A continuous stratigraphical record of the Upper Kimmeridgian to Lower Berriasian palaeoenvironmental changes in a pelagic setting: the Veliky Kamenets section (Pieniny Klippen Belt, Ukraine)
Integration of magnetic stratigraphy with bio and chemostratigraphy gives a good opportunity to create a high resolution chronostratigraphic framework with a potential for global correlation of sedimentary and biotic events. Pelagic and hemipelagic sediments are especially suitable for tracing long term palaeoenvironmental changes. The Upper Jurassic and Lower Cretaceous deep marine sediments of the Pieniny Klippen Belt (PKB, Carpathians) originated in the eastern prolongation of the Alpine Tethys, in the Penninic Vahic ocean (e.g. Stampfli Hochard, 2009) The Veliky Kamenets section (PKB, Ukraine) (Fig. 1) is a unique locality which shows excellently exposed Lower Jurassic to lowermost Cretaceous sedimentary succession. The Toarcian Berriasian part is precisely dated with calcareous dinoflagellates, calpionellids and ammonites Rehakova et al. 2011) Our new study is complemented by nannofossil biostratigraphy as well. The rocks were especially suitable for palaeomagnetic studies Lewandowski et al. 2005) We present results of an integrated bio magneto and chemostratigraphic study of the Upper Kimmeridgian to Lower Berriasian interval of the section, spanning ca. 10 My. The interval studied extends from the Upper Kimmeridgian (Parvula Acme Zone) to Lower Berriasian (the standard Calpionella Zone, Elliptica Subzone) Succession of magnetozones from M23r to M18n has been identified. The Kimmeridgian/Tithonian boundary (Borzai/Pulla zonal boundary) is correlated for the first time with the transition between M22r and M22n polarity zones. It is close to the FO of the nannofossil Conusphaera mexicana minor and closely corresponds to the position of Kimmeridgian/Tithonian boundary in the recently studied S'Adde section (Sardinia, Muttoni et al. 2018) In the Upper Tithonian, the occurrence of the characteristic nannofossil genus Acadialithus is registered. The Tithonian/Berriasian boundary, defined as Colomi/Alpina Subzonal boundary, occurs in the middle of the M19n2n polarity zone. It coincides with the first occurrences of the two stratigraphically important nannofossil species: Nannoconus steinmannii minor and N. kamptneri minor. The position of Tithonian/Berriasian boundary against magnetostratigraphy is consistent in all Western Tethyan sections (e.g. Grabowski 2011) Magnetic susceptibility reveals a long term decrease which is interpreted as an effect of intensifying carbonate sedimentation and dilution of detrital particles in carbonate matrix. The interpretation is supported by lowering content of K and Th which accounts for decreasing amount of terrigenous material. The increasing carbonate productivity resulted in acceleration of sedimentation rate and stepwise demise of Saccocoma microfacies since polarity chron M19r. The same decreasing trend is observed in stable isotope stratigraphy. The major fall of d 13 C values from 2.5 %0 to 1.6 %0 occurs between the Upper Kimmeridgian and the Middle Tithonian (polarity zone M20r) Throughout the Upper Tithonian and Lower Berriasian the carbon isotopic ratio is relatively stable fluctuating between d 13 C values of 1.4 to 1.7 %0. Acknowledgement: The magnetostratigraphic investigations were partially funded by GA CR project n. GAP210/16/09979S. The stable isotope study and gamma ray spectrometry were supported by the project 61.2301.1501.00.0 of the PGI NRI (Warsaw) Biostratigraphic studies were funded by the project APVV 14 0118 (Comenius University) Final interpretation has been performed within the frame of the project 2016/21/B/ST10/02941 of the National Science Centre, Poland. Figure 1: General view of the Veliky Kamenets active quarry (present state) with Tithonian/Berriasian boundary indicated. Grabowski J. (2011) Magnetostratigraphy of the Jurassic/Cretaceous boundary interval in the Western Tethys and its correlations with other regions: a review. Volumina Jurassica 9, p. 105 128. Lewandowski M. Krobicki M. Matyja B.A. Wierzbowski A. (2005) Palaeogeographic evolution of the Pieniny Klippen basin using stratigraphic and palaeomagnetic data from the Veliky Kamenets section (Carpathians, Ukraine) Palaeogeography, Palaeoclimatology, Palaeoecology 216, p. 53 72. Muttoni G. Visconti A. Channell J.E.T. Casellato C.E. Maron M. Jadou l F. 2018. An expanded Tethyan Kimmeridgian magneto biostratigraphy from the S'Adde section (Sardinia) implications for the Jurassic timescale. Palaeogeography, Palaeoclimatology, Palaeoecology 503, p. 90 101. Rehakova D. Matyja B.A. Wierzbowski A. Schlogl J. Krobicki M. Barski M. (2011) Stratigraphy and microfacies of the Jurassic and lowermost Cretaceous of the Veliky Kamenets section (Pieniny Klippen Belt, Carpathians, Western Ukraine) Volumina Jurassica 9, p. 61 104. Stampfli G. Hochard C. (2009) Plate tectonics of the Alpine realm. In: Murphy, J.B. Keppie, J.D. Hynes, A.J. (eds) Ancient orogens and modern analogues. Geological Society London, Special Publications 327, p. 89 111. 1.