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81.
82.
Hydrocarbons occur in two regional, Upper Cretaceous limestone units—the Turonian-Coniacian Petrel Member, and the Santonian-Maastrichtian Wyandot Formation. The units form important seismic markers beneath the Scotian Shelf and the Grand Banks of Eastern Canada. They mainly consist of bioturbated chalk and minor amounts of calcareous mudstone. A search for source rock using the Δ log R technique showed intervals with source potential, but testing of core and cuttings by Rock-Eval analysis showed no source potential. Three issues are the main cause for the inconsistency: (1) unconsolidated shales that likely included organic material were lost during sample washing; (2) severe contamination by mud additives; and (3) presence of gas. The organic matter found on the shelf has been strongly oxidised, but the distal facies of these limestone units and condensed shale units above and below may yet have potential to form source rock, beyond the studied areas.  相似文献   
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84.
Average concentrations of incompatible elements and isotopes of radiogenic Sr, Nd and Pb in a 350 km long belt of Central European volcanics (CECV) resemble those in OIB in general and in OIB from the N Atlantic in particular. This similarity allows to infer comparable sources for CECV and OIB which might have been located in the lower mantle according to seismic tomography and chemistry, with the latter unlike a MORB source. The incompatible element contribution of lower mantle origin can be modelled from primitive mantle minus continental crust and upper mantle inventories. Alkali basaltic magmas from the modelled source are close in composition to CECV and OIB. The continental crust contains almost half of the silicate Earth's content of Rb, K, Pb, Ba, Th and U, which were mobilized to a major extent through dehydration of subducted ocean crust. Related losses from the lower mantle had to be replaced by deep subductions of oceanic lithosphere recognized from their isotopic imprint. From a balance based on Nd isotopes it can be concluded that average CECV contains 60% matter from residual primitive mantle and 40% from deeply subducted lithosphere (including some young upper mantle materials). Plume products from separate CECV regions developed, within 45 Ma, from rather depleted to more primitive isotopic signatures. Four periods of volcanism from Eocene to late Quaternary time are explained as four pulses of an almost stationary ultrafast plume uprise as modelled by Larsen and Yuen (1997). Magma production has increased from the first to the third pulse with the peak during Miocene time in the Vogelsberg region. The final pulse produced the Quaternary Eifel volcanoes. Tectonism from the Alpine orogen has probably triggered the synchronous volcanism of CECV, Massif Central etc. The European lithospheric plate has moved under the control of the opening Atlantic almost in an eastern direction with a velocity of 1 cm per year and has shifted extinct volcanoes off their source channels. Received: 10 July 1998 / Accepted: 10 February 1999  相似文献   
85.
The application of kriging-based geostatistical algorithms to integrate large-scale seismic data calls for direct and cross variograms of the seismic variable and primary variable (e.g., porosity) at the modeling scale, which is typically much smaller than the seismic data resolution. In order to ensure positive definiteness of the cokriging matrix, a licit small-scale coregionalization model has to be built. Since there are no small-scale secondary data, an analytical method is presented to infer small-scale seismic variograms. The method is applied to estimate the 3-D porosity distribution of a West Texas oil field given seismic data and porosity data at 62 wells.  相似文献   
86.
Within the German Tropospheric Research Programme (TFS) numerous kinetic and mechanistic studies on the tropospheric reaction/degradation of the following reactants were carried out: oxygenated VOC, aromatic VOC, biogenic VOC, short-lived intermediates, such as alkoxy and alkylperoxy radicals.At the conception of the projects these selected groups were classes of VOC or intermediates for which the atmospheric oxidation mechanisms were either poorly characterised or totally unknown. The motivation for these studies was the attainment of significant improvements in our understanding of the atmospheric chemical oxidation processes of these compounds, particularly with respect to their involvement in photooxidant formation in the troposphere. In the present paper the types of experimental investigations performed and the results obtained within the various projects are briefly summarised. The major achievements are highlighted and discussed in terms of their contribution to improving our understanding of the chemical processes controlling photosmog formation in the troposphere.  相似文献   
87.
Daily meteorological observations have been made at the old astronomical observatory in Stockholm since 1754. Complete daily mean series of air temperature and sea level pressure are reconstructed from the observational data for 1756–1998. The temperature and pressure series arereconstructed and homogenized with the aid of metadata, statistical tests and comparisons with data from other stations. Comparisons with independently reconstructed daily series for nearby Uppsala (1722–1998) show that the quality of thedaily Stockholm data is good, although the reliability is lower before the mid-19th century. The daily temperature data show that the colder winter mean temperatures of the late 18th to early 19th centuries were connected with a particularly high frequency of very cold winter days. The warmer summers of the same period are more connected with a general shift of the temperature distribution towards higher temperatures than in the late 20th century.  相似文献   
88.
Dendroclimatological sampling of Scots pine (Pinus sylvestris L.) has been made in the province of J?mtland, in the west-central Scandinavian mountains, since the 1970s. The tree-ring width (TRW) chronology spans several thousand years and has been used to reconstruct June?CAugust temperatures back to 1632 bc. A maximum latewood density (MXD) dataset, covering the period ad 1107?C1827 (with gap 1292?C1315) was presented in the 1980s by Fritz Schweingruber. Here we combine these historical MXD data with recently collected MXD data covering ad 1292?C2006 into a single reconstruction of April?CSeptember temperatures for the period ad 1107?C2006. Regional curve standardization (RCS) provides more low-frequency variability than ??non-RCS?? and stronger correlation with local seasonal temperatures (51% variance explained). The MXD chronology shows a stronger relationship with temperatures than the TRW data, but the two chronologies show similar multi-decadal variations back to ad 1500. According to the MXD chronology, the period since ad 1930 and around ad 1150?C1200 were the warmest during the last 900?years. Due to large uncertainties in the early part of the combined MXD chronology, it is not possible to conclude which period was the warmest. More sampling of trees growing near the tree-line is needed to further improve the MXD chronology.  相似文献   
89.
<正>1.Introduction Spectacular advances have been made in the atmospheric sciences on a global level during a period of one hundred years or more,which is arguably most evident through"the quiet revolution of numerical weather prediction"(Bauer et  相似文献   
90.
Following an earlier climatological study of North Pacific Polar Lows by employing dynamical downscaling of NCEP1 reanalysis in the regional climate model COSMO-CLM, the characteristics of Polar Low genesis over the North Pacific under different global warming scenarios are investigated. Simulations based on three scenarios from the Special Report on Emissions Scenarios were conducted using a global climate model (ECHAM5) and used to examine systematic changes in the occurrence of Polar Lows over the twenty first century. The results show that with more greenhouse gas emissions, global air temperature would rise, and the frequency of Polar Lows would decrease. With sea ice melting, the distribution of Polar Low genesis shows a northward shift. In the scenarios with stronger warming there is a larger reduction in the number of Polar Lows.  相似文献   
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