Jurassic-Cretaceous Phosphatic Events in the Pieniny Klippen Basin (carpathians) – Palaeoceanographic Conditions of the Western Tethys

In Europe the Polish Carpathians form the northern part of the great arc of the Alpine mountains, which stretch more than 1.300 km from the Vienna Forest (Austria) to the Iron Gate on the Danube River (Romanian/Serbian state border). The Alpine Tethys constitutes important palaeogeographic elements of the future Carpathians, developed as an oceanic basin during the Jurassic as a result of the break-up of Pangea. The Pieniny Klippen Belt (PKB) is a boundary zone between the Outer and Central Western Carpathians and palaeogeographicaly is interpreted as a separate branch of the north-westernmost Tethyan Ocean (Pieniny Klippen Basin). The PKB is composed of several successions of mainly deep and shallower-water limestones, covering a time span from the Early Jurassic to Late Cretaceous. This strongly tectonized structure is currently about 600 km long and 1–20 km wide, stretching from Vienna in the west to Romania in the east. The several facies successions accumulated in subtidal/neritic shelf environments of the submarine swell (so-called Czorsztyn Ridge and its southeastern slope), while palaeogeographical orientation of this Czorsztyn Ridge was from NE to SW. These successions can be distinguished, from shallowest zone (Czorsztyn Succession) trough transitional zone (Niedzica and Czertezik successions) up to deepest one (Branisko and Pieniny successions) in the axial part of this basin. During the Mesozoic history at least three phosphatic events took place within this basin: (i) Early Bajocian, (ii) Berriasian and (iii) Albian times. In the late Early Bajocian time (i), just after Czorsztyn Ridge originated by tectonic uplift, sedimentary features recorded condensation episode during start of crinoidal limestones sedimentation (even up to 150m in thickness). The base of the crinoidal limestones are very sharp and directly overlying, with stratigraphical hiatus (ca. 2Ma), the oxygen-depleted dark/black Fleckenkalk/Fleckenmergel-type deposits of Toarcian-lowermost Bajocian in age. This part of crinoidal limestones consists of phosphatic concretions pavements, large phosphatic macrooncoids, light-greenish clasts of micritic limestones, pyrite concretions, and fossils as ammonites, brachiopods and bivalves. Phosphatic concretions occur in almost all PKB successions exclusively within lowermost part of crinoidal beds as isochronous event. Very rapid change of sedimentation from oxygen-depleted environments (during Toarcian-earliest Bajocian) to carbonate sedimentation is record of rapid vertical tectonic uplift of the Czorsztyn Ridge and adjacent areas and may be also reflect palaeoceanographical changes after this tectonic movements and origin of upwelling currents. The second (ii), Berriasian episode of phosphatisation has been connected with post-Tithonian time tectonic uplifting of the Czorsztyn Ridge and surroundings. The presence of phosphate-rich deposits (phosphorites and microbial phosphate macrooncoids), which should be localized in a palinspastic reconstruction near shelf-edge slope boundary, supported idea of upwelling currents as well. The third (iii), Albian episode of phosphatisation of marly deposits on sea-floor occupied by the Czorsztyn Succession zone are represented by phosphatic: stromatolites, lithoclasts and microbialite-coatted bioclasts of upwelling currents in origin again. Usually, these are on the base of Albian marls/marly limestones which covered erosional surfaces of older limestones with several fossil-karst phenomena originated as effect of at least two episodes of tectonic uplift and emersions. This research was sponsored by a grant from the AGH University of Krakow (16.16.140.315).