Martin Kamen was a giant of twentieth century science. Trained as a physical chemist, he was the co-discoverer of radioactive Carbon 14, which has transformed many areas of science as a tracer and as ...a way to date artifacts. He later switched to the study of metabolism and biochemistry and made important contributions to the understanding of nitrogen fixation and photosynthesis. Finally, he studied cytochromes, primarily from anoxygenic photosynthetic bacteria.
The siliciclastic succession of the Ediacaran Chernyi Kamen Formation in the Central Urals of Russia contains a rich complex of Ediacaran fossils that represent
in situ
benthic populations buried in ...life position. The present work reports
Beltanelliformis konovalovi
sp. nov. found as a paleocommunity of organisms and studied for their morphology and spatial distribution. Unlike the type species (
B. brunsae
), new fossils are preserved within fine-grained sandstone beds as three-dimensional pancake-like or flattened discoidal single, paired, or occasionally aggregated bodies with an ultra-thin rim. Statistical analysis shows significant predominance of small individuals in the paleocommunity, which in turn manifests different spatial distribution in comparison with larger ones. In addition, the studied paleocommunity exhibits patterns of self-organization in extremely shallow marine environment and adaption to periodic desiccation. These results provide quantitative support for the more complex ecology of
Beltanelliformis
and also expand the range of taphonomic possibilities of macroscopic life in the terminal Neoproterozoic.
Monumentalna romanička bazilika sv. Krševana u Zadru trobrodne je podjele od čega je začelje južnoga broda bilo namijenjeno kultu akvilejskoga mučenika sv. Krševana. Tome u prilog govori ...arhitektonska forma začelja: dvoetažnost i promišljena osvijetljenost samog prostora. Tako je pod razinom svetišta koje je sezalo do drugoga para stupova oblikovana omanja kripta s podužim i užim pristupnim hodnikom do prostorije u kojoj se sve do početka 20. st. nalazila konfesija s ranokršćanskim sarkofagom. Sarkofag je bio vidljiv preko otvora probijenog posred pregradnog zida konfesije te je za pretpostaviti da je imao određenu vezu s kultom akvilejskog mučenika, zadarskog sveca zaštitnika. Povrh konfesije, u dijelu svetišta južnog bočnog broda, nalazio se svečev oltar. Apostolski vizitator Valier svjedoči da se tijelo sveca nalazilo u sklopu oltara, a to potvrđuje i Priuli koji navodi drvenu škrinju, mramorni sarkofag u kojem je smješteno tijelo te kamen-relikviju ex-contactu na kojem je svetac pogubljen. U crkvi se tijekom ranog novog vijeka nalazila i škrinja s narativnim prizorima iz svečeva života. Cijeli je ambijent, odnosno kapela podignuta po južnom boku glavne apside posvećena sv. Krševanu bila osvjetljena jednim manjim prozorom u apsidi i dvama jednostavnim monoforama na južnom brodu čime se i arhitektonski naglašava važnost prostora.
The monumental Romanesque basilica of St. Chrysogonus (Krševan) in Zadar is divided into three naves, of which the rear of the southern nave was assigned to the cult of the Aquileian martyr St. Krševan. This is supported by the architectural form of the rear: the two-story structure and the well-planned lighting of the space itself. Thus, under the level of the sanctuary, which reached to the second pair of columns, a smaller crypt was formed with a long and narrow access corridor to the room where, until the beginning of the 20th century, there was a confessional with an early Christian sarcophagus. The sarcophagus was visible through the opening cut in the middle of the dividing wall of the confessional, and it can be assumed that it had a certain connection with the cult of the martyr of Aquileia, the patron saint of Zadar. Above the confessional, in the part of the sanctuary of the southern side nave, there was the saint's altar. The apostolic visitor Valier testifies that the saint's body was in the altar, and this is confirmed by Priuli, who mentions the wooden chest, the marble sarcophagus in which the body was placed, and the ex-contactu relic stone on which the saint was executed. During the early modern century, the church housed a chest with narrative scenes from the lives of saints. The entire environment, that is, the chapel built on the south side of the main apse, is dedicated to St. Krševan was lit by one smaller window in the apse and two simple monophores on the south nave, which architecturally emphasizes the importance of the space.
