Uwagi o budowie geologicznej "Trasy Łazienkowskiej" w Warszawie

Abstract

SOME REMARKS ON GEOLOGICAL STRUCTURE OF ŁAZIENKOWSKA BRIDGE ROUTE Summary Earth works carried out in the com-se of construction of Łazienkowska bridge route revealed in the subsurface a .3-4 m thick bed of Quaternary deposits. In its lower pan the bed is built of Podlasie-Mazovian(Q3m3) boulder clays and gravels which are overlayed by deposits from their scouring and by upbuilt embankment. The bed overlays erosionally truncated and glacitectonically folded Pleistocene and in places Tertiary deposits. Two complexes may be distinguished in these deposits: the upper Pleistocene formation, mainly built to particles and rock debris transported from the north by icesheets, and 8 lower complex, the main element of which is material transported from the south, from the area of the Holy Cross Mts. And their margins. The Pleistocene complex, 10 to 50 m thick, comprises a few horizons of deposits melted out of ice masses and deposited in this area (Q3m3 and Q3m1 boulder clays). These horizons are separated by deposits from washing of these boulder clays (transversally bedded sands; gravels, and fluvioglacial pebbles – Q3fg2, Q3fg), and by stagnant-lake deposits (bedded clays, silts with sandy streaks - Q3z2, Q3z1, Q2z). In the profile displayed by the road cut the deposits Q3 are very well-developed, whereas Q2 deposits are greatly reduced. Tertiary-PreglaciaI complex is about 55 m thick. Its basal part is represented by clay layers, 3-8 m thick,• intercalated by sandy streaks. Upwards the sandy deposits increase in thickness at the expense of clay layers and in the top part of this complex, there are sands and gravels with thin clay intercalations. It is assumed that the lowermost part of this complex belongs to the Miocene, central part - about 45 m thick - to the Pliocene, and the uppermost 10 m thick part represents the Preglacial (Q1). The series assigned to the Preglacial is devoid of any exotics of northern origin. The deposits underlaying Q3m3 series are glacitectonically disturbed. In general, the older the deposits, the stronger are the disturbances. Deposits of Q2, Q1, P1, and M series were subjected to the stress of ice masses three or four times, whereas Q3m1- fg1 - z1 deposits - two times, and Q3m2 – fg2 – z2 - only once. The first fold forms of stress origin (narrow antyclines and wide synclines) were initiated by Q2 ice-sheet and modified and complicated by subsequent ice-sheets. These forms could only have been formed there, where sandy deposits intercalated by clay-silty beds and laminae occurred within the zone effected .by the stress of overlaying ice-sheet mass. Continuous fold forms originated, when the series with predominating contribution of clay occurred close to the surface; in places where clay intercalations of sandy series were occasional, fold forms were formed of a number of blocks of different size.