Glacial Surges and Flood Legends

Emiliani et al. (1) propose that a peakin the oxygen isotope profile for a sedi-ment core from the Gulf of Mexico repre-

sents a sudden influx of glacial meltwaterfrom the Mississippi River 11,600 years

before the present (B.P.), and that the at-tendant rise in sea level initiated legendsabout floods around the world, includingthe deluge described by Plato as havingoccurred 9000 years before the age of So-lon.

Emiliani et al. apparently take theircue from a study by Kennett andShackleton (2), which attributes a peakin oxygen isotope profiles from the west-ern Gulf of Mexico to freshwater influxfrom the wasting Laurentide ice sheet inthe Great Lakes area about 17,000 to11,500 years B.P. In an apparent attemptto make the explanation more specific,Emiliani et al. note that Bloom's curve

showing the rate of retreat of the Lauren-tide ice sheet (3) has a conspicuous knickfor the Valders readvance of 11,800years B.P., representing a 2 percent in-crease in ice area. They further noteBloom's suggestion that the Valders iceadvance into the Lake Michigan, LakeSuperior, and Lake Winnipeg lowlandsmay have been a glacial surge, which is arapid distension of a glacier beyond itsnormal terminus, perhaps resulting fromthe buildup of water beneath the ice.They assume that the wastage of the dis-tended ice lobe should be equally rapid,accounting for a sea-level rise of "deci-meters per year."

This series of arguments from glacialsurge to the dialogues of Plato involvesseveral important weaknesses and unjus-tified speculations:

1) A normal ice advance results in a

lowering of sea level. The curve of latest-Quaternary sea-level change does notshow the temporary 2-m fall and thenrapid rise expected from the Valders 2percent increase in ice area and presum-

ably in ice volume. A surge might explainthe discrepancy, because it involves no

change in the mass budget of the glacierand thus no change in climate. However,there is so much scatter in the radio-carbon dates on which the sea-level curveis based that it is not possible to deter-mine whether a 2-m fluctuation in sea

level occurred at this time.2) The Valders ice advance entered

only the Lake Michigan, the Green Bay,and possibly the Huron basins. Late-Wisconsin advances into the westernLake Superior Basin and the Lake Winni-peg Basin were not necessarily contem-poraneous with the Valders ice advance

1268

of 11,800 years B.P., and in any case

they were not very substantial (4). Thechange in ice sheet area should thereforebe less than the 2 percent calculatedby Bloom.

3) A surge of the Lake Michigan lobeas far south as Milwaukee, along with a

possibly contemporaneous surge into theupper part of the Lake Huron Basin,should decant the water of proglaciallakes into the Mississippi River. Roughcalculations of the water volume in-volved show that sea level would rise a

small fraction of a centimeter. As the icemelted, some of the water would bestored once again in proglacial lakes,thereby reducing the rate of subsequentrise in sea level.

4) Recent study of the glacial stratig-raphy and geomorphology around LakeMichigan indicates that the so-called Val-ders ice advance of 11,800 years B.P. ex-

tended only to Two Creeks, Wisconsin,and that the 350-km advance to Milwau-kee was older (5). This revision reducesthe "Valders" ice volume changes andpotential marine effects substantially.

5) It is true that a surge carries an icelobe beyond its normal, climatically de-termined equilibrium limit, and that thedistended portion stagnates and is sub-ject to melting. This melting is not neces-

sarily instantaneous, however, for stag-nant ice produced by surging can persistfor thousands of years after its emplace-ment. Such is the case, for example, withglacial surges in the Yukon, because ofthe development of a protective cover ofrock debris melted out ofthe ice (6). Evenif the surged ice lobe were clean, calcula-tions based on mid-latitude solar radia-tion as well as those based on ablationrates for modern mid-latitude glaciersshow that it would take a great manydecades to melt the several hundredmeters of ice involved. The rate of sea-

level rise in this case would be less thana centimeter per year-hardly cata-strophic.

