Nowe dane o skałach kambru i dolnego ordowiku z okolic Wiśniówki w Górach Świętokrzyskich

Abstract

 W okolicach Wiśniówki k. Kielc zbadano geofizycznie i geologicznie skały kambru i tremadoku.

W iłowcach i mułowcach występujących wśród piaskowców kwarcytowych, eksploatowanych w kamieniołomach Wiśniówka Duża i Wiśniówka Mała, odkryto zespoły Acritarcha z przewodnimi skamieniałościami: Timofeevia lancarae (Cram. Diez de Cram.), Vang., T. phosphoritica Yang. W warstwach z przekopu komunikacyjnego na Wiśniówce Dużej stwierdzono ponadto: Vulcanisphaera cf. nebulosa Deun., V. frequens Gork., Goniosphaeridium cf. mochtiensis (Górk.) Kjells. i Peteinosphaeridium trifurcatum typicum (Eis.) Eis. Cram. Diez Rodr. W górnej części kompleksu piaskowców kwarcytowych na Wiśniówce Dużej, Wiśniówce Małej i Podwiśniówce zidentyfikowano zbliżone petrochemicznie bentonity i tufity. Wzniesienia rejonu Wiśniówki tworzy najprawdopodobniej wąsko promiennie sfałdowany, dwa razy powtórzony ten sam kompleks piaskowcowy.

NEW DATA ON CAMBRIAN AND LOWER ORDOVICIAN ROCKS IN THE VICINITIES OF WIŚNIÓWKA IN THE GÓRY ŚWIĘTOKRZYSKIE MTS

In the Wiśniówka-Podwiśniówka region, two major complexes of mainly Sandstone Cambrian rocks have been mapped with the use of geophysical (electrical resistivity profiling) methods and subsequently covered by geological surveys (Fig. 1). The complexes run parallel to one another in WNW-ESE direction, building top parts of elevations. The Wiśniówka Mała sandstone quarry is situated at southern elevation, and the Wiśniówka Duża - at the northern. The sandstone complexes differ from adjoining Cambrian strata in high apparent resistance. The complexes resamble one another in the course and characteristic features of electrical resistivity profiling curves. The curves often appear markedly symmetric, especially when the surveyed sandstone complexes are wide (Figs. 2-5).

Moreover, a number of transversal faults, mainly strike-slip and oblique-slip in character, were traced in the vicinities of Wiśniówka. The faults, varying from some dozens to several hundred meters in amplitude, are usually NNE- SSW oriented (Figs. 1, 2, 5).

Studies on mudstones and claystones intercalating quartzitic sandstones in the Wiśniówka Duża and Wiśniówka Mała sections have resulted in first records of Acritarcha (Table 2). The species

Timofeevia phosphoritica Vang., T. lancarae (Cram. et Diez.) de Cram. Vang., Multiplicisphaeridium

sp., Baltisphaeridium sp., Micrhystridium sp., Vulcanisphaera sp., and Leiosphaeridia sp. have been found in material from both the Wiśniówka Duża and Wiśniówka Mała localities. Species of that assemblage occur from the Middle Cambrian to Lower Tremadocian.

In mudstones and claystone exposed in a transportation cutting to the Wiśniówka Duża quarry there have been found Timofeevia phosphoritica Vang., T. lancarae (Cram. Diez) de Cram. Vang.,

Multiplicisphaeridium sp. 2, Vulcanisphaera frequens Górk., V. cf. nebulosa Deun., V. sp., Micrhystridium sp., Baltisphaeridium sp., Goniosphaeridium cf. mochtiensis (Górk.) Kjells., Peteinosphaeridium trifurcatum typicum (Eis.) Cram. Diez. Rodr., and Domasia sp. The species are known to co-occur in the Lower Tremadocian.

The Acritarcha assemblages found in Cambrian strata from Wiśniówka are comparable with those described from Spain, Belgium, Ireland, USSR, and Canada.

The rocks were covered by petrographic studies. Microscopic studies showed that some claystones from the top of quartzitic sandstone series display features typical of bentonites and tuffites and comparable with those of such rocks from the Cambrian in eastern part of the Góry Świętokrzyskie Mts.

Thermic and x-ray studies showed that the above mentioned clay rocks are mainly built of mixed- leyered illite-montmorillonite structures with a very small contents of swelling layers, and a marked admixture of kaolinite. (Figs. 6, 7). The rocks differ from Cambrian bentonites from eastern Góry Świętokrzyskie Mts in high content of kaolinite, so their position appears somewhat isolated in relation to those from the Opatów area (Table 1).

The studies show that strata exposed in the two quarries at Wiśniówka (and newly opened quarry at Podwiśniówka) are very similar in lithology. The sequences display pyroclastic intercalations (bentonites and tuffites) in the uppermost part and appear to be of the same age. Taking into account results of studies on macrofauna, the strata may be dated at the Middle Cambrian (J. Czarnocki 1929, 1950) and mahl1y Upper Cambrian (S. Orłowski, 1968a, b; J. Bergstrom, 1973). It is not excluded that the sandstone complex from Wiśniówka is built Middle Cambrian rocks in lower part, and possibly Upper Cambrian ones in the upper.

Dark-gray claystones and mudstones from the northern cutting at Wiśniówka Duża are of the Lower Tremadocian age. They rest on the Cambrian without any tectonic unconformity.

Similarly as in the Opatów area, Cambrian strata from Wiśniówka represent nearshore sediments, in part “mottled” and with pyroclasts. It is not excluded that the general tectonic conformity obscures here some sedimentary gaps which partly reduce overall thickness of the Cambrian-Tremadocian section. Such gaps are inferred at the Middle-Upper Cambrian boundary as well as Upper Cambrian-Tremadocian (it seems, that the lowermost part of “Łysogóry Beds” is missing in the Wiśniówka Duża quarry). This conclusion is further supported by the nature of sedimentary environment of the strata from Wiśniówka, i.e. that of nearshore shoals and migrating bars (barrier zone).

In the Late Cambrian, depth of the marine basin became drastically reduced (even emergence is not excluded) in area of the Main Range, due to tectonic reasons. This has been accompanied by increase in volcanic activity in the proximity of the Góry Świętokrzyskie Mts.