Najstarsze skamieniałości dolnego kambru Gór Świętokrzyskich

Abstract

THE OLDEST FOSSILS OF LOWER CAMBRIAN AGE IN THE ŚWIĘTOKRZYSKIE MTSSummaryThe paper deals with the oldest formations of the Lower Cambrian, distinguished as Sub-Holmia zone (J. Samsonowicz 1960) in the eastern part of the Świętokrzyskie Mountains (the Klimontów anticlinorium and the area of “Kotuszów island”). Among the fauna representatives were cited: Hylithes sp., Volborthella sp., Lingulella sp. and Coleoloides sp., the last one being also illustrated (J. Samsonowicz 1962). In the Sub-Holmia zone also microflora has been encountered, and the zone subdivided into the Bazów Beds and the Jasień Beds (R. Michniak, S. Orłowski 1963). The thickness of this member is thought to be about 200m. In the central part of the Świętokrzyskie Mts. J. Czarnocki (e.g. 1927) has divided the Lower Cambrian into several members, the lowermost of which - the zone I - may correspond to the Sub- Holmia zone. The following are representatives cited by him from zone I: Torelella laevigata, Hyolithus zbelutkensis, Volborthella cf. tenuis, and certain, closely indeterminable fragments of Holmia.Both the discovery of the pre-Cambrian deposits at Kotuszów by J. Samsonowicz in 1955, and the new data on the pre-Cambrian in the basement of the Miocene within the Carpathian foredeep somewhat explained the regionally important, but so far disputable problem of the Cambrian - pre-Cambrian boundary. To solve this problem a bore hole Bazów IG-1 was drilled in the years 1962-1963 (Fig. 1). situated on the almost horizontally deposited Bazów Beds. The bore hole, deepened down to a depth of 1502,7 m, pierced clastic formations that revealed strong disturbances in the tectonics and sedimentation (Fig. 2). The microflora found in this bore hole was of considerable importance in determining both Cambrian and Eocambrian (L. Jagielska 1963, 1965), thus affected also the previous opinions published on the interpretation of the Cambrian – pre-Cambrian contact in the Świętokrzyskie Mts. (e.g. Cz. Żak 1963, 1965, 1966; K. Lendzion. Cz. Żak 1968).The bore hole Bazów IG-1 reveals the presence of fauna and flora discovered: by the present authors (Tables I–V). These fossils allow the deposits pierced to be referred to the Cambrian. Of considerable importance are here: Hyolithes, Pelagiella sp., Trapezovitus sp. and Ostracoda, distinctly resembling too genera Aluta and Indiana. The studies made by the authors demonstrate that the Sub-Holmia zone has justly been referred to the Cambrian. The representatives of Pelagiella sp., Ostracoda and Trapezovitus sp. would no doubt point to the occurrence of the fragments of the Holmia zone, as well. This concerns the deposits lacking trilobites, which can hardly be distinguished within these series probably repeatedly folded together with the Sub-Holmia Cambrian deposits of the area in study. According to Cz. Żak's suggestions, the subdivision of the Sub-Holmia zone into the Bazów Beds and the Jasień Beds is questioned. At present, the thickness of the Sub-Holmia zone may hardly be determined in detail, since neither the bore hole made at Bazów, nor the other bore holes from the region under consideration, reached the Cambrian – pre-Cambrian contact. Nevertheless, this thickness is undoubtedly greater than so far supposed. The lowermost part of the Lower Cambrian from Bazów shows a considerable analogy to the lowermost part of the Aldan stage, i.e. to the Tommot stage of the Siberian platform. According to the present authors, the bore hole examined demonstrates that the microflora is here of low stratigraphical value. At present, it is referred to Acritarcha, and the authors revise now the previous determinations according to new classifications. It has also been emphasized that the fragments of the genus Laminarites are scarcely represented in the Sub-Holmia zone which, in turn, is characterized by the presence of some algae determined as Form 1. These probably show some features approximate to the algae commonly found in the Cambrian formations – i.e. Rhodophyta and Cyanophyta (e.g. K. B. Korda, 1961).