ISSN 0933-0704 GEOWEW 6. Jahrgang, Heft 7 Juli 1988 Seite 197-226 Geowissenschaften Organ der Alfred-Wegener-Stiftung

Inhalt Klaus Heine Nachrichten 218 Late Quaternary Glacial Chronology of the Mexican Volcanoes Tagungen 220 Jungquartäre Glazialchronologie mexikanischer Vulkane 197 Meinungen 221 Andre Lambert Hochwasser im Alpenraum, Pulsschläge der Erosion 206 Zeitschriftenschau 224

Bücher 226 Die Erdatmosphäre im Präkambrium Entwicklung des atmosphärischen Sauerstoffs Im nächsten Heft 226

Titelbild Gebänderte Eisensteine (Itabirite) sind ein

Hinweis auf weitgehend Oz-freie subaerische Verwitterungs- und Transportvorgänge, aber oxidierende Bedingungen in marinen Teilbe• reichen bei der Fällung des Eisens. M. Schid- lowski und H. Wiggering (S. 212) ziehen un• ter anderem daraus Rückschlüsse auf die Ent• wicklung des atmosphärischen Sauerstoffs im Präkambrium (Foto: H. L. James).

Kuratorium G. Anger, Leverkusen • K.-P. Arnold, Wien thal-Zellerfeld • Andre Lambert, Zürich • E. U. Förstner, Hamburg • H. G. Gierloff- P. Löhnert, Münster • Diethard E. Meyer, Es• Emden, München • F. Goerlich, Bonn • H. sen-Kupferdreh • W. Pflug, Aachen • H. v. Hagedorn, Würzburg • P. Halbach, Clausthal- Philipsborn, Regensburg • H. Rischmüller, Zellerfeld • M. Hantel, Wien • A. Hoschützky, Hannover • D. Schumann, Darmstadt • A. Bonn W. R. Jacoby, Mainz • H. Kulke, Claus• Semmel, Frankfurt

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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 , , Iztaccihuatl, La und ausgeführt.

Während des Jungquartärs lassen sich an den höchsten Vulkanen fünf Gletschervorstöße '/ Neovolcanica nachweisen. Die M I-Vergletscherung datiert ® glaciated auf etwa 36 000 bis 32 000 a BP, der MII- Vorstoß erfolgte um 12000 a BP, und die © proved MHI-Vergletscherung, der zwei Vorstöße © presumed und eine Rückzugsphase angehören, begann vor ungefähr 10 000 a BP und endete um 8500 © (>4000m a BP. Während des Holozäns rückten die 1104° Gletscher um 3000 bis 2000 a BP und zwi• schen 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, . Circles indicate the location of the volcanoes.

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

Die Gecrwissenschaften / 6. Jahrg. 1988 / Nr. 7 © VCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1988 0933-0704/88/0707-0197 $ 02.S0/0 4 La Malinche (West) La Malinche (East) ~ 2900m qs.1. ~2900m as.1. fAh(andosol) La Malinche (West) tluviotile Sediments breccia -2910 m as.l 2770 m as.l. ^fes?^ breccio, lominoted breccia MMill^iMMI^lMl 3sn >Mr,:<^-/hrprnn rni irsp moraine • ijiiiuüiiiii 'Ah 7690 ±100 ~ tobawith '-—— l andesite moraine t M III 2i)I andesite pumice, paitly toba breccio I moraine IM III 1 )1 fluvio-glacial sands 76^5*80 19320*360 toba PWJ/ce - 7715*80 iiiiiiniiii 'A^ 19^25*345 rB pumice (marker horizon]... ]Ah'— ... töO 1 (marker paleosoil) rB pumice .12060* 165* ^ - toba fAh (MI) moraine moraine (MIlH fA ffBöl) , fBv toba •18280±500 andesite, distorted -20735*460* tobpumica e tluviotile Sediments pumice -.toba , nQfuvel li-qravell ^fluviotile Sediments (sand) °°A°o 8.0 moraine- (pre-Middle Wisconsin) wird durch den M Ii-Vorstoß um 12 000 a BP 2 Chronology Different Late Quaternary stratigraphic suc- dokumentiert, der aber nur in der Nähe des cessions for each volcano are recognizable Golfes von Mexiko nachweisbar ist. Im Holo- Independent of the Standard Mexican glacial within this area. The slopes of the volcanoes zän gab es keine bedeutenden Temperatur- sequence published by Sidney White [1, 2], a are dissected by barrancas (erosion gullies), und Niederschlagsschwankungen. Es muß chronostratigraphy based on comprehensive radiating from the Upper parts of the forest hervorgehoben werden, daß das Stadial der research on La Malinche volcano, Pico de belt and descending towards the basins (Fi- Jüngeren Dryaszeit nicht durch Gletscher• Orizaba, Iztaccihuatl, Popocatepetl, and Ne- gure 3). Thus the stratigraphic successions schwankungen repräsentiert wird. vado de Toluca Volcano was developed [3]. can easily be traced from one barranca to an- 6 1 Introduction TIqLoc crater maar, 3000m a.s.l 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 in- vestigations give more and more evidence that the classical West European chronostrati- graphy 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 t4C dates marked with stars refer to the western flank of the volcano.

