Földrajzi értesítő, 1967

Vita - Dr. Kádár László: Létezett-e az európai pleisztocénben egynél több eljegesedési időszak?

The loess region in the South of the Polish-German Lowland lies in the periphery of the periglacial zone and in the foreground of the piedmont region where the rivers from the South and the solifluction processes from the North have deposited fine sediments, wich became loess immediately by the diagenesis. The considerable trouble taken today for the interest of dating quaternary deposits with the aid of loess stratigraphy looks to be labour lost, if we know that the loess material is mostly not a dust deposited evenly over vast spaces from the air, but an alluvial silt or a slope debris laid down locally [2, 14, 15, 16]. This material became loess, and changed again into loam on its surface under unchanged periglacial climatic conditions in accordance with the evolution of alluvial fans and their terraces. Loess develops today in such regions where podsol, brown earth, chernozem or degraded chernozem are the zonal soils alternating with the intrazonal soils solody, solonetz and solonchak. As loess is formed in the present time to, it can not be reputed to be a sole glacial sediment. But all this kinds of soils were present during the glacial period in Middle Europe in a variegated spatial order determined by the relief and the grain size of surface sediments. Loess can be formed and weathered both in glacial periods and in interglacial ones, so that loess stratigraphy is erroneonsly regarded as an effect of climatic changes [14, 15, 16]. It has been similarly detected during the last years that river terraces are indepen­dent from climatic changes, too, because the development of the various terraces is a regular feature of river activity [14, 19, 20]. The succession of vegetation zones goes in the same way from the tundra through the pine and the mixed forest to the deciduous one around a polar ice cap this being in recession, as is the succession of vegetation on a delta filling in an ice-cold lake in the periglacial zone. In the case of a progressing ice cap and of a transgressing lake the suc­cession will be again the same in reverse turn. Similarly though the pollen columns of the peat bogs reflect more or less correctly the climatic history of the postglacial time in the once ice covered regions, the diagrams from the periglacial belt which often show interruptions or repetitions in the succession of vegetation, do not prove the existence of interglacial or interstadial periods. The most famous family of the extinct pleistocene animals in Europe are the Elephantidae. From the descendants of the Pliocene Elephas meridionalis the most pri­mitive quaternary Elephas antiquas ranged in forests and is reputed as an interglacial animal, while the more advanced Elephas trogontherii and the Elephas primigenius, the mammoth, which lived in the tundra belt, are taken for creatures of the glacial periods. But they could be contemporaries too, ranging in the quite different biotops of the variegated periglacial region. So there are no geographic, no geologic, no géomorphologie, no palaeontologic evidences of more Pleistocene glaciation periods. A. PENCK fell victim to a geographic error, when he secured the victory of the polyglacial opinion, because the periglacial zone was unknown to him. He tried to find the causes of the repeated quaternary glaciations in celestial mechanics. Though it was possible to find a parallelism between the supposed four or five glacial periods and between the curve of solar radiation calculated later by M. MILAN­KOVITCH [23, 24, 25, 39] for the last one million years, some investigators displeased at the changing of the temperature tried to explain the process of glaciation and déglaciation by a more complex evolution of climatic processes [1, 32, 33]. But such changes of solar radiation and of the climates may be follow beckwards through the Pliocene and the whole Tertiary era too, when there was no glaciation in the Northern hemisphere. In consequence of that the cause of glaciations is quite another one. A polar ice cap can not be accumulated on the open sea even at the most favorable climatic conditions, because the ice-sheet immersing into the seawater would be melted from below. And inversely the ice cap becomes heaped sooner or later even under un­favorable conditions, if the pole is over a continent. The North pole was at the end of the Tertiary era in the northern part of the Pacific ocean. During the Pleistocene it crossed the north-western part of North America and caused a glaciation in the whole world. In the Holocene the pole arrived the Arctic Ocean and the quaternary ice cap melted away again [18]. This was a non-recurrent process independent from the oscillations of solar radia­tion and from climatic changes. It produced but a single Pleistocene glaciation without any recession phases. Namely neither the geomorphological and geological facts nor the biogeographical and palaeontological ones indicate a supposition of such general oscil­lations.

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