before the Neither Emiliani nor Shackle- Shackleton reasoned that tide turned again in the 1990s as data ton are alive to correct my reconstruc- abyssal bottom water could not have from terrestrial climate records (paly- tion of events, but Bob Ginsburg been much colder during ice ages nology, tropical snow-line elevations, remembers. His off-hand suggestion because it is close to the freezing point noble gases in tropical groundwater), that a bunch of travel-weary graduate today. So he measured the compositions porewaters from deep-sea cores, and students go to a talk on forams was any- of coexisting planktonic and benthic new paleothermometers (Mg/Ca, thing but. He knew Emiliani from his forams in two samples spanning the last Sr/Ca, alkenone unsaturation index) own graduate-school days at Chicago. glacial–interglacial transition in a tropi- confirmed that the tropics did cool sig- He knew what we were in for, if we cal South Pacific deep-sea core. He sup- nificantly during glacial maxima after all. took the bait. Thanks Bob. plemented his data with paired benthic- Today the respective contributions of planktonic results from Atlantic and temperature and ice volume to the REFERENCES AND NOTES Caribbean cores published by Emiliani. foram isotope record are thought to lie (1) Urey, H.C., 1948, Oxygen isotopes in Because benthic forams are larger and about halfway between Shackleton’s nature and in the laboratory: Science, v. less abundant, fewer individuals con- estimate and Emiliani’s. 108, p. 489-496. tributed to each analysis: the result was Both went on to greatness. In (2) Emiliani, C., 1995, Two revolutions in scatter in the data because bioturbation 1967, Emiliani was appointed Chairman the Earth Sciences: Terra Nova, v. 7, p. can disturb the mean age of a few shells of Geology and Geophysics at the 587-597. more readily than a few hundred, lead- Marine Institute (later Rosenstiel School (3) Epstein, S., 1997, The role of stable ing to asynchroneity between the two of Marine and Atmospheric Sciences) isotopes in geochemistries of all kinds: populations in a sample. Nevertheless, and of Geological Sciences on the main Annual Reviews of Earth and Plane- the best-fit line in a benthic-planktonic campus of the University of Miami, tary Sciences, v. 25, p. 1-21. cross-plot of the data had a slope close (4) Emiliani, C., 1954, Temperatures of positions he held until his retirement in Pacific bottom waters and polar super- to unity–as much isotopic change in 1993. He was instrumental in the estab- ficial waters during the Tertiary. Sci- bottom water as surface water (14). This lishment of the Deep-Sea Drilling Proj- ence, v. 119, p. 853-855. meant that ice volume was the domi- ect by NSF in 1968, with its emphasis (5) Emiliani, C., 1955, Pleistocene temper- nant factor. on paleoenvironmental records (15). atures: Journal of Geology, v. 63, p. Shackleton’s paper (14) Versed in the classics and virtually all of 538-578; Emiliani, C., 1995, op. cit. appeared in Nature on 01 July 1967 and science and its history, he was a spell- (6) Smith, J., 1836, On indications of was a direct attack on Emiliani’s asser- binding teacher and his textbook, Plan- changes in the relative level of Sea and tion that foram isotope change was pre- et Earth (1992), and The Scientific Land in the West of Scotland: Pro- dominantly a paleotemperature record. Companion (1987, 1995) filled a niche ceedings of the Geological Society, Despite the uncertainty as to whether I now occupied by Wikipedia. London, v. 2, p. 427-429. heard Emiliani on my first trip to Miami Shackleton became a key par- (7) Smith, J., 1837, On the Climate of the with Ginsburg (Spring 1967) or my sec- ticipant in CLIMAP, a multi-institution- newer pliocene tertiary period: Pro- ceedings of the Geological Society, ond (Spring 1968), it is likely that Emil- al NSF project to reconstruct LGM (last London, v. 3, 118-119. Smith’s collect- iani knew what was coming, even if it glacial maximum) sea-surface tempera- ed papers on geology were conve- hadn’t yet arrived. Moreover, the dagger tures globally, as a boundary condition niently republished as Researches in had a twist. Shackleton needed to for climate models. Resulting collabora- Newer Pliocene and Post-Tertiary explain why Emiliani’s planktonic tions at Lamont led to the recognition Geology. John Gray, Glasgow, 199 p., species from different depths did not with magnetostratigrapher Neil Opdyke 1862. 16

