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Chapter 7 Climatic Changes in the Early and Middle Pleistocene
Chapter 7
CLIMATIC CHANGES IN THE EARLY AND MIDDLE PLEISTOCENE 7.1. Introduction The factual information presented in Section I1 on climatic changes in the Pleistocene allows us to describe natural zones and climates of the Northern Hemisphere within all orthoclimathems. The framework of this book, however, does not allow us to describe all of the more than twenty recognized orthoclimathems. Moreover, the main purpose of this work is to elaborate the time structure of the past climates. The reconstruction of natural zones and climatic environments of the Pleistocene orthoclimathems will perhaps be done in future. Therefore, we present below a concise review of the natural environments and climates of the 12 regions in the Northern Hemisphere that have been considered earlier with an emphasis on the most important events. Since this review is going to be quite brief, we shall not overburden it with references, which have been given in Section 11.
7.2. The sixth (Giinz) kryo-superclimathem, 1.17 - 1.0 Ma The beginning of the sixth SCT conditionally called the Giinz superclimathem coincides with the base of the Sicilian stage in its type area in the vicinity of Palermo, where it is dated at 1.2 - 1.15 Ma (Ruggieri and Sprovieri, 1977; Ruggieri et al., 1984). Its prototype can be the double Menapian kryomer in the Netherlands (Van Hammen et al., 1971; Zagwijn et al., 1971; Zagwijn, 1975) and the Port Katon - Kvemonataneby) kryomer of the Ponto - Caspian Basin in the USSR. According to palaeomagnetic data, these kryomers are found below the Jaramillo boundary. In the sequences on Tsvermagal Mount this cold stage occurs within the normal polarity event (= Cobb Mountain ?, 1.1 Ma). In North America the standard of the sixth superclimathem is the Nebraska “B” moraine underlain with the Coleridge ash of the Pearlett S-type dated by the fission-track method at 1.27 Ma (Easterbrook and Boelstorff, 1981). In the Patagonian Andes it is correlated with the moraine of the greatest piedmont glacier with an age of about 1.2 Ma (Mercer, 1978) and in New Zealand it is associated with the kryomer containing the Pikihikura ash with fission-track date of 1.06 Ma (Hornibrook, 1981). In the deep-sea sequences the sixth SCT is fixed by the first appearance of small Gephyrocapsa of about 1.13 Ma in the roof of zone NN 15 (Rio, 1982) and Mesocena elfiptica of about 1 Ma (Berggren et al., 1980). In the DSDP key site 504 near the coasts of Ecuador it corresponds to the zone of the Mesocene cool peak, which falls between 1.3 and 1.0 Ma (Bukry, 1983). The correlation of the sixth superclimathem with the isotope curve cannot be accurate, because the number of isotope stages below stage 25 does not coincide in different authors.
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Climatic conditions of the sixth SCT can first of all be estimated by the data on the extent of glaciation. The advancement of the Laurentian ice sheet, which led to the formation of the B-type tills, reached as far as Nebraska. It cannot be excluded that the lower tills on Island Banks were also associated with that glaciation. In Europe, there is also indirect evidence of glacier advancement at that time at least as far as the Volga/Oka watershed. For instance, while examining the Middle Goryanka alluvial deposits in the Don Basin associated with the normal polarity zone (probably, the Cobb Mountain event), Krasnenkov discovered pebbles of the Scandinavian crystalline rocks washed out from the north through the river valley, which presumably (Fursikova, 1982) linked the upper reaches of the Volga and the Don. Thus, it can be seen that the Menap - Nebraska "B" - Gunz glaciation was not smaller but even greater than the Wurm glaciation. This conclusion has been corroborated by strong evidence that the Cassian - Calabrian regression dated at about 1.1 to 1.0 Ma was very extensive (Ambrosetti et al., 1972). At the time of this regression and the Iron Creek glaciation the Bering Strait was drained, which can be inferred from the appearance of the Asian migrants in North America (Archidiskodon haroldcooki) and the American migrants among the Oler fauna. The vestiges of periglacial climate of the sixth SCT have been preserved in the 11yichevsk loess in the Ukraine and Wucheng loess on the Ordos Plateau in China as well as in the loess sequences with Kuruksai fauna in Soviet central Asia and several stages of polygonal-vein ice in the lower Oler suite of north-eastern Asia containing fauna of the early Irvington type. The tundra steppe phyto- and zoocenose moves from Central Asia to central Europe, where it is represented by the Graze climatic zone (Chaline, 1977). Thus, it can be stated that the sixth superclimathem is an intense and evidently multi-phase global cooling accompanied by extensive advancement of ice sheets (as far as 41"N in North America and 56"N (?) in Europe) and loess formation. Clear traces of the lacustrine transgressions in the arid zone have also been preserved since this cold stage. Among them there are the Middle Apsheron transgression of the Caspian Sea and that of the lacustrine beds, unit F, in the section of site KM3 on Lake Sierls (Smith et al., 1983). Both transgressions are dated by the presence of normal polarity event n3 ( = Cobb Mountain ?).
7.3. The fifth (Giinz - Mindel) thermo-superclimathem, 1.0 - 0.76 Ma The standard of the fifth thermo-superclimathem is the Portuensian transgression and its Black Sea equivalent, the Tsvermagal transgression with stratotypes on Mount Tsvermagal and along the Chakhvata River. In the deep-sea sequences the fifth thermo-SCT corresponds to isotope stages 25 - 21. Along the Mediterranean coast the Sicilian deposits are incorporated into the third and fourth marine terraces lying at a height of 105 to 30 m above sea level (Zeuner, 1959, 1965; Kaiser, 1965); for example, that is level U on Mallorca according to Butzer (Bowen, 1978). In eastern central Baja California, they presumably correspond to high marine terraces near Santa Rosalia and San Climente, the earliest being estimated by Ortlieb at one million years old (The XZth ZNQUA Congress, Abstracts, vol. 11, p. 229).