6) The "peak" on the oxygen isotopecurve [figure 5 in (1)], even if it were statis-tically significant, is based on two sam-

ples apparently representing 20 cm ofthickness in the core. The sedimentationrate for this interval, according to the ra-

diocarbon dates, indicates that about1350 years are involved in the two san'i-

ples. Furthermore, each of the two datedcarbon samples represents 20 cm of sedi-ment and a similar span of time. Thechronological control is therefore notgood. The selection of a precise datewithin a few decades of 1 1,600 years B.P.,

as required for a catastrophe, is i

justified.7) Using more conspicuous oxyi

isotope anomalies in three cores from 1western Gulf of Mexico, Kennett aShackleton (2) made a more reasonalcase for the freshening of seawaterglacial meltwaters produced during Ientire wastage of the ice sheet in IGreat Lakes area. Kennett and Shackton correlated the three cores by mat(ing the midpoints of a major biostrzgraphic zone boundary dated at ab(11,000 years B.P. in other cores from tGulf of Mexico and Caribbean Sea. Tpeaks are dated on the assumptionconstant sedimentation rate at each sbefore 1 1,000 years B. P. In the core wthe highest sedimentation rates,; tsharpest and most reliable peak (weight sample points) is dated as coverithe entire interval between about 17,0and 11,500 years B.P.; in the other tocores, the peak occurs at about 20,00015,000 years B.P. and 12,000 to 10,0years B.P. The differences among tdates for the four cores involved (thicores of Kennett and Shackleton and ocore of Emiliani et al.) indicates tithere is little basis for placing the evcprecisely at 11,600 years B.P.

8) In view of the uncertainty associed with the effects of a "Valders" ice 9

vance on ocean isotopic composition asea level, and the uncertainties in datiand correlation, it is hardly justified totribute flood legends around the worlda single such catastrophic geologic ev4for which there is no evidence. The aceracy of the figure of 9000 years, attruted by Plato to a catastrophic delulis accepted by few archeologists and htorians. Plato wrote in the 4th centLB.C., quoting conversations between 'lon (who lived 200 years before) aEgyptian priests (who were encouragiSolon to tell stories of his ancestorThe priests told Solon a story of the stmergence of Atlantis 9000 years bef(by great earthquakes and deluges, aPlato elaborated on the account. Maexplanations for the story and the datihave been offered, including the eruptiof the volcanic island Santorini (Thein the Aegean Sea (7). This eventcurred about 1450 B.C., accordingboth archeological dating and radcarbon analysis, and it is believedsome to have been responsible for the 4

struction of the Minoan culture on CreThe date is closer to 900 than 9000 yebefore Solon, and the discrepancycommonly attributed to an error in trscription or translation of early do,ments (8).

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Few anthropologists or archeologiststake seriously any attempt to attribute a

flood myth to a single worldwide eventso many thousands of years before. Af-ter all, Greece was still inhabited by hunt-ers and gatherers 11,600 years ago-a

people far different from those in theworld of Solon and Plato (9). Myths are

easily generated by people who live in a

natural setting and transmit their cultureorally, and the tales are readily embel-lished by the storyteller, are substan-tially modified, and often are even

merged with other myths (10).H. E. WRIGHT, JR., JULIE STEIN

Centerfor Ancient Studies, UniversityqfMinnesota, Minneapolis 55455

References and Notes

1. C. Emiliani, S. Gartner, B. Lidz, K. Eldridge,D. K. Elvey, T. C. Huang, J. J. Stipp, M. F.Swanson, Science 189, 1083 (1975).

2. J. P. Kennett and N. J. Shackleton, ibid. 188,147(1975).

3. A. L. Bloom, in Late Cenozoic Glacial Ages, K.K. Turekian, Ed. (Yale Univ. Press, New Ha-ven, Conn., 1971), pp. 355-379.

4. H. E. Wright, Jr., Geol. Soc. Am. Mem. 136(1973), p. 251; in Geology of Minnesota, P. K.Sims and G. B. Morey, Eds. (Minnesota Geolog-ical Survey, Minneapolis, 1972), pp. 515-547.

5. D. M. Mickelson and E. B. Evenson, Geology 3,587 (1975).

6. V. Rampton, Can. J. Earth Sci. 7, 1236 (1970).7. D. Vitaliano, Legends of the Earth (Indiana

Univ. Press, Bloomington, 1973).8. J. V. Luce, Lost Atlantis; New Light on an Old

Legend (McGraw-Hill, New York, 1969), p. 181.9. T. Jacobson,J. Field Archaeol. 1, 303 (1974).

