This article presents the sixth and final contribution in a series of papers focused mainly on the K-Ar dating of the Oligocene and Neogene (Miocene and Pliocene) intraplate basaltic volcanics of the Lower Silesia, SW Poland. The present paper includes 22 new K-Ar dates from the West Sudety Mountains and their northern foreland. The K-Ar dates range from 30.7 to 22.2 Ma. The data are supplied with geological description of the sampled outcrops, petrographic, geochemical and palaeomagnetic data of the analysed samples. Palaeomagnetic investigation confirmed the existence of two important volcanic episodes distinguished already in 1997: the reversed polarity Odra Event (mean age 28.2±1.2 Ma), and the normal polarity Gracze Event (mean age 26.28±1.8 Ma).
New data are presented in relation to the worldwide definition of the Oxfordian/Kimmeridgian boundary, i.e. the base of the Kimmeridgian Stage. This data, mostly acquired in the past decade, supports the 2006 proposal to make the uniform boundary of the stages in the Flodigarry section at Staffin Bay on the Isle of Skye, northern Scotland. This boundary is based on the Subboreal-Boreal ammonite successions, and it is distinguished by the Pictonia flodigarriensis horizon at the base of the Subboreal Baylei Zone, and which corresponds precisely to the base of the Boreal Bauhini Zone. The boundary lies in the 0.16 m interval (1.24–1.08 m) below bed 36 in sections F6 at Flodigarry and it is thus proposed as the GSSP for the Oxfordian/Kimmeridgian boundary. This boundary is recognized also by other stratigraphical data – palaeontological, geochemical and palaeomagnetic (including its well documented position close to the boundary between magnetozones F3n, and F3r which is placed in the 0.20 m interval – 1.28 m to 1.48 m below bed 36 – the latter corresponding to marine magnetic anomaly M26r).The boundary is clearly recognizable also in other sections of the Subboreal and Boreal areas discussed in the study, including southern England, Pomerania and the Peri-Baltic Syneclise, Russian Platform, Northern Central Siberia, Franz-Josef Land, Barents Sea and Norwegian Sea. It can be recognized also in the Submediterranean-Mediterranean areas of Europe and Asia where it correlates with the boundary between the Hypselum and the Bimmamatum ammonite zones. The changes in ammonite faunas at the boundary of these ammonite zones – mostly of ammonites of the families Aspidoceratidae and Oppeliidae – also enables the recognition of the boundary in the Tethyan and Indo-Pacific areas – such as the central part of the Americas (Cuba, Mexico), southern America, and southern parts of Asia. The climatic and environmental changes near to the Oxfordian/Kimmeridgian boundary discussed in the study relate mostly to the European areas. They show that very unstable environments at the end of the Oxfordian were subsequently replaced by more stable conditions representing a generally warming trend during the earliest Kimmeridgian. The definition of the boundary between the Oxfordian and Kimmeridgian as given in this study results in its wide correlation potential and means that it can be recognized in the different marine successions of the World.
Abstract Terminal Triassic environmental changes are characterized by an integrated study of lithology, litho- and cyclostratigraphy, paleontology, mineralogy, geochemistry and rock magnetism in the Tatra Mts. The Carpathian Keuper sequence was deposited in an arid environment with only seasonal rivers, temporal lakes and swamps with scarce vegetation. Combination of a wide range of δ 18 O values (-0.7 to + 2.7) with negative δ 13 C values documents dolomite precipitation either from brackish or hypersaline lake water, or its derivation from pore water comparably to the Recent Coorong B-dolostone. Negative δ 13 C values indicate microbial C productivity. Rhaetian transgressive deposits with restricted Rhaetavicula fauna accumulated in nearshore swamps and lagoons. Associations of foraminifers, bivalves and sharks in the Zliechov Basin were controlled by physical factors. Bivalve mollusc biostromes were repetitively destroyed by storms, and temporary firm bottoms were colonized by oysters and burrowers. Subsequent black shale deposition recorded input of eolian dust. Bottom colonization by pachyodont bivalves, brachiopod and corals started much later, during highstand conditions. Facies evolution also revealed by geochemical data, C and O isotope curves reflect eustatic and climatic changes and help reconstruct the evolution of Rhaetian marine carbonate ramp. The Fatra Formation consists of 100 kyr eccentricity and 40 kyr obliquity cycles; much finer rhythmicity may record monsoonlike climatic fluctuations. Fluvial and eolian events were indicated by analysis of grain size and content of clastic quartz, concentrations of foraminiferal ( Agathammina ) tests in thin laminae indicates marine ingression events. Magnetic susceptibility (MS) variations reflect the distribution of authigenic and detrital constituents in the sequence. Increasing trend of MS correlates with the regressive Carpathian Keuper sequence and culminates within the bottom part of the Fatra Formation. Decreasing trend of MS is observed upwards the transgressive deposits of the Fatra Formation.
