Abstract
In recent years, numerous wells have been completed in the area of the Zloczew Graben. Drill cores and data collected from wells have led to the recognition of an Upper Oxfordian–Lowermost Kimmeridgian sequence and to the construction of a 3D model of the graben with distribution of facies. Six facies types were distinguished, composed of numerous microfacies representing outer-, middle-, and inner-ramp depositional systems. The boundary of the Planula/Platynota zones is indicated by the transition from mid-inner carbonate ramp facies to mixed, carbonate–siliciclastic outer-ramp facies, as well as by appearance of debrites and calciturbidites. The distribution of gravity-flow deposits reflects the pattern of fault zones of the Zloczew Graben and their Late Jurassic activity. Comparison of Oxfordian–Lowermost Kimmeridgian facies types from central and southern Poland enabled the reconstruction of the general facies architecture in the Polish part of the northern peri-Tethyan shelf belonging to the Malopolska Block. The distribution of Upper Oxfordian–Lowermost Kimmeridgian facies follows the block structure of the basement and was controlled by reactivation of Paleozoic tectonic blocks in the Late Jurassic. The results of studies in the Polish basin correspond well to Upper Oxfordian–Lower Kimmeridgian sequences known from the ramp systems of western Europe where the basic change in deposition, from a carbonate ramp towards mixed, carbonate–siliciclastic sedimentation, was related to both North Atlantic and western European tectonics.
Highlights
The Złoczew Graben is located at the boundary of the Złoczew High and the Wielun Upland (Fig. 1)
The knowledge of facies development of Upper Jurassic sediments in the remaining areas of central and southern Poland is based on rarely published data from wells (e.g., Gutowski et al 2005; Złonkiewicz 2009; Krajewski et al 2011a and references therein)
The presence of Lower Kimmeridgian (Platynota zone) deposits is confirmed by the marker horizon with hiatus concretions observed in the Złoczew Graben, which is of regional correlative importance in central Poland (Krajewski et al 2014)
Summary
The Złoczew Graben (central Poland) is located at the boundary of the Złoczew High and the Wielun Upland (Fig. 1). Reconstruction of the Late Jurassic facies architecture of this broad, epeiric carbonate shelf located in central and southern Poland is difficult and controversial due to insufficient knowledge of microfacies development and facies distribution. The concepts of depositional system development are based mostly on data from Upper Jurassic outcrops located in the northeastern and southwestern margins of the Holy Cross Mountains and KrakówCzestochowa, and Wielunuplands (Fig. 1) (e.g., Kutek et al 1977; Matyja et al 1989; Matyszkiewicz et al 2006a and references therein). The knowledge of facies development of Upper Jurassic sediments in the remaining areas of central and southern Poland is based on rarely published data from wells (e.g., Gutowski et al 2005; Złonkiewicz 2009; Krajewski et al 2011a and references therein). The Upper Oxfordian deposits from central and southern Poland were assigned to the deep-water open shelf, so-called sponge megafacies
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