10. One such story is in Dorothy Vitaliano's readablebook about myths and geology (7, p. 151): "Ahighly illuminating example of how a legend canbe transferred from one culture to another literal-ly overnight was related by Alice Lee Marriottin a New Yorker article some years ago. Whenshe was collecting the folklore of a South Dako-ta tribe, she was challenged one day by the oldIndian who was her informant to tell him one ofthe tales of her people. She thereupon relatedthe story of 'the Brave Warrior and the WaterMonsters'-Beowulf. Few changes were neces-sary; it was 'all within the patterns of legendarybehavior, which the old man could understand,and I reflected that there might be more to thisuniversal-distribution-of-folklore than I had real-ized.' A little later she heard him relate the storyto an audience of his people, 'and I must admitthe old man made a better story of it than I did.A born, creative storyteller, he added bits hereand there to round the tale out and make itricher. So must the story of Beowulf have gone,many centuries ago, from hearer to hearer, im-proved and embellished until at last it was writ-ten down.' The punch line of her article told howa few years later in an ethnological journal shecame across a paper entitled 'Occurrence of aBeowulf-like myth among North American In-dians,' published by a graduate student who, inviolation of an unwritten law among ethnolo-gists, had been using the same informant."

28 October 1975; revised 12 February 1976

It is reassuring to read in Emiliani etal. (1) that isotopic curves from the Gulfof Mexico are being viewed in terms of"the dynamics of the Laurentide icesheet." However, this view was antici-pated by Kennett and Shackleton (2)who discussed these phenomena in rela-tion to their isotopic analysis of cores

from the western Gulf of Mexico. Unfor-tunately, their cores do not have abso-lute age calibration, but the conclusions

24 SEPTEMBER 1976

of Kennett and Shackleton and the inter-preted chronology seem very realistic.Certainly at times of maximum extensionof the Laurentide ice a broad sector of itsfront-some 2800 km (straight-line dis-tance) from Montana to western Pennsyl-vania-was draining into the Gulf ofMexico via the Mississippi River and itstributaries. Such drainage continued dur-ing the waning phases of a glaciation un-

til the ice front retreated sufficiently foralternate drainage routes to be opened,mainly to the St. Lawrence River, as rec-

ognized by Kennett and Shackleton (2).The abrupt shift of glacial meltwatersfrom the Mississippi to the St. Lawrenceroute has been documented by Broeckeret al. (3) on the basis of an abrupt changein sediment type off the Mississippi del-ta.

Unfortunately Emiliani et al. have un-

derestimated the effects of the meltingice sheet on the isotopic composition ofGulf of Mexico waters in that they con-

sider only meltwater flow in the south-ward direction during the "Valders"readvance, which they date at 11,600years before the present (B.P.). The re-

port of Emiliani et al. (1) presents some

misconceptions about the fluctuations ofthe Laurentide ice front near the end ofthe last glaciation that need some clari-fication. Our investigations over the last5 years or so (4, 5) have shown that (i)the "Valders" readvance did not forman exaggerated ice lobe in the Lake Mich-igan Basin as previously believed and (ii)the type Valders Till as traced from Val-ders, Wisconsin, underlies rather thanoverlies the Two Creeks forest bed.Therefore, the till overlying the TwoCreeks forest bed has been renamed"Two Rivers Till" (5) and is evidence ofthe "Two Rivers" readvance (6). Thereis no longer any reason to believe thatthe Two Rivers (formerly "Valders")readvance was an ice surge because therevised ice front position now indicatesthat the amplitude of that readvance was

about 60 percent of earlier estimates.Thus, the ice front at that time did not ex-

ceed that of the preceding (Port Huron)readvance in the Lake Michigan Basin,as previously believed. In fact, the PortHuron readvance was of much greateramplitude than the Two Rivers read-vance, and it has not been considered a

surge. Furthermore, it has been sug-

gested (7) that the Two Rivers ("Val-ders") readvance was essentially con-

fined to the Lake Michigan Basin withonly very limited counterparts, if any atall, in other ice lobes along the southernfront of the Laurentide ice sheet. Inshort, the readvance formerly called

