Chronology of the Mexican Volcanoes

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ISSN 0933-0704 G E O W E W 6. Jahrgang, Heft 7 Juli 1988

Seite 197-226

Geowissenschaften

Organ der Alfred-Wegener-Stiftung

Inhalt Klaus Heine

Late Quaternary Glacial Chronology of the Mexican Volcanoes

Jungquartäre Glazialchronologie

mexikanischer Vulkane 197 Andre Lambert

Hochwasser im Alpenraum, Pulsschläge

der Erosion 206

Die Erdatmosphäre im Präkambrium Entwicklung des atmosphärischen Sauerstoffs

Nachrichten 218

Tagungen 220

Meinungen 221

Zeitschriftenschau 224

Bücher 226

Im nächsten Heft 226

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Klaus Heine Late Quaternary Glacial

Chronology of the Mexican Volcanoes

Jungquartäre Glazialchronologie mexikanischer Vulkane

Zusammenfassung

Die Gliederung der jungquartären Gletscher- vorstöße in der Cordillera Neovolcanica (Zentralmexiko) basiert auf tephrochronolo- gischen Korrelierungen, Radiokarbondatie- rungen, fossilen Bodensequenzen, Pollenana- lysen sowie geomorphologischen und sedi- mentologischen Kriterien. Die Untersuchun- gen wurden an den Vulkanen Nevado de Toluca, Ajusco, Iztaccihuatl, La Malinche und Pico de Orizaba ausgeführt.

Während des Jungquartärs lassen sich an den höchsten Vulkanen fünf Gletschervorstöße nachweisen. Die M I-Vergletscherung datiert auf etwa 36 000 bis 32 000 a B P , der M I I - Vorstoß erfolgte um 12000 a BP, und die MHI-Vergletscherung, der zwei Vorstöße und eine Rückzugsphase angehören, begann vor ungefähr 10 000 a BP und endete um 8500 a BP. Während des Holozäns rückten die Gletscher um 3000 bis 2000 a B P und zwischen 1590 und 1850 A . D . (Kleine Eiszeit) vor. Seit etwa 1850 A . D . schmelzen die Glet- scher zurück.

Die Glazialgeschichte Zentralmexikos bestä- tigt die Hypothese, daß das jungquartäre Klima in den Randtropen zwischen etwa 18000 und 10000 a BP relativ trocken war und daß feuchtere Phasen auf das Ende des Sauerstoff-Isotopen-Stadiums 3 sowie für das frühe Holozän beschränkt waren. Eine kurze, jedoch markante Niederschlagszunahme

Fig. 1. Map of the Cordillera Neovolcanica, Mexico. Circles indicate the location of the volcanoes.

Fig. 2. View from the basin of Puebla- Tlaxcala to the Sierra Nevada with de Po- pocatepetl on the left and the Iztaccihuatl on the right.

' / Neovolcanica

® glaciated

Die Gecrwissenschaften / 6. Jahrg. 1988 / Nr. 7

© VCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1988 0933-0704/88/0707-0197 $ 02.S0/0

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4

La Malinche (West)

~ 2900m qs.1.

La Malinche (West)

-2910 m as.l

2770 m as.l.

• ijiiiuüiiiii 'Ah

~ tobawith '-—— l andesite

andesite breccio

MMill^iMMI^lMl

moraine

iiiiiiniiii 'A^

^ - toba

19320*360

19^25*345 toba

rB pumice (marker horizon]...

fAh (MI) moraine

fB

^v

toba andesite, distorted pumice

moraine t M III 2i)I

pumice, paitly toba

I moraine IM III 1 )1 fluvio-glacial sands

PWJ/ce - ] A h ' — ...

töO 1 (marker paleosoil)

•18280±500

La Malinche (East)

~2900m as.1.

fAh(andosol) tluviotile Sediments

breccia

^ f e s ? ^

breccio, lominoted breccia

>Mr,:<^-/hrprnn rni irsp 3sn

7690 ±100

76^580 771580

° ° A ° o 8.0 moraine-

rB pumice .12060* 165*

moraine

^(MIlH

fA f f B ö l ) ,

toba -20735460

pumice

tluviotile

Sediments

-.toba , n Qfuvel

^l

(pre-Middle Wisconsin)

li-qravel

^ f l u v i o t i l e Sediments (sand)

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wird durch den M Ii-Vorstoß um 12 000 a BP dokumentiert, der aber nur in der Nähe des Golfes von Mexiko nachweisbar ist. Im Holo- zän gab es keine bedeutenden Temperatur- und Niederschlagsschwankungen. Es muß hervorgehoben werden, daß das Stadial der Jüngeren Dryaszeit nicht durch Gletscher- schwankungen repräsentiert wird.

