R e p r i n t e d f r o m

WTiÄ T M ^ T l ^ ^ GEOGRAPHY

I ¡M M • 1 CLIMATOLOGY

1 Í 1 L Í U J U m

Palaeogeography, Palaeoclimatology, Palaeoecology 112 (1994) 113-123

The late-glacial moraine sequences in Mexico: is there evidence for the Younger Dryas event?

Klaus Heine Department of Geography, University of Regensburg, 93040 Regensburg, Germany

Received 20 January, 1994; revised and accepted 31 March, 1994

ELSEVIER

PALAEO GEOGRAPHY

CLIMATOLOGY

ECOLOGY

EcHtors-in-Chief

P. De Deckker Department of Geo logy The Austra l ian Nat ional Universi ty Canberra A.C.T. 0200 • Austral ia Tel.: 61 6 2492070 Fax: 61 6 2495544

C. Newton Department of Geo logy Syracuse Universi ty Syracuse, N Y 13244 U S A Tel.: 1.315.4432674

F. Surlyk Institute of General Geo logy Universi ty of Copenhagen 0ster Voldgade 10 DK 1350 Copenhagen K Denmark Tel.: (45) 35 32 24 53 Fax: (45) 33 14 83 22

G. F. Elliott, London R. M . Forester, Denver, C O L. A . Frakes, Ade la ide, S.A. B. Funnel l , Norwich M . Gaetani , M i lan F. Gasse , Orsay J . Gray, Eugene, OR A. Hal lam, B i rm ingham M . Hambrey, Liverpool J . Harris, Boulder, CO Hou Hong-fei , Beij ing J . A . E. B. Hubbard, London T. J . Hughes, Orono, M E K. Kelts, Minneapo l is , M N M. Leinen, Narragansett, Rl M . O. Manceñido, La Plata

V. Markgraf, Boulder, CO A. E. M. Nairn, Co lumb ia , S C E. C. O lson , Los Ange les , C A N. D. Opdyke, Gainesvi l le , FL Pinxian Wang , Shangha i W. Prel l , Providence, Rl R. A . Reyment, Uppsala S. Sav in , C leve land, OH M. Stuiver, Seattle, W A P. Swart , M iam i , FL D. H. Tarl ing, P lymouth T. N. Taylor, Co lumbus , OH H. Thierstein, Zürich F. B. van Houten, Pr inceton, N J H. Visscher, Utrecht D. H. Yaalon, Je rusa lem

Editorial Board

A. Azzarol i , Florence C. Babin , Vi l leurbanne E. J . Barron, Universi ty Park, PA Y. K. Bentor, La Jo l l a , C A W. A . Berggren, Woods Hole, M A K. Birkenmajer, Krakow H. J . B. Birks, Bergen A. J . Boucot, Corval l is , OR H. Chamley , Vi l leneuve d 'Ascq K. Chinzei , Kyoto M. B. Cita, Mi lan A. E. Cockba in , South Perth, W.A . T. J . Crowley , Col lege Stat ion, T X R. V. Dingle, Cape Town J . C. Duplessy, Gif-sur-Yvette J . Ehlers, Hamburg A. A . Ekdale, Salt Lake City, UT

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F A L A E O S E L S E V I E R * Palaeogeography, Palaeoclimatology, Palaeoecology 112(1994) 113-123 =

The late-glacial moraine sequences in Mexico: is there evidence for the Younger Dry as event?

Klaus Heine Department of Geography, University of Regensburg, 93040 Regensburg, Germany

Received 20 January, 1994; revised and accepted 31 March, 1994

Abstract

Geomorphologie, paleopedologic, tephrostratigraphic, and palynologic investigations together with radiocarbon dates provide ages for several late Quaternary glacier advances on the volcanoes of central Mexico. On the volcanoes La Malinche, Nevado de Toluca, and Iztaccihuatl, glacier advances have been dated older than 12,000 yr B.P. and between about 10,000 and 8500 yr B.P. The glacial chronostratigraphies from different volcanoes do not indicate a Younger Dryas glacial advance. During the late Quaternary phases with glacier advances can be correlated to changes in Laurentide ice sheet meltwater discharge into the Gulf of Mexico on the one hand and into the North Atlantic Ocean on the other hand. The central Mexican glacial history shows a regional pattern that is different from that of the Rocky Mountains or the South American Andes.

