VARIATION IN GEOGRAPHIC DISTRIBUTION OF MAMMALS IN PLEISTOCENE: EXPLANATION WITH ASTROCLIMATOLOGY

Xu Qinai Institute of Vertebrate Paleontology and Paleoanzhropology, Academia Sinica  

In western Europe, there were three important cold stages when the Siberian fauna got there. They were correlated with the oxygen isotope Stages 16, 6 and 2-4 respectively (Boni- fay, 1980). The first cold fauna from Siberia reached western Europe in Stage 16. The fauna consisted of Canis etruscus mosbachensis, Gulo gulo schlosseri, Mustela palerminea and Vulpes praeglaciaiis. All of them were archaic types. The second cold fauna from Siberia got to western Europe in Stage 6. The fauna included Canis lupus, Gulo gulo, Mustela erminea, Alopex lagopus, Mammuthus and Coelodonta antiquitatis. All of them were different with the first cold fauna and belonged to the advanced types. The third cold fauna arrived in western Europe in Stages 2-4. The composition of the last two faunas are similar (Fig. 1). The first cold fauna stayed in western Europe for quite a long period (76,000 years), while the last two faunas stayed there in a short time (Bonifay, 1980). Three clear cold periods were found in Qinghai-Xizang (Tibet) Plateau. The last glacial period was correlated with oxygen isotope Stages 2-4 or the L_1 stage of Chinese loess. Its moraines were the smallest among the three periods. The penultimate glacial period, corresponding to Stage 6 or the L_2 stage of Chinese loess, developed the largest glaciers of the Plateau in Pleistocene and the snowline dropped about 300m below that of the last glacial period (without taking into account the uplift of the Plateau). Moraines of the last glaciation but two were well developed in the Plateau and they correspond to or slightly smaller in scope than those of the penultimate glacial period. They had undergone considerably long period of weathering, which turned them red in color. They compared favorably with Stage 16 or the L_6 of the loess. Therefore, the three levels of the cold faunas in western Europe can exactly be correlated with the three clear cold periods in Qinghai-Xizang (Tibet) Plateau. So the Pleistocene glacial periods did obey the law of the global climactic changes (Shi Yafeng, Li Bingyuan, Li Jijun, et al., 1991). The Milankovitch theory can explain the historical facts of the frequent and repeated alternation of the glacial (or cold stages) and the in terglacial (or warm stages) with the natural slow changes in the geometry of the earth's orbit. However, it can not explain why the climate was much colder in Stage 6 than that in Stages 2-4, and why the influence was much more severe in Stage 16, 6 and 2-4 than that in the other cold stages. In recent years, we modified the Milankovitch theory (Xu Qinqi, 1988; Xu Qinqi and Huang Yuzhen, 1991). The average incoming olar radiation in the winter half-year of the northern hemisphere on the earth's surface in each oxygen isotope stage (Di) were calculated (Table 1). We got Xi (the average incoming solar radiation in the summer half-year of the northern hemisphere on the earth's surface in each oxygen isotope stage) in the similar way. We found that the relationship between Di and the temperature in the world is roughly in positive correlation. This principle is named the First Law of Astroclimatology. The relationship between Xi and the temperature in the world is in approximately negative correlation. This principle is called the Second Law of Astroclimatology. The phenomena of the classical North European glacial stages were explained with applications of the data of Di (Xu Qinqi and Huang Yuzhen, 1991). The variation in geographical distribution of mammals in Pleistocene may also be explained with applications of the data of Di. The value of D_16 is 457.27 ly/day. It is the smallest among the Di during the last 734,000 years. So the climate in Stage 16 was much colder than that in the other cold stages. It is in the Stage 16 that *he archaic Siberian fauna or the first cold fauna reached western Europe. The value of D_6 is 458.09 ly/day. It is the smallest, among the Di in the last 500,000 years. Therefore the second cold fauna got to