1 Introduction

With respect to the classical Late Weichselian climatic fluctuations of Western and Central Europe many scientists tried to establish si- milar chronostratigraphies of climatic varia- tions for other parts of the world. Recent investigations give more and more evidence that the classical West European chronostratigraphy of the Late Weichselian is in many de- tails a regional stratigraphy and cannot be transferred to other areas of the world.

Therefore it is necessary to focus our atten- tion on many different parts of the world, especially on the tropics and subtropics in Or- der to establish a great number of seperate chronostratigraphies. Here I will present the results of investigations carried out during the last three decades in the central Mexican highland (Puebla/Tlaxcala area) by several scientists who were involved in the German- Mexican Mexico Project of the German Science Foundation (Figures 1 and 2).

Fig. 3. Barranca (erosion gully) at the eastern flanks of the Iztaccihuatl.

Fig. 4. Some sections from the La Malinche volcano showing the rB-marker horizon and different glacial deposits. The t 4C dates marked with stars refer to the western flank of the volcano.

Fig. 5. The barranca Xotanacatla on the western flank of La Malinche volcano. The dark horizon at the base of the section is the fossil soil , f B o l \ the ,rB' pumice marker horizon is indicated by the thin line in the lo- wer part of the andesite breccia.

Fig. 6. Pollen diagram of the Pleistocene/

Holocene boundary at the La Malinche volcano. The glaciations M III and M I V are clearly documented by the pollen assembla- ges. According to Ohngemach and Straka (1983).

2 Chronology

Independent of the Standard Mexican glacial sequence published by Sidney White [1, 2], a chronostratigraphy based on comprehensive research on La Malinche volcano, Pico de Orizaba, Iztaccihuatl, Popocatepetl, and Ne- vado de Toluca Volcano was developed [3].

6

Different Late Quaternary stratigraphic successions for each volcano are recognizable within this area. The slopes of the volcanoes are dissected by barrancas (erosion gullies), radiating from the Upper parts of the forest belt and descending towards the basins (Fi- gure 3). Thus the stratigraphic successions can easily be traced from one barranca to an-

T I q L o c c r a t e r m a a r , 3 0 0 0 m a.s.l

Abb. 6-11 Pollendiagramna Tlaloc I, Baumpollensumme = 100 % als Bezugsbasis.

1 Abschnitt: 284 bis 256 cm, Ende der Zeit alpiner Grasfluren, bis etwa 8500 vor heute.

2. Abschnitt. 252 bis 227 cm, Pinus hartwegii-Ztit.

3 Abschnitt: 223 bis 189 cm, Erlenzeit.

4. Abschnitt: 185 bis 150 cm, K i e f e r n v o r s t o ß . 5 Abschnitt: 150 bis 90 cm, pollenarm oder pollenleer.

6. Abschnitt: 90 bis 55 cm, Zeit lichter K i e f e r n m i s c h w ä l d e r 7. Abschnitt: 50 bis 35 cm, Tannenzeit, um etwa 2000 vor heute.

8 Abschnitt: 35 bis 0 cm, Kiefernmischwaldzeit.

Analysen O H N G E M A C H

O I

Ilustr. 6-1 1 Diagrama polinico Tlaloc I, suma de polen a r b ö r e o = 100 % como base de referencia.

1. periodo: 284 a 256, finales del periodo de zacatonales, hasta alrededor de 8.500 anos antes de hoy (BP) 2. periodo: 252 a 227 cm, periodo de Pinus hartwegii.

3. periodo: 223 a 189 cm, periodo de alisos.

4. periodo: 185 a 150 cm, avance de pinos.

5. periodo: 150 a 90 cm, pobre en polen o exento de polen.

6. periodo: 90 a 55 cm, periodo de bosques ralos mezclados de pino.

7 periodo: 50 a 35 cm, periodo de abeto, de alrededor de 2.000 afios antes de hoy (BP).

8 periodo: 35 a 0 cm, bosque mezclado de pino.