1. Introduction

To test the global relevance of the classical late Weichselian climatic fluctuations of Western and Central Europe many scientists tried to establish chronostratigraphies of climatic variations for other parts of the world. Recent investigations, however, from many different parts of the world, lend support to the supposition that the classical late Weichselian European chronostratigraphy in many aspects is a regional stratigraphy and thus cannot uncritically transferred to other areas of the world.

Of especial interest in global paleoclimate research are the tropics and subtropics and their response to climate change. Here I will present the results of investigations carried out during the last 25 years in the central Mexican highland.

Studies on Mexican glacial sequence were published by White (1962, 1986), White and Valastro (1984) and White et al. (1990), and based

on comprehensive research on the volcanoes L a Malinche, Pico de Orizaba, Iztaccihuatl, Popocatepetl and Nevado de Toluca by Heine (1975, 1984a, b, 1988a, 1989) (Fig. 1). Several late Quaternary moraine sequences can be recognized for each volcano within the area. The slopes of the volcanoes are dissected by erosion gullies (bar­rancas) which show the stratigraphic position of the moraines and tills and their relation to peri-glacial deposits, paleosols, debris flows, fluvial gravels, fluvial sands, loess-like so-called "toba" sediments, lava flows, ignimbrite deposits, and tephra. Different tephra layers as well as specific paleosols are useful stratigraphic markers in the late Quaternary deposits. To determine the strati­graphic sequence of tephra, both field characteris­tics and laboratory analyses were carried out. Radiocarbon dating of tephra layers was restricted to woody materials imbedded in the volcanic deposits. In addition wood fragments contained in gravel layers, peats, and calcrete deposits were

0031-0182/94/57.00 © 1994 Elsevier Science B.V. All rights reserved SSDI 0031-0182(94)00033-5

Fig. 1. Location of the volcanoes mentioned in text. 1 = Nevado de Colima (4180 m); 2- Nevado de Toluca (4558 m); 5= Ajusco (3952 m); 4= Tláloc (4160 m); 5= Telapón (4200 m); 6= Iztaccihuatl (5286 m); 7= Popocatepetl (5452 m); 8= La Malinche (4461 m); 9= Cofre de Perote (4282 m); 10= Pico de Orizaba (5700 m).

dated by radiocarbon. A l l radiocarbon dates are given as conventional 1 4 C ages. In some cases also archaeologic data were used for age correlation of late Quaternary deposits. Relative age-dating methods were used to demonstrate age difference in the till sequence. Such relative dating methods include topographic position, morphologic shape of the moraines, rock weathering parameters, thickness of eolian 4 f ctoba" sediments, soil proper­ties, and vegetation cover. Pollen analyses in sedi­ment cores from small volcanic craters, maars, and lakes covering the last 35,000 years were used for paleoclimatic inferences (Straka and Ohngemach, 1989).

2. Late glacial moraines and tills (15,000-8500 yr B.P.)

2. L Ld Malinche volcano

A sequence of late Quaternary lateral and termi­nal moraines is exhibited in Barranca Colorado on the western slopes of the L a Malinche volcano (Fig. 2). The moraines of group M III are dated

between 12,000 to 8500 yr B.P. based on tephra correlation. The underlying rB pumice marker horizon and the M II debris layer (Fig. 3) give the maximum age of 12,060±165 yr B.P. (Hv 4244) and the overlying tephra layers a minimum age of 8240±300 yr B.P. (W-1909). After the deposition of the rB pumice at about 12,000 yr B.P., "toba" sediments document a phase of eolian influence. This phase ended with the development of a soil (Typic Hapludand); this phase of soil forming is wide-spread and recognized all over central Mexico. These fossil soils (fBo2, see Heine, 1975) developed between 12,000 and 10,000 yr B.P. Based on extensive field observations and sedi­mentation rate calculations of the "toba" deposits as well as of an estimation of the time needed for the fBo2 soil development (Heine, 1975), the gla­cial advance of the group M III moraines was estimated to have occurred after circa 10,000 yr B.P.