"Valders" was a relatively minor read-vance and should not be considered asurge even in the Lake Michigan Basin.The isotopic curve for the Gulf of Mex-

ico [figure 5 in (1)] is very striking in thatthe most dramatic change in isotopic val-ues occurs prior to 11,600 years B.P., infact, prior to 12,220 years B.P. Betweenabout 14,500 and 12,220 years B.P. the8180 value shifted from -0.3 to -2.20per mil. This shift of 1.9 per mil is 75 per-cent of the entire range of 8180 values incore GS7102-9. The curve of 8180 valuesactually flattens out after 12,200 yearsB.P. and begins to decrease toward pres-ent-day values after 10,865 years B.P.The large shift in isotopic values be-

tween 14,500 and 12,220 years B.P. cor-responds exactly to the time of major re-treat of the Laurentide ice front. Kennettand Shackleton (2) have placed the great-est deviation in their isotopic values atabout 13,500 years B.P. At 14,500 yearsB.P. the ice was at or near its maximumextent throughout much of the UnitedStates sector, but by about 12,000 yearsB.P. both the James River ice lobe andthe Des Moines ice lobe had retreatedsome 1200 km, the Lake Huron lobesome 400 km, and the Erie lobe some 400to 500 km. In contrast, the documentedretreat of the Lake Michigan lobe wherethe subsequent Two Rivers advance oc-curred was only about 300 km (8). Themeltwater of all of these lobes drained in-to the Mississippi system, introducingvast amounts of 180-poor water over a2000- to 2500-year interval. We contend,along with Kennett and Shackleton (2),that this important retreat of the Lauren-tide ice was responsible for the dramaticshift in isotopic values in Gulf of Mexicowaters.On the other hand, the disintegration

of the Two Rivers ("Valders") ice-surge or not-occurred at a time whenthe configuration of the Laurentide icefront was such that (i) all the meltwatereast of the state of Michigan drainedeastward via the St. Lawrence River intothe Atlantic Ocean and (ii) much of themeltwater in the Canadian Plains sectorwas temporarily stored in Glacial LakeAgassiz before draining into the Missou-ri-Mississippi system. Lake Agassiz hadan areal extent of about 31,000 km2 atany given time and an average depth ofabout 100 m (9), and thus containedsome 3100 km3 of glacial meltwater.Therefore, the meltwater in the Cana-dian Plains sector did not run off immedi-ately to the Gulf of Mexico. Moreover,after 9500 years B.P., if not earlier, muchor all of the Lake Agassiz outflow passedeastward via Lake Superior to the St.

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Lawrence (9). The importance of thesedrainage changes can be seen clearly inthe curve for core GS7102-9 [figure 5 in(1)] which shows little isotopic change be-tween 12,220 and 10,865 years B.P., a pe-riod encompassing much of the Twocree-kan retreat and all of the Two Rivers("Valders") advance and retreat. Thus,we contend further, much as Kennettand Shackleton did (2), that the isotopicvalues ceased their rapid decline afterabout 12,200 years B.P. and shifted to-ward present-day values at the time of di-version of the major part of meltwaterdrainage away from the Gulf of Mexicoto the Atlantic Ocean.One further point concerns the coinci-

dence "within all limits of error" ofdates of 11,600 years B.P. both for the"Valders" event as seen by Emiliani etal. (1) and for the deluge "9000 years be-fore Solon." In the first place, the age forthe "Valders" event (11,600 years B.P.)is an interpolated age without any as-signed confidence limits. Second, if thedate for Solon's flood is a true calendardate, it may be out of phase with the ra-diocarbon age for the "Valders" eventby as much as 600 years. Dendrochrono-logical calibration of radiocarbon dates(10) has shown the radiocarbon dates tobe consistently 600 to 700 years tooyoung in the calendrical range from 3600to 5350 B.C. (5550 to 7300 years B.P., ap-proximately). The calibration curve doesnot yet extend beyond 7300 calendaryears ago, but it is unlikely that a radio-carbon year equals a calendar year at11,600 years B.P.

Several conclusions seem in order:1) The isotopic curve for the Gulf of

Mexico does faithfully reflect the majorevents of the Laurentide ice front.

2) The focus of Emiliani et al. (1) onthe "Valders" (Two Rivers) advanceand retreat does injustice both to the icesheet record and to the isotopic recordbecause the most dramatic shifts in bothof them occurred in the period betweenabout 14,500 and 12,200 years B.P., asdemonstrated by Kennett and Shackle-ton (2).

3) The Two Rivers ("Valders") read-vance was almost certainly not a surge,the surge hypothesis being based on a re-construction of ice lobation now shownto be incorrect.