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In the Bering Sea the fifth thermo-SCT is marked by the Anvil warm-water transgression, at the time of which the Pacific molluscs and foraminifera easily invaded the Polar Basin and moved along the Canadian shelf as far as the Norwegian Basin (Herman and Hopkins, 1980; Gudina et al., 1984). At that time for many years pack ice did not exist in the Polar Basin, which means that the then Arctic climate was much warmer than nowadays. This is recorded quite well in the cores from the central Polar Basin (Clark, 1982; Herman, 1975). In the loess sequences, the fifth thermo-SCT is represented by three soil horizons: the soil L - K - J (Kukla, 1977; Fink and Kukla, 1977)-Nogai (Lebedeva, 1972) and the Shirokino pedocomplex (Veklich, 1982). In the Danube Basin and in the Ukraine they are all of subtropical type formed in a hot climate under seasonally humid conditions. The soils are associated with Banatica mollusc assemblages. In the European forest zone the fifth thermo-SCT is represented by three recently discovered interglacials. In the Netherlands it is the Bavel, Leerdam and Waardenburg thermochrons (Zagwijn, 1985), in West Germany it is the Waterson, Pinneberg and Osterholtz thermochrons (Menke and Behre, 1973). Their analogues are recognized in eastern Europe in the West Siberian Lowland. The spore and pollen record of all three therrnomers reveal forest, mainly broad-leaved assemblages containing a number of endemic forms such as Eucommia, growing now in southeastern Asia, and Tsuga requiring uniform precipitation. At that time the flora contained a large number of exotic species (over 25%). The fifth thermo-SCT is divided by two cold phases corresponding to isotope stages 24 and 22. They are represented by the Chumbur loess sequences in the Sea of Azov region, by the Linge and Dorst - Elba kryomers in north-western Europe and the Mediterranean Vallonnet and Ficarazzi kryomers. According to the data of Byelorussian (Voznyachuk, 1978, 1985) and Polish (Lindner, 1981, 1984) scientists, northern Europe witnessed at that time the formation of an ice sheet whose size was about the size of the Wurm glaciation. It seems likely that the lowest tills from the sequences in the vicinity of Moscow (Lika till), in the upper reaches of the Kama and in the Irtysh issue (Mansi till) were formed during this glaciation, although it is more probable that they developed later (during stage 20). The most ancient interglacial of the Russian Plain (Mikelevshchina) with Arucites johnstruppi and Brusenia bielorussica is more likely to correspond to isotope stage 21. The fifth SCT is associated with a certain mammalian complex, which is everywhere represented by a transient Tamanian - Tiraspolian fauna with the latest representative of the southern elephant (Archidiskodon meridionah enikendis) and the Pleistocene rodentia with Mimmomys rarricepoides (= M . oeconomus). Many authors recognize this fauna as an individual assemblage (Petropavlovka - KaraiDubina - Sent-Prest complex and so on). On the whole we may state that climatic environment throughout the fifth SCT was similar to the Late Pleistocene, i.e. warm interglacials with summer temperature exceeding the present one by 2 - 5°C alternated with short phases of cold and arid climate. Such frequent changes of climatic and consequently natural environment was observed in particular by the Byelorussian and Lithuanian palynologists in the sections of the Brest and Daumantai series (Makhnach et al., 1981; Kondratene, 1979). It is natural that frequent climatic fluctuations inducing shifts in the natural
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zones were favourable for fast evolution of mammalian fauna and our distant ancestor Homo erectus, who at that time migrated from Africa to Europe and Asia. In the Caspian Basin the fifth SCT corresponds to a long Tyurkyan - Duzdag regression, whose age determined by ash horizon “B” in Azerbaijan by the fissiontrack method is found to be 950 - 1,050 ka (Ganzey, 1984) and by the K/Ar method as 850 k 250 ka (Zubakov, 1974). The Tyurkyany sequences are evidently observed in the Jaramillo event. In the sequences of Lake Sierls, the Great Basin, the fifth superclimathem is evidently associated with unit “E” represented by alternating salt and lacustrine ooze deposits, which have also been found in the Jaramillo subzone (Smith et al., 1983). 7.4. The fourth (Mindel) kryo-superclimathem, 760 - 585 ka The fourth kryo-superclimathem is associated with three successive ice advances synchronous with isotope stages 20, 18 and 16 that left behind moraines in the central part of the Russian Plain, the Lika, Setun - Lipetsk and Pereksha- Don, three tills in Byelorussia, in Poland (Narew, Nida and San tills) and in North America (tills of types A). They correspond to three kryochrons in the Netherlandish sequences (“Glacials A - B - C”) and the Early Elsterian glaciation. The last ice advance was the greatest Pleistocene one in many regions of the Northern Hemisphere. That is why it was recognized in the Don Basin as the Dnieper one. Actually the Don
......1 --2 -
3 --4
-5
-~--6-7
-8
-1-9
Fig. 7.1. Inferred boundaries of glacial advances in western Eurasia. 1 - Narew-Unstrut (OCT 22 or 20?) and Nida-Narev-Kama-Mansi (OCT 20?). 2 San - Setun - Lipetsk (OCT 18), 3 - Don - Dzukiya - Mogielanka - Podkamennaya Tungusska (OCT 16), 4 - Elster- Wilga-Dainava-Oka (OCT 14 or 12?), 5 - Saale-Odra-Dnieper (Early Moscow) - Samarovo - Bakhta (OCT 10- S), 6 - Warthe - Late Moscow - Yenisei (OCT 6 ) , 7 Weichsel - Vistula - Valdai - Ermakovo (OCT 5d - 4 - 2), 9 - Dryas 111.
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and Dnieper moraines of the Russian Plain appeared to be rhythm analogues, i.e. they formed during the same climatic phase of a 400 ka rhythm but at different cycles (Fig. 7.1). The “Mindel” SCT is divided by two interglacials, when the climate was relatively cold. During the first (Ilyinka - Karchevo - Akulovo - Kozi-Grzbiet - Westerhoven) interglacial, central Europe was covered by mixed forests and inhabited by subtropical animals. For instance, porcupines (Hystrix) penetrated as far as Czechoslovakia and Byelorussia. The second (Moiseevo - Pilczyca) warming was more moderate and the summer temperature probably did not reach the present one. A deep Flaminian sea regression is K/Ar dated at 680 - 706 ka by Lacium ash and reached its maximum during isotope stage 18. Isotope stage 19 corresponds to the end of a relatively cold Portuensio transgression, when the Mediterranean was inhabited by Hyalinea baltica. It probably corresponds to the Tiltim - Bolgokhtoch Pinakul marine glacial layers with poor foram and ostracod fauna studied by Gudina (1969); Gudina et al., (1984), Slobodin and others (Danilov et al., 1984). In the Ponto - Caspian Basin the “Mindel” glaciation has long been acknowledged t o correspond t o a double Baku transgression, whose water got through the Manych Strait into the Black Sea depression and probably through the Bosporus Strait into the Aegean depression. The Baku or Platovo layers with Didacna parvula, D. rudis are folded into the upper portion of the Chauda - Baku stage, which had not been subdivided earlier. According to the fission-track method, the age of the Baku stage is between 500 and 700 ka. The analogue of the Baku transgression in the sequences of Lake Sierls appears t o be ooze of unit “D” dated by the Brunhes - Matuyama reversal (Smith et al., 1983). The “Mindel” kryo-SCT has everywhere a pronounced faunal characteristic: it is associated with a typical Tiraspolian - Galerian fauna including in addition to Marnrnuthus trogontherii many tundra-forest animals such as Ovibos, Rangifer, Dicrostorzyx, Lemmus and others (Alexandrova, 1976; Agadzhanyan and Erbaeva, 1985; Vangengeim, 1970). The entire complex of geological and palaeontological evidence shows that the climatic cooling of the fourth SCT was very strong. At the same time it is impossible t o fail to draw the conclusion that this period was more favourable for the expansion of ice sheets than orthoclimathems 24 - 22. That means that the climate of the fourth SCT was rather “snowy”. Does this only refer to the Northern Hemisphere? There is no direct evidence to compare the situation in the two hemispheres. However, taking account of the almost identical peaks of isotope stages 22 and 16 (as well as 12 and 6) and an undoubtedly great volume of ice in the Northern Hemisphere within stages 18- 16 (and 8-6) compared with stages 24 - 22 (and 14 - 12), we can reach the conclusion that the culminations of the surface glaciation in both hemispheres were asynchronous.