Fig. 5. The barranca Xotanacatla on the we• 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. stern flank of La Malinche volcano. The 2. Abschnitt. 252 bis 227 cm, Pinus hartwegii-Ztit. 3 Abschnitt: 223 bis 189 cm, Erlenzeit. dark horizon at the base of the section is the 4. Abschnitt: 185 bis 150 cm, Kiefernvorstoß. fossil soil ,fBol\ the ,rB' pumice marker ho• 5 Abschnitt: 150 bis 90 cm, pollenarm oder pollenleer. 6. Abschnitt: 90 bis 55 cm, Zeit lichter Kiefernmischwälder rizon is indicated by the thin line in the lo- 7. Abschnitt: 50 bis 35 cm, Tannenzeit, um etwa 2000 vor heute. 8 Abschnitt: 35 bis 0 cm, Kiefernmischwaldzeit. wer part of the andesite breccia. Analysen OHNGEMACH

Ilustr. 6-1 1 Diagrama polinico Tlaloc I, suma de polen arböreo = 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) Fig. 6. Pollen diagram of the Pleistocene/ O 2. periodo: 252 a 227 cm, periodo de Pinus hartwegii. I 3. periodo: 223 a 189 cm, periodo de alisos. Holocene boundary at the La Malinche vol• 4. periodo: 185 a 150 cm, avance de pinos. cano. The glaciations M III and M IV are 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. clearly documented by the pollen assembla- 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. ges. According to Ohngemach and Straka Analisis OHNGEMACH (1983). other by different layers of glacial and peri- (Figure 6). Furthermore, relative age-dating cier advance between 36 000 and > 32 000 yr glacial deposits, paleosols, debris, fluvial gra- methods were used to demonstrate age dif- BP as well as tills deposited during the M II- vels and sands, and loess-like so-called „toba" ferences in the tili sequence; such relative glaciation about 12 000 yr BP. Lateral and end Sediments which are interbedded with dating methods include topographic Posi• moraines deposited during the M Ill-glacia- flows, ignimbrite deposits and tephra (the tion, morphologic shape of the moraines, tion between 10000 and 8500 yr BP show term tephra pertains to all pyroclastic frag- rock-weathering parameters, thickness of well preserved morainal forms, so do the Ho• ments, such as fine and coarse ash, lapilli, vol- eolian „toba" Sediments, soil properties [5], locene neoglacial deposits which are divisible canic bombs, and blocks). Different tephra and Vegetation cover (including liehen data into two advances (M IV: 3000-2000 yr BP; layers as well as some paleosols are very use- of Holocene glacial and periglacial deposits) M V: Little Ice Age). An outline of the local ful as stratigraphic markers within the Late (Figure 7). stratigraphy of the glacial deposits on the Quaternary deposits of the volcanoes (Figu- eastern slopes of La Malinche volcano (Figure res 4 and 5). In determining the stratigraphic The chronology of the Late Quaternary gla• 7), mainly based on paleosols (fBol, fBo3) succession of tephra, both field character- cial deposits is summarized in Figure 8. The and tephra layers (marker horizon rB), provi- istics and laboratory examinations were car- chronology of La Malinche volcano is best des sufficient Information on how different ried out. Radiocarbon dating of tephra layers known. There, most of the late glacial tills are Late Quaternary stratigraphic successions was restricted to charcoal logs and branches related to volcanic rocks and tephra as well as were elaborated. imbedded in the volcanic deposits. In addi- to organic materials that are dateable by ra• tion to these data paleosols, wood fragments diocarbon. By means of tephrochronologic Deposits of the other volcanoes of the Mexi• from gravels, peat, and calcrete (caliche) de• methods valley-to-valley correlation of tills is can , stemming from the major posits were dated by radiocarbon. Other age possible. The general distribution and dimen- glaciations of the Late Quaternary are determinations of Late Quaternary deposits sions of the Late Quaternary of La are being attempted by studies in archaeology Malinche volcano and problems associated and prehistory. Pollen studies in cores of Sedi• with the identification and differentiation of Fig. 7. Scheme of the stratigraphy of the ments in small volcanic craters, maars, and la- each advance and their age relation- Late Quaternary deposits on the eastern kes [4] cover the time span of approximately ships were discussed by the author in pre- slopes of La Malinche volcano. The 14C da- 35 000 to 0 yr BP. The results were compared vious papers [6, 7]. Tills with poorly preserv- tes marked with stars refer to the western with the chronology of the glacial deposits ed moraine forms are those of the M I-gla- flank of the volcano. 7 LA MALINCHE Relative age-dating methods 4461m Vegetation cover (lichens) topographic Position morphologic shape

