Zależność składu głazowego od frakcji w osadach glacjalnych zlodowacenia południowopolskiego

Abstract

Dependence of rock composition on the grain fraction in glacial deposits Percentage of erratics coming from eastern and western Fennoscandinavia was studied in the deposits of South-Polish glaciation. In the east-Fennoscandinavian group the following rocks were taken into account: post-orogenic granites, transitional rocks between post-orogenic granites and porphyries, granite-porphyry, Aland quartz-porphyry and red Baltic porphyry. From west-Fennoscandinavian rocks were considered: Upsala, Sala, Stockholm and Siljan granites, porphyry from the area of Dalarna and brown Baltic porphyry, granites and porphyries from southern Sweden. Proportions between the rocks coming from eastern and western Fennoscandinavia are as follows: from 10:1 to 12:1 for the fraction 0 .6 — 1 cm; 7:3 for the fraction 1—2 cm; 2:1 for the fraction 2— 6 and 6—10 cm; 9:1 for the fraction coarser than 10 cm. The fractions finer than 1 cm and above 1 0 cm are not suitable for a characterization of the rock composition of moraines in the deposits of South-Polish glaciation. Their composition should be examined in any fraction in the size interval 1— 10 cm. Since crystalline erratics are rare in moraine deposits under study, it is most advantageous for statistical purposes to take into consideration the whole size interval 1—1 0 . Weathering of the deposits from which the material for determinations has been derived does not affect the quantitative proportions between the rocks from eastern and western Fennoscandinavia in the size intervals 2—6 and 6—10 cm. In the size interval 1—2 cm the effect of weathering is slight, whereas in the fraction 0.6 — 1 cm it becomes conspicuous.