7.5. The third (“Mindel - Riss”) therrno-superclimathern, 585 - 350 ka Ancient alluvial strata of buried valleys known as Mariinsk and Strelitsa suites on the Don River, the Gunki suite on the Dnieper River and the Tobolian and Larjyak
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suites in West Siberia, are the standard of the third thermo-SCT in the continental sections in the USSR territory. They include at least two interglacials: Muchkap and Likhvin on the Don River, Vorogovo and Panteleyev on the Yenisey, and Scorodum and Chembakchino on the Ob River. The lower part of these strata is characterized by the remains of the Late Tiraspolian mammalian fauna and at the same time by thermophylic Kolkotovian complex of freshwater molluscs with Viviparus tiraspofitanus (on the Dniester), Corbicula fluniinalis etc. The above interglacial of 370 - 500 ka, according to the thermoluminescene dating technique, which correlates with the 11 - 13th isotopic stages, contains mammalian fauna of the Singulian type with Palaeloxodon antiquus and Arvicola mosbachensis and Volgan type with Mammuthus chosaricus and A . chosaricus. It corresponds to the Likhvin interglacial of the Russian Plain and the Holstein of western Europe. At the same time the latter two names are used to designate the whole third SCT. Interglacial alluvial members are divided in the West Siberian sections by silting regional stages with tree stubs and forest-tundra pollen spectrum (Sarchikha kryomer = the 12th or 14th isotopic stages), which corresponds to the last findings of the Tiraspolian fauna. In Kukla’s scheme (1977) the equivalent of the Sarchikha kryomer is called Elster-11, and that of Vorogovo and Muchkap is called “Holstein - Frimmersdorf”. In the sections of drilling wells in the Russian Plain the third SCT is called the Odintsovo - Roslavl (Moskvitin, 1957) - Shklov (Goretsky, 1980) interglacial. It has three individual optima according to its spore-pollen characteristics: the lower Glasov ( = Lyubny, OCT 15c) with oak and elm peak, and the second Pepelovo ( = Lysogorsk, OCT 15a) with hornbeam peak, and the third Galich (OCT 13) with Likhvinian-like pollen diagram (Moskvitin, 1958, 1967, 1976; Goretsky, 1983; Yolovicheva, 1979; Chebotareva, 1984; The Moscowian ice sheer . . ., 1982). Since this triple interglacial lay on the moraine of maximum glaciation, i.e. was traditionally considered, on the Dnieperian, then the Odintsovo - Shklov triple interglacial was identified as the “second Middle Pleistocene”. Only Vosnyachuk (1965, 1978) assumed the Shklov - Roslavlian layers to be of Cromerian age. This idea was confirmed by Biryukov (Marginal Formations. . ., 1985, p. 106), who found the Tiraspolian rodent fauna with Mimomys intertnedius in the Glazov layers of the stratotype section near the city of Roslavl. Now we can name the entire third SCT the Odintsovian comparing it with isotopic stages 15c, 15a and 13, and two intermediate kryomers (Podrudnya and Oka) with stages 15b and 14. In Poland, the Great and Mazovian interglacials (Rozicky, 1969) were analogues of the Odintsovo thermo-superclimathem divided now into two interglacials - Ferdynandow and Barcowike-Mokre (Lindner, 1984; Moijski, 1985). In marine sections of the Mediterranean and the Black Sea, the third SCT includes the Tarquinian - Uzunlarian triple transgression (Table 6.1 ) separated by bipartial Nomentanan - Palaeoeuxin erosion phase, the equivalent of the Oka - Elster I1 glacial advance. In the section of marine sediments in the north of Eurasia, the Tarquinian is equivalent to the Kolva - Ust’ Solenaya layers with rather warm water for the Arctic complex of foraminifera, and the Riano - Padimei - Kochos layers with a cooler complex. All this agrees with the interpretation of the Mindel-Riss given by Penck and Bruckner (1909) and particularly by Beck (1934) and Eberl (1930), who revealed in
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the “great” and long-term Mindel - Riss two interglacials: Kander and Gluch (Moskvitin, 1970), which now can be synchronized with isotopic stages 14 and 12. This supposition of the author (Zubakov, 1968c) has been confirmed now by considerably larger extensive data. In loess sequences, the Mindel - Riss (without inverted commas now) thermoSCT is represented by a triple (sometimes quadruple) pedocomplex called the Tsokur pedocomplex in the Asov Basin and the Gorodskoi pedocomplex in the Don Basin. In the Ukraine, it corresponds to the Martonosha, Lubny and Zavadovka soils with Acheulian flint tools. The latter serve as indicators of the soil of the third SCT in Asia and in the Mediterranean Basin (Terra Amata and others). Thus, the third SCT is a well-documented triple interglacial, corresponding to isotopic stages 15, 13 and 11. They differ distinctly by their palaeontological characteristics (the Late Tiraspolian, Singilian and Volgan mammalian complexes, Kolva and Padimei foraminifera complexes). During all these interglacials the climate was very warm with temperatures exceeding the modern one by 2 - 3 ° C (Kondratiene, 1977; Zagwijn, 1973, 1975; Makhnach et al., 1981), while the moisture content was different. The middle, Likhvin - Holstein, interglacial was characterized, judging by the predominance of dark coniferous forest, by tsuga, hornbeam and the presence of yew in the forests of the middle zone of Europe, by more humid, even marine, climate extending almost as far as the Urals. Winter was particularly warm with temperatures of 2 - 4°C higher than at present, which allowed subtropical plants such as vine (Vilis),yew and animals such as Hystrix, Macaca and Hippopotamus as well as Pdaeoloxodon antiquus to penetrate northwards of the present border. This enables one to conclude that the narrow time sections along the optimum of the Likhvin - Holstein (OCT 13) and Glasovo - Cromer s.str. (OCT 15) interglacials can be used for spatial palaeoclimatic reconstructions. In particular, the former, since it is quite recognizable in the deep-sea sections: it lies just under LAD Pseudomiliania lacunosa, 440 ka ago. 7.6. The second (Riss) kryo-superclimathem, 350 - 130 (170?) ka