4) The isotopic curve of core GS7102-9 from the Gulf of Mexico does not re-cord the Two Rivers ("Valders") eventbecause at the time of that event andthereafter most of the meltwater of theLaurentide ice front drained via the St.Lawrence into the Atlantic Ocean, asconcluded by Kennett and Shackleton(2).

1270

5) The correspondence in calendarage between Solon's flood and the TwoRivers ("Valders") event is more appar-ent than real because of variations in ra-diocarbon activity.

WILLIAM R. FARRANDDepartment ofGeology andMineralogy, University ofMichigan,Ann Arbor 48109

EDWARD B. EVENSONDepartment ofGeological Sciences,Lehigh University,Bethlehem, Pennsylvania 18015

References and Notes

1. C. Emiliani, S. Gartner, B. Lidz, K. Eldridge,D. K. Elvey, T. C. Huang, J. J. Stipp, M. F.Swanson, Science 189, 1083 (1975).

2. J. P. Kennett and N. J. Shackleton, ibid. 188,147(1975).

3. W. S. Broecker, M. Ewing, B. C. Heezen, Am.J. Sci. 258, 429 (1960).

4. W. R. Farrand, Geol. Soc. Am. Abstr. Pro-grams 2, 387 (1970); D. M. Mickelson and E. B.Evenson, Geology 3, 587 (1975).

5. E. B. Evenson, Geol. Soc. Am. Bull. 84, 2281(1973).

6. The Valders Till was the source of the name ofthe Valderan Substage, a time-stratigraphic unitencompassing the time immediately followingthat of the Two Creeks forest bed. Because ofthe revised position of Valders Till relative tothe forest bed, we are suggesting the term"Greatlakean" as a replacement for the mislead-ing term "Valderan" (E. B. Evenson, W. R.Farrand, D. M. Mickelson, D. F. Eschman, L.J. Maher, Quat. Res. N. Y., in press).

7. A. Dreimanis and R. P. Goldthwait, Geol. Soc.Am. Mem. 136 (1973), p. 96; H. E. Wright, C. L.Matsch, E. J. Cushing, ibid., p. 165.

8. V. K. Prest, Geol. Surv. Can. Map 1257A(1969).

9. J. A. Elson, in Life, Land and Water, W. J.Mayer-Oakes, Ed. (Univ. of Manitoba Press,Winnipeg, 1967), p. 37.

10. E. K. Ralph, H. N. Michael, M. C. Han, MAS-CA Newsl. (University of Pennsylvania MuseumApplied Science Center for Archaeology, Phil-adelphia) 9 (No. 1), 1 (1973).

17 November 1975; revised I March 1976

The recent reports by Kennett andShackleton (1) and Emiliani et al. (2) areimportant because in them an attempt ismade to link the isotopic record -of theoceans (more specifically the Gulf ofMexico) with the complex history of thesouthern margin of the Laurentide icesheet. In a companion technical com-ment, Farrand and Evenson (3) state whyserious reservations must be expressedagainst the correlation of Emiliani et al.of a shift in the isotopic record in coreGS7102-9 with the "Valders" readvance.My purpose in this comment is to pointout that the suggested rise in sea levelof "decimeters per year" (2) at about11,600 years before the present is far toorapid.

Let us take the extreme case of a surgealong the entire southern margin of theLaurentide ice sheet. Since we are corn-cerned only with order-of-magnitude cal-culations, I will take the 2800-kmstraight-line figure of Farrand and Even-son (3) as the length of the perimeterdraining southward. Let a 100-km surgeoccur with an average ice thickness of 1

km. Furthermore, assume that this icemass (2800 by 100 by 1 km) melted in asingle year. The mass of water containedin this surge is 2.5 x 1014 mi3, whereasthe area of the world oceans is3.61 x 1014 m2. The global ocean equiva-lent rise contained in this ice mass is thusonly about 0.7 m. As a result, there is nocompelling reason to correlate the "Val-ders" readvance with the folklore of theflood, and certainly the suggested rateof sea-level rise cannot be ascribed tosuch an event. There is already muchdifficulty in accounting for the rapidretreat of the Laurentide ice margin asit is (4) without having to considelthe energy requirements necessary forablating the ice sheet at a rate that wouldlead to a "decimeters per year" rise insea level.

