Czwartorzęd i morfogeneza okolic Łomży

Alicja Bałuk




The morphologically differentiated Łomża area includes the Narew river valley and the morainic plateau (Fig. 1). The Narew river valley, that above Łomża has the features of a narrow water-gap, changes its character and attains the width of 5 km. A well-pronounced form in the morainic plateau is the Łomżyczka depression. It narrows southward and disappears at the foot of the. Czerwony Bór hills.
In the Łomża area the Pleistocene is underlain by Miocene and Oligocene sediments (Figs. 2 and 4). They have been partly eroded and their top surface shows altitude differences of several tens of metres. The differences in altitude point to a valley – known also from the adjacent areas – in the Sub-Quaternary basement. The occurrence of the Podlasie Glaciation sediments (G) in the bottom of the valley indicates its age to be older than this glaciation. South-Polish Glaciation sediments belonging to two stades (P1 and P2) filled the valle'y and the area was levelled almost completely. The relief was modelled by erosional processes active during the Mazovia Interglacial (M). The then formed incision were filled with debris prior to the invasion of the continental glacier of the Middle-Polish Glaciation. Within the deposits of this glaciation three till horizons have been distinguished corresponding to the following stades: the maximum (Ś1), the Mazovia-Podlasie (Ś2), and the North-Mazovia (Ś3). In the area occupied by the present Łomżyczka depression a deep furrow was formed during the North-Mazovia stade, the last glaciation period in the Łomża area. The deposits filling the furrow were mostly pelites and pelitic sands of the dammed-lake type. Their accumulation commenced at the close of the North-Mazovia stade and continued through the long period of dying out of the Middle-Polish continental glacier till the Eemian Interglacial. In the interglacial a small relict lacustrine basin existed where organic sediments were laid down (Figs. 1, 4–6).
The Łomżyczka furrow tilled with sediments was captured by the Narew river during the modelling of the valley. The remodelling and adjustment of the northern part of the furrow depression by the Narew river took place when the gate part of its valley was formed. Probably the Narew gate in the Łomża area was opened during the North-Polish Glaciation. At that time a sand layer, several metres thick, was formed covering the Eemian organic sediments and the entire present surface of the Łomżyczka depression (Figs. 2–6). The alluvial sequence of the gate part of the Narew river valley is shown in Fig. 7.
Attention should be drawn to the relationship between the Łomżyczka furrow and the Czerwony Bór ridge (Fig. 1). It may be assumed that Czerwony Bór represents an outwash cone deposited at the mouth of the furrow.

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