When will the present interglacial end?

QUATERNARY RESEARCH a, 341349 (1972)

When Will the Present Interglacial End?

NILS-AXEL MOURNER ‘l

Received May 9, 1972

We are now living under interglacial climatic conditions, the Present Interglacial or Flandrian Interglacial Age. It will certainly be followed by the Future Ice Age. The major cold/warm changes seem to have a cyclicity of ~0,500 yr. We have been in the second cycle (characterized by cooler climate’) after ‘the Last Ice Age for 2200 yr and will continue to be so for another 8300 ir. By analogy with the conditions during the Last Interglacial it is concluded that this cycle will remain mod- erately warm. With the end of the third cycle at about 18,800 years AP, the Present Interglacial will end and the First Future Glacial Age begin. Further information about the climatic conditions during the “cold” cycle 117,700-107,200 y. a. is necessary, however, before a really well-founded prediction can be made.

RANK AND NOMENCLATURE OF THE PRESENT PERIOD OF INTERGLACIAL CLIMATIC

CONDITIONS

From the end of the Last Ice Age (the Weichselian-Wisconsin Ice Age) we have been living under interglacial conditions. This interglacial can be named the Flandrian Interglacial Age or the Present Interglacial. It covers the same period of time as the local North European chronostratigraphic unit “Postglacial” (not to be confused with the facies term “postglacial”).

The boundary between the Weichselian Glacial Age and the Flandrian Interglacial Age also marks the boundary between the Pleistocene Epoch and the Holocene Epoch (Fig. 1) .

The Flandrian Interglacial Age will end when the First Future Glacial Age (or the Kukla Glacial Age as suggested in 1968 by the author) starts. The Holocene Epoch, on the other hand, will, of course, continue up

1 Department of Geology, University of Stock- holm, Box 6801, S-113 86 Stockholm, Sweden.

to the next epoch boundary, and will therefore probably cover several future glacials and interglacials (MGrner, 1969). It is need- less to speculate about the end of the Holo- cene Epoch. The end of the Flandrian Inter- glacial Age, on the other hand, can probably be fairly well established from the cyclicity of the climatic changes in the past.

CHRONOLOGY AND CLIMATIC CY CLICITY

Unfortunately, nonabsolute chronologies prevent really reliable correlations and final understanding of the climatic changes. How- ever, the major cold/warm changes seem to correspond to astronomical changes (closely discussed by Kukla, 1969, 1970, this volume) having a cyclicity of about 11,000 yr. This climatic cyclicity has, of course, not come to an end with the end of the Last Ice Age. It seems reasonable to assume that the history of the Present Interglacial will, in general, be a repetition of the history of the Last Interglacial, although the astronomical situation (the eccentricity of the orbit) is somewhat different. If we, therefore, had

341 Co yright 0 1972 by Academic Press, Inc. A$ rights of reproduction in any form reserved.

342 MiiRNER

known the characteristics of the climatic cy- long major cold and warm intervals (corre- cles after the second last glacial/interglacial sponding to a complete cycle of 21,000 yr), boundary (Termination II, according to which was found to agree well with available Broecker and van Donk, 1970), and espe- dates (and precessional cycle). cially, which cycle corresponded to the be- ginning of the Last Ice Age, we would have been able to give a good prediction of the climatic changes in the future. This is not yet the case, however, because of insufficient number and quality of dates, preventing final correlation between our various climatic records.

THE PRESENT INTERGLACIAL

The Flandrian (or Postglacial) “climatic optimum” was undoubtedly passed long ago. The first climatic deterioration (leading to the end of the “climatic optimum”) seems to have occurred 3480 radiocarbon yr BP (Miirner, 1969a, p. 425, 196913; Nichols, 1970 ; Curray et al., 1969). A second, even stronger, climatic deterioration occurred about 2200 BP (von Post, 1944)) recorded by several different parameters (Morner, 1972d) in areas representing the whole globe (pollen diagrams, sea level curves, deep-sea curves, etc.). It is of the greatest interest to know whether or not any of these climatic deterioration marks the end of a

The continental glaciations in America and Europe during the Last Ice Age record cold/warm changes that are correlatable (Gross, 1967; MGrner, 1970, 1972a, 1972b) despite reliable dates for the older part. This is illustrated by Fig. 2, which also includes Emiliani’s deep-sea stages and the main sea level data. Time scale in Fig. 2 is hypothetical and based on a repetition of 10,500 yr

Era -

?

