The upper Bathonian Ammonites first found in North Siberia

The upper Bathonian Ammonites Cadoceras perrarum Voron. and Kepplerites ex gr. rosenkrantzi Spath are reported for the first time from the western coast of Anabar Bay, loosely collected. Both ammonoids represent index species of two biostratigraphic units: the Cadoceras barnstoni Beds and Cadoceras variabile Zone. The occurrence of genus Kepplerites (Kosmoceratidae) in North Siberia is evidence in favor of the migration of that family into the seas of the Arctic region.     

H<Emphasis Type="Italic">α</Emphasis> survey of the local volume: Isolated southern galaxies

We present our Hα observations of 11 isolated southern galaxies: SDIG, PGC 51659, E 222-010, E 272-025, E 137-018, IC 4662, Sag DIG, IC 5052, IC 5152, UGCA 438, and E 149-003, with distances from 1 to 7 Mpc. We have determined the total Hα fluxes from these galaxies. The star formation rates in these galaxies range from 10^?1 (IC 4662) to 10^?4 M _⊙ yr^?1 (SDIG) and the gas depletion time at the observed star formation rates lies within the range from 1/6 to 24 Hubble times H ₀ ^?1 .     

The upper Bathonian ammonite zonation of East Siberia

Modifications to the upper Bathonian zonal scale for northern East Siberia provided by the newly available paleontological record on Middle Jurassic reference sections in the Arctic regions of Yakutia and by the revised earlier collections, are justified. The oldest East Siberian members of Cadoceras are found to be characteristic not of the initial Callovian age as believed by Russian paleontologists, but of the terminal Bathonian age as was previously shown in the biostratigraphic scheme of East Greenland. The succession of zones and index species analogous to that of the latter is revealed in the studied region and the zonal boundaries in Siberia and East Greenland are inferred to be synchronous. Finds of Cadoceras calyx in the upper Bathonian scale permitted, for the first time, the recognition of a corresponding zone. The Bathonian-Callovian boundary is placed between the calyx and anabarense zones. The upper Bathonian zonal scale of northern East Siberia is now in total agreement with the East Greenland zonal scale.     

New ammonite zonation of the lower Callovian in North Siberia

The lower Callovian succession observable in cliffs of Anabar Bay and Bolshoi Begichev Island is described with consideration of zonal subdivisions and beds with ammonites. The unified summary biozonation suggested for North Siberia includes the Cadoceras elatmae Zone with C. frearsi and C. elatmae (instead former C. anabarense) subzones, subsequent C. tschernyschewi and C. tolype zones, and successive C. cf. sublaeve, Rondiceras milaschevici, and Cadoceras ex gr. durum (formerly part of the middle Callovian) beds. As in Siberia and East Europe there are species in common C. elatmae (Nik.), C. frearsi (Orb.), C. tolype Buck., and C. emelianzevi Vor.; certain ammonite zones of Siberian succession are directly correlated with the East European, East Greenland and standard zonations. It is concluded that the lower Callovian is completely represented in Siberia. The lower part of the interval, formerly attributed to the middle Callovian, represents the upper part of the lower Callovian Substage. Zones established in the lower Callovian succession of Siberia are contiguous, whereas equivalents of the Elatmae Subzone and Tschernyschewi Zone have not been distinguished in sections of East Greenland. Evolutionary trends of species in subfamily Cadoceratinae are preliminary discussed.     

Problems of Oxfordian and Kimmeridgian stratigraphy in northern Central Siberia (Nordvik Peninsula section)

The Oxfordian–Lower Hauterivian section of the Nordvik Peninsula (northern Central Siberia) is a reference for developing zonal scales for various fossil groups and improving the Boreal zonal standard. In the middle 1950s–late 1980s, it was studied extensively by geologists, stratigraphers, lithologists, and experts on various fossil groups. These studies yielded rich fossil and microfossil collections and a set of parallel zonal scales for various faunal groups. Recently, a new detailed ammonite zonation of the Oxfordian and Kimmeridgian units of this section has been proposed. These results contradict the previous biostratigraphic data on ammonites, foraminifers, and palynomorphs. In the present paper, all the biostratigraphic data on the Oxfordian and Kimmeridgian units of the Nordvik Peninsula (Cape Urdyuk-Khaya) and northern Central Siberia undergo a comprehensive analysis and comparison with those on the Boreal Realm. The ammonite-constrained stratigraphic position of the lower Upper Jurassic in the Cape Urdyuk-Khaya section is interpreted as Upper Oxfordian or Middle Oxfordian. In our view, this difference in the understanding is due to the misidentification of some Oxfordian ammonite forms. The zones based on other fossil groups (foraminifers, dinocysts) which were distinguished in the Upper Oxfordian and Kimmeridgian sections of the Nordvik Peninsula are well traceable circumarctically. Their stratigraphic position in various regions of the Northern Hemisphere is constrained by ammonites and bivalves. However, if we use the last alternative ammonite zonation of this section part, hardly explicable contradictions will appear in interregional foraminiferal and dinocyst correlations.     

Jurassic and Cretaceous stratigraphy of the Anabar area (Arctic Siberia,Laptev Sea coast) and the Boreal zonal standard

Recent integrated studies of Mesozoic reference sections of the Anabar area (northern Middle Siberia, Laptev Sea coast) and the reinterpretation of all the previous data on a modern stratigraphic basis permit considerable improvement of the bio- and lithostratigraphic division and facies zoning of Jurassic and Cretaceous sediments in the region. Analysis of abundant paleontological data allows the development or considerable improvement of zonal scales for ammonites, belemnites, bivalves, foraminifers, ostracods, dinocysts, and terrestrial palynomorphs from several Jurassic and Cretaceous intervals. All the zonal scales have been calibrated against one another and against regional ammonite scale. Reference levels of different scales useful for interregional correlation have been defined and substantiated based on the analysis of lateral distribution of fossils in different regions of the Northern Hemisphere. It provides the possibilities to propose and consider parallel zonal scales within the Boreal zonal standard for the Jurassic and Cretaceous periods. A combination of these scales forms an integrated biostratigraphic basis for a detailed division of Boreal-type sediments regardless of the place of their formation and for the comparison with the international stratigraphic standard as far as a possible use of a set of reference levels for correlation.     

Peculiarities of Stratospheric Temperature Stratification Measurements by the Microwave Radiometry Method

Izvestiya, Atmospheric and Oceanic Physics - In this paper, we consider the peculiarities of using the microwave radiometry method for remote sensing of the thermal stratification of the high...