Alexander M. Popov

Relationship between δ13C and δ18O values of the RecentNautilus and brachiopod shells in the wild and the problem of reconstruction of fossil cephalopod habitat

Ontogenetic change in δ18O values of the investigatedNautilus pompilius Linne shell in the Philippines (Tagnan, Panglao Islands, Bohol Island area) confirms data, in whichNautilus in the wild shows a marked increase in oxygen isotopic composition between embryonic and post-embryonic stages. The increase in δ18O in post-embryonic septa reflects a migration into colder, deeper (about 300 m) waters. Judging from the isotopic composition of aboral and adoral parts of the last septum, the amplitude of the short term vertical migration for the investigated sample seems to be about 70 m. Relative fluctuation in δ13C values for the livingNautilus, as well as living brachiopods, might be connected with annual cycles of the phytoplankton development. The negative δ13C excurse (−2.5‰) fixed in the septa 9 of the investigatedNautilus pompilius shell seems to be connected with a weakening of phytoplankton bioproductivity related to low solar activity. It is suggested that ammonoids, like livingNautilus spent the most part of their lives near the sea-floor but unlikeNautilus and late Cretaceous belemnites they did not experience, apparently, significant short-term vertical migration.

New maastrichtian oxygen and carbon isotope record: Additional evidence for warm low latitudes

The Cretaceous period was generally characterized by greenhouse conditions. Nevertheless, our data on isotopic composition of biogenic carbonates from the Koryak Upland and Sakhalin (Russian Far East) show that during the Maastrichtian, temperatures dropped sharply at high and middle latitudes, with only a slight warming in the early Late Maastrichtian. At the same time, there is contradictory evidence on climatic conditions for low latitude areas during Maastrichtian time. The new and previously published isotopic data on Maastrichtian mollusks in the Western Interior Seaway (North America) (WIS) and some other areas suggest that tropical deep-sea surface temperatures calculated from the oxygen isotopic composition of the majority of investigated Maastrichtian planktic foraminifera are, obviously, underestimated. Unusually low isotopic temperatues were obtained for tropical planktic foraminifera. This probably reflects both local conditions provoked, first of all, by the influence of tropical upwelling zones, and the ability of Maastrichtian planktic foraminifera to migrate within a large vertical interval in the tropical zone in conditions of weakly stratified (well-mixed) ocean. The average tropical deep-sea surface paleotemperature estimates for the Maastrichtian could have been about 26.6–30.2°C, but, apparently, did not reach the level denoted for the Late Albian and Turonian (32±3°C). Negative carbon-isotopic shifts at the end of the early Maastrichtian and the Cretaceous-Tertiary boundary time seem to be connected with the fall of temperature and eventual reduction of oxygen content in the atmosphere and hydrosphere.

Recovery of brachiopod and ammonoid faunas following the End-Permian crisis: Additional evidence from the lower Triassic of the Russian Far East and Kazakhstan

After the End-Permian mass extinction, ammonoids reached levels of taxonomic diversity higher than in the Changhsingian by the Dienerian Substage of the Induan. However, brachiopods exhibit a prolonged delay in recovery, and their taxonomic diversity had not recovered to Late Permian levels even by the Olenekian. The differential patterns of recovery between these two clades may reflect fundamental differences in physiology and behavior. Brachiopods were benthic organisms that were dependent on specific trophic sources, and their general reduction in size during the Early Triassic may have been a response to a relative paucity of food resources. In contrast, ammonoids were sluggishnektic organisms that utilized a wider range of trophic sources and that suffered no comparable size decrease during the Early Triassic. Brachiopods may have been at a disadvantage also due to vulnerabilities associated with their larval stage, during which they had to locate a suitable substrate for settlement. In contrast, ammonoids had no larval stage and juveniles may have been dispersed widely into favorable habitats. These factors may account for differences in the relative success of ammonoids and brachiopods at high-latitude regions following the End-Permian mass extinction: ammonoids successfully recolonized the Boreal region during the Early Triassic whereas brachiopods did not.

Late Permian to Middle Triassic palaeogeographic differentiation of key ammonoid groups: evidence from the former USSR

Palaeontological characteristics of the Upper Permian and upper Olenekian to lowermost Anisian sequences in the Tethys and the Boreal realm are reviewed in the context of global correlation. Data from key Wuchiapingian and Changhsingian sections in Transcaucasia, Lower and Middle Triassic sections in the Verkhoyansk area, Arctic Siberia, the southern Far East (South Primorye and Kitakami) and Mangyshlak (Kazakhstan) are examined. Dominant groups of ammonoids are shown for these different regions. Through correlation, it is suggested that significant thermal maxima (recognized using geochemical, palaeozoogeographical and palaeoecological data) existed during the late Kungurian, early Wuchiapingian, latest Changhsingian, middle Olenekian and earliest Anisian periods. Successive expansions and reductions of the warm– temperate climatic zones into middle and high latitudes during the Late Permian and the Early and Middle Triassic are a result of strong climatic fluctuations.

Permian to earliest Cretaceous climatic oscillations in the eastern Asian continental margin (Sikhote-Alin area), as indicated by fossils and isotope data

Palaeozoological, palaeobotanical and geochemical analyses of Lower Permian to the lowermost Cretaceous sediments exposed in the southern Russian Far East (Bureya–Jiamusi–Khanka superterrane and the Sergeevka terrane), and higher latitude areas (northern Russian Far East and Spitsbergen) suggest a direct relationship with global climatic events defined by the data from oxygen-isotopic palaeotemperatures. Several positive carbon-isotopic anomalies discovered within the uppermost Cisuralian, Guadalupian, early Lopingian and Aalenian–Bajocian intervals are possibly connected to strong hydrological intermixing of oceanic waters under the influence of considerable thermal gradients.