”

0

N

0

z

y1

”

Weichselian

18,800AP

AD 1972

10,000 BP 12,700

9zooo

2 13,000

Holsteinian

244.000

Neogane 10

25

FIG. 1. Subdivision of the Cenozoic Era (cf. van Eysinga, 1971; British National Committee for Geology, 1969 ; MBrner, 19691~).

THE INTERGLACIAL END 343

major climatic cycle. In my opinion, the deterioration at about 2200 BP marks the end of the first warm cycle after the Last Ice Age.

For climatic-astronomical reasons, Kukla (1969, 1970) puts the last glacial/interglacial boundary at about 10,500 BP. With a duration of about 11,000 yr for each major warm o’r cold cycle, this would mean that we very soon would reach into a new cold cycle. At the INQUA VIII Congress in Paris (1969) it was proposed that the Pleis- tocene/Holocene boundary - and by that also the last glacial/interglacial boundary- should be placed at “the date 10,000 BP, measured in radiocarbon years.”

However, several facts (Greenland IsO curve, sea level data, glaciation curves, deep- sea data, etc.) seem to indicate that an even more drastic climatic change occurred at about 12,700 radiocarbon yr BP (Morner, 1970, 1972b, c and d). This is 10,500 yr prior to the distinct deterioration at 2200 yr BP. A cyclicity of 10,500 yr for the major cold/warm changes (Fig. 2) fits perfectly well with all available dates. This suggests that the first cycle, characterized by warm climate, after the Last Ice Age ended 2200 y. a., and that we are now in the second cycle, which will last for another 8300 yr and be characterized by cooler climate. The third cycle will again be characterized

Postgloc,al g, Flandrian 1 ice free 1 ice free c ~t~C_e~e~ 1 ice free

;g _ _ _ _ _ _ _ _ _. _ __ ._...... .___.__._.. - ..,. Hsngelo Thorncl. II 3 M,d

k stadial Seminory Till Port f strotificd P, a Moershoofd Tharncliffe I Talbot

Plcaront E II I

5 G,.S+e Soil it drif’ I I I

I I -.- main #nOi” Sunnybrooklill Da..-..:,.” I main

~--iion Early

: 0rsrup 1 valley erosion 1 “’ Pierre

0. I T . 111 u ._ 7 0

P”-, :”

P,a-w,“D rtadial Scarborough I yI

Stadial Formation BdccancourTill till5

Formation 1 Sdl ‘? ( Stod.

FIG. 2. Regional correlations (Morner, 1972a). Curve to the left gives a generalized picture of the major cold/warm changes during the last 130,000 yr (grey = cold), Time scale (in thousands of years BP) is hypothetical, and based on a periodicity of 10,500 yr for the major cold/warm changes (corresponding to a complete cycle of 21,000 yr), which was found to agree well with available dates (and precessional cycle). The first two columns illustrate the north European stratigraphy in glaciated areas (Southern Scandinavia) and nonglaciated areas (the Netherlands), respectively. The next four curves illustrate the North American stratigraphy in the Scarborough Bluff section in Toronto, the Eastern Great Lakes region in general, the Illinois State region, and the Washington State region, respectively. The next two columns show Emiliani’s paleotemperature stages, and the main sea level information (B = Barbados, T = Tyrrhenian), respectively. The last column gives the Ages and Subages according to the present author (MBrner, 1971). For particulars, see MGrner (1972a).

344 M6RNER

by warm climate. It will end 18,800 yr AP, a date which will probably mark the end of the Present Interglacial.

By comparisons with the conditions during the Last Interglacial we can learn, whether the second cycle, which we are now living in, can be expected to lead to a new ice age or to a small climatic deterioration, only.

THE LAST INTERGLACIAL

The Last Interglacial, the Eemian-Sanga- mon Interglacial Age, ended with the begin- ning of the Pre-Briirup Stadial in Europe and the Pre-St. Pierre Stadial in North America (Fig. 2). The question is, however, whether this first stadial of the Last Ice Age corresponds to the second or the fourth climatic cycle after the second last glacial/ interglacial boundary (Termination II).

