Czwartorzędowe zasypanie rejonu Miedzianki koło Chęcin

Abstract

Quaternary cover around Mt. Miedzianka in The Holy Cross MtsSUMMARYThe area studied is situated at SW margins of the Paleozoic core of the Holy Cross Mts, at the western part of Chęciny anticline. The core of the anticline is built of Cambrian shales and siltstones, whereas its limbs of Devonian limestones markedly more resistant to weathering, also as compared to clay-sandy Lower Triassic rocks that contact the limbs from the south (cf. Figs 1-2). The structure of the anticline is also markedly influenced by a dense network of faults of two predominating directions, viz. WNW-ESE and NNE-SSW, which were repeatedly reactivated during the late Tertiary time (Lindner 1971a). These lithological and tectonic factors resulted in the formation of deep river valleys discharging waters towards the south in the late Tertiary and early Quaternary time (denivelations may be estimated at 100-150 m). The oldest Quaternary deposits are represented in valleys by weathering cIays (Fig. 2), up to 10 m thick, and directly covering the Devonian limestones. The Cracow (Mindel) Glaciation is represented by two series of tills, indicating twofold entering of the icesheet (cf. Figs 2-3). Data from numerous boreholes show that the icesheet never covered the whole area but rather was stopped by the hills. This gave rise to an oasis surrounded by ice and sheltered by those hills (Figs 3-4), and in which deposition of silts and afterwards of sands took place. During the Great (Holstein) Interglacial, an extensively deep valley (30 to 50 m deep) was formed subsequently filled by vast amount of gravels and sands (Fig. 2); it discharged waters towards the south, into the contemporaneous pre-Nida river valley (Hakenberg & Lindner 1971). Mid-Polish (Riss) icesheet was stopped at the distance of 7–9 km NW of the region. The morphological analysis shows that drainage basin of the upper Hutka river could not discharge waters from the front of the icesheet, and it was the time of acceleration of slope processes. A valley eroded 15–20 m down the present water level in the river was presumably formed during the optimum Eem Interglacial. This valley was buried during the post-optimum part of the Eem Interglacial and BaItic (Wòrm) Glaciation time. The subsequent erosion resulted in the formation of a terrace situated about 3 m above the present water level, and it was accompanied by intense eolian processes. The final erosional and depositional processes in the Hutka valley active during the Holocene, are responsible for the development of the flood-plain.