On the Chronology of the Prehistoric Glacial Ice Cover

abstract

The first ice age indicated in Fig. 2.5 dates back to 120–140 ka. It is the second to last ice age, the pre-last High Glacial maximum or the Riß Ice Age (Stage-I). Traces of this older ice age exist in High Asia, for instance in the Dhaulagiri-Annapurna Himalayas . These traces consist of petrified, i.e., fossilized moraine deposits. They have turned loose rock into hard rock, i.e., tillite. The present author has described two such tillite locations north of the Himalayan main range and three such locations south of it (Fig. 2.1: No. 2) (Kuhle in Zeitschrift für Geomorphologie Zeitschrift für Geomorphologie, Suppl. 41, vol I, vol II, Abb. 1–184:1–229, 1982, Abb. 184; Zeitschrift für Geomorphologie 41:1–383, 1983). Further locations are found in the Zagros Mountains (Fig. 2.1: No. 1) (Kuhle 1976) and at the northern margin of Tibet (Fig. 2.1: No. 3) (Kuhle in Reports on the North-Eastern part of the Quinghai-Xizang (Tibet) Plateau by the Sino-German scientific expedition 1981. Science Press, Beijing, pp. 176–244, 1987a; pp. 250–315, 1987b). Here they indicate ΔELAs (snowline depressions) of ca. 1400 m. These traces of the Riß Ice Age are extremely scarce, however, if compared with the dramatic trace density of the last High Glacial maximum, or the Würm Ice Age (Fig. 2.5, Stage 0). That those older glacier traces are hardly preserved anywhere and therefore negligible is not really strange. For one reason this is because of the immense temporal distance. Since the Würm Ice Age, an Interglacial, another Glacial and a second Interglacial, as well as a Holocene Postglacial have taken place. The geomorphological transformation of these various phases has led to the almost complete destruction of the Riß glacier traces in almost every location. This situation is due to the mountain relief; the vertical distance and steepness have accelerated the entire morphodynamic process.