In deep-sea records, the Last Interglacial appears to be represented by Stage 5 in Emiliani’s (1955) palaeotemperature scheme, and Zone X in the foraminifera zonation by Ericson and Wollin (Ericson et al., 1961). This is an oversimplification, however. Emi- liani’s Stage 5 has been subdivided by Shackleton (1969) into five substages (5a- 5e) ; 5a, 5c and 5e corresponding to warmer periods, 5e forming the climatic optimum, and 5b and 5d corresponding to cooler periods. Zone X by Ericson and Wollin does not correspond to the entire Stage 5 of Emiliani ; only Substages 5e, 5d and 5c, judging from cores Al74-4 and V12-122, which are analysed in both respects (Wollin et al., 1971, Figs. 2 and 4; Emiliani, 1964, Fig. 6). This suggests that there is an important boundary “hidden” between Sub- stages 5c and 5b. This is also indicated by core 280 (Emiliani, 1958 ; Olausson, 1960), as illustrated by Fig. 3 ; the charac- teristic interglacial sedimentation of chalk ooze is restricted to Substages 5e-5c. Fur- thermore, there is a distinct cold peak in Substage 5b (cycle 4).

The sequence of elevated shorelines on

Barbados has provided good dates of the last three high sea levels (Mesolella et al., 1969), viz., Barbados I at about 82,000 BP, Barbados II at about 105,000 BP and Bar- bados III at about 125,000 BP. These three high sea levels fit perfectly well with the three warm cycles calculated from the astronomical data. They also seem to fit well with the three warm peaks of Emiliani’s Stage 5 (Figs. 2 and 3). Therefore, most chronological works are based on the Bar- bados dates.

According to Steinen et al. ( 1971), the Barbados III and II high sea levels are separated by a regression of about 75 m. This regression is based on information from a boring, located at a place where the Barba- dos II and I shore levels cannot be separated. The 75-m regression, therefore, has an uncertain stratigraphic position, and may as well fall between the Barbados I and II high sea levels (which would be in concord- ance with other records, e.g., the Mallorca sea level curve by Butzer and Cuerda, 1962). A 75-m regression must correspond to major continental glaciations in Europe and America, It closely corresponds to the eustatic drop calculated by Mijrner (1971, Fig. 4) for the Pre-Briirup Stadial (cf. (Fig. 2).

The Greenland IsO curve (Dansgaard et ul., 1969, 1971) shows climatic changes that seem to be fairly easily correlatable with glaciation curves and palynological results (Mijrner, 1971, Fig. 3 ; Dansgaard et al., 1971, Fig. 9). The time scale is quite float- ing-not to say misleading-however (Miir- ner, 1972c). In my opinion (Mijrner, 1971, 1972c), the Last Interglacial is represented by two warm periods (with very rapid ice accumulation), separated by a cold period (with slow ice accumulation).

The cold/warm changes as recorded by the continental glaciations in Europe and North America, seem to be directly correlatable (Fig. 2; Miirner, 197Za, 3972b). The absence of reliable dates of the Ear-

CORE 280

Strat. 6 0’8 %o % coca, Sed. rate Cycle


FIG. 3. Stratigraphy (Olausson, 1960), 180 curve (Emiliani, 1958), percentage of CaCO, (Olausson, 1960) and sedimentation rate in mm/year (this paper) of deep-sea core 280. Time scale is hypothetical, based on an assumed cyclicity of 10,500 yr for the major cold/warm changes. Stratigraphical column shows: chalk ooze = grey, marl ooze = white, marle ooze and mud = dashed, red clay = dotted. Time scale suggests distinct changes of the sedimentation rate. The changes of sedimentation rate follow the general climatic trends. The Last Interglacial comprised three major climatic cycles, and the Last Ice Age seven cycles. Sedimentation of chalk ooze (grey areas) is restricted to the Present Interglacial and Substages 5e and 5c of the Last Interglacial.

liest Weichselian-Wisconsin Subage and the Eemian-Sangamon Interglacial Age (Fig. 2) prevents final correlations with the deep-sea records and the sea level data, leaving three alternatives open (Fig. 4).

Alternative III, which (roughly) corresponds to Emiliani’s opinion (Emiliani, 1970, 1971), is hard to accept, for example,

because cycle 1 corresponds to a full interglacial with high eustatic sea level, whereas the Ohe (Gerdau, Treene) Interstadial (which separated the Warthe and Drenthe Stadials of the Saalian Glacial Age) had interstadial climate with much continental ice left, at least, in northern Europe.