The Siberian Traps volcanism is widely considered the main cause of the end-Permian mass extinction, the greatest biological crisis in the Earth history. While the extinction is interpreted as ...catastrophic and sudden with estimates of duration of approximately 35–40 thousand years from marine strata in South China, various lines of evidence have emerged for a more complex, prolonged, and diachronous extinction pattern. We present here the results of a multidisciplinary study of the Permian-Triassic continental transition in the Kuznetsk Basin, Russia. The region is proximal to the Siberian Traps LIP and the detrimental effects of the flood basalt volcanism in the Kuznetsk Basin may have been of similar scale as in the main area of the Siberian Traps distribution (Tunguska and Taymyr regions). Whereas earlier work has placed the Permian-Triassic boundary position between the coal-bearing Tailugan Formation and the volcanoclastic Maltsev Formation, here we revised the traditional model using three independent methods: radioisotopic CA-IDTIMS U-Pb zircon ages, δ13Corg isotope values and paleomagnetic proxies. The regional extinction of the humid-dominated forest flora (cordaites) and the aridity-induced biotic turnover in the Kuznetsk Basin occurred 820 kyr earlier than the end-Permian extinction event recorded in South China at 251.94 Ma. The biota in Kuznetsk Basin at the turnover subsequently diversified (with some exceptions) across the Permian-Triassic transition.
By compiling a large taxonomic database, we find that marine and terrestrial biotic diversity in Siberia progressively increased from the beginning of the Permian up to the middle Roadian (early Guadalupian global glacial event). After that time, the diversity at the species and generic level progressively and slowly declined towards the aforementioned latest Changhsingian (252.76 Ma) biotic turnover. Starting from this time, the biota rapidly diversified in the latest Changhsingian and Early-Middle Triassic. We suggest that the Permian-Triassic mass extinction mostly occurred in the tropics and subtropics due to the strong climatic warming, which was relatively low in late Changhsingian and gradually but quickly extends in the latest Changhsingian to an abnormally high temperature and extremely low oxygenated water in the oceans that was deadly for most marine animals. The warm climate shift poleward during Permian-Triassic transition in the middle-high latitudes caused the replacement (turnover) of the humid-related biotas by the dry climate-related and more diverse communities, which continued to expand throughout the Triassic in both marine and terrestrial habitats. The pattern of the Permian-Triassic event in both marine and terrestrial habitats was more intricate in terms of extinction, turnover, and diversity of biota within the different climatic zones and environmental habitats than has been generally considered.
•Permian-Triassic transition in Kuznetsk Basin (Russia) constrained with CA-IDTIMS dates.•Regional biota evolutionary turnover in the region occurs 820 kyr earlier than in South China.•The biota in Kuznetsk Basin diversified across the Permian-Triassic transition.•Permian-Triassic extinction mostly occurs in the tropics due to the strong climatic warming.•Siberian basalts as a cause of the extinction at the P-T boundary remain questionable.
Dickinsonia in the central Urals occurs in a succession transitional from marginal marine to non-marine. Even within this sequence Dickinsonia appears to be restricted to the least marine facies ...interpreted as a coastal lagoon surrounded by tidal flats. Another puzzling aspect is the complete absence of other Ediacaran taxa that are usually found together with Dickinsonia in other fossil localities. In fact, the Sinii Kamen Member of the Cherny Kamen Formation yielded an assemblage of Ediacaran macrofossils including aspidellamorph and mawsonitomorph holdfasts, frondomorphs, palaeopascichnids, and concentric ring structures of microbial origin; however, fossils of Dickinsonia have never been found in this association.
This paper provides a detailed geological description of the Serebryansky Kamen gabbro massif and copper–precious metal mineralization found for the first time within it. The first data on the ...distribution and localization of disseminated copper–precious metal mineralization in the central part of the massif have been obtained. It was found that copper sulfides (bornite, chalcopyrite, digenite, and chalcocite) are predominantly hosted in melanocratic taxitic varieties of amphibole gabbro. Elevated precious-metal concentrations were measured and precious-metal minerals were identified for the first time in gabbro enriched in sulfides in the northern part of the Ural platinum belt. The Pd–Pt–Fe–Cu intermetallic compounds, sulfide (vysotskite), tellurides (merenskyite, Pd-melonite, kotulskite), bismuthotellurides (michenerite), arsenides, platinum and palladium arsenotellurides (sperrylite, arsenopalladinite), and native gold were identified. Based on a geochemical survey, the resources of copper and precious metals in the Serebryansky Kamen gabbro massif are 760.1 kt of Cu and 97.1 t of precious metals, dominated by Au and Pd. The identified mineralized zones are comparable to the complex Volkovsky deposit in size, structure, and composition. A geological and genetic model is proposed, which can be widely used in prospecting for copper and precious metals in the gabbroic parts of dunite–clinopyroxenite–gabbro massifs.
In this historical perspective, we focus on selected discoveries that Albert Frenkel (1919-2015) made all by himself - single-handedly - which is the discovery of photophosphorylation and NAD ...reduction in anoxygenic photosynthetic bacteria. Then, we present various aspects of his research life through his unpublished letters with some key scientists in his research field. To give a glimpse of his personal life, we have also provided some photographs.
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