Abstracts of Symposium 55 and some papers from other related Symposia.

Pleistocene Climatic Records of East and Central Asia Based on Micromorphological and Mineralogical Indicators of Loess-Paleosol Sequences

Arnt BRONGER, Renate WINTER, Geograph. Institut, Univ. Kiel, D-24098 Kiel,
Thomas HEINKELE, Institut f. Bodenschutz u. Rekultivierung T.U. Cottbus, D-03044 Cottbus, Germany.

For loess-paleosol stratigraphy and paleoclimatic deductions it is necessary to classify buried paleosols genetically and typologically, a procedure which allows comparison between profiles. Observations in the field are often not sufficient, partly because most of the buried soils are truncated. Some other important diagnostic features which can be recognised in modern soils, e.g. chemical properties, have also disappeared or have been undergone post-pedogenic changes. For instance progressive decomposition of organic material with advancing age during the upper Pleistocene and even early Holocene prevents us to designate most buried Chernozems and Phaeozens as Mollisols. Another example in loess areas is, that all buried soils are more or less recalcified, so in contrast to modern soils pH- or base saturation values are of no use. It is therefore necessary to study the sequences of processes in buried soils to provide information about pedogenesis as well as diagenesis. Micromorphology is of special significance, for it provides a complete view of soil development through different stages even in polygenetic pedocomplexes. It can, e.g. distinguish between secondary and primary carbonates. This genetic distinction allows to indicate genetically different soils especially in pedocomplexes. Micromorphology also provides an unequivocal indication of clay illuviation, associated in temperate climates with a forest vegetation. - Mineralogical investigations allow to dry conclusions regarding the type and intensity of weathering and pedogenic clay mineral formation which makes further paleoclimatic interpretation possible. For this it is necessary to establish the original petrographic homogeneity of the parent material from which any soil was developed.

The loess-paleosol sequences of the Luochuan section, Shaanhi, China and of the Karamaydan and Chasmanigar sections in the Tajik Depression are well comparable especially for the Brunches chron. Earlier paleomagnetic dating of these sections gives a reliable chronostratigraphic framework. The above mentioned paleopedological investigations allow the reconstruction of a paleoclimatic history for the upper pert of the Brunches chron (S4 to S1 resp. PK IV to PK I) which is not only very similar in East and Central Asia but also well comparable with that of the Carpathian Basin / SE Central Europe. The uppermost soil in the S5-pedocomplex in the Luochuan section was regarded to be more strongly developed than the younger (and older) paleosols. The chronostratigraphical equivalent in Karamaydan, however, shows a pedocomplex "PK V". Thus the strongly developed B or Bt horizons do not show large differences and represent interglacials even rather similar to the Holocene, some of them show a more moist climate. The most detailed loess-paleosol sequence at Karamaydan (PK I-X) can very well be compared with the ¹⁸O-record of the Brunches chron. From the present knowledge the loess paleosol sequence at Chasmanigar (PK X - PK XXX) provides the most detailed sequence for the Matuyama chron in Central Asia. It gives even more paleoclimatic information than the loess profiles in China and the deep-sea curves knows so far.

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