rock weathering thickness of toba soil properties

7405 ±145 (Hv4757)

75901100 (Hv4758)-

7645 t 80 (Hv4243 7715 i 80 (Hv4884)

12060±165(Hv4244)*- 207351460 (Hv4245f 81101300 (W-1927)' 23940t1000(W-1908)' 1925)* 25920110001W-1911 )*- 173501 550IW-1913 )* 2750 m

HEINE 1987 38895H200 ( Hv4241 ) -\ known. Figures 9 to 11 give evidence of the sits on Pico de Orizaba (Figure 9), the south- high volcanoes of and La locations of the glacial and periglacial depo- ern part of Iztaccihuatl (Figure 10), and the Malinche the Holocene glacial deposits of the Nevado de Toluca volcano (Figure 11). The M IV and M V phase do not occur. Instead of glacial deposits of these volcanoes are compa- glacial deposits periglacial forms and deposits Fig. 8. Correlation diagram. Geologic- rable to the Late Quaternary stratigraphic developed here (rock glaciers, ice-cored mo• climatic unit boundaries are based on ra- succession of La Malinche volcano. Apart raines, rock debris) [9]. diocarbon ages, tephrochronologic corre- from the M Il-glaciation [8] that did not exist lations, soil development, pollen analyses, on the Nevado de Toluca volcano, five glacier 3 Results sedimentologic criteria, and topographic advances of the Late Quaternary can be trac- position. Pollen zones according to Ohn- ed on the slopes of Pico de Orizaba and Iz• In the correlation diagram (Figure 8) most gemach and Straka (1983). taccihuatl, whereas on the flanks of the not so geologic-climatic unit boundaries are based 8 CO CD

ö g CO c=

I 1 •1 [ Radiocarbon dates 1 $ Valsequillo area MV 1 t 1 + Rio Frio Pass 1 x Malinche volcano 1 O Iztaccihuatl, Popocatepetl MIV 1 • Nevado de Toluca volcano XX A El Seco/Orierrral area fBo3 • Tlaxcala area • Pico de Orizaba

* 1 v Rio Lerma • Ajusco • • Dating by archaeology.historical MIII2 iL sources

1 fBo2 1 1 MM xu 1 • 1 A 1 X X1 fBol x 1 *l*x x| 4 1Sü l 1 X A MI 1 l •I 1 + x+ : % i, ' lA J x103a BP

'inusAtixed^ jj ferest Abes Pmus/Mixed forest iE<£

I ^ 1 rXA. • VI (V) JIV

i IV fffflifffffl

Pinus I Pinus,poor in Quercus Pinus with Quercus Pinus, rieh in withoutl Quercus Quercusl