J. T. ANDREWSInstitute ofArctic and AlpineResearch and Department ofGeological Sciences, University ofColorado, Boulder 80309

References

1. J. P. Kennett and N. J. Shackleton, Science 188,147 (1975).

2. C. Emiliani, S. Gartner, B. Lidz, K. Eldridge,D. K. Elvey, T. C. Huang, J. J. Stipp, M. F.Swanson, ibid. 189, 1083 (1975).

3. W. R. Farrand and E. B. Evenson, ibid. 1931269 (1976).

4. J. T. Andrews, Arct. Alp. Res. 5 (No. 3, part 1).185 (1973).

24 November 1975

None of the above authors seems to beaware of the fact that the eastern Gulf ofMexico is scavenged by 29 ± 5 x 10 m3sec-' of Gulf Stream water [the LoopCurrent (1)]. The measured isotopic ef-fect [2.5 per mil; see (2) and (3)] demon-strates, for the top 200 m, where 50 per-cent of the transport occurs, a salinitydecrease of 8.3 percent for an ice melt-water composition of -30 per mil (2) or adecrease of 16.6 percent for a composetion of -15 per mil (4). Correspondin1fluxes are 1.2 x 106 and 2.4 x 106sec-', and corresponding sea-level risesare 10.5 and 21.0 cm year'. Renewedprecipitation from the thawing northernNorth Atlantic (5) and northeastern Pa-cific was probably feeding the channeledsurges which best explain the magnitudeof the flood. Although it is not possibleto establish exactly the duration of theflood because reworking by benthicmetazoa spreads out the oceanic record,I reject Wright and Stein's indiscrimi-nate usage of age estimates to discountour 14C ages as well as Farrand and Ev-enson's preference for estimated ages todocumented 14C ages. Furthermore, Iwish to point out to Farrand and Even-son that maximum flooding in a contin-uously flushed basin does not corres-

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)ond to maximum change in isotopic:omposition but to zero change at the,eak. I would point out to Andrews thatialid conclusions cannot be drawn from-alculations which fail to take precipi-.ation into account.The isotopic evidence demonstrates

:hat there was a massive flood in the Gulf)f Mexico, peaking about 11,600 yearsigo. Since nature is self-consistent, I;uggest that those who have commentedn our report revisit their tunnel valleysmd spillways to look for the matchingwvidence.With respect to Plato and the "At-

antis Connection," I refer the reader to6).

CESARE EMILIANI)epartment of Geology,7niversity of Miami,Wiami, Florida 33124

References and Notes

I. W. D. Nowlin, Jr., Oceanol. Int. 6, 28 (1971);W. J. Merrell, Jr., J. M. Morrison, R. L. Moli-nari, W. D. Nowlin, Jr., I. H. Brooks, R. Yager,in Proceedings ofthe Second Cooperative Inves-tigations for the Caribbean and Adjacent Re-gions Symposium (Unesco, New York, inpress).

2. J. P. Kennett and N. J. Shackleton, Science 188,147 (1975).

3. C. Emiliani, S. Gartner, B. Lidz, K. Eldridge,D. K. Elvey, T. C. Huang, J. J. Stipp, M. F.Swanson, ibid. 189, 1083 (1975).

4. C. Emiliani, ibid. 154, 851 (1966).5. _ _ and J. Geiss, Geol. Rundsch. 46, 576

(1958).6. C. Emiliani, in Sea Frontiers (International

Oceanographic Foundation, Virginia Key, Mi-ami, in press).

7. Only 3 weeks were allowed by the editors ofScience for the preparation of this reply. Sincemy co-authors of (3) are presently scatteredfrom Florida to Taiwan, it was impossible tocontact them. This reply, therefore, is necessari-ly written by the senior author alone. I amgrateful to G. Maul for discussions on the east-ern Gulf Loop Current. Financial support wasprovided by the National Science Foundation(grants GX36155, GA36189X, and DES 74-23459).