The moraines of group M III can be attributed to three individual advances. The moraine M III 1 is separated from the moraine M III 2 by a thin layer of pumice and "toba" material and a weakly developed A h soil horizon. The moraines of group

^ S a n J u a n T e p u l c o , \ )

moraine

bg rock glacier

>I pre-Wisconsin I M I

II Mil III Mill IV MW

> TD

>- a fe a CD

fan deposits H pre-Wisconsin

^ Wisconsin and Holocene

f:; glacial boulders

y-, steep and high scarp

^ crest

scarp

volcanic cone

Fig. 2. La Malinche volcano. Glacial geomorphology. The sections of Fig. 3 are indicated by circles (1-6).

M III 2 are divided into two different till layers, again with a weakly developed A h horizon on top of the older till. According to investigations on age-dependent formation of andosols at different altitudes and on different material (Miehlich, 1991) the soil forming period of the fossil soils interbed-ded in the group III moraines could only have taken a short time (some tens of years), whereas the formation of the fossil soil underneath the moraine M III 1 must have lasted a minimum of 500 years.

On the eastern slopes of La Malinche volcano, the terminal moraines of group M III are found often at about 2930-3000 m a.s.l. A n erosional cut in the tills of the moraine M III 2 show the glacial sediments and their correlation to fossil soils and different tephra horizons (Fig. 3). The moraine material is unweathered and overlain by

toba. A weakly developed brown-earth soil of half a meter thickness was formed after the retreat of the glaciers and before the eruption of the volcanic tephra. Estimating the weathering thickness of the toba/debris sediments overlying the moraine and l 4 C ages of the tephra layers the retreat of the glaciers occurred not earlier than approximately 1000 years before the fall of the volcanic breccia, pumice, and ashes. Therefore, we assume that the M III glacier advances happened during the early Holocene between roughly 10,000 and 8500 yr B.P. For further details see Heine (1975. 1988a) and Heine and Ohngemach (1976).

2.2. Nevado de Toluca volcano

The geomorphologic map of the summit area of the Nevado de Toluca volcano (Fig. 4) shows

- western slopes -

summit area (Malde1968)

- 2910m a s.l. 2770m os I

."-- - lobo with - .ffdesite .V''V"" andesrte V>V/ breccia

Ah

V - -toba toba > *A-j»rJebnsond UQba & « o ^ pumice

2700m as I ~2900mosl

rBpumice ...••••••••Mil' fBV «Bou {gy

toba purrace (markerhorizon)

•fAh tBv

younger till

/ ^ - . . e . 1AhUBo3) ¿?£ m o r o , n e ( M n i 2 2 )

moraine (Mill 2,) pumice.portly tobo moranelMlIU,) fluvp-gtoccl sands

_''ce" Wh,

18.280 i500 (Hv13918)

rí o*Pofr moraine . ^ P ^ o ^ o (pn?-MddleWisconsr)

pumice

(D

5750*280 tW-1912) i n o n 74501250 (W-1923) 2930m as I. 82401300 (W-1909)

- eastern slopes —

-2900m asi ITAh(andosol)

w ^ g » g v S . 7.405l145(Hv4757) ,./t>5 ¿ breccia, lominoted

76901100 (Hv 4758)

76451 80(Hv4243) .715! 80(Hv4884) pumice (marker horizon)

moraine (Mil) fAhltBol) toba pumice (marker horizon) Tluviatile sediments tobo , qrovel

A oo . Txfiff'otile sed'nients (sond) On f°r/o °r?o° o o °d moraine ¿ O O ° °-2,

Fig. 3. La Malinche volcano. Late Quaternary sediments and tephrostratigraphic correlations.

GEUFLUCTION TALUS

H<1850A.D.