HOLOCENEl P L E I T 0 C E N E

llllllll coid more humid HUI more arid irrm cool alternating more humid - more arid HEINE 86 36 000 years three major periods with climati- cally induced high erosion intensities and gla• cier 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 develop• ment 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 fluctu• ations 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 chronostratigra- phy 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 radio• carbon dates only. Furthermore, White's In• terpretation of the field evidence of volcano K. HEINE 1975, ergänzt 1987 Ajusco is in some respect incorrect: the Mar• Fig. 9. Geomorphological map of the Pico either on maximum or minimum radiocarbon ques tili' consists of ignimbrite material with de Orizaba. (1) glacier and fossil ice beneath dates or on relative criteria. In most cases ra- a well developed fritted horizon underneath; debris, (2) M V moraine, (3) M IV moraine, diometric controls are very reliable and the most of White's moraines are walls and ridges (4) M III 3 moraine, (5) M III 1 + 2 moraine, presented boundaries will probably not be consisting of debris layers and caused by the (6) M I moraine, (7) cirque, (8) U-shaped shifted along the time bar. erosion; his Holocene moraines appear to be valley, (9) röche moutonee, (10) ice move• volcanic lava flows. So far White's discussion ment directions, (11) rock glacier (Little Ice The most interesting results are: Compared of controversial stratigraphic relationships Age), (12) striated blocks on moraine, (13) with the North American glacial stratigraphy and Chronologie problems in the „Report of talus, (14) debris flows, (15) thufur, (16) cra- the data from Mexico show that there is a cer- the International Geological Correlation ter, (17) steep walls, (18) lava flow, (19) crest, tain synchroneity of the glacier fluctuations Programm", Project 24 (Quaternary Gla• (20) valley, barranca, (21) edge versus Valley, of Mexico with North America's during the ciations in the Northern Hemisphere) does (22) Upper timber line, (23) well with brook, Little Ice Age. But neither during the Early not evaluate the kind, quantity, and quality of (24) path. Holocene nor during the Late Pleistocene is available data and the criteria used for cor• there synchroneity of Mexican with North relation of glacial deposits. American glacier fluctuations [10, 11]. In Figure 13 the correlation and chronostrati- A palaeoclimatic Interpretation may be deduc- graphy of the glacial deposits of the Cordil- ed from the scheme of the three-dimensional lera Neovolcanica of central Mexico are development of the natural environment of shown. Correlations are based on all available the central Mexican highland during the Late evidence of the central Mexican highland, Quaternary (Figure 12). During the past and the reliability of the chronostratigraphy 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 BP 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 intro- 12 3 456 789 duction, I will now summarize the results. 11 First, the classical West European chronostra- tigraphy of the Late Weichselian cannot be cial transferred to the Late Quaternary glacial se- md quence of central Mexico. ive-

;ra- 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- ith ern part of the Iztaccihuatl massif. (1) gla- lth; 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- ion 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). 12 MY MW Min MII MI Fig. 12. Scheme of three-dimensional devel- altitude 321 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- 3 like toba-sedimentation), (7) intensive flu• 36ax10 vial erosion, strong mass movement proces• temperature J ses, (8) accelerated soil erosion (caused by men). humidity Fig. 13. Quaternary glacial stratigraphy and chronology of central Mexico. 77777. + + + + '///// + -*- + + '//StA

13

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

TIME TIME Sra. Nevada DIVISIONS SCALE NEVAD0 DE T0LUCA AJUSCO IZTACCIHUATL LA MALINCHE PICO DE ORIZABA OXYGEN ISO• (yecrs) P0P0CATEPETL TOP STAGES <1690ADJ

10000 10,190+215« 11000 11,050+130«V 11,470+90»*,. 11,420+120» 12000 11,850+220»$ 11.950+100 14000 15,090+150» ~f%, 16000 16,765+550 <_> 18000 18128015001117800*^1 19,150+ 4701 19,320+360