20 July 1976; revised 28 July 1976

Criteria for the Discovery of Chemical Elements

The availability of suitable heavy-ionmccelerators in a number of laboratoriesn Europe and the United States shouldnake it possible to synthesize and identi-y additional heavy transuranium ele-nents. The predicted small yields of;uch nuclides require identification ofdtomic number to be made with individ-ial atoms. This places a large burden on

-he experimenter and can lead (and inact has led) to differences of opinion as

o the extent of experimental proof re-

iuired to establish definitely that the pro-luction of a new element has been ob-;erved. There is also the possibility that;uperheavy elements may be found iniatural sources. We attempt here to de-ine criteria for adequate proof that a

iew element has been synthesized or

ound in nature, and identified-that is,liscovered.The basic criterion, of course, must be

he proof, by some means, that the atom-c number (Z) of the new element islifferent from the atomic numbers of all,reviously known elements. This means,n general, that the atomic number;hould be established. It should not beiecessary to establish the mass number,-xcept insofar as this evidence is directly-elated to the method used for establish-ng the atomic number.Chemical identification constitutes an

deal proof that an element with a newmtomic number has been produced. Twomportant requirements should be met inhis kind of experiment. First, the chem-cal procedure should be of a type that isialid for application to individual atoms;.he use, for example, of ion exchange4 SEPTEMBER 1976

adsorption-elution or partition betweensolvents has been shown to meet thiscriterion in many situations, and suchmethods also provide safeguards againstcomplicating surface adsorption and en-

trainment effects. Second, it must bepossible to determine the presence or

absence of the new element in the appro-priate chemical fractions in an unequivo-cal manner. If the new element is ob-served through its decay by high-energyalpha-particle emission or spontaneousfission, or both, the chemical identifica-tion can be confined to separation fromall known elements with atomic numbergreater than lead (Z = 82).

Unfortunately, chemical identificationis not always feasible in the initial experi-ments, as demonstrated by the reporteddiscoveries of the last several syntheticelements; this circumstance has contrib-uted significantly to the competingclaims for the discovery of these ele-ments. (No such differences of opinionhave arisen over the discoveries, basedon chemical identification, of mendelevi-um and earlier transuranium elements.)Fortunately, there are methods based on

the observation and use of nuclear prop-erties that should be adequate to furnishunambiguous identification of atomicnumber.

Also satisfactory is the identificationof characteristic x-rays in connectionwith the decay of the isotope of the newelement. In actual practice this is likelyto involve measurement of the half-lifeand precise, unique energies of the alphaparticles of the new element in coinci-dence with the characteristic x-rays of

the daughter nuclide. However, it mightbe possible to measure characteristic x-rays of the new element itself (primaryproduct) if these can be associated withthe subsequent immediate decay of thisnuclide. Thus, such short-lived x-rays,which may be emitted in the course of,or as an aftermath of, the production ofthe primary product, might be followedvery shortly by emission of alpha parti-cles or fission fragments which could bedetected by delayed coincidence tech-niques. The characteristic x-rays must,of course, be distinguished from gammarays of similar energies-perhaps byidentification of the complex structure ofthe x-rays.The proof of a genetic decay relation-

ship through an alpha-particle decaychain in which the isotope of the newelement is identified by the observa-tion of previously known decay productsshould be acceptable. This method de-pends on measurement of the half-lifeand precise, unique energies of the alphaparticles of the new isotope, and mea-surement and identification of the half-life and decay properties of the daughter,whose identity, including atomic num-ber, has been previously established.Time correlation between parent anddaughter should be established. Use of agenetic relationship as evidence for anew element implies that the mass num-ber of the new element isotope is experi-mentally determined by its relationshipto a daughter nuclide of known massnumber.

Detection of a spontaneous fission ac-tivity and measurement of its half-lifecannot per se establish that an elementwith a new atomic number has been pro-duced. Even when additional informa-tion, such as fragment mass and kineticenergy distributions, can be obtained,the atomic number assignment for newelements cannot be made on this basisalone since the systematics and theo-retical predictions cannot be extrapolat-ed with the necessary certainty into newregions. Similarly, the use of the predict-ed half-lives for spontaneous fissiondecay and alpha decay and of predictedalpha-decay energies cannot yet be con-sidered sufficiently reliable for establish-ment of the atomic number of a newelement.The present understanding of produc-

tion yields, excitation functions, angulardistributions, and so forth is not suf-ficient to allow measurements to estab-lish with certainty that a nuclide with anew atomic number has been produced,although such data may be useful assupportive evidence. It is particularlydifficult to establish and interpret the

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Glacial Surges and Flood LegendsH. E. WRIGHT JR. and JULIE STEIN

DOI: 10.1126/science.193.4259.1268 (4259), 1268-1269.193Science 

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