CD 0 £

fegfel UttlelceAge (MY)

E T I 3,5-2,0yrBP (MIY)

e523<11.5yrBP(Mm) ES2i>11,5yrBP(Mn)

i late advance <11.5yrBP(MHI)

I early advance E^>11,5yrBP(MII,MI)

[ir) U-SHAPED VALLEY

+ + V » >• s. ': ÄVV' ' <-y / — * '

A >'v 9 9 ° 4 5 ' V

A / ' f 'I

KjTILL ^1 DEBRIS

FLOW

DEBRIS f M l VOLCANIC FLOW LOBE LMJpLUG

WUPPER TIMBERLINE

IROAD

p 7 ) ROCHE . r y i CREST [#1 CRATER ra HUT L-i-lMOUTONEE L L J 0 " " 1 LSU|_AKE LJ-liaiiitu* [M]ROCK EZDBARRANCA S ^ L A K E

itude in meters)

K.Heine 1993

Fig. 4. Nevado de Toluca volcano. Glacial and periglacial geomorphology. The sections of Fig. 5 are indicated by circles (/ and 2).

several moraine systems. The moraines of group M III are developed on the northwestern, northern and southeastern slopes. Apart from the north­western slopes where Holocene rock glaciers over­ride the recessional moraines of group M III, many small recessional moraine walls are found between the M III terminal moraines and the summit areas of the volcano.

Tephrostratigraphic investigations document, that the moraines of group M III are underlain by a characteristic yellow-brown pumice/lapilli layer

that can be traced all over the Nevado de Toluca volcano (Fig. 5). This layer is the result of a violent Plinian-type eruption (Cantagrel et al., 1981; Bloomfield and Valastro, 1974) that took place at about 11,600 yr B.P. (Bloomfield and Valastro, 1974). The layer is called the Upper Toluca Pumice. Charcoal from thin layers between the Upper Toluca Pumice and the underlying soil, fluvial sands, weathered Tertiary andesite, and valley-fill lahar deposits was dated to 11,850 + 220 yr B.P. (Tx-1601), 11,470±90 yr B.P. (Tx 1602),

4200 m a.s.l.

-<0 °°o'o

Ah (andosol)

moraine (Mill)......--'"

'weathered (pumice) (UpperToluca Pumice) pumice ash

¿120 m a.s.l

».0 <- - °

Tephra sequences (Bloomfield & Valastro Cantagrel et al. 1981)

1974;

-;TTTTT|||in||i

7 ¿ / Upper Toluca Pumice

(andosol) fBv

/ "f*Bb2

(D fBol

Lahar

Lahor

11,050*130 (Tx-11,470 ± 90 (Tx 11,850 i 220 (Tx-

950±100 (Tx-Lower Toluca

f24.4l'0 ± 590(Tx-25,620 ± 680 (Tx-24330 ± 670 (Tx-25020 ± 590 (Tx-25250 ±760 (Tx-23340 ± 600 (Tx-24,260 ± 670 (Tx-24,590 ±280 (Tx-24,440 ±550 (Tx-

121,170 ±170 (Tx-

1603) :-l6

1601) •1600) Pumice 1518) 1519) 1520) 1521) 1522) 1523) 1524) 1596) 1597) 1598)

Fig. 5 . Nevado de Toluca volcano. Late Quaternary glacial sediments and tephrostratigraphic correlation with the sections of Bloomfield and Valastro (1974).

11,050±130 yr B.P. (Tx 1603), and 11,950± 100 yr B.P. (Tx 1600) (Bloomfield and Valastro, 1974).

The upper Toluca Pumice was overridden by a glacier advance. At many sites glacial deposits rest on the Upper Toluca Pumice layers (Fig. 5). It is striking that the Upper Toluca Pumice deposits are deeply weathered. Even in altitudes above 4000 m thick andosols developed on the pumice beds documenting a long period of undisturbed soil formation after the eruption of the tephra ca. 11,600 yr B.P. Fully developed andosols are found in such altitudes only after several thousand years of weathering (Miehlich, 1991). Therefore, the glacier advance forming the moraines of group M III must have happened at the earliest after 10,000 y r B . P .

2.3. Iztaccihuatl

Late Quaternary glacial sequences were investi­gated by White (1962), Heine (1975, 1988a), and Vázquez Selem (1989, 1991). Unfortunately, no exact dating of the late glacial moraines was pos­sible. To obtain more 1 4 C dates for the late glacial moraines, I cored the sediments between the moraine walls of group M II and M III in the Apatlaco valley on the southern slopes of

Iztaccihuatl (Fig. 6). The sedimentary sequence is shown in Fig. 7.

