Climatic changes in the Hungarian Miocene

Review of Palaeobotanyand Palynology, 65 (1990): 71-74

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Elsevier Science Publishers B.V., Amsterdam

Climatic changes in the Hungarian Miocene Esther Nagy

Hungarian Geological Institute, Budapest (Hungary) (Received September 16, 1988; revised and accepted January 25, 1990)

ABSTRACT Nagy, E., 1990. Climatic changes in the Hungarian Miocene. Rev. Palaeobot. Palynol., 65: 71-74. Samples from 32 boreholes and outcrops of the Miocene in Hungary have been studied palynologically. The spores and pollen grains have been classified into tropical, subtropical and temperate elements. Changes in the number of species in the elements and their frequencies through the Miocene (25 to 5.6 m.y.) indicate changes in climate. Tropical elementsdominate the early Miocene, decrease to a certain degree in the middle Miocene and almost totally disappear at the end of the late Miocene. The number of subtropical elements increases in the early Miocene and decreases subsequently whereas there is a gradual increase in the number of temperate elementsthroughout the whole period. This evidenceindicates a trend of slow cooling in the climate of the Hungarian Miocene.

Introduction Samples from hundreds of boreholes, pits, mine galleries etc., from the Hungarian Miocene (25 m.y. to 5.6 m.y.) have been studied palynologically. Suitable samples were selected for interpretive studies (Nagy, in press), such as the palaeoclimatological evaluation presented here. This evaluation is based on samples from 32 boreholes and pits. The spores and pollen have been divided into tropical, subtropical and temperate groups, as far as possible. An additional group has been distinguished; this is the cosmopolitan group consisting of taxa of unknown climatic requirements. Absolute spore and pollen values for the three climatic groups have been plotted for the samples arranged in stratigraphic sequence. These curves are plotted against a time scale using the results of Hungarian radiometric dates (Vass et al., 1985). The age stages adopted are those in use by Hungarian geologists. The climatic curves are entirely empirical and are based on climatic interpretations of the spores and pollen. They show the climatic conditions which prevailed in 0034-6667/90/$03.50

what is now Hungary in Miocene time. The localities o f mines and pits used in this study are shown in Fig. 1 and climatic curves on Fig.2.

Early Miocene In the early Miocene, Hungary was part of the Central Paratethyan area and there are three stratigraphic stages: the Egerian, the Eggenburgian and the Ottnangian. The Egerian (Fig.2) spans the Oligo-Miocene boundary. Tropical elements dominate the basal part and most of these are ferns of the shrub layer. In the tree canopy, Sapotaceae is abundant, there are a few palms and some other species (Plicatopol-

lis plicatus, Engelhardtioidites microcoryphaeus, Pentapollenites pentangulus) indicate a tropical climate. The macroclimate, however, is marked by m a n y subtropical representatives of the tree canopy, viz. Tricolporopollenites cingulum, several Coniferae, Pinus (Pinuspollenites latisaccatus), Ginkgo and Keteleeria. Shrub level sfibtropical representatives are significant also, e.g. Rhus, Myrica and at the herbaceous level, Compositae. Thermophilous and temperate zone species may be

© 1990 - - Elsevier Science Publishers B.V.

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iacea). In the upper part of the Egerian, there are considerable numbers of tropical species (ferns, Sapotaceae, palms), but the subtropical species show a marked increase in number. In conclusion, the climate was subtropical throughout Egerian time, but the floral association contained a number of tropical species. The temperate element probably lived on north-facing hillslopes, in riparian forests and in deep valleys. The climate of the Eggenburgian was somewhat cooler, more humid and more uniformly subtropical when compared with the Egerian. Subtropical elements predominate and the tropical species are mainly ferns. Together, these two groups usually outnumber the temperate zone species although the latter are usually present in relatively low numbers, probably representing the vegetation of the mountains.

The climate of the Ottnangian is definitely subtropical. When compared with the Eggenburgian, the Ottnangian has a much larger temperate floral element. The riparian forests contained higher numbers of subtropical ferns and the tropical element was present among the deciduous trees (Sapotaceoidaepollenites and two types of palms, viz. Sabalpollenites and Monocolpopollenites tranquillus). There is, however, an increase in the number of specimens of temperate-zone species in the deciduous element (Salix, Pterocarya, Juglans, Tilia, Liquidamber, Acer, Caprifoliaceae). In Early Ottnangian time, the coal-forming deep bogs of central and northern Hungary indicate a locally warm subtropical climate. The tree canopy of forests elsewhere contain many temperate zone species, as previously mentioned. The mountain forests contained Picea, Abies and Tsuga, which suggests a fall in temperature and cooler macroclimate; this is clearly identified in the upper part of the Ottnangian.