Latest Permian and Triassic carbonates of Russia: new palaeontological findings, stable isotopes, Ca-Mg ratio, and correlation

The seven recently discovered events, respectively occurring at (1) early Dorashamian, (2) middle Olenekian, (3) early Anisian, (4) latest Ladinian-?earliest Carnian, (5) late Carnian, (6) early Norian and (7) early Rhaetian intervals, are characterised by anomalously high value of δ 13 C (2.5–6.9‰) and a more or less considerable decline in Ca-Mg ratio in organogenic carbonates of the Tethyan Realm The geochemical variations appear explaiable by high bioproductivity of marine basins during periods of transgressions and warm climate. The highest δ 13 C values identified in Triassic limestones of the Malaya Laba (6.9‰) and Sakhrai (4.2‰) River basins in North Caucasus and Primorye region (4.9‰) fall at the middle Olenekian Tirolites-Amphistephanites Zone and its equivalents. Oxygen isotope analyses of well preserved brachiopod shells from the Nikitinskaya and Urushtenskaya Suites show that shallow-water temperatures in North Caucasus fluctuated during Early Dorashamian time about 24°C, which is in agreement with our previous data from the Dorashamian Paratirolites kittli Zone in Transcaucasia (around 22–24°C). Similar temperatures appear to have occured in the Tethys at least during the middle Olenekian time.

Early differential diagnosis of the severity of acute pancreatitis

There is a great need for early verification of the severity of acute pancreatitis (AP). The early stage of pathogenesis of AP is characterized by endothelial dysfunction which could be determined by wavelet analysis of skin temperature (WAST) technique. The aim is to investigate whether the dysregulation of microvascular tone caused by endothelial dysfunction and detected by WAST can be a significant indicator in early differential diagnosis of AP severity. The WAST performed in the frequency range of 0.0095–0.02xa0Hz during the contralateral cold test. Forty nine patients with AP aged 19–65 participated in this study. The control group included 12 healthy volunteers aged 20–65. Dysregulation of vascular tone during the contralateral cold test was observed in all patients with AP. The basal amplitudes of skin temperature oscillations in patients with AP were much lower than in healthy volunteers and progressively decreased as the disease severity increased. In patients with mild and moderate AP only the vasodilator component is destroyed, but vasoconstriction still operates. In patients with severe AP both mechanisms of endothelial vascular tone regulation are destroyed. Patients with AP have abnormal microvascular reactions related to the endothelial mechanism of vascular tone regulation. Based on the initial values of amplitudes and the indices of vasoconstriction and postcold vasodilatation, the WAST method makes it possible to evaluate two related but different characteristics of the endothelial dysfunction in patients with AP on admission which can be a significant indicator in early differential diagnosis of AP severity.

Pole to Equator Temperature Gradient for Coniacian Time, Late Cretaceous: Oxygen and Carbon Isotopic Data on the Koryak Upland and Hokkaido

The purpose of this study was to estimate the Coniacian latitudinal thermal gradient in the Northern Hemisphere. Both hemipelagic (ammonoids) and benthic (brachiopods and bivalves) δ18O and δ13C records were used. They originated from Coniacian shallow-water sequences across a wide range of paleolatitudes, from the Koryak upland (northern Kamchatka, Russian Far East) in the north, to Hokkaido (Japan) in the south. Among Coniacian ammonoids, both migrants from Hokkaido living in high latitudes (Kamchatka) and endemic forms dwelling in middle-low latitudes (Hokkaido) indicate seemingly close optimal growth temperatures. Nevertheless, certain differences in climatic conditions, prevailing during high-latitude coldest seasons, undoubtedly provoked growth cessation in some groups of ammonites. Our isotopic study suggests latitudinal temperature changes of only 0.12 °C per degree of latitude for the Northern Hemisphere in Coniacian times, while the average annual temperature in North Kamchatka seems about 3.3 °C lower than that in Hokkaido.

Nitrogen and Carbon Isotope Data of Olenekian to Anisian Deposits from Kamenushka/South Primorye, Far-Eastern Russia and Their Palaeoenvironmental Significance

The Kamenushka Formation, exposed in the northern part of South Primorye (Kamenushka-1 and Kamenushka-2 sections), is one of the few localities in the world with richly fossiliferous Lower–Upper Olenekian sedimentary successions. Lower to Middle Triassic ammonoid-, brachiopod- and conodont-bearing silty-clayey deposits of the Kamenushka-1 and Kamenushka-2 sections have been isotope-geochemically investigated in detail. As a result, these sections, together with the previously investigated Abrek Section, exposed in the southern part of South Primorye, provide almost complete 15Norg- and 13Corg- records for the Lower Triassic of this region. Nine N-isotope intervals and the five negative C-isotope excursions, reflecting, apparently, unstable climatic and hydrological conditions, have been distinguished in the Lower Triassic of South Primorye. On the basis of the new C-isotope data the Mesohedenstroemia bosphorensis Zone (upper part), Shimanskyites shimanskyi and Neocolumbites insignis zones of South Primorye are correlated now with the Lower Smithian part of the Yinkeng Formation, the Upper Smithian part of the Helongshan Formation and the Middle Spathian part of the Nanlinghu Formation in South China, respectively, as has been observed in the Abrek, Kamenushka-2, West Pingdingshan and Majiashan sections.

N and C Isotopic Compositions of the Lower Triassic of Southern Primorye and Reconstruction of Habitat Conditions of Marine Organisms after Mass Extinction at the End of the Permian

Data on the N and C isotopic composition are presented for the Lower Triassic claystones of the Abrek section of southern Primorye (Far East). The results showed five N isotopic intervals and several negative C isotopic excursions of the Induan–lower Olenekian stages of the Abrek section.