The second kryo-SCT includes the sediment envelope with buried river valleys formed during the third superclimathem. It is represented by genetically unhomogeneous series: in the north by moraine and fluvio-glacial deposits that correspond to two advances of the ice sheets (Dnieper - Moscow, Saale I - I1 - Illinois I - 11) of which the second was maximum; in the periglacial zone, by lake sediments and periglacial formation. In the extraglacial zone, the equivalents of moraines in the interstream areas are two loess horizons (Orel and Dnieper in the Ukraine), and terrace levels on the Caspian Sea (two upper Khazarian terraces). These sediments are characterized by the presence of remains of the Volgan ( = Khazarian = Aldenian) mammalian fauna with Mammuthus chosaricus, M.primigenius fraasi, M .pr.pa vlovae, Coelodonta antiquifat is, Equus cabaIlus, Discrostonyx simplicior etc., which were distributed over great areas in Eurasia. The geomorphological criterion was important in dissecting the sediments of the
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second superclimathem. In this case, of particular importance was the final advance o f the Warthe ice sheet, whose end-moraine belt occurred in the North Germany lowland and further eastwards to Moscow. Here, it was associated by some researchers with the moraine of the Kalinin glaciation (Moskvitin, 1967, 1976) and by the others with the Moscow glaciation (Markov et al., 1965). In West Siberia also, some researchers (Saks, 1948) correlated with the Warthe the Zyryan moraine, while others (Zemtsov and Shatsky, 1953), the Tazovian moraine. Unreliability of morphostratigraphic substantiation was fatal for the chronostratigraphy of the glacial formations of the Central Russian Plain and West Siberia. It appears now that this led t o an incorrect interpretation of borehole logs, in which for the most part the interglacial strata were revealed (frequently bedded in the erratics), and naturally to incorrect correlation of interglacial sequences. It turned out that Moskvitin (1967, 1976) was right and the Warthe moraine corresponds in reality to the Kalinin one in the Upper Volga Basin. However, its age proved to be older; according to thermoluminescence dates it is 140 - 200 ka and corresponds to isotopic stage 6 like the age of the Yenisey ( = “Zyryanka”?, Taz?) moraine in Siberia. Consequently, the Moscow moraine in the Upper Volga appeared to be an equivalent of the Dnieper one in the Chekalian type section, and the “Dnieper” moraine from the well sections in the Moscow region, of the Lower Pleistocene (the Don) one. Thus, there appeared great stratigraphic discrepancies. These were partly removed in 1984- 1985 due to investigations carried out by geologists from the Central Geological Survey (Krasnenkov et al., 1984; Shik, 1981; Marginal Formations . . ., 1985). Now it is clear that the time extent of the Moscow glaciation is greater than that of the entire second kryo-SCT. The Moscow glacial complex of the upper reaches of the Volga includes the Kaluga OCT corresponding to the Liwiec stage in Poland and Fuhne in GDR (isotope stage 12 or lo), the Dnieper OCT land and Fuhne in GDR (isotope stage 12 or lo), the Dnieper OCT ( = the Warthe, stage 6). It is possible that there is one more intermediate glacial advance corresponding to isotope substage 7b. These orthoclimathems are separated by the Chekalin - Domnitz - Zbojno - Hoogevin (stage 11 or 9) thermomer and the Cheremoshnik “B” - Grabowka - Treene ( = stage 7) thermomer. The first has thermoluminescence dates of 300 - 340 ka and the second 180 - 245 ka. A similar situation occurs in North America, where the Illinois complex is traditionally considered (Reed et al., 1965) to consist of three horizons : Liman, Monican and Buffalo-Hart separated by three horizons of weathering (humbotill). Definite confirmation of two interglacials within the second SCT is a series of dates of speleothems from the caves of the Rocky Mountains in Canada, revealing two nonglacial intervals between 215 and 320 ka and between 185 and 235 k a (Harmon et al., 1979). These estimates correspond t o the thermoluminescence dates for intraRiss thermomers in the USSR and in Poland. In the deep-sea section the second SCT is synchronized with isotopic stages 10 - 8 (or 12-8?). The maximum shift of 6180 is associated with stage 6, whereas the greatest extent of the Northern Hemisphere glaciation and the greatest (Ostian) regression correspond to stage 8. From this we can conclude that either the Antarctic ice sheet was much more extensive within stage 6 or, as Williams et al. (1981)
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believe, within the same stage there formed in the Arctic a sea ice cover more than 1 km thick resting on the sea bottom. There is no reliable information about the climate within stages 11, 9 and 7 . After Zagwijn (1973), the temperature of the warmest summer months during the Hoogevin thermomer (stage 1 l ? ) was 1 "C lower than the present one, and during the Bantega interstadial (stage 9?) it was 3°C lower (Fig. 5.2).
RCsumC (1) For the last three million years of geological history the most distinct climatic and at the same time biostratigraphic boundary is the end of the Villafranchian in the continental sequences and the onset of the Sicilian transgression in the Mediterranean. This boundary coincides with the first continental glaciation of Eurasia and the erosional phase, with which the formation of the modern river systems begins. This boundary is everywhere dated at 1 f 0.1 Ma. (2) The time structure of the Early and Middle Pleistocene climate (1.17 - 245 ka BP) is much more complicated than was thought earlier. During that time there were no less than 10 t o 12 global coolings accompanied with the advances of ice sheets far into the middle latitudes and the same number of global warmings accompanied with the glacioeustatic transgressions. (3) The global observation of all orthoclimathems is frought with difficulties. Therefore, only superclimathems can be recognized as inter-regional units of the Early and Middle Pleistocene. There are five of them and it is advisable to give them, through international agreement, the Alpine nomenclature.
