Acta Geologica Polonica

Over three thousand specimens representing the superfamily Trochoidea Rafinesque, 1815 [Trochidae Rafinesque, 1815 and Calliostomatidae Thiele, 1924 (1847)] from the upper Upper Badenian = Kosovian = lower Serravallian (middle Miocene) marine deposits of Ukraine, housed in the collections of the Polish Academy of Sciences Museum of the Earth in Warsaw (MZ), are studied herein. The abundant material has allowed for investigations of the intraspecific variation and revision of earlier determinations. As a result, 21 species belonging to 5 genera have been identified, described and illustrated, of which one is new [Clanculus (Clanculopsis) krachi sp. nov.] and one is left in open nomenclature. Granulifera O. Anistratenko, 2000 is considered a junior subjective synonym of Clanculopsis Monterosato, 1879; Granulifera pulla O. Anistratenko, 2000 is considered a junior subjective synonym of Monodonta tuberculata Eichwald, 1830; Gibbula sytovae Amitrov, 1961 is considered a junior subjective synonym of Trochus miocaenicus Mayer, 1853; Gibbula volhynica Friedberg, 1928 is considered a junior subjective synonym of Trochus novemcinctus von Buch, 1830; and Trochus buchii du Bois de Montpéreux, 1831 is suppressed in favour of the senior subjective synonym Trochus puschii Andrzejowski, 1830. The geographic distribution and stratigraphic ranges of the taxa are given. Six species are known only from the Polish-Ukrainian part of the Fore-Carpathian Basin. The protoconch features are systematically studied in the Trochidae and Calliostomatidae from this area for the first time.

The mid-Ludfordian pronounced, positive carbon isotope excursion (CIE), coincident with the Lau/kozlowskii extinction event, has been widely studied so far in shallow-water, carbonate successions, whereas its deep-water record remains insufficiently known. The aim of this research is to reconstruct the sedimentary environments and the palaeoredox conditions in the axial part of the Baltic-Podolian Basin during the event. For these purposes, the Pasłęk IG-1 core section has been examined using microfacies analysis, framboid pyrite diameter and carbon isotope measurements. The prelude to the event records an increased influx of detrital dolomite interpreted as eolian dust, coupled with a pronounced decrease in the diameter of the pyrite framboids, indicating persistent euxinic conditions across the event. The event climax is recorded as the Reda Member and consists of calcisiltites, composed of calcite microcrystals (‘sparoids’), which are interpreted as suspensoids induced by phytoplankton blooms in the hipersaturation conditions present in the epipelagic layer of the basin. Both the prelude and climax facies show lamination, interpreted as having resulted from periodical settling of marine snow, combined with hydraulic sorting within a ‘benthic flocculent layer’, which additionally may be responsible for a low organic matter preservation rate due to methanogenic decomposition. Contrary to the observed basinward CIE decline in the benthic carbonates in the basin, the Reda Member records an extremely positive CIE (up to 8.25‰). Given the pelagic origin of the sparoids, the CIE seems to record surface-water carbon isotope ratios. This points to a large carbon isotope gradient and kinetic fractionation between surface and bottom waters during the mid-Ludfordian event in a strongly stratified basin. The Reda facies-isotope anomaly is regarded as undoubtedly globally triggered, but amplified by the stratified and euxinic conditions in the partly isolated, Baltic-Podolian basin. Hence, the common interpretation of the basin record as representative for the global ocean needs to be treated with great caution.

Jurassic and Lower Cretaceous successions of the Manín Unit of the Central Western Carpathians are exposed in Butkov Quarry in the Middle Váh Region, Slovakia. A significant part of the macrofauna belonging to neocomitid ammonites, formerly classified under the genus Teschenites Thieuloy, 1971, occurs in deposits spanning the Valanginian/Hauterivian boundary. The original definition of Teschenites was accompanied by uncertainties in the taxonomic and stratigraphic position of its original type species, i.e., Hoplites neocomiensiformis Uhlig, 1902. The present contribution focuses on and provides a possible taxonomic solution by establishing the new genus Tescheniceras. In Butkov Quarry, the new genus includes five species. Tescheniceras flucticulum (Thieuloy, 1977), the type species, is the most abundant. Tescheniceras callidiscum (Thieuloy, 1971), the subzonal species for the uppermost Valanginian (Thieuloy 1971b), occurs only sporadically. Because Acanthodiscus radiatus (Bruguiére, 1789), the index species for the basal Hauterivian (radiatus Zone) in the international ammonite zonation, does not occur in the locality, the basal Hauterivian is indicated by the first appearance of the genus Spitidiscus Kilian, 1910.