Alternative II, which corresponds to the

346 M6RNER

opinion expressed in some other papers of this volume, is also hard to accept, mainly because the Earliest Weichselian would be very long compared to the Eemian, the Odderade Interstadial and the Pre-Odderade Stadial would be very long compared to the short time suggested by the information from their deposits, and the Odderade Inter- stadial would correspond to the SO,OO@high sea level, though the ice margin seems to have been in Southern Scandinavia during the Odderade Interstadial (Mijrner, 1972a, Fig. 9).

Alternative I is advocated in this paper, because it gives a logical interpretation of the glacial records, as well as the Greenland IsO curve, the deep-sea data and the sea level records. However, new facts may ap- pear “tomorrow” that changes the picture. One of the most promising parameters for the establishment of good correlations between deep-sea data and continental glacial records seems to be the palaeomagnetism, provided the Blake-reversed event found by Smith and Foster (1969) in deep-sea cores at around Emiliani’s Substages 5d-5c, is real (cf. Watkins, 19772, p. 563).

Advocating Alternative I (Fig. 4), it is

of the greatest interest to learn how cold the midinterglacial cold cycle (cycle 2,) of the Last Interglacial was. Figure 5 summarizes the most important records :

1. The pollen diagrams of Europe (van der Hammen et al., 1971, Fig. 2) record a very small deterioration of the climate in the middle of the Eemian-Pangaion Interglacial.

2. The Greenland IsO curve (Dans- gaard et al., 1969, 1971) record a cold period with its peak reaching -34%,, (MGrner, 1971, Fig. 3).

3. The regressional period between the Barbados II and III high sea levels (Mesolella et al., 1969) corresponds to the same cold period.

4. A regression of very small ampli- tude has been recorded between the Tyrrhenian IIa and IIb high sea levels on Mallorca (Butzer and Cuerda, 1962). It corresponds to the midinterglacial cold cycle, and suggests that the glacial advance was very small or insignificant.

5. The Last Interglacial corresponds to the older part of Emiliani’s Stage 5 in the deep-sea stratigraphy, viz.,

yYi 1 K,“p”,p 1 1 M$,r;r 1 I Alternative I I 1 Alternative II I I Alternative III I

60,000

FIG. 4. Climatic cycles according to Kukla (1969) and Mijmer (this paper; 197Za), and three alternatives of how to correlate these cycles with the main continental climatic record from Europe and the climatic deep-sea stages by Emiliani. Arrows indicate dates of Barbados high sea levels.


the three cycles which Shackleton the midinterglacial cold cycle and (1969) named Substages 5e, 5d records a weak cooling. and SC. Substage 5d corresponds to All the above-mentioned records (Fig. 5)

96700 B.P. 107200 117,700 128.200

Cycle 3 Cycle 2 Cycle 1

I I

I Eemian II Eemion Stadial Eemian I

FIG. 5. The threefold division of the Last Interglacial, the Eemiar-Sangamon Interglacial. Two interglacial warm cycles are separated by a weak cold cycle. (A) Pollen diagram from the Netherlands (van der Hammen et al., 1971, Fig. 2). (B) Pollen diagram from Philippi, Greece (Zoc. cit.). (C) The Greenland 180 curve (Dansgaard et al., 1969, 1971). (D) The sea level changes ; main curve from Mallorca (Butzer and Cuerda, 1%2), range of Barbados II and III dates, and range of all available dates (e.g., Emiliani and Rona, 1969). (E) The 180 curve of deep-sea core 280 (Emiliani, 1958) ; substages according to Shackleton (1969). The Present Interglacial, the Flandrian Interglacial Age, is supposed to pass the same three cycles as the Last Interglacial. Today, we seem to have reached 2200 yr into cycle 2, which will continue for another 8300 yr. The entire Flandrian Interglacial is supposed to end in 18,800 yr, when the First Future Glacial Age will start.

348 MijRNER

suggest that the midinterglacial cold cycle of the Last Interglacial only led to a small cooling with little or insignificant glacial advance. Therefore, I expect that the present midinterglacial cold cycle, which we seem to have been living in for the last 2200 yr and which we will continue to live in for the coming 8300 yr, will lead to a similar small cooling with little or insignificant glacial advance.

CONCLUSIONS

The Present Interglacial, the Flandrian Interglacial Age, will certainly be followed by a Future Glacial Age. The end of the Present Interglacial could probably be very precisely predicted after we learned the climatic changes of the past in more detail.