Analisis O H N G E M A C H

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other by different layers of glacial and periglacial deposits, paleosols, debris, fluvial gravels and sands, and loess-like so-called „toba"

Sediments which are interbedded with lava flows, ignimbrite deposits and tephra (the term tephra pertains to all pyroclastic fragments, such as fine and coarse ash, lapilli, volcanic bombs, and blocks). Different tephra layers as well as some paleosols are very use- ful as stratigraphic markers within the Late Quaternary deposits of the volcanoes (Figu- res 4 and 5). In determining the stratigraphic succession of tephra, both field character- istics and laboratory examinations were carried out. Radiocarbon dating of tephra layers was restricted to charcoal logs and branches imbedded in the volcanic deposits. In addi- tion to these data paleosols, wood fragments from gravels, peat, and calcrete (caliche) deposits were dated by radiocarbon. Other age determinations of Late Quaternary deposits are being attempted by studies in archaeology and prehistory. Pollen studies in cores of Sedi- ments in small volcanic craters, maars, and la- kes [4] cover the time span of approximately 35 000 to 0 yr BP. The results were compared with the chronology of the glacial deposits 7

(Figure 6). Furthermore, relative age-dating methods were used to demonstrate age dif- ferences in the tili sequence; such relative dating methods include topographic Posi- tion, morphologic shape of the moraines, rock-weathering parameters, thickness of eolian „toba" Sediments, soil properties [5], and Vegetation cover (including liehen data of Holocene glacial and periglacial deposits) (Figure 7).

The chronology of the Late Quaternary glacial deposits is summarized in Figure 8. The chronology of La Malinche volcano is best known. There, most of the late glacial tills are related to volcanic rocks and tephra as well as to organic materials that are dateable by radiocarbon. By means of tephrochronologic methods valley-to-valley correlation of tills is possible. The general distribution and dimen- sions of the Late Quaternary glaciers of La Malinche volcano and problems associated with the identification and differentiation of each glacier advance and their age relationships were discussed by the author in pre- vious papers [6, 7]. Tills with poorly preserved moraine forms are those of the M I-gla-

cier advance between 36 000 and > 32 000 yr BP as well as tills deposited during the M II- glaciation about 12 000 yr BP. Lateral and end moraines deposited during the M Ill-glaciation between 10000 and 8500 yr BP show well preserved morainal forms, so do the H o - locene neoglacial deposits which are divisible into two advances ( M IV: 3000-2000 yr BP;

M V : Little Ice Age). A n outline of the local stratigraphy of the glacial deposits on the eastern slopes of La Malinche volcano (Figure 7), mainly based on paleosols (fBol, fBo3) and tephra layers (marker horizon rB), provi- des sufficient Information on how different Late Quaternary stratigraphic successions were elaborated.

Deposits of the other volcanoes of the Mexi- can volcanic belt, stemming from the major glaciations of the Late Quaternary are

Fig. 7. Scheme of the stratigraphy of the Late Quaternary deposits on the eastern slopes of La Malinche volcano. The^{1 4}C da- tes marked with stars refer to the western flank of the volcano.

LA MALINCHE

_4461m

Relative age-dating methods Vegetation cover (lichens)

topographic Position morphologic shape

rock weathering thickness of toba

soil properties

7405 ±145 (Hv4757) 75901100 (Hv4758)- 7645 t

7715 i

80 (Hv4243 80 (Hv4884) 1 2 0 6 0 ± 1 6 5 ( H v 4 2 4 4 ) * - 207351460 ( H v 4 2 4 5 f

81101300 (W-1927)' 23940t1000(W-1908)' 25920110001W-1911 )*- 173501 550IW-1913 ) *

38895H200 ( Hv4241 ) - \

1925)*

2750 m

H E I N E 1987

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known. Figures 9 to 11 give evidence of the locations of the glacial and periglacial depo-

Fig. 8. Correlation diagram. Geologic- climatic unit boundaries are based on ra- diocarbon ages, tephrochronologic corre- lations, soil development, pollen analyses, sedimentologic criteria, and topographic position. Pollen zones according to Ohn- gemach and Straka (1983).

