Properties of the Frequency Spectra of the Sea Surface and Land Surface Air Temperature Anomalies in a Simple Stochastic Climate Model with Fluctuating Parameters

Izvestiya, Atmospheric and Oceanic Physics - The frequency properties of the spectra of sea surface temperature (SST) and land surface air temperature (SAT) anomalies are analyzed based on a simple...     

Structure of the Middle Urals,east of the main Uralian Fault

In the Middle Urals, volcanic-arc and back-arc basin rocks of Ordovician to Devonian age occur in the Tagil Synform. These outboard terranes were thrust westwards in the late Carboniferous onto continental margin associations of late Proterozoic and Palaeozoic age, now exposed in the Central Uralian Uplift. The Main Uralian Fault coincides approximately with the suture separating the outboard terranes from the East European Platform margin. New fieldwork in the hinterland of the Middle Urals in the area east of the Tagil Synform has found structural evidence favouring E-directed thrusting of accreted terranes and eugeoclinal allochthons in the late Palaeozoic. The upper tectonic units are composed of ophiolite mélange and volcano-sedimentary rocks of Ordovician to Devonian age; they are thrust onto high-grade gneisses, some of possible microcontinental affinities, extensively intruded by mid-Palaeozoic granitic plutons. The nappes in the hinterland are refolded by major upright antiforms and synforms that fold the entire tectonostratigraphy. After thrust assembly, all tectonic units east of the Main Uralian Fault were intruded by late Carboniferous to early Permian granites. Reflection seismic profiles (recorded to 8 s TWT), recently reprocessed at Cornell University, image the major fold structures and demonstrate that they are restricted to the upper crust, being underlain by an extensive zone of flat-lying middle crustal reflectivity. At 10–15 km depth the latter appears to truncate all structures, including the late- to post-tectonic granitoids and extensional faults, east of the Main Uralian Fault. Previous studies (potential-field, refraction- and wide-angle-reflection seismics) have identified an anomalously deep crust under the Tagil Synform and have concluded that the root zone of the orogen is located beneath this belt. The new evidence presented here supports this interpretation, with back-thrusting of the oceanic rocks eastwards over Palaeozoic accreted terranes. © 1998 John Wiley & Sons, Ltd.     

Strontium Isotope Composition in Limestones of the Dal’nyaya Taiga Group in the Patom Basin: Vendian Reference Section of Siberia

New data on the 87Sr/86Sr ratio variations in carbonate rocks of the Dal’nyaya Taiga Group in the Vendian reference section (Ura Uplift, Central Siberia) are presented. The 87Sr/86Sr variations correlate with the sequence-stratigraphic scheme reflecting evolution of the paleobasin, δ13C variations, and paleontological data. Limestones with a high (>1050 µg/g) Sr concentration, which do not show any signs of alteration of the Sr isotope system, were used for reconstructing the secular 87Sr/86Sr variations. Increase in the 87Sr/86Sr ratio from 0.70755 to 0.70823 complicated by subordinate fluctuations was established in seawater during the accumulation of the Dal’nyaya Taiga Group carbonate rocks. Duration of the postglacial deposition of the Dal’nyaya Taiga Group is estimated at no less than 14–15 Ma. Secular variations of the 87Sr/86Sr ratio measured in the Dal’nyaya Taiga Group limestones are similar to changes of this ratio after the Marinoan glacial period. The Sr and C isotope correlations suggest a prolonged hiatus between the Dal’nyaya Taiga and Zhuya groups.     

Carbon Isotope Evidence of Methanogenesis in Sediments of the Dal’nyaya Taiga Group (Lower Vendian of the Patom Basin,Siberia)

Lithology and Mineral Resources - The results of lithological, petrographic, and C–O isotope studies of various types of the diagenetic and postdiagenetic carbonate cement in silty mudstones,...     

Seismogenic Nature of Fluid-Dynamic Structural Parageneses of the Uryakh Gold Ore Field (Northeastern Transbaikalia)

Geology of Ore Deposits - New data on the geological structure and ore-bearing structural parageneses of the Uryakh gold ore field are presented. The formation of the deposit occurred in dynamic...