The major cold/warm changes have a cyclicity of about 11,000 yr; 10,500 yr according to this paper.

Climatically, the Present Interglacial, seems to have started 12,700 y. a. The first major climatic cycle ended 2200 y. a. We are now living in the second cycle (characterized by cooler climate) and will continue to do so for another 8300 yr. The third cycle will end at about 18,800 yr AP, when the First Future Glacial Age is supposed to begin.

The Last Interglacial is supposed to have comprised three major climatic cycles (last- ing from 128,200 to 96,700 BP). The second cycle-the counterpart to the cycle which we are now living in-seems only to have led to a small cooling with little or insignificant glacial advance.

The second cycle of the Present Intergla- cial (which we are now living in) can-by analogy with the conditions during the Last Interglacial-be expected to lead to no sig- nificant glaciation ; roughly keep the present conditions (modulated by climatic cycles of shorter periodicity) for another 8300 yr.

The Present Interglacial, on the whole, will end with the third interglacial cycle at about 18,800 AP.

Insufficient information about the climatic conditions during the second cycle of the Last Interglacial, prevent us giving a final answer to the question raised. At present we can only express our own opinions. The key to the future is still to be found in the past.

ADDENDUM BY AUTHOR

Several articles in this volume provide material strongly in favor of Alternative II of Fig. 4. This would mean that we are now rapidly approaching a future situation equiv- alent to the “Pre-B&up Stadial” (cf. Fig. 2)) characterized by continental glaciation over Fennoscandia and the Kolar Peninsula and tundra or park-tundra conditions in most of the rest of Europe (the “Pre-St. Pierre Stadial” of North America was similarly characterized by continental glaciation over northeastern North America and alpine glaciations in the mountain re- gions of the West Coast).

REFERENCES

British National Committee for Geology, Strat. Corn. Geol. Sot. London (1969). Recommenda- tion on stratigraphical usage. Proceedings of the Geological Society of London, 1969, No. 1655, pp. 139-166.

BROECKER, W. S., and VAN DONK, J. (1970). In- solation changes, ice volumes, and the 01s record in deep-sea cores. Reviews of Geophysics and Space Physics 8, (l), 69-198.

BUTZER, K. W., and &ERDA, J. (1962). Coastal stratigraphy of southern Mallorca and its impli- cation for the Pleistocene chronology of the Mediterranian Sea. Jozwml of Geology 70, 398- 416.

CURRAY, J. R., EMMEL, F. J., and CRAMPTON, P. J. S. (1%9). Holocene history of a strand plain, Lagoonal Coast, Nayarit, Mexico. Mem. Silitp. Intern. Laguneras Costeras. UNAM- UNESCO, Nov. B-30, 1967, Mexico, pp. 63-100.

DANSGAARD, W., JOHNSEN, S. J., MBLLER, J., and LANGWAY, C. C. (1969). One thousand centuries of climatic record from Camp Century on the Greenland Ice Sheet. Science 166, 377-381.

DANSGAARD, W., JOHNSEN, S. J., CLAUSEN, H. B., and LANGWAY, C. C. (1971). Climatic record re- vealed by the Camp Century ice core. IN “The Late Cenozoic Glacial Ages.” (K. K. Turekian, Ed.), pp. 37-56. Yale Univ. Press.


EMILIANI, C. (1955). Pleistocene temperatures. Journal of Geology 68, 538-578.

EMILIANI, C. (1958). Paleotemperature analysis of core 280 and Pleistocene correlations. Jozlrnal of Geology 68, 264-275.

EMILIANI, C. (1964). Paleotemperature analysis of the Caribbean Cores A254-BR-C and CP-28. Geological Sociefiy of America Bulletin 75, 129- 144.

ENIILIANI, C. (1970). Pleistocene temperatures. Science 168, 822-825.

EIIILIANI, C. (1971). The Last Interglacial : paleo- temperatures and chronology. Science 171, 571- 573.

EMILIANI, C., and RONA, E. (1969). Caribbean cores P6304-8 and P63@4-9: New analysis of absolute chronology. A reply. Science 168, 1551- 1552.

ERICSON, D. B., EWING, M., WOLLJN, G., and HEEZEN, B. C. (1961). Atlantic deep-sea sediment cores. Geological Society of America Bul- letin 72, 173-286.

VAN EYSINGA, F. W. B. (1971). “Geological Time Table.” Elsevier Publ. Co., Amsterdam.

