Petrographical Laboratory in Department of Geomorphology
PETROGRAPHICAL LABORATORY
The studies of the Petrographical Laboratory concern with the petrographical composition of pebbles (4.0-12.5mm) and boulders (20.0-60.0mm) of till sediments in the Great Poland Lowland. The finer fraction is divided into ten petrographical groups (Trembaczowski 1961, 1967, Böse 1989):
K - crystallines,
S - sandstones and quartzites,
TU - Palaeozoic shales and siltstones,
F - flints,
KK - Cretaceous chalk,
PK - Palaeozoic limestones,
D - Devonian dolomites,
L - lydite,
Q - quartz,
WQ - white quartz
The results obtained served as base data for counting the so-called stone coefficients, of which the most frequent used are the following:
O/K: quotient of the sum of sandstones, Palaeozoic shales and siltstones, flints, Cretaceous chalk, Palaeozoic limestones to crystallines;
K/W: quotient of the crystallines to Palaeozoic limestones and Devonian dolomites;
A/B: quotient of the low-resistant rocks (sandstones and quartzites, Palaeozoic shales and siltstones, Cretaceous chalk, Palaeozoic limestones, Devonian dolomites) to resistant ones (crystallines, flints, quartz,white quartz).
The coarser fraction is studied towards the presence of indicator erratics (Lüttig 1958, Smed 1994) and statistical ones (Vinx 1993). The method relies on pointing to source regions of the possibly most numerous stone population in Scandinavia and Baltic depression. It indicates consequently, the probable route of a glacier or/and its individualized streams.
The collection of indicator erratics has been formed as a result of a field work and expeditions to Scandinavia.
Macropetrographical methods are completed by the analyses in a microscale and they contain: the roundness classification (Krygowski 1964), the degree of mat surface of a quartz grain (Cailleux 1942, Gozdzik 1995). In the latter method the following mat surfaces are distinguished:
RM - mat rounded (the lowest boundary of a grain roundness is 0.7, according to Krumbein 1941),
EL - polished rounded,
C - broken,
EM - having intermediate properties of RM (EM/RM) or EL (EM/EL),
NU - unabraded.
Consequently, these are studied in scanning electron microscope SEM, where the source and processes, affecting a hard quartz grain, are named.
Böse M., 1989: Methodisch-stratigraphische Studien und paläomorphologische Untersuchungen zum Pleistozän südlich der Ostsee. Berliner Geogr. Abh. 51, s. 114
Cailleux A., 1942: Les actions eoliennes periglaciares en Europe. Mem. Soc. Geol. de France 46, s.176
Gozdzik J., 1995: Wybrane metody analizy ksztaltu ziarn piasków dla celów paleogeograficznych i stratygraficznych. [w]: E. Mycielska-Dowgiallo i J. Rutkowski (red.): Badania osadów czwartorzedowych, 115-132
Krygowski B., 1964: Graniformametria mechaniczna. Teoria i zastosowanie. Prace Kom. Geogr.-Geol. PTPN 2.
Lüttig G., 1958: Methodische Fragen der Geschiebeforschung. Geolog. Jahrb. 75: 361-418
Smed P., 1994: Steine aus dem Norden. Geschiebe als Zeugen der Eiszeit in Norddeutschland. Gebrüder Borntraeger. Berlin, Stuttgart; s. 194
Trembaczowski J., 1961: Przyczynki do metodyki badan granulometryczno-petrograficznych utworów morenowych. Ann. Univ. M. Curie-Sklodowska, sec. B, 16(3): 63-95
Trembaczowski J., 1967: Granulometryczno-petrograficzna charakterystyka glin zwalowych Wysoczyzny Koninskiej. Prace Inst. Geol. 48
Vinx R., 1993: Hochauflösende Rekonstruktion von Eistransportwegen: Die "Leitserienmethode". Archiv für Geschiebekunde, 1(11): 625-640.
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