CLIMATIC CHANGES IN THE EARLY AND MIDDLE PLEISTOCENE 7.1. Introduction The factual information presented in Section I1 on climatic changes in the Pleistocene allows us to describe natural zones and climates of the Northern Hemisphere within all orthoclimathems. The framework of this book, however, does not allow us to describe all of the more than twenty recognized orthoclimathems. Moreover, the main purpose of this work is to elaborate the time structure of the past climates. The reconstruction of natural zones and climatic environments of the Pleistocene orthoclimathems will perhaps be done in future. Therefore, we present below a concise review of the natural environments and climates of the 12 regions in the Northern Hemisphere that have been considered earlier with an emphasis on the most important events. Since this review is going to be quite brief, we shall not overburden it with references, which have been given in Section 11.
7.2. The sixth (Giinz) kryo-superclimathem, 1.17 - 1.0 Ma The beginning of the sixth SCT conditionally called the Giinz superclimathem coincides with the base of the Sicilian stage in its type area in the vicinity of Palermo, where it is dated at 1.2 - 1.15 Ma (Ruggieri and Sprovieri, 1977; Ruggieri et al., 1984). Its prototype can be the double Menapian kryomer in the Netherlands (Van Hammen et al., 1971; Zagwijn et al., 1971; Zagwijn, 1975) and the Port Katon - Kvemonataneby) kryomer of the Ponto - Caspian Basin in the USSR. According to palaeomagnetic data, these kryomers are found below the Jaramillo boundary. In the sequences on Tsvermagal Mount this cold stage occurs within the normal polarity event (= Cobb Mountain ?, 1.1 Ma). In North America the standard of the sixth superclimathem is the Nebraska “B” moraine underlain with the Coleridge ash of the Pearlett S-type dated by the fission-track method at 1.27 Ma (Easterbrook and Boelstorff, 1981). In the Patagonian Andes it is correlated with the moraine of the greatest piedmont glacier with an age of about 1.2 Ma (Mercer, 1978) and in New Zealand it is associated with the kryomer containing the Pikihikura ash with fission-track date of 1.06 Ma (Hornibrook, 1981). In the deep-sea sequences the sixth SCT is fixed by the first appearance of small Gephyrocapsa of about 1.13 Ma in the roof of zone NN 15 (Rio, 1982) and Mesocena elfiptica of about 1 Ma (Berggren et al., 1980). In the DSDP key site 504 near the coasts of Ecuador it corresponds to the zone of the Mesocene cool peak, which falls between 1.3 and 1.0 Ma (Bukry, 1983). The correlation of the sixth superclimathem with the isotope curve cannot be accurate, because the number of isotope stages below stage 25 does not coincide in different authors.
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Climatic conditions of the sixth SCT can first of all be estimated by the data on the extent of glaciation. The advancement of the Laurentian ice sheet, which led to the formation of the B-type tills, reached as far as Nebraska. It cannot be excluded that the lower tills on Island Banks were also associated with that glaciation. In Europe, there is also indirect evidence of glacier advancement at that time at least as far as the Volga/Oka watershed. For instance, while examining the Middle Goryanka alluvial deposits in the Don Basin associated with the normal polarity zone (probably, the Cobb Mountain event), Krasnenkov discovered pebbles of the Scandinavian crystalline rocks washed out from the north through the river valley, which presumably (Fursikova, 1982) linked the upper reaches of the Volga and the Don. Thus, it can be seen that the Menap - Nebraska "B" - Gunz glaciation was not smaller but even greater than the Wurm glaciation. This conclusion has been corroborated by strong evidence that the Cassian - Calabrian regression dated at about 1.1 to 1.0 Ma was very extensive (Ambrosetti et al., 1972). At the time of this regression and the Iron Creek glaciation the Bering Strait was drained, which can be inferred from the appearance of the Asian migrants in North America (Archidiskodon haroldcooki) and the American migrants among the Oler fauna. The vestiges of periglacial climate of the sixth SCT have been preserved in the 11yichevsk loess in the Ukraine and Wucheng loess on the Ordos Plateau in China as well as in the loess sequences with Kuruksai fauna in Soviet central Asia and several stages of polygonal-vein ice in the lower Oler suite of north-eastern Asia containing fauna of the early Irvington type. The tundra steppe phyto- and zoocenose moves from Central Asia to central Europe, where it is represented by the Graze climatic zone (Chaline, 1977). Thus, it can be stated that the sixth superclimathem is an intense and evidently multi-phase global cooling accompanied by extensive advancement of ice sheets (as far as 41"N in North America and 56"N (?) in Europe) and loess formation. Clear traces of the lacustrine transgressions in the arid zone have also been preserved since this cold stage. Among them there are the Middle Apsheron transgression of the Caspian Sea and that of the lacustrine beds, unit F, in the section of site KM3 on Lake Sierls (Smith et al., 1983). Both transgressions are dated by the presence of normal polarity event n3 ( = Cobb Mountain ?).
7.3. The fifth (Giinz - Mindel) thermo-superclimathem, 1.0 - 0.76 Ma The standard of the fifth thermo-superclimathem is the Portuensian transgression and its Black Sea equivalent, the Tsvermagal transgression with stratotypes on Mount Tsvermagal and along the Chakhvata River. In the deep-sea sequences the fifth thermo-SCT corresponds to isotope stages 25 - 21. Along the Mediterranean coast the Sicilian deposits are incorporated into the third and fourth marine terraces lying at a height of 105 to 30 m above sea level (Zeuner, 1959, 1965; Kaiser, 1965); for example, that is level U on Mallorca according to Butzer (Bowen, 1978). In eastern central Baja California, they presumably correspond to high marine terraces near Santa Rosalia and San Climente, the earliest being estimated by Ortlieb at one million years old (The XZth ZNQUA Congress, Abstracts, vol. 11, p. 229).