8

sits on Pico de Orizaba (Figure 9), the south- ern part of Iztaccihuatl (Figure 10), and the Nevado de Toluca volcano (Figure 11). The glacial deposits of these volcanoes are comparable to the Late Quaternary stratigraphic succession of L a Malinche volcano. Apart from the M Il-glaciation [8] that did not exist on the Nevado de Toluca volcano, five glacier advances of the Late Quaternary can be traced on the slopes of Pico de Orizaba and Iz- taccihuatl, whereas on the flanks of the not so

high volcanoes of Nevado de Toluca and L a Malinche the Holocene glacial deposits of the M IV and M V phase do not occur. Instead of glacial deposits periglacial forms and deposits developed here (rock glaciers, ice-cored moraines, rock debris) [9].

3 Results

In the correlation diagram (Figure 8) most geologic-climatic unit boundaries are based CO CD

ö

g

CO c =

I 1

•

1

[ Radiocarbon dates

$ Valsequillo area + Rio Frio Pass x Malinche volcano O Iztaccihuatl, Popocatepetl

• Nevado de Toluca volcano A El Seco/Orierrral area

• Tlaxcala area

• Pico de Orizaba v Rio Lerma

• Ajusco

• Dating by archaeology.historical sources

M V t

¹¹

Radiocarbon dates

• Tlaxcala area

• Ajusco

1 1

Radiocarbon dates

• Tlaxcala area

• Ajusco

MIV

¹₁

Radiocarbon dates

• Tlaxcala area

• Ajusco

XX

Radiocarbon dates

• Tlaxcala area

• Ajusco

f B o 3

Radiocarbon dates

• Tlaxcala area

• Ajusco

* 1

Radiocarbon dates

• Tlaxcala area

• Ajusco

•

Radiocarbon dates

• Tlaxcala area

• Ajusco

MIII2 iL

Radiocarbon dates

• Tlaxcala area

• Ajusco

f B o 2

¹1

M M

¹₁ ^x_•^u

1

1 A

f B o l

^X ^X¹₁ _{* l}_{* x}xx |

4 1 ^{S ü l}

1 X A

M I

¹

l •I

1

: % i, ' l A

J +

^{x +}

'inusAtixed^ j j ferest Abes Pmus/Mixed forest i E < £

I ^ 1^rXA. •

x10³a BP

VI (V) JIV i IV

Pinus I withoutl Quercusl

Pinus,poor in Quercus

fffflifffffl Pinus with Quercus Pinus, rieh in

Quercus

H O L O C E N E l P L E I T 0 C E N E

l l l l l l l l coid

i r r m cool more humid H U I more arid

alternating more humid - more arid HEINE 86

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Fig. 9. Geomorphological map of the Pico de Orizaba. (1) glacier and fossil ice beneath debris, (2) M V moraine, (3) M IV moraine, (4) M III 3 moraine, (5) M III 1 + 2 moraine, (6) M I moraine, (7) cirque, (8) U-shaped valley, (9) röche moutonee, (10) ice move- ment directions, (11) rock glacier (Little Ice Age), (12) striated blocks on moraine, (13) talus, (14) debris flows, (15) thufur, (16) cra- ter, (17) steep walls, (18) lava flow, (19) crest, (20) valley, barranca, (21) edge versus Valley, (22) Upper timber line, (23) well with brook, (24) path.

K. HEINE 1975, ergänzt 1987

either on maximum or minimum radiocarbon dates or on relative criteria. In most cases ra- diometric controls are very reliable and the presented boundaries will probably not be shifted along the time bar.

The most interesting results are: Compared with the North American glacial stratigraphy the data from Mexico show that there is a certain synchroneity of the glacier fluctuations of Mexico with North America's during the Little Ice Age. But neither during the Early Holocene nor during the Late Pleistocene is there synchroneity of Mexican with North American glacier fluctuations [10, 11].

A palaeoclimatic Interpretation may be deduc- ed from the scheme of the three-dimensional development of the natural environment of the central Mexican highland during the Late Quaternary (Figure 12). During the past

36 000 years three major periods with climati- cally induced high erosion intensities and glacier advances can be distinguished: (1) 36 000 to > 32 000 yr BP, (2) around 12 000 yr BP, and (3) 10000 to 8500 yr BP. These periods coincide with climatic changes from relative aridity to greater humidity. The scheme shows that there is no synchroneous development of the trend of temperature on the one hand with the trend of humidity on the other hand. The temperature curve is characterized by an increase between 36 000 and 32 000 yr BP, a decrease between ca. 26 000 and 16 000 yr BP, and an increase with minor fluctuations during the period 16 000 to 8000 yr BP.