GROSS, H. (1967). Eine ganz ungewijhnlich vollstgn- dige Fernkonnektierung letzeiszeitlicher Schich- tenfolgen von Nordarmerika nach Europa. Quar- t& 18, 157-161.

VAN DER HAMMEN, T., WIJMSTRA, T. A., and ZAGWIJN, W. H. (1971). The flora record of the Late Cenozoic of Europe. In “The Late Cenozoic Glacial Ages.” (K. K. Turekian, Ed.), pp. 391-424. Yale Univ. Press.

KUKLA, J. (1969). The cause of the Holocene climate change. Geologie en Mijnbouw 48, 250- 274.

KUKLA, J. (1970). Correlations between loesses and deep-sea sediments. Geologiska FBreltingens i Stockholm Fiirhandlingar 82, 148-180.

MESOLFZLLA, K. J., MATTHEWS, R. K., BROECKER, W. S., and THURBER, D. L. (1969). The astronomical theory of climatic changes: Barbados data. Journal of Geology 77, 250-274.

M~RNER, N.-A. (1969a). The Late Quaternary history of the Kattegatt Sea and the Swedish West Coast : deglaciation, shorelevel displace- ment, chronology, isostasy and eustasy. Sveriges

Geol. Uvtdersb’kn. C-840, 487 pp. MOURNER, N.-A. (1%9b). Eustatic and climatic

changes during the last 15,000 years. Geologic ea Mijnbouw 48, 389-399.

MGRNER, N.-A. (1969c). Discussion regarding the Pleistocene-Holocene boundary (contribution by Mijrner). Third Bull Subcom. Study Holocene INQ U-4, June 1969, p. 44.

MBRNER, N.-A. (1970). Comparison between Late Weichselian and Late Wisconsin ice marginal changes. Eiszeitalter Gegenwart 81, 173-176.

MGRNER, N.-A. (1971). The position of the ocean level during the interstadial at about 30,000 BP -A discussion from a climatic-glaciologic point of view. Canadian Journal of Earth Science 8, 132-143.

MOURNER, N.-A. (1972a). The cold/warm changes during the Last Ice Age: with special reference to the stratigraphy at DGsebacka and Ellesbo in southwest Sweden. Stockholm Contributions t’o Geology 84 :4, 51-77.

MBRNER, N.-A. (1972b). World climate during the last 130,000 years. Report Section 12, 24th Znter- rtational Geol. Congress, Montreal 1972, 72-79.

MOURNER, N.-A. (1972c). Time scale and ice accumulation during the last 125,000 years as indicated by the Greenland 018 curve. Geol. Maga- zine 108 (l), 17-24.

MOURNER, N.-A. (1972d). Climatic changes during the last 30,ooO years as indicated by land, sea and air data. Manuscript.

NICHOLS, H. (1970). Late Quaternary pollen diagrams from the Canadian arctic barren grounds at Pelly Lake, northern Keewatin, N.W.T. Arc- tic Alpine Research 2, 43-61.

OLAUSSON, E. (1960). Description of sediment cores from the North Atlantic. Reports of the Swedish Deep-Sea Expedition 7, 229-286.

VON POST, L. (1944). Pollenstatistiska perspektiv pb jordens klimathistoria. Ymer 1944, 79-113.

SHACKLETON, N. J. (1969). The last interglacial in the marine and terrestrial records. Proceed- ings of the Royal Society of London, B, 174, 135-154.

SMITH, J. D., and FOSTER, J. H. (1969). Geomag- netic reversal in Brunhes Normal Polarity Epoch. Science 163, 565-567.

STEINEN, R. P., HARRISON, R. S., and MATTHEWS, R. K. (1971). Eustatic low stand sea level between 105,000 and 125,000 BP: evidence from the subsurface of Barbados. Abstracts win’th pro- grants, Geological Society of America, 1971 An- nual Meeting, Washington, DC, pp. 720-721.

WATKINS, N. D. (1972). Review of the develop- ment of the Geomagnetic Polarity Time Scale and discussion of prospects for its finer defini- tion. Geological Society of America Bulletin 88, 551-574.

WOLLIN, G., ERICSON, D. B., RYAN, W. B. F., and FOSTER, J. H. (1971). Magnetism of the Earth and climatic changes. Earth and Planetary Science Letters 12, 175-183.

Documents

When will the present interglacial end?