Sukcesja osadowa miocenu w rejonie zrębu Ryszkowej Woli (obszar Sieniawa–Rudka), zapadlisko przedkarpackie: wyniki facjalnej i stratygraficznej interpretacji danych wiertniczych oraz sejsmiki 3D

Abstract

Miocene succession at the Ryszkowa Wola high (Sieniawa–Rudka area), Carpathian Foredeep Basin: facies and stratigraphic interpretation of wellbore and 3D seismic data.S u m m a r y. The Polish Carpathian Foredeep Basin (PCFB) is the northern compartment of a foreland basin system that surrounds the Carpathian orogenic belt. The axis of the eastern part of the PCFB plunges gently towards SE, where the Miocene basin-fill succession exceeds 2000 metres in thickness. The Miocene succession developed in shallow marine ramp settings and is subdivided into 3 lithostratigraphic units: sub evaporitic (onshore-to-nearshore), evaporitic, and supra-evaporitic (offshore-to-estuarine). The upper unit includes a siliciclastic series (Upper Badenian–Sarmatian), which constitutes the main segment of the succession. It displays an asymmetric, shallowing-up trend, expressed by the following sequence: hemipelagic→turbiditic→deltaic→low-energy nearshore-to-estuarine facies associations. Sediment accummulation in the basin has been significantly overprinted by higher-frequency cyclicity and encloses several genetic stratigraphic sequences bounded by MFS surfaces. An early phase of the basin development was characterised by high-rate subsidence and slow-rate sedimentation (hemipelagic facies). The turbiditic facies association identified within the Sieniawa–Rudka area resulted from southward progradation of a submarine fan/prodeltaic depositional system, mainly fed from the northern and north–western continental margins of the basin. An overall SE–ward palaeoslope inclination controlled the main phase of the deltaic progradation, which had gradually replaced the turbiditic systems. The late deltaic phase was characterised by ENE palaeotransport directions. The final phase of the basin filling took place in shallow-water, low energy, nearshore-to-estuarine environments. In the early stage of the basin development, a complex system of NW–SE elongated basement pop-ups and flower structures in the Miocene succession were produced by reactivation and inversion of Mesozoic basement faults. The growth of these positive structures modified local subsidence patterns and affected the organisation of depositional systems of the siliciclastic series. A narrow elevation of the RyszkowaWola High (RWH) gradually grew above one of the pop-up structures. Complex structural-stratigraphic hydrocarbon traps developed along the RWH, due to interaction between the growth of local faults and the development of the successive depositional systems. Tidally-modified delta-top and estuarine facies are the most common hydrocarbon hosts within individual sequences of the „deltaic” segment of the succession..