CLIMATIC CHANGES IN H U N G A R I A N MIOCENE

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spore species (Phaeoceros and Ophioglossum) indicate a Mediterranean climate. Anthocerotaceae, Gleichenia and some other spore species (Mecsekisporites) are certainly tropical elements. Cyrilla species, of tropical origin, complement the swamp forests. The Badenian is floristically the richest of all the Miocene stages and represents the full-scale expansion of the Karpatian vegetation. The tropical elements increase, especially in the lower Badenian: fern spores Mecsekisporites and Bifacialisporites are accompanied by Cycas, Alangium, Symplocos, palms and Sapotaceae. The curve of abundance of the tropical elements, however, does not rise above either the curve of the subtropical or temperate elements. The number of species in both the subtropical and temperate elements increase slightly also. In many localities the final member of the middle Miocene, the middle Badenian, cannot be distinguished. Where it is distinct, e.g. in the eastern half of the Mecsek Range, it is characterised by brown-coal-forming Taxodium deep bogs. Small peaks on the tropical curve and large peaks on the subtropical curve are typical of these coalforming periods. Late Miocene

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Fig.2. Changes in the tropical, subtropical and temperate floral elements in the Hungarian Miocene. The quantitative palynological data are based on absolute pollen counts•

Middle Miocene

The middle Miocene may be divided into three parts, the Karpatian and the early and middle Badenian stages. The Karpatian stage is characterised by a marked change in the flora, the majority of the new species being subtropical. Temperate zone elements also appear and both subtropical and temperate curves show identical belaaviour though somewhat flattened (Fig.2). Species of the temperate zone bryophyte, Riccia, lived in mountain forests of Ulmus, Tilia and Acer and in the mixed deciduous forests of Carya, Liquidamber, Alnus and Betula of riparian forests. A few of the

The late Miocene consists of the late Badenian, the Sarmatian, the Pannonian and the early and late Pontian stages. As a result of the late Badenian transgression and a cool spell, the flora becomes impoverished, with the number of taxa very low. The persisting forest vegetation is confined to the more arid, higher altitude deciduous forests and in many places, the hillside piedmont forest leftovers. The Sarmatian climate was dependent on various geological changes and an overall cooling. The kinship of the flora suggests that the study area came into contact with the Eastern Paratethys. The planktonic organisms show a decrease in the salinity of seawater. Macrofloral data and palynological results suggest a kind of aridity with droughts in summer. Some tropical species vanish and there are no Gymnospermae. Of 97 tropical spore taxa in the Badenian, only 16 are found in the Sarmatian and of 57 tropical angiosperms only

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12 species persist. A kinship to temperate floras is proposed for many o f the new species appearing in the Sarmatian. The curves of subtropical and temperate species run parallel. The climate of the Sarmatian must have been subtropical Mediterranean or warm temperate. The floral elements of the early Pannonian are almost identical to those of the Sarmatian, suggesting not such a marked change in climate as that seen between the Badenian and Sarmatian. The planktonic organisms suggest a continued reduction in salinity of the inland sea. A further decline in the tropical elements (from 16 to 10 species of spores and 13 to 8 of angiosperms respectively) suggests a further intensification of the overall cooling of the climate. These tropical species seemed to have lived as undershrubs in the undergrowth, wherever present. These species are not found in northern Hungary. The subtropical and mediterranean species are reduced in number also. A slight increase in temperate zone species only is observed. Quantitatively, these temperate species became more important and the trend is towards dominance. The climate is warm temperate with a winter rainfall, as suggested by the predominant deciduous element. In the late Pannonian-Pontian time, there is a slight increase in the number of species when compared with the early Pannonian. The tropical element is further reduced and its members may occur in brown-coal bogs as undershrubs of swamp forests. The subtropical conifers occur in greater numbers in these swamps and swamp forests, indicating the local climate. The mediterranean species are limited in number even though, in the southwest part of the country, a marked mediterranean influence in the flora is still recognisable even today. The temperate element has increased considerably when compared to the early Pannonian: 25 in the former and 8 in the latter, respectively. The temperate element includes 9 species of Sphagnum, 10 of Coniferae (formerly 5 in the Early Pannonian) and 71 of Angiospermae (formerly 63). In the late Pannonian, the climate

E. NAGY

seems to have been warm temperate. In sheltered, south facing areas and in the deep bogs, a local subtropical climate prevailed. Conclusions

The palynology shows a warm, subtropical climate with many tropical elements in the early Miocene. In the middle Miocene, the climate was subtropical also, with subtropical elements dominant, but there is a gradual increase in temperate elements. In the late Miocene, the tropical elements disappear and the temperate elements become dominant. The climate had become warm temperate. It is remarkable that in palaeoclimatological interpretations of shallow water molluscs in the northwest Pacific (Ogasawara, 1987), a "first climatic optimum" has been identified at 15 m.y. and this coincides with the period of rising temperature in the middle Badenian of Hungary. The "second climatic optimum" in the northwest Pacific corresponds with the warm period at 13 m.y. in the lower third of the Sarmatian in Hungary. The "coooling of the late Miocene" that Ogasawara identified at 7 and 8 m.y. corresponds in turn to the cold spell identified in the upper interval of the Pannonian in Hungary. These palaeoclimatological studies suggest that these climatic changes may be global in extent and additional long distance correlations may be worthwhile, but this requires accurate dating if correlations are to be convincing. References

Nagy, E., in press. Evaluation of the Hungarian Miocene sporomorphs. Geol. Hung. Ser. Palaeontol. Int. Geol. Hung. Budapest. Ogasawara, K., 1987. Shallow-marine molluscan succession during the Neogene of Northwest Pacific Region and its palaeoclimatologic implications. Fourth Int. Cong. Pac. Neogene Stratigr. Berkeley,California, Abstr.: 82-83. Vass, D., Re!bcok,I., Balogh, K. and Halmai, J., 1985. Revised radiometric time-scalefor the Central Paratethyan Neogene. MAFI I~vk.LXX.VII Congr. Reg. Comm. Mediterr. Neogene Stratigr. Proc., pp.423-434.