Stratygrafia i rozwój facjalny dewonu i dolnego karbonu południowej części podłoża zapadliska przedkarpackiego

Abstract

Badania litologiczne, mikrofacjalne i mikropaleontologiczne w otworach Niwki 3 i Swarzów 9 umożliwiły wydzielenie jednostek litologicznych, ustalenie stratygrafii i przeprowadzenie korelacji lito stratygraficznej utworów dewonu i dolnego karbonu podłoża zapadliska przedkarpackiego. Wyniki tych badań pozwoliły także na korektę istniejących poglądów na stratygrafię i rozwój facjalny tych osadów.

STRATIGRAPHY AND FACIES DEVELOPMENT OF THE DEVONIAN AND LOWER CARBONIFEROUS IN SOUTHERN PART OF THE CARPATHIAN FOREDEEP

Lithofacies, microfacies and micropaleontological studies made it possible to establish lithostratigraphy of the Devonian and Lower Carboniferous in the borehole columns Niwki 3 and Swarzów 9 (Fig. 2) and to correlate the strata with those from other boreholes in the Carpathian Foredeep.

Mottled clastic rocks developed in the Old Red facies were dated at the Middle Devonian. Devonian and Lower Carboniferous rocks were found to occur in sedimentary continuity. Mottled terrigenous complex was dated at upper Tournaisian. These findings were subsequently used in correlation of Devonian and Lower Carboniferous strata in area between Tarnow and Rzeszów.

The analysis of basic unpublished reports on some major borehole columns from that area (Bratkowice 1, Niwiska 3, Niwiska 7, Trzebownisko 1 and Zalesie 1) showed that Devonian and Lower Carboniferous rocks from these columns closely resemble those from the columns Niwki 3 and Swarzów 9 in development. In borehole columns Bratkowice 1, Niwiska 3, Niwiska 7, Trzebownisko

1 and Zalesie 1, rocks developed in the Old Red facies clearly display transition to a higher, carbonate member of the Devonian and they are two times thicker than in the column Niwki 3 (Fig. 3). If Old Red strata from the column Niwki 3 are correctly dated at the Middle Devonian, it would follow that they may extend somewhat higher in the above mentioned boreholes, especially as the overlaying carbonate rocks are very thin there (60–140 m thick). The latter are mainly represented by marly and micritic or, sometimes, crystalline dolomites. They were identified as knobby limestones, detrital micritic limestones, crinoid limestones and organogenic-detrital liinestones (Swarzów 9; Table 2) and Styliolina limestones, knobby limestones and micritic limestones (Niwki 3; Table 1).

Lithological character and very small thickness (from about 150 to 300 m but a half of the sequence is formed of clastic Old Red strata) of the Devonian indicate very low rate of sedimentation and stratigraphic condensation (for comparison, Devonian strata occurring west of the studied area are about 500 m to over 1,000 m thick).

In the boreholes Bratkowice 1 and Niwiska 7, dolomitic rocks are overlain by mottled terrigenous complex identical as that from the borehole Swarzów 9, dated at the upper Tournaisian.

In the borehole Zalesie 1, facies equivalents of that mottled complex include terrigenous-carbonate rocks (Fig. 4). Facies differentiation of the upper Tournaisian (Fig. 1) was determined by presence of a local uplift. A land existing at that time was delineating extent of the area of sedimentation of mottled terrigenous complex. In some distance of that land there were originating terrigenous-carbonate rocks, and further – carbonate ones.