Peryglacjalne struktury szczelinowe na wychodniach skał paleozoicznych w Kielcach

Abstract

W artykule zanalizowano stanowisko peryglacjalnych struktur szczelinowych rozwiniętych w odsłoniętej, silnie zwietrzałej i zaburzonej serii łupków frańskich, wchodzących w skład jądra synkliny szydłówkowskiej. struktury te są złożonymi pseudomorfozami po żyłach lodowych. Rozwinęły się prawdopodobnie w fazie zstępującej würmskiego okresu zimnego.PERIGLACIAL FISSURE STRUCTURES ON OUTCROPS OF PALEOZOIC ROCKS AT KIELCEAt Kielce periglacial fissure structures are developed in Frasnian shales cropping out at the base of Szydłówek Górny denudational treshold (Figs. 1--3). Their origin was related to zone of active permafrost. A network of regular contraction fissures 1.5-2.2 m deep, 0.5-1.5 m wide at the top and 6-10 m distant from one another in polygons has originated in this zone.The fissures were originally infilled with ice veins. At present their infilling consists of medium-grained sands with admixture of coarser sandy and silty grains (Fig. 4A). The infilling mainly consists of quartz grains (92%) as well as of some feldspar, amphibole and garnet grains and dolomite and shale debris, angular and partly rounded grains predominate in the 0.75-0.5 mm fraction (Fig. 4B).The granulation and grain roundness indices evidence a complex genesis of the infilling. The material is mainly glacifluvial, seasonally washed out and enriched in dolomite debris during the transportation and in shale debris in fissures. It initially penetrated a free space between ice and fissure walls and subsequently, after burial of ice veins, also top parts of the fissures. The melting of buried ice resulted in gradual subsidence of the material and disturbance of its original structure. The structure is vertical-wavy in lower part of the fissures and horizontal-concave in the upper part.Periglacial fissure structures from Kielce represent complex pseudomorphoses after ice veins. They were infilled synchroneously with their formation and later along with melting of ice. It may be assumed that they originated in the descending phase of the Würm cold period because of the lack of the Quaternary covers.