Osady czwartorzędowe i ich podłoże w południowo-zachodniej części Ziemi Lubuskiej

Abstract

Podłoże czwartorzędu południowo-zachodniej części Ziemi Lubuskiej było kształtowane przez różnorodne procesy geologiczne, w tym czwartorzędowe ruchy tektoniczne, które doprowadziły do powstania depresji i rowu Żytowania. W wyniku zaburzającej (glacitektonicznej) działalności lądolodów utworzyły się depresje sięgające 123 m p.p.m. i elewacja osadów trzeciorzędowych wznosząca się do 100 m n.p.m. Na podstawie nowych materiałów wiertniczych i geofizycznych zakwestionowano zasadność wyróżnienia na tym obszarze kopalnej doliny Odry. wskazując że strefy zwiększonej miąższości osadów czwartorzędowych, wiązane dotychczas z doliną pra-Odry, są wynikiem zjawisk tektonicznych lub glacitektonicznych.

QUATERNARY DEPOSITS AND THEIR BASEMENT IN SOUTH-WESTERN PART OF ZIEMIA LUBUSKA

The area of 350 km² occurring amongst Krosno Odrzańskie, Gubin and Cybinka was studied. Substratum structure was recognized on the basis of the 250 profiles of boreholes analysis, geophysical studies and mapping. Also results of palaeobotanic, faunistic and Iithological-petrographic works were utilized. Substratum of Quaternary deposits in the area consists of Miocene formations. In cored borehole piercing these deposits the underlying Oligocene and Cretaceous formations were proved. Oligocene formations in the sandy·clayey facies are Rupelian in age. The Oldest documented deposits are the Lower Miocene sands and silts. They are separated by Iower coal seam, which in northern and central parts of the area occurs in form of three coal layers. The lower coal seam has pollen spectrum typical of V palynologic phase Ulmaceae and is correlated with the Ścinawa seam (according to S. Dyjor, 1978 and S. Dyjor, H. Kościówko, 1982).

In Połęck area the Lower Miocene deposits to the height of 45 m above sea level are uprised forming a horst, but in Chlebowo trough are thrown down about 50 m in relation to former position and their bottom lies at the height of 130-140 m below sea level.

The Middle Miocene sedimentary complex embraces 4 members. The lower coal seam is separated from the upper one by a silty-arenaceous series up to 40 m (Fig. 4, layer 6), the upper coal seam on the other hand, is separated from the highest one by another silty-arenaceous series up to 65 m thick (Fig. 4, layer 8). The palynological spectrum of the upper coal seam belongs to VlIIth palynological phase Cyrillaeeae pollenites exactus.

Thickness of the upper coal seam in the Cybinka deposit reaches 20 m and is to the found at the depth of 40-60 m below sea level. In Grzmiąca graben beds of the member are thrown down 20 m whereas in Chlebowo graben they are thrown down 30 m and are at depth of 65-80 m below sea level.

As belonging to Upper Miocene were recognized silty-argillaceous-arenaceous sediments (Fig. 4 layer 10) reaching in the glacitectonic disturbation zone thickness of 65 m. These formations are there strongly folded and uprised to the height of 100 m above sea level.

In the studied area Pliocene and older Quaternary sediments are absent. The oldest known Quaternary sediments are bound with continental glacial transgression of the Lower Stadial of the South-Polish Glaciation.

Subquaternary surface is a result of the activity of tectonic erosive-denudation and glacitectonic processes. Depression and graben of Żytowań are the elements of the Quaternary deposits substratum the origin of which was tectonically conditioned. Tectonic activity during the South-Polish Glaciation coused 100 m throw down of substratum formations. A marginal lake having at least 30 m in length filled with glacifluvial formations 125 m thick was formed. Marginal lake's deposits may be correlated with the so called Radzików series, separated by S. Skompski (1981). In the substratum of Quaternary deposits the subglacial troughs were distinguished (Chlebów and Trzebiechów troughs) and Rąpice-Maszewo plain as the substratum elements formed by erosion and denudation.

Origin of the Chlebów through is bound with the continental glacier of the Upper Stadial of the South-Polish Glaciation. Fossil bottom of the Trzebiechów trough reached 10 m below sea level and its origin is bound with Upper Stadial of this glaciation.

Rąpice -Maszewo plain comprises about 200 km² in surface. Its fossil surface occurs at 10-30 above sea level. It was formed since the Miocene by tectonic and erosive-denudation processes. Here, a row of tectonic rifts were proved which probably extinct in the Upper Miocene deposits. During Quaternary the preglacial stream valley waters erosion reached to the height of 10 m below sea level. Fragments of this level (in Chlebów region) became folded due to the transgressing continental glaciers pressure.

In the substratum of the Quaternary deposits there occurs also a row of forms being the result of disturbing (glacitectonic) activity of continental glaciers. Bottom of the Rzeczyce depression reaches 60 m below sea level and its origin is associated with the Lower Stadial of the South-Polish Glaciation transgression. The Białków depression and most probably also the Wyżyska one are of the same age. The fossil bottom of the letter goes down to 124 m below sea level.

Origin of the Cybinka-Lubogoszcz ridge is bound with overthrust of the successive continental glaciers, among which the most intensely elevation was piled up by the Upper Stadial of the South-Polish Glaciation. The Upper Miocene became here raised up to the height of 100m above sea level foldings of the substratum are reaching here to the height of 60 m below sea level.

In the light of the writer's studies there is no basis to distinguish the Pra-Odra Valley in this area, and zones of increased thickness of Quaternary deposits (to 187 m) bound heretofore with river erosion are conditioned by tectonic (Żytowań depression and graben) or glacitectonic (Wężyska and Rzeczyca depression) phenomenna.