Najstarsze plejstoceńskie osady organiczne w odkrywce Bełchatów (formacja Łękińsko); doniesienia wstępne

Abstract

THE QLDEST PLEISTOCENE ORGANIC DEPOSITS IN THE BEŁCHATÓW OPEN CUT (ŁĘKIŃSKO FORMATION); PRELIMINARY REPORT Summary The organogenic deposits in the Bełchatów open cut (KIeszczów Graben) named the Łękińsko Formation lie below the Elsterian deposits and just above the Pliocene sands. Łękińsko Formation is supposed as the Cromerian age although the pollen analysis is not finished, yet. The formation consists of three informal members. The lower one consists of the brownish clay of thickness 0,5 m. The middle member-consists of the sands and greyish clays of thickneess about 0,5–1,0 m. The uppermost member consists of fluvial deposits, mostly the peat, telmatic mud, organogenic brownish silts as well as massive green silts, sandy silts and greyish sands. The thickness of fluvial deposits is about 2–3 m. These three informal members are expected to be three interglacial horizons of the Cromer Complex. Moreover, the deposits of Łękińsko Formation consist of the large amount of the Tertiary derived minerals. This is the largest value among the Pleistocene formations in the Bełchatów open cut and indicates the lowermost lithostratigraphical position. The deposits of Łękińsko Formation are exposed only in the area of the Mesozoic Łękińsko Anticline (a part of the Kleszczów Graben). It is suggested this area was an active sedimentary basin during Cromerian. Than, the deposits have been uplifted and folded Now, they lie in the axis of the local anticlinal structure and only about 30–40 m below the surface (150–160 m a.s.l.), whereas some of the younger Pleistocene formations lie further down in the other parts of the Bełchatów open cut.