The postglacial climatic Optimum was reached between 8000 and 5000 yr BP. Dur- ing the Holocene, only between ca. 3000 and 2000 yr BP, and during the Little Ice Age the climate was slightly cooler and wetter, thus causing minor advances.

4 Discussion

Comparisons of the Standard Mexican glacial sequence elaborated by White [1, 2] and White & Valastro [12] with our above- mentioned Late Quaternary chronostratigraphy suggest that certain glaciations on Ajusco are comparable to those on other volcanoes of the Mexican volcanic belt. Without going into detail I would like to mention that White [1] describes absolute dating exclusively on Ajusco volcano and that his Standard Mexi- can glacial sequence is based on seven radiocarbon dates only. Furthermore, White's In- terpretation of the field evidence of volcano Ajusco is in some respect incorrect: the M a r - ques tili' consists of ignimbrite material with a well developed fritted horizon underneath;

most of White's moraines are walls and ridges consisting of debris layers and caused by the erosion; his Holocene moraines appear to be volcanic lava flows. So far White's discussion of controversial stratigraphic relationships and Chronologie problems in the „Report of the International Geological Correlation Programm", Project 24 (Quaternary Gla- ciations in the Northern Hemisphere) does not evaluate the kind, quantity, and quality of available data and the criteria used for correlation of glacial deposits.

In Figure 13 the correlation and chronostratigraphy of the glacial deposits of the Cordil- lera Neovolcanica of central Mexico are shown. Correlations are based on all available evidence of the central Mexican highland, and the reliability of the chronostratigraphy

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ati- is very high. In Mexico maximum Late Qua-

*la- ternary glaciations occurred approximately 000 33 000-35 000 yr BP, around 12 000 yr B P BP, and 8500-10 000 yr BP. Thus maximum Late ods Wisconsin glaciations in Mexico may have cive occurred at the end of oxygen isotope stage 3 :me and at the beginning of the Holocene. There op- is no synchroneity of glacial events regarding ane the Mexican glaciers and the North American her Cordilleran and Laurentide or even the Fen- zed noscandian ice sheets. Glacial advances and ) yr recessions are time-transgressive, and their 300 diachronous nature is indicated by the diffi- :tu- culty in using glacial deposits for stratigra- BP. phic correleations between regions or conti- ivas nents.

>ur-

»nd 5 Conclusions

the

hus Referring to the questions raised in the introduction, I will now summarize the results.

First, the classical West European chronostratigraphy of the Late Weichselian cannot be cial transferred to the Late Quaternary glacial se- md quence of central Mexico.

ive-

; r a- Secondly, the glacial history of central Me-

sco xico Supports the hypothesis that Late Qua- s of ternary climates were relatively dry between ing ca. 18 000 and 10 000 yr BP. Data from glacial lite Mexican sequences suggest that major in-

on creases in precipitation were restricted to iso- :xi- tope stage 3 as well as to the Early Holocene.

110-

in- ino

[ar- Fig. 10. Geomorphological map of the south- i t h ern part of the Iztaccihuatl massif. (1) gla-

l th ; cier, (2) moraine wall, (3) cirque, (4) U - ges shaped Valley, (5) striated ground, (6) röche the moutonee, (7) crest, (8) upper timber line,

be (9) brook.

ion

iips Fig. 11. Geomorphological map of the Ne-

t 0f vado de Toluca volcano. (1) talus, (2) ,Glatt- i^{o n} hang' (straight smooth slope), (3) rock gla-

;la- cier (youngest phase of Little Ice Age), (4) oes rock glacier (older phase of Little Ice Age),

r 0f (5) rock glacier ( M IV phase), (6) rock glacier or- (early Holocene), (7) small moraine wall, (8) debris flow, (9) debris flow lobe, (10) mo- raine, (11) moraine, not clearly indentified, ati- (12) U-shaped valley, (13) tili, (14) röche 111- moutonee, (15) rock, (16) volcanic plug, (17)

are crest, (18) valley, barranca, (19) upper tim- ble ber line (ca. 4000 m a. s. 1.), (20) crater lake, nd, (21) dry lake, (22) road, (23) hut (altitude in ,hy meters).

