Wstępna ocena warunków i możliwości powstawania ropy naftowej w utworach wschodniej części fliszu podhalańskiego

Abstract

PRELIMINARY ESTIMATION OF CONDITIONS AND POSSIBILITIES OF FORMATION, OF OIL DEPOSITS IN THE EASTERN PART OF THE PODHALE FLYSCHSummaryThe Podhale flysch or the flysch series is the upper part of the Podhale Palaeogene. It represents a rock member, about 4000 m in thickness, referred to Middle Eocene (Lutetian) - Lower Oligocene (F. Bieda, 1963). The Palaeogene formations occur between the Tatra Mts. and the Pieniny Klippen Belt in a zone of about 15-16 km in breadth, running from west to east. They form a relatively straight synclinorial trough (Podhale trough), the southern limb of which, locally thrown by longitudinal faults of a W-E direction, adjoins the Tatra Mts. (near-Tatra zone). The narthern limb, in turn, folded at the tectonical contact with the Pieniny Klippen Belt (near-Pieniny zone), is cut off at the very contact (Figs. 2-4). As a result of exhaustive investigations made by J. Gołąb (1959), S. Sokołowski (1959) and L. Watycha (1959), the Palaeogene formations have been subdivided into several members, mainly on the basis of lithological evidences (Fig. 5).Carbonate nummulite series (15-200 m in thickness) occurs at the surface only in the near-Tatra zone. It transgresses here with its various members on the Tatra rocks of the Sub-Tatra series, slightly eroded before the Eocene. Within the flysch series or Podhale flysch, more than 3500 m in thickness, Szaflarskie beds have been distinguished as the oldest member (Lower Bartonian, F. Bieda, 1959) that occurs in the area of the northern limb of the trough only. They consist mainly of variously bedded, and variously grained, conglomerate-like sandstones, and of siltstones (Fig. 6). The overlying Zakopiańskie beds, as well as the higher Chochołowskie and Ostryskie beds, are represented in both limbs of the trough. In the near Tatra region, the Zakopiańskie beds rest immediately on the carbonate nummulite series. The lower member of these beds, i.e. the shale member with ferruginous dolomites, is built up mainly of siltstones and shales, secondarily of sandstones. The upper member of the Zakopiańskie beds of sandstone-shale nature, is characterized by the predominance of sandstone banks, over shales and siltstones, increasing upwards. The flysch formations were laid down in a shallow reduction sea. Materials were brought mainly from the area of the Tatra Mts., and in the north, from the near-Pieniny continental bar. The central part of the trough continuously lowered, but its shores were labile. The northern shore continually subsided due to the pre-folding processes, from the Priabonian up to the time at which it was submerged (Middle Oligocene). In that period, the southern shore (Tatra shore) continually rose and moved northwards. Due to these movements, a region approximately 70 km in breadth, comprising the near-Pieniny zone the Pieniny Klippen Belt, and the Magurska bar, was subsided during the main folding phase of this region, and the deposits of the Podhale flysch approached the Magurska series at a distance of 2-5 km. In the northern part of the trough, a considerable amassment of rock series, adjacent to the Sub-Tatra and Tatra series, and to the formations of the Pieniny Klippen Belt, took place. All the series were squeezed and pressed, forming various discoidal members arranged steeply in stages. Such geological situation and bitumen manifestations forced to initiate new researches on conditions and possibilities of formation of oil deposits in the Podhale flysch formations. In the first phase, due to methodical and technical reasons, the researches were restricted only to the siltstones which occur in the Szaflarskie beds and in the lower member of the Zakopiańskie beds. Samples were taken from the rocks pierced by bore hole Zakopane IG-1 and from exposures (Fig. 1). As a result of the geochemical examinations made by J. Calikowski (1967) it has been ascertained that bitumens of the Podhale flysch are found to occur in considerable amounts. They have not been formed in the rocks under examination, but are of migration origin.