(8) Forbes, E., 1846, On the connexion Letters, v. 33, L15706, doi: between the distribution of the exist- 10.1029/2006GL026923 ing fauna and flora of the British Isles (14) Shackleton, N., 1967, Oxygen isotope and the geological changes which have analyses and Pleistocene temperatures affected their area, especially during re-assessed: Nature, v. 215, p. 15-17. the epoch of the Northern Drift: (15) Shor, E.N., 1985. A chronology from Memoirs of the Geological Survey of Mohole to JOIDES. in Drake, E.T., Great Britain, v. 1, p. 336-403. and Jordan, W.M., eds., Geologists and (9) Maclaren, C., 1842, The glacial theory ideas: a history of North American of Prof. Agassiz: American Journal of geology: Geological Society of Ameri- Science and Arts, v. 42, p. 346-365. ca Centennial Special Volume 1, p. (10) Shaler, N.S., 1874, Preliminary report 391-399. on the Recent changes of level on the (16) Shackleton, N.J., and Opdyke, N.D., coast of Maine: Memoirs of the 1973, Oxygen isotope and paleomag- Boston Society of Natural History, v. netic stratigraphy of equatorial Pacific 2, p. 321-323, 335-340; Jamieson, T.F., Core V28-238: oxygen isotope tem- 1882, On the cause of the depression peratures and ice volumes on a 105 and re-elevation of the land during year and 106 year scale: Quaternary the glacial period: Geological Maga- Research, v. 3, p. 39-55. zine, v. 9, p. 400-407, 457- 466. (17) Emiliani, C., and Shackleton, N.J., (11) Tyndall, J., 1861, On the absorbtion 1974, The Brunhes epoch: isotopic and radiation of heat by gases and paleotemperatures and geochronology: vapours, and on the physical connex- Science, v. 183, p. 511-514. ion of radiation, absorbtion, and con- (18) Hays, J.D., Imbrie, J., and Shackleton, duction – the Bakerian Lecture: Philo- N.J., 1976, Variations in the Earth’s sophical Magazine, Ser. 4, v. 22, p. orbit: pacemaker of the ice ages: Sci- 169-194, 273-285; Tyndall, J., 1863, ence, v. 194, p. 1121-1132. On radiation through the Earth’s (19) Emiliani, C., and Geiss, J., 1959, On atmosphere: Philosophical Magazine, glaciations and their causes: Geologis- Ser. 4, v. 25, p. 200-2006. Tyndall’s col- che Rundschau, v. 46, p. 576-601; lected papers on atmospheric science Emiliani, C., 1969, Interglacial high were conveniently republished as Con- sea levels and the control of Green- tributions to Molecular Physics in the land ice by the precession of the Domain of Radiant Heat. Longman’s, equinoxes: Science, v. 166, p. 1503- Green and Co., London, 446 p., 1872. 1504; Emiliani, C., 1978, The cause of (12) Elderfield, H., 2006, Professor Sir the ice ages: Earth and Planetary Sci- Nicholas Shackleton: The Independ- ence Letters, v. 37, p. 349-352. ent, Obituaries, 08 February. (13) Emiliani, C., 1955, op. cit.; Emiliani, C., 1966, Isotopic paleotemperatures: NOTE Science, v. 154, p. 851-857; Olausson, E., 1963, Evidence of climatic "Exception to Geoscience Canada's Style changes in North Atlantic deep-sea Guide applies to this column only." cores, with remarks on isotopic pale- otemperature analysis: Progress in Oceanography, v. 3, p. 221-252; Dans- gaard, W., 1961, The isotopic compo- sition of natural waters, with special reference to the Greenland ice cap: Meddelelser om Grønland, v. 165(2), 120 p.; Shackleton, N., 1967, Oxygen isotope analyses and Pleistocene tem- peratures re-assessed: Nature, v. 215, p. 15-17; Dansgaard, W., and Tauber, H., 1969, Glacier oxygen-18 content and Pleistocene ocean temperatures: Science, v. 166, p. 499-502. For a recent estimate, supportive of Olaus- son and Shackleton, see Sima, A., Paul, A., Schulz, M., and Oerlemans, J., 2006, Modeling the oxygen isotopic composition of the North American Ice Sheet and its effect on the isotopic composition of the ocean during the last glacial cycle. Geophysical Research