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In the Bering Sea the fifth thermo-SCT is marked by the Anvil warm-water transgression, at the time of which the Pacific molluscs and foraminifera easily invaded the Polar Basin and moved along the Canadian shelf as far as the Norwegian Basin (Herman and Hopkins, 1980; Gudina et al., 1984). At that time for many years pack ice did not exist in the Polar Basin, which means that the then Arctic climate was much warmer than nowadays. This is recorded quite well in the cores from the central Polar Basin (Clark, 1982; Herman, 1975). In the loess sequences, the fifth thermo-SCT is represented by three soil horizons: the soil L - K - J (Kukla, 1977; Fink and Kukla, 1977)-Nogai (Lebedeva, 1972) and the Shirokino pedocomplex (Veklich, 1982). In the Danube Basin and in the Ukraine they are all of subtropical type formed in a hot climate under seasonally humid conditions. The soils are associated with Banatica mollusc assemblages. In the European forest zone the fifth thermo-SCT is represented by three recently discovered interglacials. In the Netherlands it is the Bavel, Leerdam and Waardenburg thermochrons (Zagwijn, 1985), in West Germany it is the Waterson, Pinneberg and Osterholtz thermochrons (Menke and Behre, 1973). Their analogues are recognized in eastern Europe in the West Siberian Lowland. The spore and pollen record of all three therrnomers reveal forest, mainly broad-leaved assemblages containing a number of endemic forms such as Eucommia, growing now in southeastern Asia, and Tsuga requiring uniform precipitation. At that time the flora contained a large number of exotic species (over 25%). The fifth thermo-SCT is divided by two cold phases corresponding to isotope stages 24 and 22. They are represented by the Chumbur loess sequences in the Sea of Azov region, by the Linge and Dorst - Elba kryomers in north-western Europe and the Mediterranean Vallonnet and Ficarazzi kryomers. According to the data of Byelorussian (Voznyachuk, 1978, 1985) and Polish (Lindner, 1981, 1984) scientists, northern Europe witnessed at that time the formation of an ice sheet whose size was about the size of the Wurm glaciation. It seems likely that the lowest tills from the sequences in the vicinity of Moscow (Lika till), in the upper reaches of the Kama and in the Irtysh issue (Mansi till) were formed during this glaciation, although it is more probable that they developed later (during stage 20). The most ancient interglacial of the Russian Plain (Mikelevshchina) with Arucites johnstruppi and Brusenia bielorussica is more likely to correspond to isotope stage 21. The fifth SCT is associated with a certain mammalian complex, which is everywhere represented by a transient Tamanian - Tiraspolian fauna with the latest representative of the southern elephant (Archidiskodon meridionah enikendis) and the Pleistocene rodentia with Mimmomys rarricepoides (= M . oeconomus). Many authors recognize this fauna as an individual assemblage (Petropavlovka - KaraiDubina - Sent-Prest complex and so on). On the whole we may state that climatic environment throughout the fifth SCT was similar to the Late Pleistocene, i.e. warm interglacials with summer temperature exceeding the present one by 2 - 5°C alternated with short phases of cold and arid climate. Such frequent changes of climatic and consequently natural environment was observed in particular by the Byelorussian and Lithuanian palynologists in the sections of the Brest and Daumantai series (Makhnach et al., 1981; Kondratene, 1979). It is natural that frequent climatic fluctuations inducing shifts in the natural
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zones were favourable for fast evolution of mammalian fauna and our distant ancestor Homo erectus, who at that time migrated from Africa to Europe and Asia. In the Caspian Basin the fifth SCT corresponds to a long Tyurkyan - Duzdag regression, whose age determined by ash horizon “B” in Azerbaijan by the fissiontrack method is found to be 950 - 1,050 ka (Ganzey, 1984) and by the K/Ar method as 850 k 250 ka (Zubakov, 1974). The Tyurkyany sequences are evidently observed in the Jaramillo event. In the sequences of Lake Sierls, the Great Basin, the fifth superclimathem is evidently associated with unit “E” represented by alternating salt and lacustrine ooze deposits, which have also been found in the Jaramillo subzone (Smith et al., 1983). 7.4. The fourth (Mindel) kryo-superclimathem, 760 - 585 ka The fourth kryo-superclimathem is associated with three successive ice advances synchronous with isotope stages 20, 18 and 16 that left behind moraines in the central part of the Russian Plain, the Lika, Setun - Lipetsk and Pereksha- Don, three tills in Byelorussia, in Poland (Narew, Nida and San tills) and in North America (tills of types A). They correspond to three kryochrons in the Netherlandish sequences (“Glacials A - B - C”) and the Early Elsterian glaciation. The last ice advance was the greatest Pleistocene one in many regions of the Northern Hemisphere. That is why it was recognized in the Don Basin as the Dnieper one. Actually the Don
......1 --2 -
3 --4
-5
-~--6-7
-8
-1-9
Fig. 7.1. Inferred boundaries of glacial advances in western Eurasia. 1 - Narew-Unstrut (OCT 22 or 20?) and Nida-Narev-Kama-Mansi (OCT 20?). 2 San - Setun - Lipetsk (OCT 18), 3 - Don - Dzukiya - Mogielanka - Podkamennaya Tungusska (OCT 16), 4 - Elster- Wilga-Dainava-Oka (OCT 14 or 12?), 5 - Saale-Odra-Dnieper (Early Moscow) - Samarovo - Bakhta (OCT 10- S), 6 - Warthe - Late Moscow - Yenisei (OCT 6 ) , 7 Weichsel - Vistula - Valdai - Ermakovo (OCT 5d - 4 - 2), 9 - Dryas 111.
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and Dnieper moraines of the Russian Plain appeared to be rhythm analogues, i.e. they formed during the same climatic phase of a 400 ka rhythm but at different cycles (Fig. 7.1). The “Mindel” SCT is divided by two interglacials, when the climate was relatively cold. During the first (Ilyinka - Karchevo - Akulovo - Kozi-Grzbiet - Westerhoven) interglacial, central Europe was covered by mixed forests and inhabited by subtropical animals. For instance, porcupines (Hystrix) penetrated as far as Czechoslovakia and Byelorussia. The second (Moiseevo - Pilczyca) warming was more moderate and the summer temperature probably did not reach the present one. A deep Flaminian sea regression is K/Ar dated at 680 - 706 ka by Lacium ash and reached its maximum during isotope stage 18. Isotope stage 19 corresponds to the end of a relatively cold Portuensio transgression, when the Mediterranean was inhabited by Hyalinea baltica. It probably corresponds to the Tiltim - Bolgokhtoch Pinakul marine glacial layers with poor foram and ostracod fauna studied by Gudina (1969); Gudina et al., (1984), Slobodin and others (Danilov et al., 1984). In the Ponto - Caspian Basin the “Mindel” glaciation has long been acknowledged t o correspond t o a double Baku transgression, whose water got through the Manych Strait into the Black Sea depression and probably through the Bosporus Strait into the Aegean depression. The Baku or Platovo layers with Didacna parvula, D. rudis are folded into the upper portion of the Chauda - Baku stage, which had not been subdivided earlier. According to the fission-track method, the age of the Baku stage is between 500 and 700 ka. The analogue of the Baku transgression in the sequences of Lake Sierls appears t o be ooze of unit “D” dated by the Brunhes - Matuyama reversal (Smith et al., 1983). The “Mindel” kryo-SCT has everywhere a pronounced faunal characteristic: it is associated with a typical Tiraspolian - Galerian fauna including in addition to Marnrnuthus trogontherii many tundra-forest animals such as Ovibos, Rangifer, Dicrostorzyx, Lemmus and others (Alexandrova, 1976; Agadzhanyan and Erbaeva, 1985; Vangengeim, 1970). The entire complex of geological and palaeontological evidence shows that the climatic cooling of the fourth SCT was very strong. At the same time it is impossible t o fail to draw the conclusion that this period was more favourable for the expansion of ice sheets than orthoclimathems 24 - 22. That means that the climate of the fourth SCT was rather “snowy”. Does this only refer to the Northern Hemisphere? There is no direct evidence to compare the situation in the two hemispheres. However, taking account of the almost identical peaks of isotope stages 22 and 16 (as well as 12 and 6) and an undoubtedly great volume of ice in the Northern Hemisphere within stages 18- 16 (and 8-6) compared with stages 24 - 22 (and 14 - 12), we can reach the conclusion that the culminations of the surface glaciation in both hemispheres were asynchronous.