Again, different tephra layers can be used as marker horizons (Heine, 1975; Miehlich, 1974; Robin, 1984; Boudal and Robin, 1989). The area of the Apatlaco valley was glaciated after the deposition of the so-called P 3 pumice layer (Miehlich, 1974; Heine, 1975). The pumice P 3 is attributed to an eruption of Popocatepetl volcano about 14,000-15,000 yr B.P. (a discussion of the P 3 pumice and its age is given by Vázquez Selem, 1989). Lozano-Garcia et al. (1993) estimate an age of ca. 16,500 yr B.P. for this pumice. The moraines of group M II (Fig. 6) indicate a glacier advance after 15,000/14,000 yr B.P. in the Apatlaco valley. Several recessional moraines show that the glacier retreated while forming terminal moraines near the coring site. The advance of the glacier forming the group M III moraine near the coring site documents that the ratio between glacier tongue and accumulation area was different from that of the glaciers of group M II; the M III glacier is characterized by a longer glacier tongue in the Apatlaco valley. This observation {clearly documents that the M III glacier advance depos­ited the long lateral moraine that dammed up the outlet of the small cirque valley. The sediment

sequence behind the moraine wall M III was formed after the M III glacier advance.

The oldest sediments of the core (Fig. 7) yield a 1 4 C age of 10,190 + 215 yr B.P. (Hv 13919). This date and correlation with different tephras of the adjacent area suggest an age of the M III glacier advance prior to ca. 10,000 yr B.P. Absence of organic material underlying the dated sample, sug­

gests that the M III moraine was deposited not much before ca. 10,000 yr B.P.

3. Results

Dated sections containing glacial deposits from three different volcanoes of the central Mexican

Apatlaco valley 3780 m a.s.l.

750 t 85(Hvtt3l5 840* 65(HvU327) n r m

880 + 965 ±

(CFR5598 -(Hv4788 hm

I860 i 60 (^14324)}^ 2.8751 75 (HvU325 ) ^ ^ - v l ; 1

andosol volcanic ash (CD andosol pumice (PI)

andosol volcanic ash (C2) J-lm

3,260 í 75 (Hv 14326 2,9901 85 Hv 14328 2515t 95(Hv14329

9JSL°.?l pumice (P 2)

3,7001110 (Hv14330H

6,1001 95(Hv14331) C

andosol

i m i i i i andosol 11111111 . rxfy***: organic mud

9.640 l440(CFR 5596) 10,190l215(Hv13919)

1 4Cages of P3pumice (Liddicocrtet al, 1974.1979; Vazquez Selem/1991) 14,7701280 125001400 14,5401 90(Tx1913)

¡í'.ljV;/:) (with reeds) sand with plants silt with plants

S ^ K J ^ p u m i c e with plants ^ s i l t with plants

•.r=r.r\sand silt

.é f i iv .^sand /¿Sggpsand and gravel

boulders

14,4501100 14,7701280 13,1801290

1x1914) Gx 878 1x1784)

Fig. 7. Apatlaco valley, Iztaccihuatl. Situation of the late Pleistocene moraines and tephra layers. 1 4 C ages in boxes refer to sections in the vicinity. The stratigraphic correlation is based on the tephra layers PI and P2 (see Heine, 1988b; Boudal and Robin, 1989).

highland give evidence for late Quaternary glacier advances that occurred between ca. 10,500 and 8500 yr B.P. (conventional radiocarbon years). Although there are no 1 4 C dates for the very onset of the so-called M III glaciation, tephrostrati-graphic correlations as well as soil development suggest that there was no glacial advance during the period 12,000-10,000 (10,500) yr B.P. Thus, during the Younger Dryas period no expansion of

glaciers occurred in central Mexico. Evidence for this was presented in earlier publications (e.g. Heine, 1975, 1988a).