western Europe from Siberia after a very long warm period (Fig. 1). The value of D_(2_4) is 458.84 ly/day. It is quite small (Table 1). So the third cold fauna arrived in western Europe then. Therefore, the migrat on of the Siberian fauna was controlled by the value of Di in Table 1. Shi Yafeng, Li Bingyuan, Li Jijun et al. (1991) explained the three clear glacial periods. of the Qinghai-Xizang Plateau in the similar way. Now we discuss the problem of Stage 14. Kukla and An (1989) point out correctly that although China is far from. northern Europe and the Alps, the apparent agreement of the number of thick loess units in China with the four classical European glacial stages deserves fur ther attention. According to their opinion, L_1,_2, L_5 and L_6 of Chinese loess are correlative with Weichsel, Warthe, Saale and Elster in Northern Europe respectively. Ding and Liu et al. (1990) published a valuable paper. They said that there is a thick unit of loess between S_(2-1) and S_(2-2) in Baicaoyuan section in North China. Its thickness is about 2.9m (Ding and Liu et al., 1990). It is named L_k (Fig. 2). It is likely that L_k represents a complete cold stage. Be cause L_1 and L_2 are correlated with Stages 2-4 and 6 separately, L_k corresponds to Stage 8. It seems that L_3, L_4, L_5 and L_6 could be correlated with Stages 10, 12, 14 and 16 respectively. Thus, L_1, L_2, L_5 and L_6 correspond to Stages 2-4, 6, 14 and 16 (Fig. 2). According to our viewpoint, the oxygen isotope Stages 2-4, 6, 14 and 16 are correlated with Weichsel, Warthe, Saale and Elster (Xu Qinqi and Huang Yuzhen, 1991). Therefore, L_1, L_2, L_5 and L_6 are correlative with Weichsel, Warthe, Saale and Elster respectively. It is similar to the viewpoint of Kukla and An's (1989). Table 1 shows that the values of D_16, D_14, D_6 and D2-4 are 457.27, 457.84, 458.09, and 458.84 ly/day separately. They are increased progressively. It means that the more older stage, the more colder climate in these four cold' stages. Therefore the older moraines lie progressively further south. As a matter of fact, it is true (Kukla, 1977; Xu Qinqi and Huang Yuzhen, 1991). I suggest that the period of the first cold fauna in western Europe included both Stage 16 and Stage 14 or both Elster and Saale (Fig. 1). In cold stages, the northern elements of mammals migrated from North China to South China. In Stage 8, the northern elements, such as Tamias wimani, Trogotherium cuvieri, Cricetulus varians, Dicerorhinus, Sus lydekkeri, Pseudaxis grayi, Megaceros pachyosteus, ScaPtochirus, Eothenomus inez and Ursus arctos reached the northern bank of the Yangtze River, i.e. Hexian County, Anhui Province (31°45'N, 118°20'E). In Stages 2-4, the northern elements, such as Scaptochirus moschatus, Ursus arctos and Cricetulus got to the southern parts of the Yangtze River, i.e. Shenxiandong cave of Lishui County, Jiangsu Profince (31~03'N, 119~010'E). At about the same time, two typical northern elements, i.e. Microtus brandtioides and Cricetulus arrived at the old town of Yuhang, Zhejiang Province (30° 20', 119°55'E). These phenomena demonstrated that the climate in Stages 2-4 was much colder than that in Stage 8. It is true. In Table 1, the value of D_(2-4) is less than that of D_8. In Stage 6, the northern elements, Crocidura wongi, Rhinolophus cf. ferrumequinum, lavio, Microtus brandtioides, Mieromys of. minutus and Hyaena sinensis arrived in Qujiang County, Guangdong Province (24°30'N, 113°16' E). it is evident that the length of migration of the northern mammals was much longer in Stage 6 than that in Stages 2-4 and Stage 8. Just as we expected the value of D_6 is much less than that of D_(2-4) and D_8 (Table 1). Therefore, the relationship Petween the climate and the value of Di is in perfect harmony during the last three cold stages (i.e. Stages 2-4, 6 and 8) in China (Fig.3) In short, the variation in geographic distribuffon of mammals in Pleistocene was controlled by the changes of the value of Di, or by the natural slow changes in the geometry of the earth's orbit.

【Key Words】： Pleistocene Mammals Geographic Distribution Astroclimatology

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