7.5. The third (“Mindel - Riss”) therrno-superclimathern, 585 - 350 ka Ancient alluvial strata of buried valleys known as Mariinsk and Strelitsa suites on the Don River, the Gunki suite on the Dnieper River and the Tobolian and Larjyak
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suites in West Siberia, are the standard of the third thermo-SCT in the continental sections in the USSR territory. They include at least two interglacials: Muchkap and Likhvin on the Don River, Vorogovo and Panteleyev on the Yenisey, and Scorodum and Chembakchino on the Ob River. The lower part of these strata is characterized by the remains of the Late Tiraspolian mammalian fauna and at the same time by thermophylic Kolkotovian complex of freshwater molluscs with Viviparus tiraspofitanus (on the Dniester), Corbicula fluniinalis etc. The above interglacial of 370 - 500 ka, according to the thermoluminescene dating technique, which correlates with the 11 - 13th isotopic stages, contains mammalian fauna of the Singulian type with Palaeloxodon antiquus and Arvicola mosbachensis and Volgan type with Mammuthus chosaricus and A . chosaricus. It corresponds to the Likhvin interglacial of the Russian Plain and the Holstein of western Europe. At the same time the latter two names are used to designate the whole third SCT. Interglacial alluvial members are divided in the West Siberian sections by silting regional stages with tree stubs and forest-tundra pollen spectrum (Sarchikha kryomer = the 12th or 14th isotopic stages), which corresponds to the last findings of the Tiraspolian fauna. In Kukla’s scheme (1977) the equivalent of the Sarchikha kryomer is called Elster-11, and that of Vorogovo and Muchkap is called “Holstein - Frimmersdorf”. In the sections of drilling wells in the Russian Plain the third SCT is called the Odintsovo - Roslavl (Moskvitin, 1957) - Shklov (Goretsky, 1980) interglacial. It has three individual optima according to its spore-pollen characteristics: the lower Glasov ( = Lyubny, OCT 15c) with oak and elm peak, and the second Pepelovo ( = Lysogorsk, OCT 15a) with hornbeam peak, and the third Galich (OCT 13) with Likhvinian-like pollen diagram (Moskvitin, 1958, 1967, 1976; Goretsky, 1983; Yolovicheva, 1979; Chebotareva, 1984; The Moscowian ice sheer . . ., 1982). Since this triple interglacial lay on the moraine of maximum glaciation, i.e. was traditionally considered, on the Dnieperian, then the Odintsovo - Shklov triple interglacial was identified as the “second Middle Pleistocene”. Only Vosnyachuk (1965, 1978) assumed the Shklov - Roslavlian layers to be of Cromerian age. This idea was confirmed by Biryukov (Marginal Formations. . ., 1985, p. 106), who found the Tiraspolian rodent fauna with Mimomys intertnedius in the Glazov layers of the stratotype section near the city of Roslavl. Now we can name the entire third SCT the Odintsovian comparing it with isotopic stages 15c, 15a and 13, and two intermediate kryomers (Podrudnya and Oka) with stages 15b and 14. In Poland, the Great and Mazovian interglacials (Rozicky, 1969) were analogues of the Odintsovo thermo-superclimathem divided now into two interglacials - Ferdynandow and Barcowike-Mokre (Lindner, 1984; Moijski, 1985). In marine sections of the Mediterranean and the Black Sea, the third SCT includes the Tarquinian - Uzunlarian triple transgression (Table 6.1 ) separated by bipartial Nomentanan - Palaeoeuxin erosion phase, the equivalent of the Oka - Elster I1 glacial advance. In the section of marine sediments in the north of Eurasia, the Tarquinian is equivalent to the Kolva - Ust’ Solenaya layers with rather warm water for the Arctic complex of foraminifera, and the Riano - Padimei - Kochos layers with a cooler complex. All this agrees with the interpretation of the Mindel-Riss given by Penck and Bruckner (1909) and particularly by Beck (1934) and Eberl (1930), who revealed in
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the “great” and long-term Mindel - Riss two interglacials: Kander and Gluch (Moskvitin, 1970), which now can be synchronized with isotopic stages 14 and 12. This supposition of the author (Zubakov, 1968c) has been confirmed now by considerably larger extensive data. In loess sequences, the Mindel - Riss (without inverted commas now) thermoSCT is represented by a triple (sometimes quadruple) pedocomplex called the Tsokur pedocomplex in the Asov Basin and the Gorodskoi pedocomplex in the Don Basin. In the Ukraine, it corresponds to the Martonosha, Lubny and Zavadovka soils with Acheulian flint tools. The latter serve as indicators of the soil of the third SCT in Asia and in the Mediterranean Basin (Terra Amata and others). Thus, the third SCT is a well-documented triple interglacial, corresponding to isotopic stages 15, 13 and 11. They differ distinctly by their palaeontological characteristics (the Late Tiraspolian, Singilian and Volgan mammalian complexes, Kolva and Padimei foraminifera complexes). During all these interglacials the climate was very warm with temperatures exceeding the modern one by 2 - 3 ° C (Kondratiene, 1977; Zagwijn, 1973, 1975; Makhnach et al., 1981), while the moisture content was different. The middle, Likhvin - Holstein, interglacial was characterized, judging by the predominance of dark coniferous forest, by tsuga, hornbeam and the presence of yew in the forests of the middle zone of Europe, by more humid, even marine, climate extending almost as far as the Urals. Winter was particularly warm with temperatures of 2 - 4°C higher than at present, which allowed subtropical plants such as vine (Vilis),yew and animals such as Hystrix, Macaca and Hippopotamus as well as Pdaeoloxodon antiquus to penetrate northwards of the present border. This enables one to conclude that the narrow time sections along the optimum of the Likhvin - Holstein (OCT 13) and Glasovo - Cromer s.str. (OCT 15) interglacials can be used for spatial palaeoclimatic reconstructions. In particular, the former, since it is quite recognizable in the deep-sea sections: it lies just under LAD Pseudomiliania lacunosa, 440 ka ago. 7.6. The second (Riss) kryo-superclimathem, 350 - 130 (170?) ka