1 2

3

4 5 6 7 8 9

11

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12 Fig. 12. Scheme of three-dimensional devel- opment of the natural environment of the central Mexican highland during the Late Quaternary. (1) glacial erosion, (2) perigla- cial processes, denudation, fluvial erosion, (3) fluvial processes, weak mass movement processes, (4) soil development (andosol above 3000 m, barro soils and vertisols be- low 3000 m), (5) weak fluvial processes, weak soil development, (6) eolian processes (loess- like toba-sedimentation), (7) intensive flu- vial erosion, strong mass movement proces- ses, (8) accelerated soil erosion (caused by men).

Fig. 13. Quaternary glacial stratigraphy and chronology of central Mexico.

13

altitude MY MW

M i n

MII

321

MI

temperature J

humidity

3 6 a x 1 03

+ + + +

+ -*- + + 77777.

' / / / / /

'//StA

Correlation of glacial deposits of the Cordillera NeovolcOnica,central Mexico (Heine 1987)

TIME DIVISIONS

TIME SCALE (yecrs)

<_>

CO

1000 2000 3000

5 000

8 000 9 000 10000 11000 12000 14000 16000 18000 20000

25000

30000 35 000 40000 -65000 TIME

SCALE

NEVAD0 DE T0LUCA A J U S C O

=1500 X

11,050+130«V 11,470+90»*,.

11,850+220»$

11.950+100

21,170+170«

23,940+600 24260+670' 24,400+430 24,410+590

25,930+670 2^620+^0,

2060 + 8 0 »

8140+80»

11,420+120»

15,090+150» ~f%,

19,150+ 4701

25,080+680•

27,190+930 •

Sra. Nevada IZTACCIHUATL P 0 P 0 C A T E P E T L

< 1 6 9 0 A D J < L 715+85» 840+65»«

990+1070 A[

1860+60«

^ 2030+55» _ T 2875+75 2990+85'

3260+751 3700+110r

o+esj^r

4805+60»*

5075+50*

10,190+215«

2 5 , 7 5 0 + ™?

<40,000* k< 35,000

L A M A L I N C H E 5 5 0 »

<1000*

1365+175-»

1550+80T^__

2670+70 £ < * R G 3 0 7 5 + 2 9 5 » ^ - ^

5760: +280$

7405+145 -7 i ^ l n 2lÄ ?690 ±100 7715+80 ¥ * * « 7

.45+80J» • 5 + 8 0 f T "# 7 9

8 1 1 0 + 3 0 0 * » » " ' * 8240+300

16,765+550

PICO DE O R I Z A B A

1730+85»

4450+70»

6320+215«

6520+170»

18128015001117800*^1 19,320+360 <j

20,735+460 <

23,940+1000 J 25,920+1000»

38,895+1200»

'19,425+345

OXYGEN ISO- TOP STAGES

4 and older

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Thirdly, a short but great increase in precipitation at about 12 000 yr BP is documented only by glacial advances on volcanoes near the Gulf of Mexico.

Fourthly, the classical Late Weichselian climatic fluctuation of the Younger Dryas period did not occur. The Mexican low-latitude stratigraphy presents a Late Quaternary tran- sition from a füll glacial dry and cold/cool climate to postglacial conditions without significant cold temperature anomalies.

Last not least, the application of tephrochro- nology supplies us with a detailed chronostratigraphy of the Late Quaternary events in Mexico, a chronostratigraphy in which stratigraphic and Chronologie relationships are much more clarified than in many other tro- pical and subtropical parts of the world.

E x p l o i t a t i o n :

Glacial advance One or more glacial advances or glaciations during the mdicated time interval

Alternate age assignments

Multiple recessional readvances Diamicton of possible glacial ongm RG Rock glaciers

•

^{1 4}^{C age}

X archeological age (sidereal time)

%

Arrows mdicate maximum or mmimum age of moraine above or below the symbol

Acknowledgements

The author is grateful to M . A . Geyh (Nieder- sächsisches Landesamt für Bodenforschung, Hannover) for radiocarbon age determinations and to the „Deutsche Forschungsge- meinschaft" for financial support during the period 1971-1986.

References

[1] S. White: Quaternary Glacial Strati- graphy and Chronology of Mexico, in: V . Sibrava, D . Q. Bowen, G . M . Richmond (Eds.): Quaternary Glaciations in the Nor- thern Hemisphere, Pergamon Press, Oxford, New York, Toronto, Sydney, Frankfurt, 1986.

S. 201-205.

[2] S. White: Late Pleistocence glacial sequence for the west side of Iztaccihuatl, Me- xico; Geological Society of America 73 (1962) 935-958.