25,930+670 2^620+^0, 30000

35 000 k< 35,000 38,895+1200» 40000 <40,000*

-65000 4 and TIME older SCALE Thirdly, a short but great increase in precipi- Acknowledgements paläoklimatische Deutung, in: H. Schroeder- tation at about 12 000 yr BP is documented Lanz (Ed.): Late- and postglacial oscillations only by glacial advances on volcanoes near The author is grateful to M. A. Geyh (Nieder• of glaciers: Glacial and periglacial forms, A. the Gulf of Mexico. sächsisches Landesamt für Bodenforschung, A. Balkema, Rotterdam, 1983. S. 291-304. Hannover) for radiocarbon age determi- [11] K. Heine: Beobachtungen und Überle• Fourthly, the classical Late Weichselian cli• nations and to the „Deutsche Forschungsge• gungen zur eiszeitlichen Depression von matic fluctuation of the Younger Dryas pe- meinschaft" for financial support during the Schneegrenze und Strukturbodengrenze in riod did not occur. The Mexican low-latitude period 1971-1986. den Tropen und Subtropen; Erdkunde 31 stratigraphy presents a Late Quaternary tran- (1977) 161-178. sition from a füll glacial dry and cold/cool References [12] S. White and S. Valastro Jr: Pleistocene climate to postglacial conditions without glaciation of volcano Ajusco, central Mexico, significant cold temperature anomalies. [1] S. White: Quaternary Glacial Strati• and comparison with Standard Mexican gla• graphy and Chronology of Mexico, in: V. cial sequence; Quaternary Research 21 (1984) Last not least, the application of tephrochro- Sibrava, D. Q. Bowen, G. M. Richmond 21-35. nology supplies us with a detailed chrono- (Eds.): Quaternary Glaciations in the Nor• stratigraphy of the Late Quaternary events in thern Hemisphere, Pergamon Press, Oxford, Mexico, a chronostratigraphy in which strati• New York, Toronto, Sydney, Frankfurt, 1986. graphic and Chronologie relationships are S. 201-205. much more clarified than in many other tro- [2] S. White: Late Pleistocence glacial se- pical and subtropical parts of the world. quence 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. Exploitation : S. 95-115. [4] D. Ohngemach and H. Straka: Beiträge zur Vegetations- und Klimageschichte im Ge• biet von Puebla-Tlaxcala. Pollenanalysen im Glacial advance Mexiko-Projekt. Das Mexiko-Projekt der One or more glacial DFG XVIII. Steiner, Wiesbaden, 1983. 161 advances or glaciations pp. + Suppl. during the mdicated time [5] G. Miehlich: Klima- und altersabhängige interval Bodenentwicklungen von Vulkanascheböden der Sierra Nevada de Mexico; Mitt. Deutsch. Alternate age assignments Bodenkundl. Ges. 18 (1974) 360-369. [6] K. Heine: Studien zur jungquartären Gla• zialmorphologie mexikanischer Vulkane - mit einem Ausblick auf die Klimaentwick• Multiple lung. Das Mexiko-Projekt der DFG VII. Stei• recessional readvances ner, Wiesbaden, 1975, 178 pp. [7] K. Heine: Neue absolute Daten zur holo- Diamicton of zänen Gletscher-, Vegetations- und Klimage• possible glacial ongm schichte zentralmexikanischer Vulkane, in: M. Hartl, V. Engelschalk (Eds.): Geographie, RG Rock glaciers Naturwissenschaft und Geisteswissenschaft, 14 C age Regensburger Geogr. Sehr. 19/20, (1985). X• archeological age 79-92. (sidereal time) [8] K. Heine: Ein außergewöhnlicher Glet• % Arrows mdicate maximum schervorstoß in Mexiko vor 12 000 Jahren. or mmimum age of Ein Beitrag zum Problem der spätglazialen moraine above Klimaschwankungen; Catena 10 (1983) 1 -25. or below the symbol [9] K. Heine: Blockgletscher- und Blockzun• Anschrift: gen-Generationen am Nevado de Toluca, Me• xiko; Die Erde 107 (1976) 330-352. Prof. Dr. Klaus Heine, Institut für Geogra• [10] K. Heine: Spät- und postglaziale Glet• phie, Universität Regensburg, Postfach 397, scherschwankungen in Mexiko: Befunde und D-8400 Regensburg.