The second kryo-SCT includes the sediment envelope with buried river valleys formed during the third superclimathem. It is represented by genetically unhomogeneous series: in the north by moraine and fluvio-glacial deposits that correspond to two advances of the ice sheets (Dnieper - Moscow, Saale I - I1 - Illinois I - 11) of which the second was maximum; in the periglacial zone, by lake sediments and periglacial formation. In the extraglacial zone, the equivalents of moraines in the interstream areas are two loess horizons (Orel and Dnieper in the Ukraine), and terrace levels on the Caspian Sea (two upper Khazarian terraces). These sediments are characterized by the presence of remains of the Volgan ( = Khazarian = Aldenian) mammalian fauna with Mammuthus chosaricus, M.primigenius fraasi, M .pr.pa vlovae, Coelodonta antiquifat is, Equus cabaIlus, Discrostonyx simplicior etc., which were distributed over great areas in Eurasia. The geomorphological criterion was important in dissecting the sediments of the
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second superclimathem. In this case, of particular importance was the final advance o f the Warthe ice sheet, whose end-moraine belt occurred in the North Germany lowland and further eastwards to Moscow. Here, it was associated by some researchers with the moraine of the Kalinin glaciation (Moskvitin, 1967, 1976) and by the others with the Moscow glaciation (Markov et al., 1965). In West Siberia also, some researchers (Saks, 1948) correlated with the Warthe the Zyryan moraine, while others (Zemtsov and Shatsky, 1953), the Tazovian moraine. Unreliability of morphostratigraphic substantiation was fatal for the chronostratigraphy of the glacial formations of the Central Russian Plain and West Siberia. It appears now that this led t o an incorrect interpretation of borehole logs, in which for the most part the interglacial strata were revealed (frequently bedded in the erratics), and naturally to incorrect correlation of interglacial sequences. It turned out that Moskvitin (1967, 1976) was right and the Warthe moraine corresponds in reality to the Kalinin one in the Upper Volga Basin. However, its age proved to be older; according to thermoluminescence dates it is 140 - 200 ka and corresponds to isotopic stage 6 like the age of the Yenisey ( = “Zyryanka”?, Taz?) moraine in Siberia. Consequently, the Moscow moraine in the Upper Volga appeared to be an equivalent of the Dnieper one in the Chekalian type section, and the “Dnieper” moraine from the well sections in the Moscow region, of the Lower Pleistocene (the Don) one. Thus, there appeared great stratigraphic discrepancies. These were partly removed in 1984- 1985 due to investigations carried out by geologists from the Central Geological Survey (Krasnenkov et al., 1984; Shik, 1981; Marginal Formations . . ., 1985). Now it is clear that the time extent of the Moscow glaciation is greater than that of the entire second kryo-SCT. The Moscow glacial complex of the upper reaches of the Volga includes the Kaluga OCT corresponding to the Liwiec stage in Poland and Fuhne in GDR (isotope stage 12 or lo), the Dnieper OCT land and Fuhne in GDR (isotope stage 12 or lo), the Dnieper OCT ( = the Warthe, stage 6). It is possible that there is one more intermediate glacial advance corresponding to isotope substage 7b. These orthoclimathems are separated by the Chekalin - Domnitz - Zbojno - Hoogevin (stage 11 or 9) thermomer and the Cheremoshnik “B” - Grabowka - Treene ( = stage 7) thermomer. The first has thermoluminescence dates of 300 - 340 ka and the second 180 - 245 ka. A similar situation occurs in North America, where the Illinois complex is traditionally considered (Reed et al., 1965) to consist of three horizons : Liman, Monican and Buffalo-Hart separated by three horizons of weathering (humbotill). Definite confirmation of two interglacials within the second SCT is a series of dates of speleothems from the caves of the Rocky Mountains in Canada, revealing two nonglacial intervals between 215 and 320 ka and between 185 and 235 k a (Harmon et al., 1979). These estimates correspond t o the thermoluminescence dates for intraRiss thermomers in the USSR and in Poland. In the deep-sea section the second SCT is synchronized with isotopic stages 10 - 8 (or 12-8?). The maximum shift of 6180 is associated with stage 6, whereas the greatest extent of the Northern Hemisphere glaciation and the greatest (Ostian) regression correspond to stage 8. From this we can conclude that either the Antarctic ice sheet was much more extensive within stage 6 or, as Williams et al. (1981)
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believe, within the same stage there formed in the Arctic a sea ice cover more than 1 km thick resting on the sea bottom. There is no reliable information about the climate within stages 11, 9 and 7 . After Zagwijn (1973), the temperature of the warmest summer months during the Hoogevin thermomer (stage 1 l ? ) was 1 "C lower than the present one, and during the Bantega interstadial (stage 9?) it was 3°C lower (Fig. 5.2).
RCsumC (1) For the last three million years of geological history the most distinct climatic and at the same time biostratigraphic boundary is the end of the Villafranchian in the continental sequences and the onset of the Sicilian transgression in the Mediterranean. This boundary coincides with the first continental glaciation of Eurasia and the erosional phase, with which the formation of the modern river systems begins. This boundary is everywhere dated at 1 f 0.1 Ma. (2) The time structure of the Early and Middle Pleistocene climate (1.17 - 245 ka BP) is much more complicated than was thought earlier. During that time there were no less than 10 t o 12 global coolings accompanied with the advances of ice sheets far into the middle latitudes and the same number of global warmings accompanied with the glacioeustatic transgressions. (3) The global observation of all orthoclimathems is frought with difficulties. Therefore, only superclimathems can be recognized as inter-regional units of the Early and Middle Pleistocene. There are five of them and it is advisable to give them, through international agreement, the Alpine nomenclature.