Starszy paleozoik z otworu Wilków (północna część Gór Świętokrzyskich)

Abstract

OLDER PALAEOZOIC IN BORE BOLE WILKÓW NORTHERN PART OF THE ŚWIĘTOKRZYSKIE MOUNTAINSSummaryBore hole Wilków, situated in the Łysogóry area (northern part of the Świętokrzyskie Mountains), has pierced the deposits of Older Palaeozoic age. The distribution of these deposits is shown in Fig. 2 and Table 1. The Upper Cambrian, mainly of clay-siltstone character, subordinately arenaceous at the bottom, makes here a complex about 150 m in thickness. Trilobite ascertained here by E. Tomczykowa (1968), i.e. Peltura scarabaeoides westergardi Henningsmoen (at a depth of 857 m) and Parabolina lobata lobata (Brögger) represent the lower Łysogóry beds, mainly of the zone 5 c. Any higher beds of Cambrian age have not been found to occur at Wilków, despite the fact that the following sub-zones have been ascertained (E. Tomczykowa, 1968) in the neighbouring section: 6 a Parabolina latilimbata Tom.,6 b Beltella rotundata Tom., 6 c Parabolina bukowiana Tom., and 6 d Parabolina acanthura (Angelin). A considerable gap exists between the Cambrian and Ordovician, since the Upper Cambrian is unconformably overlain with the Caradocian deposits of the zone Diplograptus multidens. Higher up, the Lower Ashgilian deposits have been found to contain trilobites Tretaspis and Eodindymene. At the contact of the Ordovician with Silurian another stratigraphical gap appears since no zones of the lowermost Llandoverian has been ascertained, as far as the zone Monograptus sedgwicki. Higher up are claystones and graptolite schists of Wenlockian age (the so-called upper Ciekoty schists) and then of Ludlovian age (the so-called Wilków schists - H. Tomczyk, 1962). The Silurian clay deposits predominate to a depth of 420 m (Fig. 2), and only in the lower part of the zone Saetograptus leintwardinensis, siltstone and then greywacke intercalations appear. The zone S. leintwardinensis is here considerably thick (432 - 273 m). These facts prove the conclusion drawn by H. Tomczyk (1956) that at the close of the Lower Ludlovian (Wilków schists) the deposits of clay lithofacies disappear, and the graptolite assemblage becomes poorer, a fact characteristic not only of the area of the Świętokrzyskie Mountains. The Upper Ludlovian deposits of the Wydryszów beds reach, in the Łysogóry area, up to 2000 m in thickness. In the section at Wilków, only the lowermost part of these beds has been pierced, from 275 to 6 m (Fig. 2). These area alternating claystones and siltstones, with intercalations of greywackes, revealing features of flysch-like deposits (J. Czarnocki, 1967), characterized by diagonal and convolute laminations, with few graptolites Pristiograptus bohemicus (Barr.). The Wydryszów beds bear a marked lithological and stratigraphical analogy to the Siedlce beds of the platform area. The whole complex of the Older Palaeozoic deposits, encountered in bore hole Wilków, show an analogous degree of tectonic disturbances, without distinct folding and cleavage. The dips, amounting to 40 - 30°, directed northwards, slightly change in the fault zones (Fig. 2). The faults are responsible here for a tectonic reduction of certain stratigraphical horizons. Particularly interesting are discordances that have taken place at the boundaries Upper Cambrian - Ordovician and Ordovician - Silurian. The great stratigraphical gaps (Table 1), observed to occur in this area, already primarily revealed features of a sedimentary hiatus, connected with the Caledonian epeirogeny. The sedimentary gap that existed before the sedimentation of the Lower Jeleniów beds of Llandeilo age, is connected with the Łysogóry phase, whereas the younger one, at the boundary Ordovician - Silurian, is related to the Taconian phase (H. Tomczyk, M. Turnau-Morawska, 1967). Summing up the tectonical problems we should emphasize that the Upper Cambrian and the Ordovician deposits of the Jeleniów and the Wólka beds, as well as the Silurian deposits, the Wydryszów beds inclusive, constitute a uniform structural stage that in the Łysogóry area was formed during the Hercynian orogeny and, maybe, began with the Young Caledonian activity at the close of the Ludlovian time.