Geological Characterization of Seismic Data, Lithofacies Delineation within the Stratigraphic Framework of Upper Miocene Sediments in Northern Banat, Serbia

Key Words: Stratigraphy, Upper Miocene, Pannonian Basin, Seismic Attributes, Lithotype Analysis, Palynology

The Upper Miocene deposits in the southeastern part of the Pannonian Basin can be categorized into three sedimentary and tectonic cycles based on the regional Neogene stratigraphy (Horváth et al., 2015). The first cycle is characterized by deep-water marlstones, claystones, and sandstone turbidites corresponding to the regional Endrőd and Szolnok formations. Overlying these, the second cycle includes sediments deposited in a delta plain environment, represented by the clastic and marly progradational series of the Algyő Formation (Magyar et al., 2013). Finally, the third cycle consists of shallow-water, transitional, and terrestrial deposits attributed to the Újfalu Formation.

The primary objective of this research was to determine progradational directions and identify sedimentary bodies within the Upper Miocene characterized by distinct lithological properties. A significant challenge involved the geological interpretation of seismic data, which, being in the time domain, has a much lower vertical resolution compared to well data. Detailed lithological analysis of well data was performed using cluster (lithotype) analysis, which groups rocks based on the physical characteristics observed in well logs. Since seismic data also reflect variations in rock physical properties, combining cluster analysis with seismic facies maps provided a robust foundation for the development of an initial 3D lithofacies model. The ultimate goal of this approach was to produce seismic facies maps that, when integrated with lithotype analysis, enhance the petroleum system model with detailed lithological and spatial distribution data. Calibration of the results culminated in the creation of final lithology facies maps.

This multidisciplinary study also incorporated palynological and sedimentological analyses of the Algyő and Újfalu formations. Sedimentological investigations involved analyzing sedimentary bodies delineated using interpreted horizons and seismic attributes. The studied sedimentary sequences, stratigraphically dated to the Upper Miocene-Pliocene (second and third cycle deposits), were characterized using seismic attributes such as "mean amplitude" and "RMS amplitude." These attributes facilitated the identification of sedimentary bodies and corroborated their characteristics as determined by lithotype analysis.

References:

• Magyar, I., Radivojević, D., Sztanó, O., Synak, R., Ujszászi, K., & Pócsik, M. (2013). Progradation of the paleo-Danube shelf margin across the Pannonian Basin during the Late Miocene and Early Pliocene. Global and Planetary Change, 103, 168–173.
• Horváth, F., Musitz, B., Balázs, A., Végh, A., Uhrin, A., Nádor, A., Koroknai, B., Pap, N., Tóth, T., & Wórum, G. (2015). Evolution of the Pannonian Basin and its geothermal resources. Geothermics, 53, 328–352.