[3] K. Heine: The Classical Late Weichse- lian Climatic Fluctuations in Mexico, in:

N . - A . Mörner, W . Karlen (Eds.): Climatic Changes on a Yearly to Millennial Basis, D. Reidel, Dordrecht, Boston, Lancaster, 1984.

S. 95-115.

[4] D . Ohngemach and H . Straka: Beiträge zur Vegetations- und Klimageschichte im Ge- biet von Puebla-Tlaxcala. Pollenanalysen im Mexiko-Projekt. Das Mexiko-Projekt der D F G XVIII. Steiner, Wiesbaden, 1983. 161 pp. + Suppl.

[5] G . Miehlich: Klima- und altersabhängige Bodenentwicklungen von Vulkanascheböden der Sierra Nevada de Mexico; Mitt. Deutsch.

Bodenkundl. Ges. 18 (1974) 360-369.

[6] K. Heine: Studien zur jungquartären Gla- zialmorphologie mexikanischer Vulkane - mit einem Ausblick auf die Klimaentwick- lung. Das Mexiko-Projekt der D F G VII. Stei- ner, Wiesbaden, 1975, 178 pp.

[7] K. Heine: Neue absolute Daten zur holo- zänen Gletscher-, Vegetations- und Klimage- schichte zentralmexikanischer Vulkane, in:

M . Hartl, V . Engelschalk (Eds.): Geographie, Naturwissenschaft und Geisteswissenschaft, Regensburger Geogr. Sehr. 19/20, (1985).

79-92.

[8] K. Heine: Ein außergewöhnlicher Glet- schervorstoß in Mexiko vor 12 000 Jahren.

Ein Beitrag zum Problem der spätglazialen Klimaschwankungen; Catena 10 (1983) 1 -25.

[9] K. Heine: Blockgletscher- und Blockzun- gen-Generationen am Nevado de Toluca, Me- xiko; Die Erde 107 (1976) 330-352.

[10] K. Heine: Spät- und postglaziale Glet- scherschwankungen in Mexiko: Befunde und

paläoklimatische Deutung, in: H . Schroeder- Lanz (Ed.): Late- and postglacial oscillations of glaciers: Glacial and periglacial forms, A . A. Balkema, Rotterdam, 1983. S. 291-304.

[11] K. Heine: Beobachtungen und Überle- gungen zur eiszeitlichen Depression von Schneegrenze und Strukturbodengrenze in den Tropen und Subtropen; Erdkunde 31 (1977) 161-178.

[12] S. White and S. Valastro Jr: Pleistocene glaciation of volcano Ajusco, central Mexico, and comparison with Standard Mexican glacial sequence; Quaternary Research 21 (1984) 21-35.

Anschrift:

Prof. D r . Klaus Heine, Institut für Geogra- phie, Universität Regensburg, Postfach 397, D-8400 Regensburg.

Chronology of the Mexican Volcanoes

Geowissenschaften

Organ der Alfred-Wegener-Stiftung

VCH

Klaus Heine Late Quaternary Glacial

Chronology of the Mexican Volcanoes

Jungquartäre Glazialchronologie mexikanischer Vulkane

Zusammenfassung

~ 2900m qs.1.

-2910 m as.l

~ tobawith '-—— l andesite

andesite breccio

moraine

^ - toba

19320*360

19^25*345 toba

fB

toba andesite, distorted pumice

moraine t M III 2i)I

I moraine IM III 1 )1 fluvio-glacial sands

•18280±500

breccia

breccio, lominoted breccia

7690 ±100

76^5*80 7715*80

rB pumice .12060* 165*

moraine

toba -20735*460*

pumice

tluviotile

-.toba , n Qfuvel

(pre-Middle Wisconsin)

1 Introduction

2 Chronology

LA MALINCHE

Relative age-dating methods Vegetation cover (lichens)

topographic Position morphologic shape

rock weathering thickness of toba

soil properties

3 Results

g

M V t

MIV

f B o 3

•

MIII2 iL

f B o 2

M M

f B o l

4 1 S ü l

M I

l •I

J +

4 Discussion

»nd 5 Conclusions

110-

3

altitude MY MW

MII

MI

temperature J

Correlation of glacial deposits of the Cordillera NeovolcOnica,central Mexico (Heine 1987)

o+esj^r

E x p l o i t a t i o n :

•

%

References

76^580 771580

toba -20735460

4 1 ^{S ü l}