The results of new palaeoenvironmental research in the Carpathians (Rowienka, Fatric succession, Poland) are presented. Magneto- and biostratigraphy, magnetic susceptibility (MS), inorganic geochemistry, gamma ray spectrometry (GRS) and stable isotopes were studied. Indications of terrigenous input and redox proxies are discussed and compared with other Western Tethyan sections, especially those from the Balkan area (Grabowski et al. , 2016) and Vocontian Basin (Morales et al ., 2013; Emmanuel & Renard, 1993). The implications of results are referred to palaeogeographic and palaeotectonic reconstructions (e.g. Haas & Pero, 2004; Schmid et al. , 2008; Plasienka, 2018). Integration of magneto- and biostratigraphic data (Grabowski & Pszczolkowski, 2006) allows to correlate precisely even very distant sections from different tectonic units. Additionally, rock magnetism and geochemical data, gamma spectroscopy and carbon isotope analysis give a useful information about the environmental conditions in a basin during sedimentation time. During the Berriasian, Fatric basin was situated at the southern shelf of the Penninic-Vahic (Alpine Tethys) ocean. The Rowienka section covers stratigraphic interval from the upper part of M16r polarity chron up to the M14r chron (Berriasian/Valanginian boundary). MS shows increasing trend in M16n magnetozone and then a slight decrease in magnetozones M15r and M15n. GRS data and content of lithogenic elements (K, Al, Th, and others) show a long term increasing contribution of terrigenous material throughout the Upper Berriasian, which is in concordance with MS data. It is interpreted as an evidence of approaching collision at the southern margin of the Central Western Carpathians (CWC) (e.g. Schmid et al. , 2008; Plasienka, 2018). The same orogenic events controlled terrigenous supply in the Late Berriasian of Western Balkan section (Barlya, Grabowski et al. , 2016) situated at the southern margin of Moesian platform. Tectonically induced continental runoff was most probably intensified by humid climate. Carbon isotope data (δ 13 C) from Rowienka (Fig. 1) correlate very well with those from Barlya (Grabowski et al. , 2016) and the Vocontian sections (Emmanuel & Renard, 1993). δ 13 C decreases towards the minimal values in the upper part of magnetozone M16n and then increases in magnetozones M15r and M15n in the uppermost Berriasian. Similar pattern may be seen in other magnetostratigraphically dated Upper Berriasian sections from the Alpine – Carpathian area as well as those without magnetostratigraphic calibration (Morales et al ., 2013). This led to a conclusion, that δ 13 C variations might be a good proxy for regional scale correlations; it’s palaeoenvironmental implications are discussed. Trace elements, such as Ba and Ni are interpreted as a palaeoproductivity proxies (Tribovillard et al. , 2006); an evidence of temporal increase of the basin productivity was found in Rowienka, in the upper part of M16r magnetic zone (lower part of the Upper Berriasian). Furthermore, total organic carbon (TOC) content in Rowienka is increasing along with the terrigenous input, which is likely an evidence of land provenance of organic matter. Investigations were financially supported by the National Science Center, Poland (project no.: 2016/21/B/ST/10/02941) and Ministry of Science and Education, Poland (project no.: 683/N-POLONIUM/2010/0).