Why do the central Mexican glaciers not read-vance during the Younger Dryas period? We sug­gest that the Mexican glaciers reflect the climatic conditions of the Gul f of Mexico. In recent years, the late Quaternary history of the Gul f of Mexico was studied in detail. Many authors show that in

10;

15-

20

25

30-

35H

38

Mexico ~Í9°N HEINE1988 (>4000m) Glacier advance Fbleosol

Popocatepetl . . tephra i Mississippi meltwater

—1P—

M M ifBo3 I im Tim

Mol

fBöl

"3P~

*>40 z z

Oglesby et al.1989

Gulf of Mexico

5-11 times the present average discharge, ~20°C cooler than present-day ambient Gulf of Mexico sea surface temperature

meltwater influence ?

cool meltwater cap very large, 6°C cooling of SST

cool meltwater cap large

low sea level causes weak loop current

meltwater influence ?

St. Law­rence mettwater

K.9

16.5

1 4 C dates • t * • Barb indicates maximum or minimum age of drift above or below this symbol

Fig. 8. Late Quaternary glacier advances, paleosols, Popocatepetl tephras, Mississippi meltwater discharge, and Gulf of Mexico sea surface temperature condition!

the circum-North Atlantic region the timing of late Quaternary deglaciation is linked to the dis­charge of glacial meltwater and precipitation runoff to the Gul f of Mexico and to the North Atlantic Ocean from Lake Agassiz and eastern North America drainage basins between 14,000 and 8000 yr. B.P. (Broecker et al., 1988, 1989;

Kennett and Shackleton, 1975; Leventer et al., 1982; Oglesby et al., 1989; Overpeck et al., 1989; Teller, 1990a, 1990b) (Fig. 8). There is no doubt that the meltwater cap leads to cooling of the Gulf of Mexico which in turn leads to about 6°C lower temperatures in central Mexico. This cooling is documented by the late Quaternary vegetation

history of the Mexican highland (Straka and Ohngemach, 1989). On L a Malinche volcano during the M III glaciation the upper tree line was lowered by about 1000 m which corresponds to a temperature depression of about 6°C. This cooling was far more substantial than during the last glacial maximum (ca. 18,000 yr B.P.). It is evident that the late Quaternary glacier advances are related to meltwater discharge events into the Gul f of Mexico (Fig. 8). Therefore, episodes of maxi­mum glaciation during the late Wisconsin occurred in two steps at times when meltwater was dis­charged into the Gul f of Mexico. In contrast during times of meltwater discharge into the North Atlantic, i.e. between 11,600 and 9900 yr B.P. the Mexican glaciers receded. This behaviour contrasts the glacier behaviour in the circum-North Atlantic region. Thus the late Quaternary Mexican glacial history shows a regional pattern that is not suit­able for uncritical correlations with the Rocky Mountains or the South American Andes.

Acknowledgements

The author thanks the Deutsche Forschungs­gemeinschaft for research support during the years 1971-1985. Radiocarbon age determinations were made in the Niedersächsisches Landesamt für Bodenforschung by M . A . Geyh. I thank A . , J., H . and C. Heine for assistance in the field and with coring. I am grateful to V . Markgraf for critically reviewing the manuscript.

References

Bloomfield, K. and Valastro Jr., S., 1974. Late Pleistocene Eruptive History of Nevado de Toluca Volcano, Central Mexico. Geol. Soc. Am. Bull., 85: 901-906.

Boudal, C. and Robin, C , 1989. Volcan Popocatepetl: Recent eruptive history, and potential hazards and risks in future eruptions. In: J.H. Latter (Editor), IAVCEI Proc. Volcanol., 1. Springer, Berlin, pp. 110-128.

Broecker, W.S., Andree, M . , Wolfli, W., Oeschger, H . , Bonani, G. , Kennett, J. and Peteet, D., 1988. The chronology of the last deglaciation: Implications to the cause of the Younger Dryas event. Paleoceanography, 3: 1-19.

Broecker, W.S., Kennett, J.P., Flower, B.P., Teller, J.T., Trumbore, S., Bonani, G . and Wolfli, W., 1989. Routing of meltwater from the Laurentide Ice Sheet during the Younger Dryas cold episode. Nature, 341: 318-321.

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