Petrographic analyses and indicator erratics of gravels of the Odra lobe

Fennoscandinavian er rat ics found in the gla cial de pos its till and in the glaciofluvial sed i ments within the main limit of the Odra gla cier lobe (NW Po land and NE Ger many), have been ex am ined in two frac tions: of 4–10 mm and 20–60 mm. The most nu mer ous in the frac tion of 4–10 mm are: crys tal line rocks (Cr; 35–40%) orig i nat ing in the Pro terozoic Bal tic Shield as well as Lower Palaeozoic lime stones (LPL; 35–40%) – from the sed i men tary sheet cov er ing the Pro tero zoic Bal tic Shield in the area of cen tral Bal tic Sea. Per cent age of sand stones (S) amounts to 10–15%. The remain ing rock types (sev eral per cent each) are: Palaeozoic shales (PS), the out crops of which are lo cal ized in Scania (Sk¯ne) and on Born holm, Cre ta ceous lime stones (CL) and flintstones (F) orig i nat ing from the west ern part of the south ern Bal tic Sea as well as quartz (Q), milk quartz (MQ) and iso lated grains of De vo nian dolomites (DD). From the anal y sis of in di ca tor er rat ics, which was car ried out in the 20–60 mm frac tion, it ap pears that mainly the out -crops lo cal ized in Sm¯land (e.g. red and grey Växjö gran ites, P¯skallavik por phy ries or Tessini and Kalmarsund sand - stones) as well as in Scania (Höör and Hardeberga sand stones) and Re gion Blekinge–Born holm (e.g. Karlshamn and Halen gran ites as well as NexÝ and Bavnodde sand stones) had been sub jected to the gla cial pluck ing. The o ret i cal boul der cen tres (TBC, Ger man: TGZ das Theoretische Geschiebezentrum, Lüttig 1958), which were cal cu lated for 23 sam ples, are lo cal ized mostly in a small area in Sm¯land, be tween 15°E–16°E and 56.5°N–58.5°N. Apart from in di ca - tor er rat ics the sta tis ti cal ones are nu mer ous, that are first of all grey and red Lower Palaeozoic lime stones with their out crops lo cal ized at the bot tom of the cen tral Bal tic Sea. Tak ing into ac count the TBC val ues of in di ca tor er rat ics as well as high per cent age of sta tis ti cal er rat ics it can be pro nounced that the sec tion of cen tral and west ern Bal tic Sea as well as the one of south-east ern Swe den had been sub jected to the heavi est gla cial pluck ing by that part of the Pleis to - cene ice-sheet which reached the stud ied area dur ing the Pom er a nian Phase.